Megathrust Earthquakes and the Subduction of Excess Sediment and Bathymetrically Smooth Seafloor

Home , 1907 Sumatra earthquake, 1932 Jalisco earthquakes, 1993 Kushiro earthquake, Aleutian Arc, Aleutian Trench, Cocos Plate

Exploring the Deep Sea and Beyond, Volume 2, themed issue Scholl et al. Great (≥Mw8.0) megathrust earthquakes and the subduction of excess sediment and bathymetrically smooth seaﬂ oor

David W. Scholl1,2, Stephen H. Kirby1, Roland von Huene1, Holly Ryan1, Ray E. Wells3, and Eric L. Geist3 1U.S. Geological Survey, Emeritus, Menlo Park, California 94025, USA 2Department of Geology and Geophysics, Emeritus, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA 3U.S. Geological Survey, Menlo Park, California 94025, USA

ABSTRACT characteristic lengthy rupturing of high- to signifi cantly modify or arrest rupture con- magnitude IPT earthquakes. In these areas tinuation (Kodaira et al., 2000; Mochizuki et al., Using older and in part fl awed data, Ruff subduction of a weak sedimentary sequence 2008; Bilek, 2010; Singh et al., 2011; Wang and (1989) suggested that thick sediment enter- further enables rupture continuation. Bilek, 2011; Trehu et al., 2012; El Hariri et al., ing the subduction zone (SZ) smooths and 2013; Wang and Bilek, 2014), as commonly do strengthens the trench-parallel distribution INTRODUCTION subducting ridges (Franke et al., 2008; Sparkes of interplate coupling. This circumstance et al., 2010; von Huene et al., 2012; Kopp, 2013) was conjectured to favor rupture continua- Ruff (1989) observed that the entrance of an and also some upper plate structures (Bejar- tion and the generation of high-magnitude “excess quantity” of sediment into a lengthy Pizarro et al., 2013). (≥Mw8.0) interplate thrust (IPT) earth- subduction (≥230–300 km) sector of subduction With respect to the posited rupture-promot- quakes. Using larger and more accurate zone (SZ) favors the nucleation there of inter- ing effect of subducted sediment, Ruff (1989) compilations of sediment thickness and plate thrust (IPT) or megathrust earthquakes of lamented that, “the statistical correlation instrumental (1899 to January 2013) and magnitude Mw8.2 or greater (Fig. 1). He con- between excess sediments and great earthquake pre-instrumental era (1700–1898) IPTs (n = jectured that subducted sediment worked to occurrence is less than compelling.” His infer- 176 and 12, respectively), we tested if a com- both strengthen interplate coupling and smooth ence that a relation did exist was drawn from a pelling relation existed between where IPT the lateral or trench-parallel distribution of population of 19 instrumentally recorded earth- earthquakes ≥Mw7.5 occurred and where coupling strength, a circumstance that promotes quakes and a then-available but incomplete and thick (≥1.0 km) versus thin (≤1.0 km) sedi- rupture continuation and the consequent genera- largely inaccurate tabulation of the thickness of mentary sections entered the SZ. tion of high-magnitude or great (≥Mw8.0) IPT sediment entering SZs. After 1989 and through Based on the new compilations, a statisti- earthquakes. January 2013, an additional 16 great (≥Mw8.0), cally supported statement (see Summary and An “excess” quantity was considered a thick- fi ve giant (≥Mw8.5), and two super giant Conclusions) can be made that high-magni- ness adequate to nourish the building of an (≥Mw9.0) IPT earthquakes broke at 14 different tude earthquakes are most prone to nucleate accretionary frontal prism. This thickness is trench sectors (Tables 1–6). These more recent at well-sedimented SZs. For example, despite commonly estimated at ≥1 km (von Huene earthquakes include the re-seized 1946 Unimak, the 7500 km shorter global length of thick- and Scholl, 1991; Clift and Vannucchi, 2004; Alaska, or Scotch Cap megathrust (Lopez and sediment trenches, they account for ~53% Scholl and von Huene, 2007). Subducting sedi- Okal, 2006). Also since 1989, accurate tables of instrumental era IPTs ≥Mw8.0, ~75% ment enters the subduction channel (see Fig. 2, and maps of the global distribution of trench- ≥Mw8.5, and 100% ≥Mw9.1. No megathrusts panel C) that physically separates the upper and sediment thickness have become available (von >Mw9.0 ruptured at thin-sediment trenches, lower plate (Cloos and Shreve, 1988a, 1988b; Huene and Scholl, 1991; Scholl and von Huene, whereas three occurred at thick-sediment Moore et al., 2007; Collot et al., 2011). Mega- 2007; Heuret et al., 2012). trenches (1960 Chile Mw9.5, 1964 Alaska thrust rupturing occurs along the top or bottom To test the Ruff conjecture concerning the Mw9.2, and 2004 Sumatra Mw9.2). or within the subduction channel. rupture-promoting effect of sediment thickness However, large Mw8.0–9.0 IPTs com- In contrast, the subduction of bathymetrically alone (we did not evaluate a strengthening effect, monly (n = 23) nucleated at thin-sediment rough seafl oor would be expected to produce a notion that has been challenged by Wang and trenches. These earthquakes are associated an uneven or heterogeneous distribution of Bilek [2014]), we compiled improved and larger with the subduction of low-relief ocean fl oor coupling strength. This situation would condi- data sets of trench-axis sediment thickness and and where the debris of subduction erosion tion short-duration rupturing typical of lower vetted instrumental (1899 through January 2013) thickens the plate-separating subduction magnitude IPT earthquakes (see Ruff, 1989; era IPT earthquakes of magnitude ≥Mw7.5 (see channel. The combination of low bathymet- Fig. 3). It is now generally recognized that, Table 5) and pre-instrumental-era (1700–1898) ric relief and subduction erosion is inferred in fact, the subducted relief of seamounts and earthquakes of estimated magnitude ≥Mw8.0 to also produce a smooth trench-parallel seamount groups, although capable of localiz- (see Table 6). Descriptively simplifi ed catalogs distribution of coupling posited to favor the ing rupture initiation (Bilek et al., 2003), tend of instrumental-era IPT earthquakes of magni-

Geosphere; April 2015; v. 11; no. 2; p. 236–265; doi:10.1130/GES01079.1; 16 ﬁ gures; 8 tables. Received 25 May 2014 ♦ Revision received 28 October 2014 ♦ Accepted 4 February 2015 ♦ Published online 11 March 2015

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Thick Trench Section (>1.0 km) A

Aleutian Trench AccretionaryAccretionary frontalfrontal prismprism PacificPaci Plate fic P late ~2 km

10 km R/V Ewing, 1994 Thin Trench Section (<1.0 km) B 4 NE Japan (Tohoku) Trench 4 Frontal Cenozoic) Slope Apron ( Prism 6 ~0.6 km 6

8 ForearcForearc BasementBasement (Late(Late Cretaceous)Cretaceous) 8 PacificP Plate acific Plate 10 10

12 10 km 12 VonVon HueneHuene etet al.,al., 11994994 km km Trench Sediment Entering Subduction Channel Subduction Channel 2 2 C oic) enoz onon (Cenozoic)(C Aprpr SlopeSlope A 4 Ecuador Trench 4

km ForearcForearc BasementBasement (Mesozoic)(Mesozoic) km SubductingSubd S NNazcaaz Plate ucting 6 ca Plate ediment 6 SubdSu bductionuct Cha ion Ch 10 km annelnnel 8 CollotCollot etet al.,al., 20022002 8

Figure 2. Seismic reflection images of: (A) a thick-sediment trench (see also Fig. 12), (B) a thin-sediment trench, and (C) a thick-sediment trench section entering the subduction channel (see also Fig. 12).

tude ≥Mw7.5 (n = 176) and pre-instrumental Because our purpose was to test for a defi ni- Based on the instrumental data listed in megathrusts of magnitude ≥Mw8.0 (n = 12) are tive association of sediment thickness versus Tables 1, 2, and 3 and the plots of Figures 4–13, listed on Tables 1–4. In these tables, IPT earth- occurrence of high-magnitude megathrust earth- a statistically supported statement (see Sum- quakes are linked to an occurrence area along a quakes—either statistically strong, weak, or not mary and Conclusions) can be made that large sector of trench distinguished by a fl uctuating there—we only used the two thickness bins IPT earthquakes are most prone to nucleate at but average sediment fi ll that can be character- noted above and did not divide sectors further well-sedimented SZs. For example, despite the ized as either thick or thin. Along thick sectors into categories of very thin (>0.5 km) or very 7500 km shorter global length of thick-sediment the average fi ll is >1.0 km, whereas that for thin thick trench sequences (>2.0 km). Nonethe- trenches (thin = ~21,500 versus thick = ~14,000 sectors is <1.0 km. Trench sectors are shown on less, as described by Heuret et al. (2012), useful km), at thick-sediment trenches occurred ~53% Figure 1. They are defi ned as a sector of trench information and insights can be gained by ana- of all earthquakes of magnitude ≥Mw8.0, ~75% axis long enough (i.e., ≥250–300 km) to support lyzing with smaller thickness increments as well of all ruptures ≥Mw8.5, and 100% of all IPTs a potential high-magnitude rupture between as including other physical parameters to assess ≥Mw9.1 (Fig. 9; see also Heuret, 2012). When observed rupture barriers and containing either the propensity of a SZ sector to break in a great the number of thin-sediment earthquakes in the a thin- or thick-sediment fi ll. megathrust earthquake. magnitude range of Mw7.5–8.4 are normalized

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length of ocean-margin SZs listed on Table 3 Colombia-EcuadorColombia-Ecuador (~35,500 km) at which megathrust earthquakes 7 ≥Mw7.5 have occurred was divided into 48 sectors identifi ed as a physically bordered or seismically identifi ed trench segment ≥250–300 km CarnegieCarnegie RidgeRidge in length containing a mostly axially continuous thin (<1.0 km) or thick (>1.0 km) sediment Figure 3. Sediment-thickness sectors (thick Peru,Peru, NorthNorth fi ll (Figs. 1 and 2). Heuret et al. (2012; Fig. 1) are red; thin are blue) of the western South 1177 used a seismic-behavior (delimiting) sectoring America trench system is delimited between NNazcaazca RidgeRidge approach identify 44 sectors that are similar to subducting aseismic ridge (e.g., Carnegie 1818 those shown on Figure 1. and Nazca Ridges), at a major change in PPeru,eru, SouthSouth Sectors listed on Tables 1–4 and shown on trend of trench axis (e.g., southern Peru Figures 1 and 3 identify trench segments that to northern Chile Trenches), at a complex display seismically observed rupture lengths system of fracture zones (e.g., the Mocha Chile,Chile, NorthNorth 3 that start and end at: (1) a subducted bathymetric fracture zone [FZ] separating the north element of large dimensions (e.g., an aseismic and south, central Chile subduction zone), JuanJuan FFernandezernandez RidgeRidge ridge, oceanic plateau, seamount group or chain, or at a plate boundary (South Chile Rise) or prominent fracture zone); (2) a plate bound- (see Tables 1, 2, and 3). Although a southern ary, e.g., South Chile Triple Junction separating sector of the Chile Trench sector is shown, NorthNorth 5 the Nazca, Antarctic, and South America plates; it is not numbered (see Tables 1, 2, and 3) Chile,Chile, CCentralentral MochaMocha and (3) an abrupt change in the regional strike because no megathrust earthquake ≥Mw7.5 FZFZ of the SZ, e.g., southern Peru to northern Chile, has been instrumentally recorded along this SSouthouth 6 western Aleutian to Kamchatka, and Kuril to sector of the sediment-charged Chile Trench SSouthouth ChileChile RRidgeidge andand Japan (Figs. 1 and 3). south of the Juan Fernandez Ridge (~33°S) TripleTriple JunctionJunction Figure 3 displays our sectoring of the (see Summary and Conclusions). ~7000-km-long SZ bordering western South America (see also fi g. 2 of Heuret et al., 2012). All sectors, thin or thick, are delimited (termi- nated) by bathymetric elements or a promi- CChile,hile, SouthSouth nent change in strike of the SZ. For example, the ~1500-km-long, sediment-fl ooded central section or segment of the Chile Trench is bordered to the north and south, respectively, by the underthrusting Juan Fernandez Ridge (~33°S) (reduced) to compensate for the disproportion- plate coupling , the condition posited by Ruff and the triple junction of the South Chile Rise ately longer occurrence length of thin- versus (1989) that promotes the lengthy (>250– (~46°S). This lengthy segment characteristically thick-sediment trench sectors in this magnitude 300 km), along-trench rupturing characteristic ruptures north and south of the deeply (~2.5 km) range (19,000 versus 7800 km, respectively) of high-magnitude megathrust earthquakes. sediment-buried Mocha-Valdivia complex of ~73% of all earthquakes ≥Mw8.0, ~75% of all For the Tohoku-Oki Mw9.0, a stratigraphically underthrusting fracture zones (FZs) (Melnick earthquakes ≥Mw8.5, and 100% of all earth- focused surface of interplate slip contributed et at., 2006; Bilek, 2010; Sparkes et al., 2010). quakes ≥Mw9.1 occurred at thick-sediment importantly to a near-trench displacement of Recognizing this observation, the central seg- trenches. 30–60 m and the launching of the horrendous ment of the Chile Trench was divided into It is important to emphasize that great IPT Tohoku tsunami (Chester et al., 2013; Moore separate north and south sectors (Figs. 1 and 3; earthquakes also ruptured adjacent to thin- et al., 2013; Ujiie et al., 2013; Nakamura et al., Tables 2 and 3). Rupture termination at the sub- sediment trench sectors, a circumstance noted 2013; Moore et al., 2015). ducted segment of the Mocha FZ is linked by by Ruff (1989) and Heuret et al. (2012). This Moreno et al. (2014) to the upward injection of observation also includes the 2014 north Chile SEDIMENT-FILL TRENCH SECTORS fl uids from the FZ into the overlying seismo- Mw8.2 that is not listed on Tables 1–4. Three genic zone. recorded giant earthquakes—1952 Kam- Rules of Trench Sectoring Similarly, the laterally continuous, sediment- chatka Mw9.0, 1963 Kuril Mw8.5, and 2011 charged Aleutian SZ tends to break in great Japan (Tohoku-Oki) Mw9.0 (Table 1)—are As noted above, large megathrust ruptures megathrusts along a western sector and a cen- each associated with the subduction of bathy- commonly initiate, terminate, or are signifi - tral sector bordered on its eastern side by the metrically smooth or low-relief oceanic crust cantly modulated at subducted high-relief Amlia fracture zone (Fig. 1), also considered to and where basal subduction erosion of the bathymetric structures or elements (Kodaira be a subsurface source of fl uid injection (Singer upper plate is prominent (von Huene et al., et al., 2000; Bilek et al., 2003; Collot et al., et al., 1996, 2007). An eastern Aleutian or Fox 1994; Scholl et al., 2011; Kopp, 2013; Wang 2004; Franke et al., 2008; Mochizuki et al., Island sector extending from the Amlia FZ east- and Bilek, 2014). The combination of under- 2008; Bilek, 2010; Sparkes et al., 2010; Singh ward to the Alaska SZ at Unimak Pass is not thrusting low-relief seafl oor and subduction et al., 2011; Wang and Bilek, 2011; Trehu known to have broken in a great IPT earthquake. erosion evidently also works to produce a et al., 2012; von Huene et al., 2012; El Hariri But the potential to do so seems high (Butler, smooth trench-parallel distribution of inter- et al., 2013; Wang and Bilek, 2014). The global 2012; Ryan et al., 2012) (Fig. 1; Table 2).

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TABLE 1. INSTRUMENTAL ERA MEGATHRUST EARTHQUAKES THAT RUPTURED AT THIN-SEDIMENT (<1.0 KM) TRENCH SECTORS Average Sector EQ Latitude Longitude Sector thickness length count Year Month Day Time (°N) (°E) Mw Trench sector count (km) (km) 1 1946 8 4 17:51:00 19.25 –69.00 7.8 Antilles, Greater, Puerto Rico Trench (~61–69W) 1 0.5 900 2 1943 7 29 6:02:00 19.25 –67.50 7.5 Antilles, Greater, Puerto Rico Trench (~61–69W) 0.5 900 3 1942 8 6 23:36:00 14.00 –91.00 7.7 Central America, Tehuantepec Ridge to Cocos Seamounts and Ridge 2 0.5 1200 (15–9N), Guatemala 4 1950 10 5 16:09:00 10.35 –85.00 7.7 Central America, Tehuantepec Ridge to Cocos Seamounts and Ridge 0.5 1200 (15–9N), Costa Rica 5 1992 9 2 0:16:42 11.20 –87.81 7.6 Central America, Tehuantepec Ridge to Cocos Seamounts and Ridge 0.5 1200 (15–9N), Nicaragua 6 1983 4 3 2:50:21 8.85 –83.25 7.5 Central America, Tehuantepec Ridge to Cocos Seamounts and Ridge 0.5 1200 (15–9N), Costa Rica 7 1922 11 11 4:32:00 –28.55 –70.76 8.3 Chile, north, Arica Bight to Juan Fernandez Ridge (18.5–33S) 3 0.5 1500 8 1995 7 30 5:11:23 –23.34 –70.29 8.0 Chile, north, Arica Bight to Juan Fernandez Ridge (18.5–33S) 0.5 1500 9 1943 4 6 16:07:00 –30.98 –71.27 7.7 Chile, north, Arica Bight to Juan Fernandez Ridge (18.5–33S) 0.5 1500 10 1966 12 28 9:08:00 –25.50 –70.70 7.7 Chile, north, Arica Bight to Juan Fernandez Ridge (18.5–33S) 0.5 1500 11 1983 10 4 18:52:37 –26.01 –70.56 7.7 Chile, north, Arica Bight to Juan Fernandez Ridge (18.5–33S) 0.5 1500 12 2007 11 14 15:41:11 –22.64 –70.62 7.7 Chile, north, Arica Bight to Juan Fernandez Ridge (18.5–33S) 0.5 1500 13 1987 3 5 19:17:20 –24.38 –70.93 7.5 Chile, north, Arica Bight to Juan Fernandez Ridge (18.5–33S) 0.5 1500 14 1972 12 4 10:16:00 33.30 140.80 7.5 IBM, north, Izu, Ogasawara Plateau to Japan Trench (~26–34.5N) 4 0.4 950 15 1965 1 24 11:00:00 –2.40 126.00 7.5 Indonesia, Ceram Sea 5 0.5 500 16 2011 3 11 5:26:00 38.32 144.37 9.0 Japan, north, Erimo Seamounts at Kuril-Japan bend to Daiichi Kashima 6 0.6 800 Seamounts (~41.5–36N) 17 1968 5 16 12:49:00 40.90 143.35 8.2 Japan, north, Erimo Seamounts at Kuril-Japan bend to Daiichi Kashima 0.6 800 Seamounts (~41.5–36N) 18 1994 12 28 12:19:23 40.53 143.42 7.8 Japan, north, Erimo Seamounts at Kuril-Japan bend to Daiichi Kashima 0.6 800 Seamounts (~41.5–36N) 19 1960 3 20 17:07:00 39.90 143.20 7.7 Japan, north, Erimo Seamounts at Kuril-Japan bend to Daiichi Kashima 0.6 800 Seamounts (~41.5–36N) 20 1978 6 12 8:14:43 38.02 142.07 7.7 Japan, north, Erimo Seamounts at Kuril-Japan bend to Daiichi Kashima 0.6 800 Seamounts (~41.5–36N) 21 1931 3 9 10:08:00 40.50 142.50 7.6 Japan, north, Erimo Seamounts at Kuril-Japan bend to Daiichi Kashima 0.6 800 Seamounts (~41.5–36N) 22 1938 11 5 8:43:00 37.01 142.01 7.5 Japan, north, Erimo Seamounts at Kuril-Japan bend to Daiichi Kashima 0.6 800 Seamounts (~41.5–36N) 23 1938 11 5 10:50:00 37.11 142.08 7.5 Japan, north, Erimo Seamounts at Kuril-Japan bend to Daiichi Kashima 0.6 800 Seamounts (~41.5–36N) 24 2011 3 9 2:45:20 38.42 142.00 7.5 Japan, north, Erimo Seamounts at Kuril-Japan bend to Daiichi Kashima 0.6 800 Seamounts (~41.5–36N) 25 1923 9 2 0:06:00 35.13 140.50 7.5 Japan, south, Daiichi Kashima Seamounts to Japan-Izu trench junction 7 0.6 800 (~36–34.5N) 26 1971 12 15 10:09:00 56.00 163.20 7.5 Kamchatka, north, Cape Kronotsky collision to Cape Kamchatka collision 8 0.6 300 (~53.5–56N) 27 1952 11 4 16:58:00 52.76 160.06 9.0 Kamchatka, south, south of Emperor Ridge collision at Cape Kronotsky to 9 0.6 700 Kuril Basin (~53.5–49N) 28 1923 2 3 16:01:00 53.85 160.76 8.3 Kamchatka, south, south of Emperor Ridge collision at Cape Kronotsky to 0.6 700 Kuril Basin (~53.5–49N) 29 1959 5 4 7:15:00 53.35 159.65 8.2 Kamchatka, south, south of Emperor Ridge collision at Cape Kronotsky to 0.6 700 Kuril Basin (~53.5–49N) 30 1997 12 5 11:27:21 54.31 161.91 7.8 Kamchatka, south, south of Emperor Ridge collision at Cape Kronotsky to 0.6 700 Kuril Basin (~53.5–49N) (continued)

Estimating Sediment Thickness est here either because of the accumulation of launch ocean-crossing tsunamis. We restricted debris shed by mass wasting from the landward this compilation to megathrust or IPT earth- Estimates of trench-fl oor sediment thickness trench slope (Strasser et al., 2013; see Fig. 2B) quakes because they are most closely related were extracted from a diverse and global set of or where a landward-thickening, wedge-shaped to convergent plate motions and are the most published and unpublished seismic-refl ection body of trench-axis turbidite deposits is thickest potent generator of tsunamigenic events (see records largely tabulated by von Huene and (see Figs. 2A, 2C, and 12). Polet and Kanamori, 2009). Each era of mega- Scholl (1991), Scholl and von Huene (2007), thrust observations, i.e., the instrumental era and most recently by Heuret et al. (2012). Num- DATA COMPILATIONS (1899 to the present), and the historical or pre- bered, alphabetically named sectors are included instrumental period (1700–1898), presents chal- on Tables 1, 2, and 3 and shown on Figures 1 Our purpose in investigating the global dis- lenges to identifying scalar moments, moment and 3. The thickness recorded on all tables was tribution of the magnitude of megathrust earth- magnitudes, and focal mechanism of coastal estimated below the inner or landward side of quakes is to recognize possible empirical trends and submerged forearc earthquakes. Doing so the trench fl oor where the underlying ocean in their occurrence settings and also the source becomes more and more diffi cult going back in crust enters the SZ. Trench deposits are thick- regions for large-magnitude earthquakes that time. Thus our ability to identify older, large IPT

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TABLE 1. INSTRUMENTAL ERA MEGATHRUST EARTHQUAKES THAT RUPTURED AT THIN-SEDIMENT (<1.0 KM) TRENCH SECTORS (continued) Average Sector EQ Latitude Longitude Sector thickness length count Year Month Day Time (°N) (°E) Mw Trench sector count (km) (km) 31 1993 6 8 13:03:57 51.36 158.75 7.5 Kamchatka, south, south of Emperor Ridge collision at Cape Kronotsky to 0.6 700 Kuril Basin (~53.5–49N) 32 1976 1 14 16:47:00 -28.43 –177.66 7.9 Kermadec, Louisville Ridge to Hikurangi Plateau (26–36S) 10 0.4 1300 33 1976 1 14 15:56:00 –29.50 –177.60 7.8 Kermadec, Louisville Ridge to Hikurangi Plateau (26–36S) 0.4 1300 34 1917 5 1 18:26:00 –29.00 –177.00 7.7 Kermadec, Louisville Ridge to Hikurangi Plateau (26–36S) 0.4 1300 35 1955 2 27 20:43:00 –28.00 –175.50 7.7 Kermadec, Louisville Ridge to Hikurangi Plateau (26–36S) 0.4 1300 36 1959 9 14 14:09:00 –28.50 –177.80 7.7 Kermadec, Louisville Ridge to Hikurangi Plateau (26–36S) 0.4 1300 37 1986 10 20 6:46:09 –28.12 –176.37 7.5 Kermadec, Louisville Ridge to Hikurangi Plateau (26–36S) 0.4 1300 38 2006 11 15 11:14:13 46.59 153.27 8.3 Kuril, north, Kuril Gap to Kamchatka (~46–49N) 11 0.6 500 39 1916 10 31 15:30:00 45.40 154.00 7.5 Kuril, north, Kuril Gap to Kamchatka (~46–49N) 0.6 500 40 1978 3 24 19:47:00 44.24 148.86 7.5 Kuril, north, Kuril Gap to Kamchatka (~46–49N) 0.6 500 41 1963 10 13 5:17:00 44.77 149.80 8.5 Kuril, south, Kuril Gap to Japan Trench/Erimo Seamounts (~46–41N) 12 0.6 800 42 1958 11 6 22:58:00 44.33 148.62 8.4 Kuril, south, Kuril Gap to Japan Trench/Erimo Seamounts (~46–41N) 0.6 800 43 2003 9 25 19:50:38 42.21 143.84 8.3 Kuril, south, Kuril Gap to Japan Trench/Erimo Seamounts (~46–41N) 0.6 800 44 1918 9 7 17:16:00 46.81 150.25 8.2 Kuril, south, Kuril Gap to Japan Trench/Erimo Seamounts (~46–41N) 0.6 800 45 1969 8 11 21:27:00 43.48 147.82 8.2 Kuril, south, Kuril Gap to Japan Trench/Erimo Seamounts (~46–41N) 0.6 800 46 1952 3 4 1:22:00 42.50 143.00 8.1 Kuril, south, Kuril Gap to Japan Trench/Erimo Seamounts (~46–41N) 0.6 800 47 1995 12 3 18:01:08 44.66 149.30 7.9 Kuril, south, Kuril Gap to Japan Trench/Erimo Seamounts (~46–41N) 0.6 800 48 1973 6 17 11:05:00 43.10 145.70 7.7 Kuril, south, Kuril Gap to Japan Trench/Erimo Seamounts (~46–41N) 0.6 800 49 1991 12 22 8:43:30 45.58 151.55 7.6 Kuril, south, Kuril Gap to Japan Trench/Erimo Seamounts (~46–41N) 0.6 800 50 1932 6 3 10:36:00 19.84 –103.99 8.1 Mexico, north, Nayarit to abundant Cocos Plate FZs (~21–17.5N) 13 0.7 800 51 1985 9 19 13:18:24 17.91 –101.99 8.0 Mexico, north, Nayarit to abundant Cocos Plate FZs (~21–17.5N) 0.7 800 52 1995 10 9 15:35:53 19.06 –104.21 8.0 Mexico, north, Nayarit to abundant Cocos Plate FZs (~21–17.5N) 0.7 800 53 1911 6 7 11:02:00 17.50 –102.50 7.6 Mexico, north, Nayarit to abundant Cocos Plate FZs (~21–17.5N) 0.7 800 54 1932 6 18 10:12:00 19.45 –103.60 7.6 Mexico, north, Nayarit to abundant Cocos Plate FZs (~21–17.5N) 0.7 800 55 1985 9 21 1:37:32 17.57 –101.42 7.6 Mexico, north, Nayarit to abundant Cocos Plate FZs (~21–17.5N) 0.7 800 56 2003 1 22 2:06:34 18.77 –104.10 7.6 Mexico, north, Nayarit to abundant Cocos Plate FZs (~21–17.5N) 0.7 800 57 1941 4 15 19:09:00 18.85 –102.94 7.5 Mexico, north, Nayarit to abundant Cocos Plate FZs (~21–17.5N) 0.7 800 58 1978 11 29 19:53:02 16.22 –96.56 7.8 Mexico, south, Cocos plate FZs to Tehauntepec Ridge (~17–15N) 14 0.7 650 59 1902 9 23 20:18:00 16.00 –93.00 7.7 Mexico, south, Cocos plate FZs to Tehauntepec Ridge (~17–15N) 0.7 650 60 1903 1 14 14:07:00 15.00 –93.00 7.6 Mexico, south, Cocos plate FZs to Tehauntepec Ridge (~17–15N) 0.7 650 61 1907 4 15 12:08:00 16.70 –99.20 7.6 Mexico, south, Cocos plate FZs to Tehauntepec Ridge (~17–15N) 0.7 650 62 1928 6 17 3:19:00 16.02 –97.04 7.6 Mexico, south, Cocos plate FZs to Tehauntepec Ridge (~17–15N) 0.7 650 63 1965 8 23 19:46:00 16.28 –96.02 7.6 Mexico, south, Cocos plate FZs to Tehauntepec Ridge (~17–15N) 0.7 650 64 1911 12 16 19:14:00 16.90 –100.70 7.5 Mexico, south, Cocos plate FZs to Tehauntepec Ridge (~17–15N) 0.7 650 65 1957 7 28 12:00:00 16.76 –99.55 7.5 Mexico, south, Cocos plate FZs to Tehauntepec Ridge (~17–15N) 0.7 650 66 1979 3 14 11:07:31 17.78 –101.37 7.5 Mexico, south, Cocos plate FZs to Tehauntepec Ridge (~17–15N) 0.7 650 67 2009 7 15 9:22:49 –45.85 166.26 7.8 New Zealand, South Island, Puysegur Trench 15 0.5 500 68 2000 11 16 4:54:00 –3.98 152.17 8.0 Papua New Guinea, New Britain Trench, eastern (151–153) 16 0.5 250 69 1966 10 17 21:41:00 –10.81 –78.68 8.1 Peru, north, Nazca Ridge to Carnegie Ridge (1–15S) 17 0.6 1700 70 1974 10 3 14:21:00 –12.25 –77.52 8.1 Peru, north, Nazca Ridge to Carnegie Ridge (1–15S) 0.6 1700 71 2007 8 15 23:40:57 –13.39 –76.60 8.0 Peru, north, Nazca Ridge to Carnegie Ridge (1–15S) 0.6 1700 72 1940 5 24 16:33:00 –11.22 –77.79 7.7 Peru, north, Nazca Ridge to Carnegie Ridge (1–15S) 0.6 1700 73 1996 2 21 12:51:01 –9.59 –79.59 7.5 Peru, north, Nazca Ridge to Carnegie Ridge (1–15S) 0.6 1700 74 2001 6 23 20:33:14 –16.27 –73.64 8.3 Peru, south, south, Nazca Ridge to Chile Trench (~16–19.5S) 18 0.5 650 75 1942 8 24 22:50:00 –14.98 –74.92 7.9 Peru, south, south, Nazca Ridge to Chile Trench (~16–19.5S) 0.5 650 (continued)

earthquakes also becomes increasingly difﬁ cult Instrumental Era (1899 to Present) sor (CMT) Project and its successor, the Global with distant time. Accordingly, the target magni- (1) U.S. Geological Survey (USGS) Centen- CMT Project: http:// www .globalcmt .org/. tude thresholds for earthquakes selected for con- nial Catalogue 1900–2007 (Engdahl and Villa- (3) Seismic moment tensors, ﬁ rst-motion sideration vary with the era. For the instrumen- senor, 2002): http://www .globalquakemodel focal mechanisms, scalar seismic moments, tal era, the target threshold was set at Mw ≥7.5 .org /what /seismic -hazard /instrumental moment magnitudes and their magnitude (Tables 5), and Mw ≥8.0 for pre-instrumental -catalogue/. proxies in the pre-digital instrumental era earthquakes (Table 6). This catalogue is based on the methodology (1899–1977): Cited literature values of indi- of Engdahl et al. (1998). We note the few excep- vidual earthquakes in Tables 5 and 6 as noted. Earthquake and Tsunami Source Data tions in using this data source. Literature values Especially valuable were the earthquake for IPT Earthquakes for those earthquakes not in these data sources magnitude summaries by Engdahl and Villa- are noted in Tables 5 and 6. sensor (2002) and reappraisals by W.H.K. Data sources for the earthquakes listed on (2) Seismic moment tensors, scalar moments, Lee (http:// www .globalquakemodel .org /what Tables 5 and 6 and also the derivative and descrip- and moment magnitudes in the digital era (1978 /seismic -hazard /instrumental -catalogue/) and tively reduced Tables 1–4, are described below: to present): The Harvard Centroid Moment Ten- E.A. Okal (personal commun., 2012). Not all

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TABLE 1. INSTRUMENTAL ERA MEGATHRUST EARTHQUAKES THAT RUPTURED AT THIN-SEDIMENT (<1.0 KM) TRENCH SECTORS (continued) Average Sector EQ Latitude Longitude Sector thickness length count Year Month Day Time (°N) (°E) Mw Trench sector count (km) (km) 76 1913 8 6 22:14:00 –17.00 –74.00 7.7 Peru, south, south, Nazca Ridge to Chile Trench (~16–19.5S) 0.5 650 77 1996 11 12 16:59:44 –14.99 –75.68 7.7 Peru, south, south, Nazca Ridge to Chile Trench (~16–19.5S) 0.5 650 78 2001 7 7 9:38:43 –17.54 –72.08 7.6 Peru, south, south, Nazca Ridge to Chile Trench (~16–19.5S) 0.5 650 79 1952 3 19 10:57:00 9.50 127.25 7.6 Philippines, Philippine Trench (4–15N) 19 0.5 1300 80 1989 12 15 18:44:07 7.88 126.96 7.6 Philippines, Philippine Trench (4–15N) 0.5 1300 81 2001 1 1 6:57:24 6.73 127.07 7.5 Philippines, Philippine Trench (4–15N) 0.5 1300 82 1938 6 10 23:03:00 25.50 125.00 7.5 Ryukyu, South (122–125.5E) 20 0.5 700 83 1971 7 14 13:01:00 –5.50 153.90 7.8 Solomon Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 21 0.4 400 84 1919 5 6 19:41:00 –5.00 154.00 7.7 Solomon Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 0.4 400 85 1971 7 26 12:03:00 –4.90 153.20 7.7 Solomon Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 0.4 400 86 1995 8 16 10:28:00 –5.51 153.64 7.7 Solomon Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 0.4 400 87 1913 5 30 11:46:00 –5.00 154.50 7.6 Solomon Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 0.4 400 88 1916 1 1 13:20:00 –4.00 154.00 7.6 Solomon Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 0.4 400 89 1939 1 30 21:08:00 –6.50 155.50 7.6 Solomon Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 0.4 400 90 1975 7 20 14:37:00 –6.61 155.10 7.6 Solomon Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 0.4 400 91 1953 4 23 16:24:00 –4.00 154.00 7.5 Solomon Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 0.4 400 92 1975 7 20 19:54:00 –7.08 155.21 7.5 Solomon Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 0.4 400 93 2007 4 1 20:39:59 –8.47 157.04 8.1 Solomon Trench, central, Woodlark Basin, Woolark Rise to Pocklington 22 0.5 400 Ridge (7.5–9.5S) 94 1939 4 30 2:55:00 –9.295 159.234 7.8 Solomon Trench, south, Pocklington Ridge to Vanuatu Trench (159–165E) 23 0.4 700 95 1931 10 3 19:13:00 –10.50 161.75 7.7 Solomon Trench, south, Pocklington Ridge to Vanuatu Trench (159–165E) 0.4 700 96 1966 6 15 11:00:00 –10.40 160.90 7.7 Solomon Trench, south, Pocklington Ridge to Vanuatu Trench (159–165E) 0.4 700 97 1900 7 29 17:09:00 –10.00 165.00 7.6 Solomon Trench, south, Pocklington Ridge to Vanuatu Trench (159–165E) 0.4 700 98 1931 10 10 19:00:00 –9.968 161.194 7.6 Solomon Trench, south, Pocklington Ridge to Vanuatu Trench (159–165E) 0.4 700 99 1977 4 21 18:04:00 –9.97 160.73 7.6 Solomon Trench, south, Pocklington Ridge to Vanuatu Trench (159–165E) 0.4 700 100 1984 2 7 21:33:00 –10.01 160.47 7.5 Solomon Trench, south, Pocklington Ridge to Vanuatu Trench (159–165E) 0.4 700 101 1988 8 10 4:38:44 –10.49 160.77 7.5 Solomon Trench, south, Pocklington Ridge to Vanuatu Trench (159–165E) 0.4 700 102 1975 10 11 14:35:00 –24.89 –175.12 7.7 Tonga, Niuatoputapu to Louisville Ridge (14.5–26S) 24 0.4 1300 103 1982 12 19 17:43:00 –24.13 –175.86 7.7 Tonga, Niuatoputapu to Louisville Ridge (14.5–26S) 0.4 1300 104 1913 6 26 21:07:00 –20.00 –174.00 7.6 Tonga, Niuatoputapu to Louisville Ridge (14.5–26S) 0.4 1300 105 1948 9 8 15:09:00 –21.00 –174.00 7.6 Tonga, Niuatoputapu to Louisville Ridge (14.5–26S) 0.4 1300 106 1934 7 18 19:40:00 –11.75 166.50 7.9 Vanuatu, north, D’Entrecasteaux Ridge to Solomon Trench (11–15S) 25 0.4 500 107 1966 12 31 18:23:00 –11.90 166.40 7.9 Vanuatu, north, D’Entrecasteaux Ridge to Solomon Trench (11–15S) 0.4 500 108 1980 7 17 19:42:00 –12.52 165.92 7.7 Vanuatu, north, D’Entrecasteaux Ridge to Solomon Trench (11–15S) 0.4 500 109 1997 4 21 12:02:26 –12.58 166.68 7.7 Vanuatu, north, D’Entrecasteaux Ridge to Solomon Trench (11–15S) 0.4 500 110 2009 10 7 22:03:28 –12.59 166.27 7.6 Vanuatu, north, D’Entrecasteaux Ridge to Solomon Trench (11–15S) 0.4 500 111 1901 8 9 13:01:00 –22.00 170.00 7.8 Vanuatu, south, D’Entrecasteauz Ridge to Hunter fracture zone (15–23S) 26 0.4 1100 112 1920 9 20 14:39:00 –19.92 168.53 7.7 Vanuatu, south, D’Entrecasteauz Ridge to Hunter fracture zone (15–23S) 0.4 1100 113 1980 10 25 11:00:24 –21.76 169.84 7.5 Vanuatu, south, D’Entrecasteauz Ridge to Hunter fracture zone (15–23S) 0.4 1100 114 1999 11 26 13:21:00 –16.42 168.21 7.5 Vanuatu, south, D’Entrecasteauz Ridge to Hunter fracture zone (15–23S) 0.5 1100 115 1911 8 16 22:41:00 7.00 137.00 7.6 Yap (10–7.5N) 27 0.4 300 TOTAL TOTAL SECTOR SECTORS LENGTH 27 21,500 FZs—fracture zones.

presumed subduction zone IPT earthquakes World Ocean based largely on the work of /historical.php; National Geophysical Data have published focal mechanisms; hence, some S.L. Soloviev (1930–1994): http:// tsun .sscc .ru Center (NGDC) Signiﬁ cant Earthquake Data- of the smaller intraplate and intraslab earth- /On _line _Cat .htm. base: http://www .ngdc .noaa .gov /nndc /struts quakes in our IPT catalogue may have been (7) Tsunami deposits: NGDC Tsunami /form?t = 101650&s = 1&d = 1; and Utsu, erroneously included. Deposits and Proxies: http:// www .ngdc .noaa Tokuji, Catalogue of Damaging Earthquakes in (4) September, 1899, Yakutat earthquakes: .gov /hazard /tsudep .shtml. the World, 2002 Online: http:// iisee .kenken .go Published epicenter (Doser, 2006) and seismic .jp /utsu /index _eng .html. scalar moment (Plafker and Thatcher, 2008). Pre-Instrumental Era (1700–1898) (5) Tsunami Data Sources in Tables 5 and (1) Epicenters and magnitude estimates Vetting Large Megathrust Earthquakes 6: National Geophysical Data Center (NGDC) in the pre-instrumental era are based largely Global Historical Tsunami Earthquakes and Run- on seismic intensity estimates and tsunami Instrumental Era Earthquakes, ups and references therein: http://www .ngdc .noaa effects from: USGS National Earthquake 1898 to Present .gov /hazard /tsu _db .shtml (Accessed 2009–2012). Information Center: Historic World Earth- For the instrumental era, earthquake epi- (6) Tsunami Laboratory, Novosibirsk, Rus- quakes (Instrumental and Pre-Instrumental): centers were required to be located in forearc sia: Historical Tsunami Database for the http:// earthquake .usgs .gov /earthquakes /world regions landward of trenches and have shallow

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TABLE 2. INSTRUMENTAL ERA MEGATHRUST EARTHQUAKES THAT RUPTURED AT THICK-SEDIMENT (>1.0 km) TRENCH SECTORS Average Sector Earthquake Latitude Longitude Sector thickness length count Year Month Day Time (°N) (°E) Mw Trench sector count (km) (km) 1 1964 3 28 3:36:00 61.02 –147.65 9.2 Alaska, east, Kodiak to Middleton Island (154–145E) 2.0 800 2 1899 9 10 21:30:00 59.39 –139.50 8.2 Alaska, east, Kodiak to Middleton Island (154–145E) 1 2.0 800 3 1899 9 4 0:22:00 59.43 –143.05 8.1 Alaska, east, Kodiak to Middleton Island (154–145E) 2.0 800 4 1979 2 28 21:27:38 60.50 –141.39 7.5 Alaska, east, Kodiak to Middleton Island (154–145E) 2.0 800 5 1946 4 1 12:29:00 53.31 –162.88 8.6 Alaska, west, Unimak Pass to Shumagin Island (~165–157E) 1.5 500 6 1938 11 10 20:18:00 55.33 –158.37 8.2 Alaska, west, Unimak Pass to Shumagin Island (~165–157E) 1.5 500 7 1917 5 31 12:07:00 54.79 –159.12 7.9 Alaska, west, Unimak Pass to Shumagin Island (~165–157E) 2 1.5 500 8 1957 3 9 14:22:00 51.56 –175.39 8.6 Aleutian, central, Amchitka Pass to Amlia FZ (~180–173W) 3 2.0 500 9 1986 5 7 22:47:44 51.33 –175.43 8.0 Aleutian, central, Amchitka Pass to Amlia FZ (~180–173W) 2.0 500 10 1996 6 10 4:03:35 51.56 –177.63 7.9 Aleutian, central, Amchitka Pass to Amlia FZ (~180–173W) 2.0 500 11 1965 2 4 5:01:00 51.21 178.50 8.7 Aleutian, western, Stalemate FZ to Amchitka Pass (~170E–180) 4 1.5 600 12 2003 11 17 6:43:31 51.14 177.86 7.8 Aleutian, western, Stalemate FZ to Amchitka Pass (~170E–180) 1.5 600 13 2010 2 27 6:34:14 –35.85 –72.72 8.8 Chile, central, north, Juan Fernandez Ridge to Mocha-Valdivia 2.5 750 FZs (~33–40S) 14 1906 8 17 0:40:00 32.99 –72.00 8.2 Chile, central, north, Juan Fernandez Ridge to Mocha-Valdivia 5 2.5 750 FZs (~33–40S) 15 1985 3 3 22:47:07 –33.14 –71.87 8.0 Chile, central, north, Juan Fernandez Ridge to Mocha-Valdivia 2.5 750 FZs (~33–40S) 16 1928 12 1 16:06:00 –35.00 –72.00 7.8 Chile, central, north, Juan Fernandez Ridge to Mocha-Valdivia 2.5 750 FZs (~33–40S) 17 1960 5 22 19:11:00 –38.29 –73.05 9.5 Chile, central, south, Mocha-Valdivia FZs to South Chile Rise 2.5 700 (~40–46.5S) 18 1960 5 21 10:02:00 –37.17 72.96 8.1 Chile, central, south, Mocha-Valdivia FZs to South Chile Rise 6 2.5 700 (~40–46.5S) 19 1975 5 10 14:27:00 –38.18 –73.78 7.6 Chile, central, south, Mocha-Valdivia FZs to South Chile Rise 2.5 700 (~40–46.5S) 20 1906 1 31 15:36:00 1.00 –81.50 8.5 Colombia-Ecuador (~7N–O) 7 2.5 800 21 1979 12 12 7:59:00 1.60 –79.36 8.1 Colombia-Ecuador (~7N–O) 2.5 800 22 1942 5 14 21:03:00 0.01 –80.12 7.7 Colombia-Ecuador (~7N–O) 2.5 800 23 1994 6 2 18:17:34 –10.48 112.84 7.7 Indonesia, Java, west, Roo Rise to Sunda Strait (6–11S) 8 1.6 1000 24 1913 3 14 12:05:00 4.50 126.50 7.8 Indonesia, Molucca-Halmahera (~1S–4N) 4.0 500 25 1932 5 14 13:11:00 0.50 126.00 7.8 Indonesia, Molucca-Halmahera (~1S–4N) 4.0 500 26 1936 4 1 20:09:00 4.50 126.50 7.6 Indonesia, Molucca-Halmahera (~1S–4N) 4.0 500 27 1957 9 24 10:01:00 5.50 127.00 7.6 Indonesia, Molucca-Halmahera (~1S–4N) 4.0 500 28 1910 12 16 14:45:00 4.50 126.50 7.5 Indonesia, Molucca-Halmahera (~1S–4N) 9 4.0 500 29 1968 8 10 20:07:00 1.40 126.20 7.5 Indonesia, Molucca-Halmahera (~1S–4N) 4.0 500 30 2007 1 21 11:28:01 1.10 126.21 7.5 Indonesia, Molucca-Halmahera (~1S–4N) 4.0 500 31 1941 6 26 11:52:00 12.16 92.57 7.5 Indonesia, Nicobar-Andaman Island to Myanmar (~11–18N) 10 5.0 800 32 1996 1 1 8:05:23 0.74 119.93 7.9 Indonesia, Sulawesi (120–125E) 2.0 500 (continued)

epicentral depths (<60 km). For those earth- with Mw >8 are known to have occurred in the subduction-zone earthquakes may be confused quakes having first-motion constraints or instrumental era. Among these, four are known with IPT earthquakes when accurate epicenter moment tensor data available, IPT earthquakes to be normal-faulting earthquakes associated information and focal mechanism constraints should have focal mechanisms with nodal with plate bending seaward of trenches: 1933 are lacking. planes approximately parallel to the local azi- Japan Mw8.6; 1977 eastern Indonesia (Sum- Large uncertainties in epicenter location muth of the trench and with one nodal plane bawa) Mw8.3; 2007 Kuril Mw8.1 and 2009 are especially problematic in distinguishing dipping shallowly toward the volcanic arc. For Tonga Mw8.1. off-trench earthquakes before ~1930 when earthquakes prior to the advent of global stan- Moreover, a number of large, shallow off- observatory timing, generally lacking radio dard seismographic networks in the 1960s, these shore intraslab earthquakes have occurred time checks, was often poor and the number of criteria are diffi cult to evaluate except for earth- since the 1960s—for example, the 31 May stations and their azimuthal distribution were quakes that have been the subjects of individual 1970 Peru Mw7.9 and the 13 January 2001 limited (see discussion by Okal et al., 2004). special study. El Salva dor Mw7.7. Finally, some large off- This problem of potential misidentifi cation of Ambiguity exists in identifying offshore IPT trench intraplate earthquakes have strike-slip large off-trench intraplate and intraslab earth- earthquakes in subduction zones because, in the mechanisms and are not potent tsunami sources. quakes as IPT earthquakes is somewhat dimin- instrumental era, great tsunamigenic off-trench, Examples include a pair of earthquakes in the ished by the fact that since 1930 these earth- outer-rise and/or outer-trench slope earthquakes Gulf of Alaska (Mw7.9 and 7.8) that occurred quakes are far less frequent in the instrumental have occurred that are only indirectly related to in 1987 and 1988, and two intraplate oceanic era than confi rmed IPT earthquakes ≥Mw7.5 SZ earthquakes. Outer-rise and/or outer-trench strike-slip earthquakes that occurred off the (22 versus 176 in Tables 1 and 2 combined) earthquakes can produce destructive onshore Sumatra Trench in 2012. None of these strike- and appear to have smaller maximum mag- strong ground motions and potentially destruc- slip earthquakes produced destructive tsunamis, nitudes (Mw8.6 versus 9.5). We assume that tive tsunami waves. Six off-trench earthquakes but they remind us that this class of offshore this lower rate of occurrence also applies to

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TABLE 2. INSTRUMENTAL ERA MEGATHRUST EARTHQUAKES THAT RUPTURED AT THICK-SEDIMENT (>1.0 km) TRENCH SECTORS (continued) Average Sector Earthquake Latitude Longitude Sector thickness length count Year Month Day Time (°N) (°E) Mw Trench sector count (km) (km) 33 1990 4 18 13:39:35 1.31 123.35 7.6 Indonesia, Sulawesi (120–125E) 11 2.0 500 34 1991 6 20 5:19:00 1.04 123.23 7.5 Indonesia, Sulawesi (120–125E) 2.0 500 35 2005 3 28 16:09:36 2.09 97.11 8.7 Indonesia, Sumatra, central, Nias Island to Explorer Ridge 12 2.0 650 (~2N–3S) 36 2007 9 12 23:49:35 –2.46 100.13 7.9 Indonesia, Sumatra, central, Nias Island to Explorer Ridge 2.0 650 (~2N–3S) 37 2004 12 26 1:01:09 3.09 94.26 9.2 Indonesia, Sumatra, north, 90E Ridge to Simeulue I (~11–2N) 3.0 950 38 1907 1 4 2.48 96.11 7.8 Indonesia, Sumatra, north, 90E Ridge to Simeulue I (~11–2N) 13 2.0 950 39 2010 4 6 22:25:19 2.05 96.71 7.8 Indonesia, Sumatra, north, 90E Ridge to Simeulue I (~11–2N) 2.0 950 40 2007 9 12 11:11:15 –3.78 100.99 8.4 Indonesia, Sumatra, south, Explorer Ridge to Sunda Strait at 6S 2.0 900 (~3–8S) 41 2000 6 4 16:28:46 –4.73 101.94 7.9 Indonesia, Sumatra, south, Explorer Ridge to Sunda Strait at 6S 2.0 900 (~3–8S) 42 2010 10 25 14:42:22 –3.48 100.11 7.8 Indonesia, Sumatra, south, Explorer Ridge to Sunda Strait at 6S 2.0 900 (~3–8S) 43 1914 6 25 19:07:00 –4.50 102.50 7.5 Indonesia, Sumatra, south, Explorer Ridge to Sunda Strait at 6S 14 2.0 900 (~3–8S) 44 1946 12 20 19:19:00 33.03 135.61 8.3 Japan, south, Nankai (31–35N) 1.5 700 45 1923 9 1 2:59:00 35.10 139.50 7.9 Japan, south, Nankai (31–35N) 15 1.5 700 46 1944 12 7 4:35:00 33.75 136.00 7.8 Japan, south, Nankai (31–35N) 1.5 700 47 1941 11 18 16:46:00 32.00 132.00 7.6 Japan, south, Nankai (31–35N) 1.5 700 48 1961 2 26 18:10:00 31.80 131.60 7.6 Japan, south, Nankai (31–35N) 1.5 700 49 1968 4 1 18:00:00 32.50 132.30 7.6 Japan, south, Nankai (31–35N) 1.5 700 50 1945 11 27 21:56:00 25.15 63.48 8.1 Makran (~57–66E) 16 7.0 900 51 1931 2 2 22:46:00 –39.50 177.00 7.6 New Zealand, Hikurangi (~38–42S) 17 3.0 400 52 1918 8 15 12:18:00 5.77 123.64 8.2 Philippines, Mindinao Cotabato (~2–7N) 18 2.5 350 53 1976 8 16 16:11:00 6.29 124.09 8.1 Philippines, Mindinao Cotabato (~2–7N) 2.5 350 54 1955 3 31 18:17:00 8.00 124.00 7.6 Philippines, Mindinao Cotabato (~2–7N) 2.5 350 55 2002 3 5 21:16:23 5.92 124.25 7.5 Philippines, Mindinao Cotabato (~2–7N) 2.5 350 56 1948 1 24 17:46:00 10.50 122.00 7.8 Philippines, Negros Trench (~9–12N) 19 2.5 350 57 2002 9 8 18:44:38 –3.27 143.38 7.6 PNG—Papua New Guinea , eastern (~141–145 E) 20 1.5 700 58 1996 2 17 5:59:30 –0.89 136.95 8.2 PNG—Papua New Guinea, western (~134–142E) 1.5 700 59 1914 5 26 14:22:00 0.01 133.31 7.9 PNG—Papua New Guinea, western (~134–142E) 21 1.5 700 60 1935 9 20 14:06:00 –3.50 141.75 7.7 PNG—Papua New Guinea, western (~134–142E) 1.5 700 61 2009 1 3 19:43:51 –0.38 132.88 7.7 PNG—Papua New Guinea, western (~134–142E) 1.5 700 TOTAL TOTAL SECTOR SECTORS LENGTH 21 14,050 Eq—earthquake; FZ—fracture zone.

earthquakes before 1930. Undoubtedly, some moments of these pre-instrumental, very large tifi ed offshore of Sumatra that have also been undisclosed intraplate and intraslab earth- IPT earthquakes approximately scale with linked to seafl oor motions associated with big quakes still exist in our catalogue, especially earthquake rupture length. The lateral extent IPT earthquakes in 1797 and 1833 (Natawidjaja those that occurred before the 1960s and dur- of these criteria as well as the “sizes” of these et al., 2006). ing World War II when station distribution observables are thus useful in estimating the Criteria B. Geologic investigations of tsu- was sparse, absolute timing of phase data was relative sizes of huge, pre-instrumental tsunami- nami deposits brought inland by the fl ow fi eld often poor, and earthquake fi rst motions were genic IPT earthquakes. of tsunami waves, such as “tsunami sand” diffi cult to interpret. Criteria A. Geologic investigations of deposits, inland coral and other rock boul- near-shore features sensitive to earthquake- ders, and high driftwood strand lines above Pre-Instrumental Era Earthquakes, related subsidence or uplift, such as ancient high tides and storm surges (Okal et al., 2003). 1700–1898 “ghost” forests killed by submergence and These deposits have been identified along Because of the scarcity of appropriate seis- buried marsh deposits overlain by muddy tsunami-receiving shorelines in many coastal mic instruments, constraints on the magnitudes tidal deposits . Substantial subsidence inferred regions around the world. A tsunami-inunda- of earthquakes were not practical before ~1899. from these deposits and their large lateral dis- tion interpretation of some of these deposits Nonetheless great and giant earthquakes have tributions are strong indicators of prior occur- is controversial in some areas (e.g., Keating been identifi ed in the literature based on the rence of giant tsunamigenic IPT earthquakes. et al., 2011). criteria (A–F) listed below related to seismic A prime example is the 26 January 1700 earth- Criteria C. Historical eyewitness reports of moment release. The lateral extent of trench quake in Cascadia (Atwater et al., 2005) where tsunami inundation limits referenced to sur- and/or near-shoreline continuity of these cri- coastal drowning evidence has been identifi ed viving cultural features and to contemporane- teria during great and/or giant earthquakes in over a stretch of coastline more than 1000 km ous positions of mean high tide. Prime exam- the instrumental era has shown that seismic long. Uplifted and tilted corals have been iden- ples are the recorded tsunami arrival in Japan of

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TABLE 3. INSTRUMENTAL ERA, HIGHEST MAGNITUDE MEGATHRUST EARTHQUATES THAT RUPTURED AT THIN- (<1.0 KM) AND THICK-SEDIMENT (>1.0 KM) TRENCH SECTORS Sector Latitude Longitude Sector length Year Month Day Time (°N) (°E) Mw Thin-trench sectors count (km) 1946 8 4 17:51:00 19.25 –69.00 7.8 Antilles, Greater, Puerto Rico Trench (~61–69W) 1 900 1942 8 6 23:36:00 14.00 –91.00 7.7 Central America, Tehuantepec Ridge to Cocos Seamounts and Ridge (15–9N), 21200 Guatemala 1995 7 30 5:11:23 –23.34 –70.29 8.3 Chile, northern, Arica Bight to Juan Fernandez Ridge (18.5–33S) 3 1500 1972 12 4 10:16:00 33.30 140.80 7.5 IBM, north, Izu, Ogasawara Plateau to Japan Trench (~26–34.5N) 4 950 1965 1 24 11:00:00 –2.40 126.00 7.5 Indonesia, Ceram Sea 5 500 2011 3 11 5:46:00 38.32 142.37 9.0 Japan, north, Erimo Seamounts at Kuril-Japan bend to Daiichi Kashima 6800 Seamounts (~41.5–36N) 1923 9 2 0:06:00 35.13 140.50 7.5 Japan, south, Daiichi Kashima Seamounts to Japan-Izu trench junction 7800 (~36–34.5N) 1971 12 15 10:09:00 56.00 163.20 7.5 Kamchatka, north, Cape Kronotsky collision to Cape Kamchatka collision 8300 (~53.5–56N) 1952 11 4 16:58:00 52.76 160.06 9.0 Kamchatka, south, south of Emperor Ridge collision at Cape Kronotsky to Kuril 9700 Basin (~53.5–49N) 1976 1 14 16:47:00 –28.43 –177.66 7.9 Kermadec, Louisville Ridge to Hikurangi Plateau (26–36S) 10 1300 2006 11 15 11:14:13 46.59 153.27 8.3 Kuril, north, Kuril Gap to Kamchatka (46–49N) 11 500 1963 10 13 5:17:00 44.77 149.80 8.5 Kuril, south, Kuril Gap to Japan Trench/Erimo Seamounts (~46–41N) 12 800 1932 6 3 10:36:00 19.84 –103.99 8.1 Mexico, north, Nayarit to abundant Cocos Plate FZs (~21–17.5N) 13 800 1978 11 29 19:53:02 16.22 –96.56 7.8 Mexico, south, Cocos plate FZs to Tehauntepec Ridge (~17–15N) 14 650 2009 7 15 9:22:49 –45.85 166.26 7.8 New Zealand, South Is, Puysegur Trench 15 500 2000 11 16 4:54:00 –3.98 152.17 8.0 Papua New Guinea, New Britain Trench, eastern, (151–153) 16 250 1966 10 17 21:41:00 –10.81 –78.68 8.1 Peru, north, Nazca Ridge to Carnegie Ridge (1–15S) 17 1700 2001 6 23 20:33:14 –16.27 –73.64 8.3 Peru, south, south, Nazca Ridge to Chile Trench (~16–19.5S 18 650 1952 3 19 10:57:00 9.50 127.25 7.6 Philippines, Philippine Trench (4–15N) 19 1300 1938 6 10 23:03:00 25.50 125.00 7.5 Ryukyu, South (122–125.5E) 20 700 1971 7 14 13:01:00 –5.50 153.90 7.8 Solomo Trench, north, New Britain Trench to Woodlark Rise (~5.5–7.5S) 21 400 2007 4 1 20:39:59 –8.47 157.04 8.1 Solomon Trench, central, Woodlark Basin, Woolark Rise to Pocklington Ridge 22 400 (7.5–9.5S) 1939 4 30 2:55:00 –9.295 159.234 7.8 Solomon Trench, south, Pocklington Ridge to Vanuatu Trench (159–165E) 23 700 1982 12 19 17:43:00 –24.13 –175.86 7.7 Tonga, Niuatoputapu to Louisville Ridge (14.5–26S) 24 1300 1934 7 18 19:40:00 –11.75 166.50 7.9 Vanuatu, north, D’Entrecasteaux Ridge to Solomon Trench (11–15S) 25 500 1901 8 9 13:01:00 –22.00 170.00 7.8 Vanuatu, south, D’Entrecasteauz Ridge to Hunter Fracture Zone (15–23S) 26 1100 1911 8 16 22:41:00 7.00 137.00 7.6 Yap (10–7.5N) 27 300 TOTAL = 21500 Sector Latitude Longitude Sector length Year Month Day Time (°N) (°E) Mw Thick-trench sectors count (km) 1964 3 28 3:36:00 61.02 –147.65 9.2 Alaska, eastern, Kodiak to Middleton Island (154–145E) 1 800 1946 4 1 12:29:00 53.31 –162.88 8.6 Alaska, western, Unimak Pass to Shumagin Island (~165–157E) 2 500 1957 3 9 14:22:00 51.56 –175.39 8.6 Aleutian, central, Amchitka Pass to Amlia FZ (~180–173W) 3 500 1965 2 4 5:01:00 51.21 178.50 8.7 Aleutian, western, Stalemate FZ to Amchitka Pass (~170E–180) 4 600 2010 2 27 6:34:14 –35.85 –72.72 8.8 Chile, central, northern, Juan Fernandez Ridge to Mocha-Valdivia FZs 5750 (~33-40 S) 1960 5 22 19:11:00 –38.29 –73.05 9.5 Chile, central, southern, Mocha-Valdivia FZs to South Chile Rise (~40–46.5S) 6 700 1906 15:36:00 1.00 –81.50 8.5 Colombia-Ecuador (~7N–O) 7 800 1994 6 2 18:17:34 –10.48 112.84 7.7 Indonesia, Java, west, Roo Rise to Sunda Strait (6–11S) 8 1000 1913 3 14 12:05:00 4.50 126.50 7.8 Indonesia, Molucca-Halmahera (~1S–4N) 9 500 1941 6 26 11:52:00 12.16 92.57 7.5 Indonesia, Nicobar-Andaman Is to Myanmar (~11–18N) 10 800 1996 1 1 8:05:23 0.74 119.93 7.9 Indonesia, Sulawesi (120–125E) 11 500 2005 3 28 16:09:36 2.09 97.11 8.7 Indonesia, Sumatra, central, Nias I to Explorer Ridge (~2N–3S) 12 650 2004 12 26 1:01:09 3.09 94.26 9.2 Indonesia, Sumatra, north, 90E Ridge to Simeulue I (~9–2N) 13 950 2007 9 12 11:11:15 –3.78 100.99 8.4 Indonesia, Sumatra, south, Explorer Ridge to Sunda Strait at 6S (~3–8S) 14 900 1946 12 20 19:19:00 33.03 135.61 8.3 Japan, south, Nankai (31–35N) 15 700 1945 11 27 21:56:00 25.15 63.48 8.1 Makran (~57–66E) 16 900 1931 2 2 22:46:00 –39.50 177.00 7.6 New Zealand, Hikurangi (~38–42S) 17 400 1918 8 15 12:18:00 5.77 123.64 8.2 Philippines, Mindinao Cotabato (~2–7N) 18 350 1948 1 24 17:46:00 10.50 122.00 7.8 Philippines, Negros Trench (~9–12N) 19 350 2002 9 8 18:44:38 –3.27 143.38 7.6 Papua New Guinea , eastern (inside Bismark Sea, ~141–145E) 20 700 1996 2 17 5:59:30 –0.89 136.95 8.2 Papua New Guinea, western (~134–142E) 21 700 TOTAL = 14,050 FZ—fracture zone.

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TABLE 4. PRE-INSTRUMENTAL MEGATHRUST EARTHQUAKES AT THICK- (>1.0 KM) AND THIN-SEDIMENT (<1.0 KM) TRENCH SECTORS Earthquake GMT time Latitude Longitude Mw Mean Mw count Year Month Day (HH:MM) (°N) (°E) estimate estimate Region Thickness 1 1700 1 27 6:00:00 45.00 –125.00 9.0 9.0 Cascadia Thick 2 1833 11 25 –3.50 102.20 8.8–9.2 9.0 Sumatra, South Thick 3 1877 5 10 2:16:00 –21.06 –70.25 8.8 8.8 Chile, North Thin 4 1868 8 13 20:45:00 –17.70 –71.60 8.5–9.0 8.8 Chile, North Thin 5 1746 10 29 3:30:00 –12.50 –77.00 8.6–8.8 8.7 Peru, North, Lima Thin 6 1730 7 8 8:30:00 –32.50 –71.50 8.7 8.7 Chile, South Central, North Thick 7 1707 10 28 4:00:00 34.10 137.80 8.4–8.6 8.5 Japan, Southwest, Nankai Thick 8 1751 5 25 5:30:00 –36.83 –71.60 8.5 8.5 Chile, South Central, North Thick 9 1837 11 7 11:05:00 –42.50 –74.00 8.5 8.5 Chile, South Central, South Thick 10 1737 10 16 15:30:00 52.50 159.50 8.3 8.3 Kamchatka, South Thin 11 1835 2 20 15:30:00 –36.50 –72.60 8.1 to 8.5 8.3 Chile, South Central, North Thick 12 1896 6 15 10:33:00 39.50 144.00 7.2–8.6 8.0 Japan, North, Sanriuku Thin

the 1700 tsunami source in Cascadia (Atwater Tabulated Data number of ≥Mw7.5 earthquakes. Consideration et al., 2005), the giant Nankaido earthquake of this circumstance is in particular important for of 28 October 1707 (Hatori, 1981), and the Tables 1 and 2 list the 176 instrumental era the earthquakes in bins Mw7.5–8.4 that record eyewitness reports of the 1946 Alaska Penin- (1898 to January 2013) ≥Mw7.5 megathrust a much higher number of earthquakes (92 of a sula Scotch Cap tsunami in the far fi eld (Okal or IPT earthquakes that, respectively, ruptured total of 115 for all magnitudes) at thin-sediment et al., 2002). at thin- (n = 115) and thick- (n = 61) sediment trenches than at thick-sediment trenches (38 of Criteria D. Historical reports of very large trenches. Table 3 tabulates just the highest a total of 61) (Fig. 5). For these bins, the aggre- (>10 m), widespread near-fi eld tsunami multi- magnitude megathrusts that occurred along 48 gate length of thin-sediment trenches is ~2.5 meter run-ups and/or damaging large (>1 m) defi ned trench sectors, 21 of which are thick- times that of thick-sediment trenches (~19,000 tsunami waves in the far fi eld. The latter may sediment and 27 of which are thin-sediment versus 7800 km). be lacking if tsunami wave-fi eld directivity is sectors. Pre-instrumental earthquakes (n = 12) To approximately compensate (i.e., normal- not expected to impact populated, developed are listed on Table 4. ize) for the greater length of thin-sediment shorelines, or where written records are lacking. trenches, the 112 earthquakes occurring in the Criteria E. Reports of widespread near-fi eld GRAPHIC RESULTS—INSTRUMENTAL Mw7.5–8.4 bins were reduced to 46 or by a fac- destruction of harbors, ports, or coastal towns IPT EARTHQUAKES tor of 41% (7800 km/19,000 km × 100 = 41%). along embayments and widely dispersed data Figure 6 displays the binned, length-compen- in the far fi eld. Binned Magnitudes sated relative percent of megathrust earthquakes Criteria F. Intense, widespread high seis- occurring at thick- and thin-sediment trenches. mic intensities based on the reported effects Occurrence Percent at Trench Sectors For thick-sediment trenches, the binned occur- of earthquake ground shaking on humans, Figure 4 shows in separate columns the rence percentages are (1) 50%, (2) 63%, buildings and other man-made structures, and percent of megathrust earthquakes in binned (3) 86%, (4) 50%, and (5) 100%. For thin- liquefaction. magnitude ranges that ruptured separately at sediment trenches, the occurrence percentages The above criteria are incapable of enabling thin- and thick-sediment trenches (Tables 1 are, accordingly (1) 50%, (2) 37%, (3) 14%, assessments of truly quantitative magnitudes, and 2, respectively). Earthquakes are binned (4) 50%, and (5) 0%. particularly for an IPT earthquake below an into five, 0.5-Mw-wide magnitude groups: estimated magnitude of about Mw8.0. Our goal (1) Mw7.5–7.9; (2) Mw8.0–8.4; (3) Mw8.5– Largest Trench-Sector Earthquakes in applying them was to identify among these 8.9; (4) Mw9.0–9.4; and (5) Mw9.5–9.9. Ruff’s conjecture that subduction of an earthquakes that had the potential of produc- excess thickness of trench-fl oor sediment is ing ocean-crossing tsunami waves—a signature Relative Occurrence of Thin- and associated with great SZ earthquakes implies of a potential high-magnitude IPT earthquake. Thick-Sediment Earthquakes that the highest magnitude earthquakes should These earthquakes in the instrumental era are The stacked columns of Figure 5 show the also cluster at well-sedimented trenches. Binned largely limited to ≥Mw~8.5. We accordingly relative percent of the combined binning of all into 0.5-Mw-wide columns, Figure 7 shows the restricted our attention to pre-instrumental megathrust earthquakes (n = 176) that occurred occurrence percent of the highest magnitude earthquakes that are comparable with the effects at thin- and thick-sediment trench sectors. For IPT earthquake that ruptured adjacent to each of ≥Mw~8.5 IPT earthquakes in the instru- thick-sediment trenches, the relative occurrence of the 48 sediment-thickness trench sectors, mental period, for which we have more infor- percentages for increasing magnitude bins 1–5 of which 21 are thick-sediment and 27 thin- mation. Based on these criteria, we identifi ed are (1) 29%, (2) 41%, (3) 86%, (4) 50%, and sediment sectors (Table 3; Figs. 1 and 3). As 12 pre-instrumental earthquakes during the (5) 100%. For thin-sediment trenches, the cor- above, the binned columns are for earthquakes period 1700–1898 (Tables 4 and 6) of magni- responding relative occurrence percentages are of (1) Mw7.5–7.9, (2) Mw8.0–8.4, (3) Mw8.5– tude ≥Mw8.0. Undoubtedly, this list is incom- (1) 71%, (2) 59%, (3) 14%, (4) 50%, and (5) 0%. 8.9, (4) Mw9.0–9.4, and (5) Mw9.5–9.9. For plete owing to lack of historical data for some The global length of thin-sediment trenches thick-sediment trenches, occurrence percent- localities, particularly in sparsely populated (~21,500 km) at which IPT earthquakes ≥Mw7.5 ages are, respectively, (1) 29%, (2) 42%, and developed regions where little or no writ- occurred is ~1.5 times longer (by ~7500 km) (3) 86%, (4) 50%, and (5) 100%. For thin-sed- ten records exist or where geological investiga- than for thick-sediment trenches (~14,000 km). iment trenches, the corresponding occurrence tions of the region’s prehistory have not been Accordingly, thinly sedimented trenches would percentages are (1) 71%, (2) 58%, (3) 14%, attempted. be expected to record a proportionally higher (4) 50%, and (5) 0%.

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TABLE 5. ACCEPTED INSTRUMENTAL ERA (1899 THROUGH JAN 2013) INTERPLATE THRUSTS (IPTS) AND Mw MAGNITUDE Earthquake Latitude Longitude no. Year Month Day Time (°N) (°E) M M type Region Tsunami observations Seismological and other notes 1 1899 9 4 0:22:00 59.43 –143.05 8.1 w* Yakutat Bay, SE T3 (AK to 3.1 m) Magnitude: Plafker and Alaska Thatcher (2008); Location: Doser (2006) 2 1899 9 10 21:30:00 59.39 –139.50 8.2 w* Yakutat Bay, SE T12 (AK to 12.2 m) Magnitude Plafker and Alaska Thatcher (2008); Location: Doser (2006) 3 1900 7 29 17:09:00 –10.00 165.00 7.6 s Solomon Islands XT Ms 7.6 (Abe, 2002) 4 1901 8 9 13:01:00 –22.00 170.00 7.8 s Vanuatu Islands T10 (VAN SOL, HI (to 1.2 m)) 5 1902 9 23 20:18:00 16.00 –93.00 7.7 s Mexico XT Ms 7.8 (Abe, 2002) 6 1903 1 14 14:07:00 15.00 –93.00 7.6 s Mexico XT Ms 7.7 (Abe, 2002) 7 1906 1 31 15:36:00 1.00 –81.50 8.5 w* Colombia-Ecuador T54 (CO to 5 m, HI to 1.8 m, NZ, Mw estimated in Okal (1992). PAN, MX, EC, JP, CA sub-m) Mgr 8.6 (Gutenberg and Richter, 1954) 8 1906 8 17 0:40:00 –29.90 –69.30 8.2 w Valparaiso, Chile T31 9CH to 1.5 m, Marquesas, JP Mw and Mo (2.8E28 dyn-cm) sub-m, AK CA, HI 1.5 m at Hilo from Okal (2005), epicenter and 0.1 m in Honolulu) from Okal (2005). Ms 8.1 (Abe, 2002) 9 1907 1 4 5:19:12 2.48 96.11 7.8 w Off Sumatera T10 (IND, SL, MAUR) Based on wave-form modeling (Kanamori et al., 2010) 10 1907 4 15 12:08:00 16.70 –99.20 7.6 s Mexico T2 (MX) Ms 7.7 (Abe, 2002) 11 1910 12 16 14:45:00 4.50 126.50 7.5 s Molucca Passage XT Ms 7.6 (Abe, 2002) 12 1911 6 7 11:02:00 17.50 –102.50 7.6 s Mexico XT Ms 7.7 (Abe, 2002) 13 1911 8 16 22:41:00 7.00 137.00 7.6 s Yap Islands XT Ms 7.7 (Abe, 2002) 14 1911 12 16 19:14:00 16.90 –100.70 7.5 s Mexico XT Ms 7.6 (Abe, 2002) 15 1913 3 14 12:05:00 4.50 126.50 7.8 s Molucca Passage T0 Ms 7.9 (Abe, 2002) 16 1913 5 30 11:46:00 –5.00 154.50 7.6 s Solomon Islands XT Ms 7.7 (Abe, 2002) 17 1913 6 26 21:07:00 –20.00 –174.00 7.6 s Tonga Islands XT Ms 7.7 (Abe, 2002) 18 1913 8 6 22:14:00 –17.00 –74.00 7.7 s Northern Chile XT 19 1914 5 26 14:22:00 0.01 133.31 7.9 s West New Guinea T3 (IND, HI). A few tsunami Mw estimate from Pacheco reports in NTL database with and Sykes (1992). Ms 8.0 no runup estimates, no NGDC (Abe, 2002). Epicenter from entries. Tsunami damage locally Okal (1999). and recorded in Honolulu, Hawaii. 20 1914 6 25 19:07:00 –4.50 102.50 7.5 s Sumatra T26 (PH, JP, HI) Ms 7.6 (Abe, 2002) 21 1916 1 1 13:20:00 –4.00 154.00 7.6 s Solomon Islands XT Ms 7.8 (Abe, 2002) 22 1916 10 31 15:30:00 45.40 154.00 7.7 North Kurils XT Ms 7.7 (Abe, 2002) 23 1917 5 1 18:26:00 –29.00 –177.00 7.9 Kermadec Islands XT Ms 7.9 (Abe, 2002) 24 1917 5 31 12:07:00 54.79 –159.12 7.9 Eastern Aleutians XT Ms 7.9 (Abe, 2002) 25 1918 8 15 12:18:00 5.77 123.64 8.2 w* Cotabato, Celebes T6 PH to 7.2 m; JP, HI both GM strong from Catabato Sea, Philippines sub-m. Big tsunami waves to Davao on S Mindinao on Celebes Sea coast of Is.; Ms 8.0 (Abe, 2002). S. Mindinao from Lebac to Glan Mgr 8.25. Okal (personal Ports; tsunami waves reported commun., 2012) gets Mw on N coast of N. Sulawesi in 8.3 with large uncertainty Indonesia across the Celebes Sea. 26 1918 9 7 17:16:00 46.81 150.25 8.2 s Kuril Islands T22 (RU to 12 m, JP, CAN, AK, Ms 8.2 (Abe, 2002). Wang HI, CA) (1981) gets Mw 8.0. 27 1919 5 6 19:41:00 –5.00 154.00 7.7 s Solomon Islands, T2 (PNG) Ms 7.9 (Abe, 2002) PNG 28 1920 9 20 14:39:00 –19.92 168.53 7.7 s Loyalty Islands XT Ms 7.7 (Abe, 2002) 29 1922 11 11 4:32:00 –28.55 –70.76 8.3 w Chile-Argentina T34 (CH to 9 m, JP, AU, CAN, Mw estimate from Kanamori Border CA, HI to 2.1 m at Hilo, AS) (1977) based on AS area. Ms 8.3 (Abe, 2002). Okal (1992) gets Mw 8.3. 30 1923 2 3 16:01:53 53.85 160.76 8.3 w Kamchatka T36 (RU to 8 m, JP sub-m, HI to Mw from Okal (1992). Mgr 8.3; 6 m at Hilo, CA sub-m) Ms 8.3 (Abe, 2002) 31 1923 9 1 2:59:00 35.10 139.50 7.9 w Nankai Trough, T103 (JP to 13 m, NZ and HI Mw estimate from Ms 8.3 Japan both sm) Abe (2002) 32 1923 9 2 0:06:00 35.13 140.50 7.5 s Sagami Trough T6 (JP, CAN) Ms 7.7 (Abe, 2002) 33 1928 6 17 3:19:00 16.02 –97.04 7.6 s Mexico T10 (MX, CA, HI, AS) Ms 7.8 (Abe, 2002) 34 1928 12 1 16:06:00 –35.00 –72.00 7.8 s Central Chile T1 (CH) Ms 8.0 (Abe, 2002) 35 1931 2 2 22:46:00 –39.50 177.00 7.6 s North Island NZ T1 (NZ) Was this a subduction event?? 36 1931 3 9 10:08:00 40.50 142.50 7.6 s Japan T7 (JP) Ms 7.8 (Abe, 2002) 37 1931 10 3 19:13:00 –10.50 161.75 7.7 s Solomon Islands T12 (SOL to 9 m, New Caledonia Mgr 7.9; Ms 7.9 (Abe, 2002) to 1.3 m; CA and HI sm) 38 1931 10 10 19:00:00 –9.968 161.194 7.6 s Solomon Islands XT Mgr 7.7; Ms 7.8 (Abe, 2002) 39 1932 5 14 13:11:00 0.50 126.00 7.8 s Molucca Passage XT Mgr 8.0; Ms 8.0 (Abe, 2002) 40 1932 6 3 10:36:00 19.84 –103.99 8.1 w Jalisco, Mexico T13 (MX to 3 m; AS, CA, HI sm). Mw from Kanamori (1977). Local tsunami runups ,0.4 m in Mgr 8.1; Ms 8.2 (Abe, Hilo, tide gauge measurements 2002); Okal (2011a) also in west coast U.S; gets Mw 8.3. 41 1932 6 18 10:12:00 19.45 –103.60 7.6 s Rivera T2 (MX to 1 m, HI sm) Mgr 7.8; Ms 7.8 (Abe, 2002) (continued)

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TABLE 5. ACCEPTED INSTRUMENTAL ERA (1899 THROUGH JAN 2013) INTERPLATE THRUSTS (IPTS) AND Mw MAGNITUDE (continued) Earthquake Latitude Longitude no. Year Month Day Time (°N) (°E) M M type Region Tsunami observations Seismological and other notes 42 1934 7 18 19:40:00 –11.75 166.50 7.9 s Vanuatu XT 43 1935 9 20 14:06:00 –3.50 141.75 7.7 s Papua New T1 (PNG) Guinea 44 1936 4 1 20:09:00 4.50 126.50 7.6 s Molucca Passage T2 (IND to 3 m) 45 1938 6 10 23:03:00 25.50 125.00 7.5 s Ryukyu, JP T3 (JP to 1.5 m) 46 1938 11 5 8:43:00 37.01 142.01 7.5 s Sanriku, Japan T18 (JP to 0.57 m) 47 1938 11 5 10:50:00 37.11 142.08 7.5 s Japan T8 (JP to 0.56 m) 48 1938 11 10 20:18:00 55.33 –158.37 8.2 s Shumagin Islands, T9 (AK, CA, HI, all sub-m) Mw from Kanamori (1977). Alaska Estabrrok et al. (1994) got Mw = 8.3 49 1939 1 30 21:08:00 –6.50 155.50 7.6 s Solomon Islands T2 (PNG, SOL to 2 m) 50 1939 4 30 2:55:00 –9.295 159.234 7.8 s Solomon Islands T3 (PNG to 1.5 m, SOL to 10.5 m) 51 1940 5 24 16:33:00 –11.22 –77.79 7.7 s Northern Peru T0 2 m 52 1941 4 15 19:09:00 18.85 –102.94 7.5 s Mexico XT 53 1941 6 26 11:52:00 12.16 92.57 7.5 s Andaman T2 (IND) 54 1941 11 18 16:46:00 32.00 132.00 7.6 s Kyushu NTL T5 (JP to 1.2 m); NGDC XT 55 1942 5 14 21:03:00 0.01 –80.12 7.7 s Colombia-Ecuador XT 56 1942 8 6 23:36:00 14.00 –91.00 7.7 s Central America XT 57 1942 8 24 22:50:00 –14.98 –74.92 7.9 s Off the coast of T3 (PU to 2 m) central Peru 58 1943 4 6 16:07:00 –30.98 –71.27 7.7 s Central Chile T14 (CH to 1 m; JP, CA, HI all sm) 59 1943 7 29 6:02:00 19.25 –67.50 7.5 s Northern Antilles XT 60 1944 12 7 4:35:00 33.75 136.00 7.8 s Tonankai, Japan T152 (JP to 10 m; AS, CA, HI all sm) 61 1945 11 27 21:56:00 25.15 63.48 8.1 s Makran T6 (IND to 1.98 m, PAK to Quittmeyer and Jacob (1979) 15.24 m, Seychelles Is.) epicenter. Mw from Byrne et al. (1992) 62 1946 4 1 12:29:00 53.31 –162.88 8.6 w Unimak Islands, T510 (multimeter runups over Mw and epicenter from Lopez Alaska much of the Pacifi c) and Okal (2006) 63 1946 8 4 17:51:00 19.25 –69.00 7.8 s Northern Antilles T8 (DR to 5 m; Bermuda, FL, NJ, PR all sm) 64 1946 12 20 19:19:00 33.03 135.61 8.3 s Nankaido, Japan T298 (JP to 6 .6.m; PU, CA, HI Mw from Kanamori (1972) and all sub-m) Tanioka and Satake (2001) 65 1948 1 24 17:46:45 10.50 122.00 7.8 s Offshore Panay, T1 (PH) NTL and NGDC no tsunami Sulu Sea, runups recorded. Mw from Philippines Okal (2011a) 66 1948 9 8 15:09:00 –21.00 –174.00 7.6 s Tonga Islands T5 (HI and AS all sm) 67 1950 10 5 16:09:00 10.35 –85.00 7.7 s Central America T6 (CR, ES, HI all sm) 68 1952 3 4 1:22:00 42.50 143.00 8.1 w Hokkaido, Japan T219 (JP to 6.5 m; HI, EC, CAN Mw from Kanamori (1977) and region all sm) Satake et al. (2006) 69 1952 3 19 10:57:00 9.50 127.25 7.6 s Mindinao, T5 (Yap, Palau, Amer. Sam, Not in Lee GEM catalogue Philippines Guam all sub-m) 70 1952 11 4 16:58:00 52.76 160.06 9.0 w Kamchatka, T290 (RU to 18 m; CH to 1.8 m, Mw from Kanamori (1976). Russia EC to 1.89 m, JP to 3 m, MX Okal (2011a), got Mw 8.9. to 1.12 m, PNG to 2.5 m, AK to 1.9 m, HI to 10.4 m, and other multi-m) 71 1953 4 23 16:24:00 –4.00 154.00 7.5 s Solomon Islands XT 72 1955 2 27 20:43:00 –28.00 –175.50 7.7 s Kermadec Islands XT 73 1955 3 31 18:17:00 8.00 124.00 7.6 s Cotabato, SW XT Mindinao, Philippines 74 1957 3 9 14:22:00 51.56 –175.39 8.6 w Andreanof Islands, T323 (Pacifi c wide to 22.8 m in Mw from Johnson et al. (1994) Alaska AK, to 16.2 m in HI) for tsunami modeling. Okal (2011a) got Mo (8.5E28 dyn-cm) and Mw 8.6 from seismic data 75 1957 7 28 12:00:00 16.76 –99.55 7.5 s Mexico T3 (MX) 76 1957 9 24 10:01:00 5.50 127.00 7.6 s Molucca Passage XT 77 1958 11 6 22:58:09 44.33 148.62 8.4 w Kuril Islands T57 (RU to 5 m, JP to 1 m; all Mm threshold in Okal 1992. sm in HI, CA AK, AS, Midway, Mw from Fukao and Kwajalein) Furumoto (1979) 78 1959 5 4 7:15:48 53.35 159.65 8.2 w Near the east T7 (HI, AK, Midway all sub-m) Mw from Okal (1992) coast of Kamchatka 79 1959 9 14 14:09:00 –28.50 –177.80 7.7 s Kermadec Islands XT 80 1960 3 20 17:07:00 39.90 143.20 7.7 s Sanriku, Japan T19 (JP sm) 81 1960 5 21 10:02:56 –37.17 72.96 8.1 s South Chile T2 (CH and HI sub-mm) Mw from Cifuentes and Silver (1989) 82 1960 5 22 19:11:00 –38.29 –73.05 9.5 w Chile T1042 (Pacifi c-wide mm) Mw from Kanamori (1977) and Cifuentes and Silver (1989). Largest EQ in the instrumental record. 83 1961 2 26 18:10:00 31.80 131.60 7.6 s Kyushu T26 (JP sm) (continued)

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TABLE 5. ACCEPTED INSTRUMENTAL ERA (1899 THROUGH JAN 2013) INTERPLATE THRUSTS (IPTS) AND Mw MAGNITUDE (continued) Earthquake Latitude Longitude no. Year Month Day Time (°N) (°E) M M type Region Tsunami observations Seismological and other notes 84 1963 10 13 5:17:00 44.77 149.80 8.5 w Kuril Islands T89 (RU to 4.5 m; JP to 1.4 m; Mw from Kanamori (1970), CA, AS, HI, Guam, Wake all sm) Kanamori (1977), and Abe and Kanamori (1980) 85 1964 3 28 3:36:00 61.02 –147.65 9.2 w Prince William T391 (Paciﬁ c Wide multi-m in AK, Mw 9.3 in ISC-GEM Catalogue Sound, Alaska HI, CA, WA, OR, CAN) (http:// www.isc .ac .uk /iscgem /download .php) 86 1965 1 24 11:00:00 –2.40 126.00 7.5 s Banda Sea T3 (IND, AS) 87 1965 2 4 5:01:00 51.21 178.50 8.7 w Rat Islands, T84 (AK to 10.7 m on Shemya Is.; Mw from Kanamori (1977) and Alaska HI, CA, RU, MX, EC, AS, Wake Wu and Kanamori (1973) Is., Kwajalein all sub-m) 88 1965 8 23 19:46:00 16.28 –96.02 7.6 s Oaxaca, Mexico XT 89 1966 6 15 11:00:00 –10.40 160.90 7.7 s Solomon Islands T2 (PNG sm) 90 1966 10 17 21:41:00 –10.81 –78.68 8.1 w Northern Peru T60 (PU multi-m to 3 m; JP, CH, Mw from Abe (1972) and Abe CR, EC, AK, HI, W Pac Terr all and Kanamori (1980) sub-m) 91 1966 12 28 9:08:00 –25.50 –70.70 7.7 s Central Chile T13 (CH, EC, PU, HI, W Pac Terr, all sm) 92 1966 12 31 18:23:00 –11.90 166.40 7.9 s Vanuatu Islands T6 (SOL mm;FIJI, AK, HI, W Pac Terr all sm) 93 1968 4 1 18:00:00 32.50 132.30 7.6 s Kyushu, Japan T63 (JP mm to 3.1 m; AK, AS sm) 94 1968 5 16 12:49:00 40.90 143.35 8.2 w off the east coast T306 (JP mm to 6 m; MX, RU, Mw from Kanamori (1977) of Honshu, CA, HI, OR, WA, AS, W Pac Japan Terr all sm) 95 1968 8 10 20:07:00 1.40 126.20 7.5 s Molucca Passage NGDC XT, NTL T11 (JP all sm) 96 1969 8 11 21:27:00 43.48 147.82 8.2 w Kuril Islands T65 (RU mm to 5 m; JP, HI, Mw from Kanamori (1977) Pac W Terr, CAN all sm) 97 1971 7 14 13:01:00 –5.50 153.90 7.8 s Solomon Islands, T32 (PNG mm to 6 m; JP, AK, PNG HI, W Pac Terr all sm) 98 1971 7 26 12:03:00 –4.90 153.20 7.7 s Solomon Islands, T39 (PNG mm to 10 m; JP, AK, PNG CA, HI, W Pac Terr all sm) 99 1971 12 15 10:09:00 56.00 163.20 7.5 s Kamchatka T12 (RU sm, AK, HI W Pac Terr all sm) 100 1972 12 4 10:16:00 33.30 140.80 7.5 s Bonin, Japan T40 (JP sm) 101 1973 6 17 11:05:00 43.10 145.70 7.7 s Hokkaido, Japan T71 (JP mm to 6 m, RU, AK, HI, W Pac Terr, mostly sm) 102 1974 10 3 14:21:00 –12.25 –77.52 8.1 w near the coast of T35 (PU sm to 0.92 m, JP, CA Mw from Kanamori (1977) central Peru HI, W Pac Terr, CAN all sm) 103 1975 5 10 14:27:00 –38.18 –73.78 7.6 s south Chile XT 104 1975 7 20 14:37:00 –6.61 155.10 7.6 s Solomon Islands T14 (PNG mm, JP sm) 105 1975 7 20 19:54:00 –7.08 155.21 7.5 s Solomon Islands XT 106 1975 10 11 14:35:00 –24.89 –175.12 7.7 s Tonga Islands XT 107 1976 1 14 15:56:00 –29.50 –177.60 7.8 w Kermadec Islands NGDC XT; NTL T9 (NZ, W Pac Mw and epicenter from Global Terr, Fiji) CMT databases 108 1976 1 14 16:47:00 –28.43 –177.66 7.9 w Kermadec Islands T15 (NZ, Fiji, AU, MX, HI, W Mw and epicenter from Global Pac Terr all sm) CMT databases 109 1976 8 16 16:11:00 6.29 124.09 8.1 w Cotabato, SW T12 NTL and NGDC T16 (PH Mw and epicenter from Global of Mindinao, multi-m in S coast of Mindinao CMT databases Philippines Isl, sub-m in Japan) 110 1977 4 21 18:04:00 –9.97 160.73 7.6 w Solomon Islands T4 (AU, W Samoa sm) Mw and epicenter from Global CMT databases 111 1978 3 24 19:47:00 44.24 148.86 7.5 w South Kurils T20 (RU, JP, Midway and Wake Mw and epicenter from Global Islands all sm) CMT databases 112 1978 6 12 8:14:43 38.02 142.07 7.7 w Sanriku, Japan T32 (JP sm) Mw and epicenter from Global CMT databases 113 1978 11 29 19:53:02 16.22 –96.56 7.8 w Mexico T1 (MX 1.5 m) Mw and epicenter from Global CMT databases 114 1979 2 28 21:27:38 60.50 –141.39 7.5 w SE Alaska T2 (AK sm) Mw and epicenter from Global CMT databases 115 1979 3 14 11:07:31 17.78 –101.37 7.5 w S. Mexico T3 (MX to 1.3 m, AS sm) Mw and epicenter from Global CMT databases 116 1979 12 12 7:59:00 1.60 –79.36 8.1 w near the coast T53 (CO mm to 6 m; EC, JP, Mw and epicenter from Global of Ecuador/ MX, HI all sm) CMT databases Colombia 117 1980 7 17 19:42:00 –12.52 165.92 7.7 w Vanuatu Islands T34 (JP, HI sm) Mw and epicenter from Global CMT databases 118 1980 10 25 11:00:24 –21.76 169.84 7.5 w Vanuatu Islands XT Mw and epicenter from Global CMT databases 119 1982 12 19 17:43:00 –24.13 –175.86 7.7 w Tonga Islands T4 (HI, AS, Tahiti all sm) Mw and epicenter from Global CMT databases 120 1983 4 3 2:50:21 8.85 –83.25 7.5 w Costa Rica, XT Mw and epicenter from Global Central America CMT databases 121 1983 10 4 18:52:37 –26.01 –70.56 7.7 w Chile T1 (CH sm) Mw and epicenter from Global CMT databases 122 1984 2 7 21:33:00 –10.01 160.47 7.5 w Solomon Islands XT Mw and epicenter from Global CMT databases (continued)

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TABLE 5. ACCEPTED INSTRUMENTAL ERA (1899 THROUGH JAN 2013) INTERPLATE THRUSTS (IPTS) AND Mw MAGNITUDE (continued) Earthquake Latitude Longitude no. Year Month Day Time (°N) (°E) M M type Region Tsunami observations Seismological and other notes 123 1985 3 3 22:47:07 –33.14 –71.87 8.0 w Central Chile T52 (CH to 3.5 m, JP, Fr. Mw and epicenter from Global Poynesia, AK, HI all sm) CMT databases 124 1985 9 19 13:18:24 17.91 –101.99 8.0 w Mexico T19 (MX mm to 3 m, EC, ES, Mw and epicenter from Global Fr. Polynesia, PU, AS, HI, CMT databases Samoa all sm) 125 1985 9 21 1:37:32 17.57 –101.42 7.6 w Mexico T2 (MX to 1.2 m) Mw and epicenter from Global CMT databases 126 1986 5 7 22:47:44 51.33 –175.43 8.0 w Central Aleutians, T66 (AK, HI, WA, AS, Wake Is., Mw and epicenter from Global Alaska JP, CH, CAN, Cook Is., EC, CMT databases Fr Polynesia all sm) 127 1986 10 20 6:46:09 –28.12 –176.37 7.5 w Kermadec Islands, T8 (French Polynesia: Rapa Mw and epicenter from Global New Zealand and Tahiti, HI, AS all sm) CMT databases 128 1987 3 5 19:17:20 –24.38 –70.93 7.5 w Chile T6 (CH, MX, HI all sm) Mw and epicenter from Global CMT databases 129 1988 8 10 4:38:44 –10.49 160.77 7.5 w Solomon Islands T2 (SOL sm) Mw and epicenter from Global CMT databases 130 1989 12 15 18:44:07 7.88 126.96 7.6 w E of Mindinao, XT Mw and epicenter from Global Philippine CMT databases Islands 131 1990 4 18 13:39:35 1.31 123.35 7.6 w N Sulawesi, XT Mw and epicenter from Global Philippines CMT databases 132 1991 6 20 5:19:00 1.04 123.23 7.5 w N Sulawesi, XT Mw and epicenter from Global Philippines CMT databases 133 1991 12 22 8:43:30 45.58 151.55 7.6 w Kurile Islands, T6 (RU sm to 0.52, JP sm) Mw and epicenter from Global Russia CMT databases 134 1992 9 2 0:16:42 11.20 –87.81 7.6 w Nicaragua, Central T36 (NIC mm to 9.9 m, CR mm; Mw and epicenter from Global America CH, MX, HI all sm) CMT databases 135 1993 6 8 13:03:57 51.36 158.75 7.5 w Kamchatka, T6 (RU, AK, HI, Midway, Wake Mw and epicenter from Global Russia all sm) CMT databases 136 1994 6 2 18:17:34 –10.48 112.84 7.7 w Java, Indonesia T25 (IND mm to 13.9 m; AU sm) Mw and epicenter from Global CMT databases 137 1994 12 28 12:19:23 40.53 143.42 7.8 w Tohoku, Japan T13 (JP sm to 0.53 m) Mw and epicenter from Global CMT databases 138 1995 7 30 5:11:23 –23.34 –70.29 8.0 w T90 (CH sm to mm to 3.0 m, PU Mw and epicenter from Global to 2.4 m, Fr Polynesia sb to mm CMT databases to 3.0 m; JP, AS, AK, HI, OR, WA,Wake, VAN all sm) 139 1995 8 16 10:28:00 –5.51 153.64 7.7 w Solomon Sea, T0 Mw and epicenter from Global PNG CMT databases 140 1995 10 9 15:35:53 19.06 –104.21 8.0 w Mexico T32 (MX mm to 11.0 m; AU, EC, Mw and epicenter from Global Fr Polynesia, HI AS all sm) CMT databases 141 1995 12 3 18:01:08 44.66 149.30 7.9 w S Kuril Is., Russia T35 (No RU, JP, AK, CA, HI, OR, Mw and epicenter from Global Midway, Wake, Fr Polynesia CMT databases all sm) 142 1996 1 1 8:05:23 0.74 119.93 7.9 w N Sulawesi, T15 (Sulawesi, IND mm to 3.43 m) Mw and epicenter from Global Indonesia CMT databases 143 1996 2 17 5:59:30 –0.89 136.95 8.2 w T108 (IND mm to 7.68 m, JP Mw and epicenter from Global mostly sm but to 1.04 m; AK, CMT databases CA, OR all sm) 144 1996 2 21 12:51:01 –9.59 –79.59 7.5 w N Peru T53 (PU mm to 5.10 m, HI sm) Mw and epicenter from Global CMT databases 145 1996 6 10 4:03:35 51.56 –177.63 7.9 w Andreanof Is., T64 (AK, HI, OR, CA, WA, AS, Mw and epicenter from Global Alaska Johnson Is., Midway Is., JP, CMT databases EC, CH all sm) 146 1996 11 12 16:59:44 –14.99 –75.68 7.7 w Peru T3 (CH, PU all sm) Mw and epicenter from Global CMT databases 147 1997 4 21 12:02:26 –12.58 166.68 7.7 w Solomons T39 (VAN, SOL sm to 3.0 m?; Mw and epicenter from Global JP, Fiji, AU, Tuvalu all sm) CMT databases 148 1997 12 5 11:27:21 54.31 161.91 7.8 w Kamchatka, T18 (RU sm to mm to 8.0 m; Mw and epicenter from Global Russia JP, AK, HI Midway all sm) CMT databases 149 1999 11 26 13:21:00 –16.42 168.21 7.5 w Vanuatu Islands T43 (VAN mm to 6.6 m; Fiji to 1 m, Mw and epicenter from Global Tahiti, JP, NZAS, Samoa W Pac CMT databases terr, CA, HI, all sm) 150 2000 6 4 16:28:46 –4.73 101.94 7.9 w Sumatra, XT XX Why not in previous CMT Mw and epicenter from Global Indonesia selection??? FM ????? CMT databases 151 2000 11 16 4:54:00 –3.98 152.17 8.0 w New Ireland, T8 (PNG mm to 3.0 m, SOL 1 m) Mw and epicenter from Global Papua New CMT databases Guinea 152 2001 1 1 6:57:24 6.73 127.07 7.5 w E Mindinao, XT Mw and epicenter from Global Philippines CMT databases 153 2001 6 23 20:33:14 –16.27 –73.64 8.3 w S. Peru X92 (PU mm to 7 m, CH mostly Mw and epicenter from Global sm but to 1.3 m locally; EC, CMT databases Cook Is., Fiji, Japan,MX, NZ, RU, Tonga, AK, CA, HI, W Pac Territories, VAN all sm. (continued)

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TABLE 5. ACCEPTED INSTRUMENTAL ERA (1899 THROUGH JAN 2013) INTERPLATE THRUSTS (IPTS) AND Mw MAGNITUDE (continued) Earthquake Latitude Longitude no. Year Month Day Time (°N) (°E) M M type Region Tsunami observations Seismological and other notes 154 2001 7 7 9:38:43 –17.54 –72.08 7.6 w S. Peru XT Mw and epicenter from Global CMT databases 155 2002 3 5 21:16:23 5.92 124.25 7.5 w S. Mindinao, T3 (PH to 3 m) Mw and epicenter from Global Philippines CMT databases 156 2002 9 8 18:44:38 –3.27 143.38 7.6 w Papua New T25 (PNG mostly mm; JP, Wake Mw and epicenter from Global Guinea Is, Yap Is all sm) CMT databases 157 2003 1 22 2:06:34 18.77 –104.10 7.6 w S. Mexico T3 (MX sm) Mw and epicenter from Global CMT databases 158 2003 9 25 19:50:38 42.21 143.84 8.3 w S. Hokkaido T51 (JP mixed sm and mm to 3.9 Mw and epicenter from Global Island, Japan m, AK, HI, CA, OR, Midway Is. ) CMT databases 159 2003 11 17 6:43:31 51.14 177.86 7.8 w Rat Islands, T20 (AK, CA, HI, OR, CH, Mw and epicenter from Global Alaska Christam Is. All sm) CMT databases 160 2004 12 26 1:01:09 3.09 94.26 9.2 w Banda Aceh T997 (Sumatra, India, Sri Lanka Mw from and epicenter from Sumatera, mm to 50.9 m, N Indian Ocean Global CMT databases Indonesia to Somalia and Andaman Sea mm, sm in Pacifi c and Atlantic Oceans) 161 2005 3 28 16:09:36 2.09 97.11 8.7 w Nias Is Sumatera, T16 (Indonesia to 3.0 m; AU, Mw and epicenter from Global Indonesia ANT, Kenya, Maldives, Oman, CMT databases Seychelles, Sri Lanka all sm) 162 2006 11 15 11:14:13 46.59 153.27 8.3 w Central Kuril T139 (RU sm to 0.33 m?, JP sm,; Mw and epicenter from Global Islands, Russia sm over much of N. Pacifi c CMT databases Basin and also S AM). Remote area. 163 2007 1 21 11:28:01 1.10 126.21 7.5 w Northern Molucca Mw and epicenter from Global Sea CMT databases 164 2007 4 1 20:39:59 –8.47 157.04 8.1 w Solomons 165 2007 8 15 23:40:57 –13.39 –76.60 8.0 w S. Peru T56 (PU to 1.0 m; CH, EC, MX, Mw and epicenter from Global AS, SAM, AK, CA, HI, Midway, CMT databases Kwajalein, VAN, Tonga, PH all sm) 166 2007 9 12 23:49:35 –2.46 100.13 7.9 w Sumatera, XT Mw and epicenter from Global Indonesia CMT databases 167 2007 9 12 11:11:15 –3.78 100.99 8.4 w Sumatera, T20 (IND sm to 0.98 m; AU, Mw and epicenter from Global Indonesia Kenya, Maldives, Oman, CMT databases Seychelles, Sri Lanka, Thailand, Diego Garcia all sm) 168 2007 11 14 15:41:11 –22.64 –70.62 7.7 w N. Chile T6 (CH to 0.13 m; PU sm) Mw and epicenter from Global CMT databases 169 2009 1 3 19:43:51 –0.38 132.88 7.7 w Irian Jaya, Indonesia 170 2009 7 15 9:22:49 –45.85 166.26 7.8 w W Coast of South T9 (NZ to 0.47 m, AU sm, HI sm) Mw and epicenter from Global Island, New CMT databases Zealand 171 2009 10 7 22:03:28 –12.59 166.27 7.6 w Vanuatu Islands T37 (VAN to 0.31 m; AU, CH, Mw and epicenter from Global PNG, MX, TONG SOL, AK, CA, CMT databases HI, AS, Fiji, Midway, Marshall Is., Wake is., PNG, CAN all sm) 172 2010 2 27 6:34:14 –35.85 –72.72 8.8 w Maule, Central T158 (CH mostly mm to 11.2 m, Mw and epicenter from Global Chile Ec to 1.08 m; PU, CR, MX, CMT databases CAN, AK, CA, HI, OR, WA, Saipan, Wake, VAN, TONG, AS, PH, RU, NZ, JP, Cook Is. All sm) 173 2010 4 6 22:25:19 2.05 96.71 7.8 w Northern Sumatra, T6 (IND all sm) Mw and epicenter from Global Indonesia CMT databases 174 2010 10 25 14:42:22 –3.48 100.11 7.8 w Southern Sumatra, T22 (multimeter near source) Indonesia 175 2011 3 9 2:45:20 38.42 142.84 7.5 w E Coast of Tohoku IPT foreshcok District, NE Japan 176 2011 3 11 5:26:43 38.32 144.37 9.0 w East coast of T5776 NGDC; Trans-Pacifi c Mw and epicenter from Global Tohoku, NE tsunami wave fi eld. CMT databases Japan Notes: Earthquake data sources: National Earthquake Information Center (NEIC); National Geophysical Data Center (NGDC); CMT—formerly the Harvard Centroid Moment Tensor Catalog, now GCMT, the Global Centroid Moment Tensor Catalog (http://www.globalcmt.org/CMTsearch.html); the Abe collection of earthquake magnitudes; the Utsu (2002) collection; and other sources as noted. Data sources: NGDC Tsunami database and the Novosibirsk Tsunami Laboratory (NTL). Abbreviations: Place Names: AK—Alaska, AS—American Samoa, AU—Australia, CA—California, CAN—Canada, CH—Chile, EC—Ecuador, HI—Hawaii, IND—Indonesia, JP—Japan, MAUR—Mauritius Island, MX—Mexico, NZ—New Zealand, PAK—Pakistan, PAN—Panama, PU—Peru, PNG—Papua New Guinea, PH—Philippines, RU— Russia, SL—Sri Lanka, SOL—Solomon Islands, VAN—Vanuatu. XT—no tsunami reports in NGDC or NTL databases; Tn—number of tsunami wave amplitude reports, n— from a given earthquake source; sub-m—submeter runup or tide-gage measurement; multi-m—multi-meter runup; *—magnitude estimated from earthquake ground motion distribution or tsunami wave amplitudes and their distributions; s—surface-wave magnitude (20 s); w*—mantle magnitude from long-period surface waves (>~100 s waves); w—moment magnitude from long-period body waves.

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Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/2/236/3333818/236.pdf by guest on 30 September 2021 Scholl et al. ) continued ( s e t o n r e h t o d n a l a c i g o l o m s i e S destruction in Cillan and Talca and the wineries in Talca destruction in Cillan and because it has not been demonstrated that occurred in a conventional subduction zone. seems too big since it is inconsistent with maximum seismic intensities in MX and the small number of reported moderate damage as far south Chillan.” (Lomnitz, Largest and most damaging earthquake for Lima in history Huancavelica, Supe, Pativilca and all towns Chancay, The situation was the same to and villages to 10.5 °S. oors in the eastern seafl Among the smoothest off-trench c. Likely directivity and lack of European records Pacifi Concepcion was destroyed….” Severe and Valparaiso. (Lomnitz, 2004). NGDC seismic intensity Central Valley area with M8.8 Maule earthquake to XI. Overlap of affected of 2010. The tectonic setting of the earthquake source and its location is a controversial topic. Large recent literature chose to exclude this event on these questions. We located in the source region of giant 1952 Kamchatka giant tsunamigenic earthquake. enough critical information. intensities to 5–7 over large near-coastal area from the Kii Peninsula, (2002). Centroid of slip likely off La Serena and Coquimbo were damaged, there was 2004). prior to 1970. “Few buildings survived in Lima, Callao, the south, at least down to Canete” (Dorbath et al., 1990). eld tsunami c may account for lack of far-fi in SW Pacifi observations in that region. due to the lack of seismic intensity data. Nominally earthquake. If the tsunami runups are to be believed, this was a very potent tsunami source likely spawned by runups and the lack of very large (>5 m) local runups. Not historical earthquake and tsunamis. JMA seismic historical earthquake and tsunamis. JMA northern Kyushu to the Izu Peninsula, ~650 km of coastal area (Miyazawa and Mori, 2009). Epicenter from Utsu seismic intensities. midpoint of high JMA Suarez and Albini (2009) suggest M* = 8.6. This magnitude Albini (2009) suggest M* = 8.6. Suarez and 4000–5000 total deaths. NEIC “Earthquakes of Peru.” “Damage over Central Chile reached as far north Santiago “Destruction in Valparaiso was total and included landslides. “Destruction in Valparaiso Africa. Heavy shaking damage in Portugal, Spain, and NW The estimated magnitude of this event is highly uncertain Epicenter unknown, location arbitrary. most destructive The 1707 Hoei earthquake was SW Japan’s 14 s n o i t a v r e s b o i m a n u s T Albini (2009). NGDC: 11 deaths. Albini (2009). NGDC: 11 Lavacha Bay, N. Kuriles Shumshu Island, 27 m, and Lavacha Bay, destruction and loss of life by tsunami Total waves. of settlement on Juan Fernandez Island. (Corralero) Lagoon, and S. of Ometepec, near Puerto and Suarez Acupulco (NSL Angel, and seiches at Group. “Historical Tsunamis” Group. “Historical larger Callao, Peru, and Japan to 2 m. “Tsunami than in 1657 and 1730” (Lomnitz, 2004). Old town of Conception completely destroyed by tsunami Indies. Azores, W. Portugal, to 30 m, Britain, Morocco, “The tsunami at Concepcion is said to have been larger than that of 1657” (Lomnitz, 2004) 12 m. NGDC T6, same as NSL. Too early for Hawaii Too T6, same as NSL. 12 m. NGDC America for written records in and W coast of North eld. the far fi Research Tsunami facilities along coastal Peru. USC dating and drowned forest dendrochronology. 7.7 m over the Philippine Sea coastlines of Shikoku Island and the Kii Peninsula (Honshu Island), The most destructive earthquake in the 1981). Nankaido region. Estimated 30,000 dead or missing. contemporaneous written records along shorelines in the Izu-Boni-Marianas arcs and along north shores of New Guinea Island where directivity and bathymetry would suggest high tsunami amplitudes. Komandorskiy Islands Bering Island, 63 m! Alaska Rat Komandorskiy Islands Bering Island, 63 m! Aleutians Norton Sound Amchitka Island 15 m. Islands highest ever observed along these coasts (Hatori, probably restricted by lack of eld effects Far-fi T3, 4 m at Acapulco. Large inundations at Alotengo Acapulco. Large inundations at T3, 4 m at NSL T7 RU Kamchatka: 48 m at Lopatka Island, 31 NSL T10 Mostly Chile and Peru in N. Honshu, Japan) T10 (Peru to 24 m). Widespread destruction of port T6 Destructive waves in Chile, Juan Fernandez Island, Europe, Lisbon, T52 Destructive multi-m waves in W. T7 Japan historical records and Cascadia tsunamiite C n o i g e R Chile Portugal Mexico Chile region, Peru Russia Zone e p * Japan:Nankaido T16 JPJapan multi-m to 25.7 m, averaging from 5 * and Vallao Lima M y t 8.8 JMA TABLE 6. PRE-INSTRUMENTAL ERA (1700 THROUGH 1889) INTERPLATE THRUST (IPT) EARTHQUAKES THRUST THROUGH 1889) INTERPLATE (1700 ERA 6. PRE-INSTRUMENTAL TABLE (°E) Mw Longitude (°N) Latitude time GMT GMT (HH:MM) 1787 3 28 16.50 –98.50 8.3 * Oaxca (San Marcos), 1737 10 16 15:30:00 52.50 159.50 8.3 * Kamchatka Peninsula, 1751 5 25 5:30:00 –36.831755 –71.60 11 8.5 1 9:50:00 * 38.73 Concepcion, Southern –9.13 8.5 * Gulf of Cadiz; Lisbon, 1707 10 28 4:00:00 33.00 136.00 8.6 8.4 1730 7 8 8:30:00 –32.50 –71.50 8.7 * Central Valparaiso, 1746 10 29 3:30:00 –12.50 –77.00 8.6 to Year Month Day 1700 1 27 6:00:00 45.00 –125.00 9.0 * Cascadia Subduction

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Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/2/236/3333818/236.pdf by guest on 30 September 2021 Megathrust earthquakes and sediment subduction ) i ) 9 m 9 d a 9 e n t 1 u continued ( a ( s t . l m i a t m s t o e e s r f e e n t e h e o t t s n a f a r i o m r i e t t a h n s t h e e o c d a d w fi Z n n M ; a o ) l d c 7 a n 8 e c a i 9 b g 1 n ( o o o t l i n t o n n a o m c a i t s o i C l a e c ) m S ) 4 r M 0 o f d 0 n n 2 i ( a t . l n b a e i m t c o continued e fi c f l u a w (1999). (–42.5*N), as in 1575, 1737, and 1960, possibly closer to Chiloe.” (Lomnitz, 2004) magnitude of this event. model. Possibly an OR/OTS event. and on Quiriquina Is.” “Felt from Chiloe to Copiopo” (Lomnitz, 2004). Classic reports of ground motion, damage, and uplift by Charles Darwin in his book of the HMS Beagle.” “Voyage magnitude of this event. s k e n O N Newcomb and McCann (1987); M* from Zachariasen et al. “Coastal epicenter between Valdivia (–39.9“Coastal epicenter between Valdivia N)and Castro I “No damage in Valdivia, but total destruction in Concepcion “No damage in Valdivia, Insuffi cient information to be confi dent of the estimated cient information to be confi Insuffi s n o i t ) a v m r /ausgeonews .jsp; Okal and e 2 s a .au b g o ) i n o .gov .gov m m t - ) i a o t /tsunami r l n m .ga a u u 7 s R m ( T o u t 1 www www r T a e r t P L a T d m N n u ; a T S e l X i D h C N I C D ( ( /ausgeonews200503 consistent with modeled far-fi eld directivity consistent with modeled far-fi Synolakis, 2008; Borrero et al., 2006, PNAS) Concepcion attained amplitude of 40 feet in the Bay.” damage as far [south] Castro (–42.5°N), Tsunami was small [AND] but amplitude in Valparaiso to shorelines with poor historical coverage at the time: http:// et al. (2005) Concepcion, 4.5 m at Juan Fernandez Island, in Peru, and possibly at Kauai, Hawaii. “Tsunami widespread damage elsewhere in Hawaii. Cisternas (Lomnitz, 2004). damaging tsunami at Juan Fernandez Islands...” m, FR Poly) G 9 6 N T T51 (JP to 21 m; HI, CA, OR all sm) T51 (JP T3 (All Sumatra) Lack of far-fi eld tsunami observations T3 (All Sumatra) Lack of far-fi T20 Chile multi-m to 24 m at Coelomu, 18 T T7 (RU to 15 m, HI Hilo 4.6 m) T10 (CH tsunami effects 800 km coastline, Hawaii to 2 T10 (CH tsunami effects a i s e n n o o i d s g n d I e n , R a l a r s I e t a a g m n USSR Hokkaido, Japan Indonesia Nankaido. Japan Chile Chile Chile u o T S e p * * * Conception, Southern * Bengkul in Sumatra, M y t 3 5 . . 8 8 9.2 8.5 0 0 5 8 . . 3 7 TABLE 6. PRE-INSTRUMENTAL ERA (1700 THROUGH 1889) INTERPLATE THRUST (IPT) EARTHQUAKES ( (IPT) EARTHQUAKES THRUST THROUGH 1889) INTERPLATE (1700 ERA 6. PRE-INSTRUMENTAL TABLE 7 9 (°E) Mw 1 – Longitude 0 0 0 0 . . 0 1 (°N) 2 – – Latitude time GMT GMT (HH:MM) 6 8 1 1 2 1 1 1 5 6 6 8 8 1 1854 121857 24 8:00:00 4 33.20 17 135.60 8.4 * –5.50 NANKAIDO JAPAN: 147.00 to 28 m; HI, CA, OR all sub-m) T17 (JP 8.0 * Bismark Sea, PNG T5 (PNG, SOL, IND) 1835 2 20 15:30:00 –36.50 –72.60 8.1 to 1833 11 25 –3.50 102.20 8.8 to 1856 10 12 0:45:00 35.50 26.00 8.3 * CRETE T1 (Egypt) 1854 12 23 0:00:00 34.10 137.80 8.3 * Enshunada, 1837 11 71841 11:05:00 –42.50 5 17 –74.001843 21:30:00 52.50 8.5 4 25 * 159.50 6:00:00 Corral, Southern Chile 8.4 T14 Chile, Hilo, Hawaii, 6 m and multi-m with 44.70 * 149.70 Kamchatka peninsula, 8.2 * Kushiro,Nemuro, E. 1828 3 30 12:35:00 –12.10 –77.80 8.2 * Central Peru XT 1 1843 2 8 10:30:00 16.50 –62.20 8.3 *Antigua Guadelupe, Indies) T1 (Antigua and Barbuda, 1.2 m, West 1819 4 12 3:00:00 –27.00 –71.50 8.5? * Caldera, North Central 1792 8 22 18:00:00 54.00 162.00 8.4 * Kamchatka PeninsulaT2 (RUS: KUR, KAM) NTL NGDC XT; 1822 11 19 2:30:00 –33.70 –71.60 8.5? *Central Valparaiso, Year Month Day

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Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/2/236/3333818/236.pdf by guest on 30 September 2021 Scholl et al. 30 s e t o n r e h t o d n a l a c i g o l o m ) s i 2 e 0 S ) 0 2 ( e b A m continued o r f of such damage reports in towns near Pisco and between Arequipa, Moquegua, Mollendo, and other towns in also Comte and Pardo (1991) for details. Okal et al. (2006) subducted Nazca Ridge and a Mo approaching 10 and Cobija. Heavy damage in Tocopilla epicenter between Antofagasta and locations inland.” (Lomnitz, 2004) Iquique, See Comte and Pardo (1991) for details. Most destructive tsunami waves in Japan in 19th century. Most destructive tsunami waves in Japan 19th century. Slow rupture probably led to low seismic intensities (I IV on MM scale (Kanamori, 1972) for this earthquake). dyn-cm. This rupture length seems incompatible with the dyn-cm. lack of inland strong-motion damage reports and Pisco and Callao (Lima) [Dorbath et al. (1990)]. Edge-wave effects? southern Peru [as well as Arica (now Chile). Felt from southern Peru [as well as (CH). Lomnitz (2004). See Guayaquil (EC) to Valparaiso cite destruction of town Pisco, Peru by tsunami waves from this event as evidence for possible rupture crossing intensity VIII. The strongly impacted region was limited intensity VIII. and incomplete. Severe local ground shaking to MM (W. Mindinao) and the NE Sulu Archipelago. Insuffi cient Archipelago. Insuffi Mindinao) and the NE Sulu (W. evidence for the pre-instrumental magnitude of 8.7. in geographic area largely to the Zamboanga Peninsula s M “Epicenter probably near Islay, PU.” “Severe damage in “Epicenter probably near Islay, Peru to Constitucion [CH]. Probable “Felt from Santa Valley, 27,122 dead and missing, largely from tsunami destruction. Information on this earthquake and its tsunami is fragmentary hquake scalar seismic moment. H—Chile; AUS—Australia here; JP——Japan; NZ—New Zealand; PU— H—Chile; HI—Hawaii; CA—California; OR—Oregon; PNAS—Proceedings of the ttp://www.ngdc.noaa.gov/hazard/tsu_db.shtml) database. XT—no runups of ttp://www.ngdc.noaa.gov/hazard/tsu_db.shtml) s f Southern California; NEIC—USGS National Earthquake Information Center; n or shaking intensities; t—tsunami magnitude; s—body wave JMA—Japan o i t a v r e s b o i m a n u s T Multi-meter (multi-m) runups in NE Japan Pacifi c Multi-meter (multi-m) runups in NE Japan Pacifi to 4.8 m, NZ to mult-m). [Tsunami damage in NZ, to 4.8 m, NZ mult-m). [Tsunami Gaviota Beach, CA. Acupulco[MX], HI, Samoa, JP, The hull The tsunami was destructive as in 1868. … of the USS Wateree that was stranded in the 1868 of the USS Wateree oated by this tsunami and came to tsunami was refl Arica” rest near the town of (mm), PU (mm), AS, AK (mm), CA (sm), HI (mm)). AK (mm), CA AS, (mm), PU “Arica destroyed by the tsunami - wave reached damage Tsunami 45 feet above the high-water mark. Talcahuano, recorded at all ports from Callao, PU to damage in NZ, “Tsunami CH, except Valparaiso”. San Pedro, CA.” (Lomnitz, AUS, Samoa, HI, JP, 2004). Hawaii to 5.5 m and recorded in California 1.5 coastlines; multi-m far-fi eld runups in Samoa to 1.7 m, coastlines; multi-m far-fi August 1918 event in the same region. earthquake 15 Islands and N. Sulawesi Island to the south in Indonesia cast doubt on whether this was a giant M8.2 tsunamigenic earthquake. Cf. the effects along the Celebes-Sea shorelines of Sangihe T T53 JP to 38.2 m, many greater than 10 widespread T53 JP T102 (CH to 24 m, PU, MX, and JP multi-m in AU, HI multi-m in T102 (CH to 24 m, PU, MX, and JP [Sulawesi, Celebes] to 4 m) T7 (Ternate T13 (PH to 7 m). Lack of destructive tsunami reports X n o i g e R Indonesia Japan Peninsula, Chile NE Japan SW Mindinao Zamboanga Philippines Sanriku, Honshu Is., e t t p * Arica, Northern Chile NZ AUS to 1 m, Marquesa, JP, T107 (CH to 18 m, s s M y t JMA 9.0 8.6 7.2 8.0 7.9 TABLE 6. PRE-INSTRUMENTAL ERA (1700 THROUGH 1889) INTERPLATE THRUST (IPT) EARTHQUAKES ( (IPT) EARTHQUAKES THRUST THROUGH 1889) INTERPLATE (1700 ERA 6. PRE-INSTRUMENTAL TABLE (°E) Mw Longitude (°N) Latitude time GMT GMT (HH:MM) T with number, e.g., T14, T107, etc., means number of tsunami runups compiled in the National Geophysical Data Center (NGDC, h T14, e.g., with number, T Notes: 1896 6 15 10:33:00 39.50 144.00 8.2 to 1878 21889 11 9 6 –19.60 169.40 8.0 1.00 * 125.60 Vanuatu 8.0 * N. Molucca Island, T1 (VAN) 1897 9 21 5:15:00 7.10 122.10 8.7? *Archipelago, Sulu NE 1894 3 22 10:23:00 42.30 145.10 8.1 s SE Hokkaido Island, 1882 9 7 7:50:00 9.50 –78.90 8.0 * Panama to 3 m, EC) T4 (PAN Year Month Day 18731875 2 29 3 28 –5.50 –21.00 146.00 167.00 8.0 8.0 * * Maclay Coast, PNG Loyalty Islands T1 (PNG) XT 1868 8 13 20:45:00 –17.70 –71.60 to 8.5 1877 5 10 2:16:00 –21.06 –70.25 8.8 * Iquique, Northern National Academy of Sciences; PNG—Papua New Guinea; SOL—Solomon Islands; IND—Indonesia; OR/OTS—outer-rise/outer-trench-slope; C National tsunami effects recorded. Gold highlight—Accepted IPT event and magnitude estimate; *—Estimated indirectly from paleogeological recorded. Gold highlight—Accepted IPT tsunami effects Laboratory (http://tsun.sscc.ru/); USC—University o Tsunami Agency; multi-m (or MM)—multi-meter; NSL—Novosibirsk Meteorological two tsunami observations; RUS—Russia; KUR, KAM—Kurile, Kamchatka; FR Poly—French Polynesia; Laboratory, Tsunami T2—National NTL Peru; AS—American Samoa; AK—Alaska; EC—Ecuador; dyn-cm—cgs unit of measure earthquake scalar moment; PH—Philippines; Mo—eart AS—American Samoa; Peru;

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Figure 10 presents the same data plotted on OccurrenceOccurrence Figure 9, but for Mw7.5–8.4 IPT earthquakes, 100100 the total number of earthquakes (n = 112) at 9090 80%80% thin-sediment sectors reduced to 41% (to n = n=92n=92 46) to compensate within this magnitude range 8080 Thick-SedimentThick-Sediment 62%62% TrenchesTrenches for the signiﬁ cantly greater occurrence length 7070 n=38n=38 (>1.0(>1.0 km)km) of thin- versus thick-sediment trench sectors 6060 (~19,000 versus 7800 km). % 5050 Thin-SedimentThin-Sediment TrenchesTrenches 4040 Largest Earthquakes 17%17% (<1.0(<1.0 km)km) 3030 23%23% Figure 11 plots the occurrence percent of just n=20n=20 n=14n=14 the highest magnitude earthquake that ruptured 2020 10%10% along each of the 48 sediment-thickness trench 1010 n=6n=6 2%2% 3%3% 2 % 1%1% n=2n=2 n=2n=2 sectors (Table 3; Figs. 1 and 3). No length com- n=1n=1 0%0% n=1n=1 0 n=0n=0 pensation was applied to this relatively small 7.57.5 8.08.0 8.58.5 9.09.0 9.59.5 MwMw thruthru thruthru thruthru thruthru thruthru population of megathrust earthquakes. 7.97.9 8.48.4 8.98.9 9.49.4 9.99.9 GRAPHIC RESULTS— PRE-INSTRUMENTAL Figure 4. Binned in ﬁ ve, 0.5-Mw-wide columns (see Tables 1 and 2), IPT EARTHQUAKES occurrence distribution of megathrust (interplate thrust [IPT]) earthquakes that separately ruptured at thick- and thin-sediment trenches. Figures 12 and 13 display, respectively, binned and continuous threshold plots of megathrust earthquakes ≥Mw8.0 that ruptured during Continuous Threshold Plots Figure 9 displays the relative percent of all the pre-instrumental recoding era (1700 through (n = 176) IPT earthquakes that ruptured at a 1898). Criteria for vetting pre-instrumental era All Earthquakes magnitude equal to or greater than a threshold magnitude and rupture mechanism are explained Figure 8 displays the separate plots of the magnitude at thick- and thin-sediment trench in the Pre-Instrumental Era Earthquakes, 1700 occurrence percent of megathrust earthquakes sectors (Tables 1 and 2). The data plotted are to 1898 section. that, separately, broke at or above a threshold not compensation for the disproportionately magnitude at thick- (n = 61 earthquakes) and thin- greater length of thin- versus thick-sediment STATISTICAL RESULTS sediment (n = 115) trench sectors, respectively. trenches. (prepared by Eric Geist)

In the previous sections, tabulated and graphic trends indicate that high-magnitude OccurrenceOccurrence 100%100% IPT earthquakes preferentially occur along n=1n=1 100100 thick-sediment trenches. These trends are fur- 86%86% ther analyzed with statistical tests using the 9090 n=6n=6 20112011 TohokuTohoku Mw9.0Mw9.0 Thin-SedimentThin-Sediment available instrumental-era data. The thick- and 8080 71%71% 19521952 KamchatkaKamchatka MMw9.0w9.0 TrenchesTrenches thin-sediment trenches defi ned in the Introduc- n=92n=92 (<1.0(<1.0 km)km) tion section are mutually exclusive categories 7070 59%59% n=20n=20 and amenable to the binomial test, an exact test 6060 50%50% 50%50% appropriate for small samples (Conover, 1971). % n=2n=2 n=2n=2 5050 41%41% Under the defi nitions for thick- and thin-sedi- n=14n=14 Thick-SedimentThick-Sediment ment trenches, the null hypothesis is that it is 4040 29%29% TrenchesTrenches equally likely that high-magnitude IPT earth- n=38n=38 3030 14%14% (>1.0(>1.0 km)km) quakes occur in either of the trench catego- n=1n=1 ries. The alternative Ruff hypothesis, which is 2020 n=130n=130 n=34n=34 n=7n=7 n=4n=4 n=1n=1 considered in this study, is that high-magni- 1010 tude IPT events occur preferentially at thick 0%0% 0 sediment trenches. The p-value associated with 7.57.5 8.08.0 8.58.5 99.0.0 9.59.5 the binomial test is the probability of obtain- MwMw thruthru thruthru thruthru thruthru thruthru ing any outcome as or more extreme than the 7.97.9 8.48.4 8.98.9 9.49.4 9.99.9 one observed, if the null hypothesis were true. “Extreme” in this defi nition means in the direc- tion of the alternative Ruff hypothesis. The Figure 5. Relative occurrence percent of megathrust earthquakes (n = 176) listed on Tables 1 p-value is calculated using the binomial distri-

and 2 for thick- and thin-sediment trenches binned in ﬁ ve, 0.5-Mw-wide categories ranging bution, with the total number of events (Ntot), from Mw7.5 through 7.9–9.5 through 9.9. the number of “successes” (i.e., events in thick-

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sediment trenches) (Nthick), and the assumed probability of success under the null hypoth-

esis (R0) as parameters to the distribution. OccurrenceOccurrence 100%100% From the outset, we chose a critical p-value of n=1n=1 0.05, below which we accept the alternative 100100 hypothesis. 9090 86%86% n=6n=6 20112011 TohokuTohoku MMw9.0w9.0 For the ﬁ rst series of tests, the probability of 8080 19521952 KamchatkaKamchatka MMw9.0w9.0 Thin-SedimentThin-Sediment success under the null hypothesis is provided TrenchesTrenches by the global lengths of the two categories of 7070 63%63% n=14n=14 (<1.0(<1.0 km)km) trenches: 21,500 km for thin-sediment trenches 6060 50%50% 50%50% 50%50% 50%50% versus 14,000 km for thick-sediment trenches, % n=38n=38 n=38n=38 n=2n=2 n=2n=2 5050 resulting in a proportion of thick-sediment 37%37% Thick-SedimentThick-Sediment trenches of R = 0.39. Shown in Table 7 are the n=8n=8 0 4040 TrenchesTrenches results of the binomial test for different cutoff (>1.0(>1.0 km)km) 3030 14%14% magnitudes. Cumulative earthquake numbers n=1n=1 are used, rather than the binned counts, because 2020 n=7n=76 n=34n=34 n=7n=7 n=4n=4 n=1n=1 of the higher sample sizes and to avoid any 1010 0%0% artifacts associated with binning. Using the 0 n=0n=0 deﬁ nition of the alternative hypothesis above 7.57.5 8.08.0 8.58.5 9.09.0 9.59.5 (high-magnitude IPT earthquakes preferentially MwMw thruthru thruthru thruthru thruthru thruthru occurring along thick-sediment trenches), one- 7.97.9 8.48.4 8.98.9 9.49.4 9.99.9 sided p-values are calculated (i.e., using only one side of the distribution). A more conser- vatively formed alternative hypothesis is that high-magnitude IPT events occur preferentially Figure 6. In bins of 0.5 Mw, relative percent Mw≥7.5 megathrust earthquakes (n = 176) either in thin- or thick-sediment trenches, such that ruptured at thin- and thick-sediment trenches with thin-trench earthquakes in bins that two-sided p-values would be calculated. Mw7.5–8.4 reduced to 41% (from 112 to 46 earthquakes) to compensate for the greater Although this alternative hypothesis is not length of thin-sediment (~19,000 km) versus thick-sediment trenches (~7800 km) in this consistent with the physical model for these Mw range. earthquakes described in the introduction, two- sided p-values are reported for completeness in Table 7. For example, out of the 39 IPT earthquakes OccurrenceOccurrence 100%100% ≥Mw8.1 that occurred in the instrumental n=1n=1 100100 era, 21 occurred at thick-sediment trenches (fourth line, Table 7). In contrast, 15.2 events 9090 86%86% n=6n=6 20112011 TohokuTohoku Mw9.0Mw9.0 are expected under the null hypothesis using Thin-SedimentThin 8080 71%71% 19521952 KamchatkaKamchatka MMw9.0w9.0 -Sediment the global lengths of each sediment thickness n=17n=17 TrenchesTrenches category. The corresponding one-sided p-value 7070 58%58% (<1.0(<1.0 km)km) n=7n=7 is 0.043, meaning that there is a 4.3% prob- 6060 50%50% 50%50% ability of having 21 or more events if the null % n=2n=2 n=2n=2 5050 42%42% hypothesis were true. Because this is below our n=5n=5 Thick-SedimentThick-Sediment critical p-value of 0.05, we accept the alterna- 4040 29%29% TrenchesTrenches tive Ruff hypothesis that Mw ≥8.1 IPT earth- n=7n=7 (>1.0(>1.0 km)km) 3030 14%14% quakes preferentially occur at thick-sediment n=1n=1 subduction zones. The two-sided p-value is 2020 n=24n=24 n=12n=12 n=7n=7 n=4n=4 n=1n=1 0.070, meaning that there is a 7.0% probability 1010 0%0% of having 21 or more events or nine or fewer n=0n=0 0 events (i.e., 30 or more IPT earthquakes along 7.57.5 8.08.0 8.58.5 99.0.0 9.59.5 thin-sediment trenches) occurring under the MwMw thruthru thruthru thruthru thruthru thruthru null hypothesis. In this case, the null hypoth- 7.97.9 8.48.4 8.98.9 9.49.4 9.99.9 esis cannot be rejected. Overall, the alternative hypothesis can be accepted for ≥Mw8.1, 8.5, and 8.7 using the one-sided p-values. For earthquakes ≥Mw8.9 and greater magnitude Figure 7. Binned in 0.5-Mw-wide columns, the relative occurrence percent of highest magni- cutoffs, the test results are increasingly affected tude megathrust that ruptured along 21 sediment-thick and 28 sediment-thin trench sectors by sample size. (see Table 3). For the second series of test, the probability of success under the null hypothesis is given by the cumulative lengths of trench sectors

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OccurrenceOccurrence 100%100% 100100 n=61n=61 n=n= 9090 115115 8080 70%70% 7070 n=43n=43 Thick-SedimentThick-Sediment (>1.0(>1.0 km)km) 6060 49%49% % n=30n=30 5050 56%56% n=64n=64 34%34% Thin-SedimentThin-Sediment 4040 n=21n=21 (<1.0(<1.0 kkm)m) 3030 18%18% 15%15% 2020 n=11n=11 n=9n=9 10%10% 25%25% n=6n=6 5%5% 5%5% 1010 n=25n=25 n=3n=3 n=3n=3 2%2% 2%2% 1616% 3%3% 2%2% 2%2% n=1n=1 n=1n=1 0%0% 0 n=18n=18 8%8% n=3n=3 0%0% n=9n=9 n=2n=2 n=2n=2 n=0n=0 7.57.5 7.77.7 7.97 . 9 88.1.1 8.38.3 8.58.5 8.78.7 8.98.9 99.1.1 9.39.3 99.5.5 99.7.7 Mw:Mw: EqualEqual ttoo oror GGreaterreater ThanThan

Figure 8. Percent occurrence of Mw≥7.5 earthquakes (n = 176) that ruptured at or above a threshold magnitude separately at thick- and thin-sediment trenches.

where Mw7.4–8.5 events have occurred in the we only use the one-sided values for testing. for ≥Mw8.9, the latter most likely because the instrumental era: 19,000 km for thin-sediment Under this null hypothesis, the alternative, Ruff sample size is too small. In summary, statisti- trenches versus 7800 km for thick-sediment hypothesis that IPT earthquakes occur along cal analysis using the binomial test supports the trenches, resulting in a thick-sediment propor- thick-sediment trenches is accepted for events conclusion that, for the most part, large-mag-

tion of R0 = 0.29 (Table 8). As before, both one- ≥Mw7.7–8.7, inclusively. The null hypothesis nitude IPT earthquakes preferentially occur at and two-sided p-values are reported, although cannot be falsiﬁ ed for earthquakes ≥Mw7.5 or thick-sediment trenches.

OccurrenceOccurrence 100100 100%100% 100%100% n=3n=3 100%100% 9090 75%75% 75%75% n=3n=3 n=1n=1 n=9n=9 n=6n=6 n=1n=1 8080 65%65% n=115n=115 60%60% 7070 60%60% n=3n=3 Thick-SedimentThick-Sediment n=64n=64 54%54% 55%55% 6060 51%51% n=11n=11 TrenchesTrenches n=21n=21 20112011 TohokuTohoku MMw9.0w9.0 % n=30n=30 (>1.0(>1.0 kkm)m) 5050 19521952 KamchatkaKamchatka MMw9.0w9.0 49%49% 4040 n=29n=29 46%46% 45%45% n=18n=18 Thin-SedimentThin-Sediment 3030 40%40% n=9n=9 40%40% n=43n=43 n=39n=39 TrenchesTrenches 35%35% n=59n=59 n=20n=20 n=2n=2 2020 n=61n=61 (<1.0(<1.0 km)km) n=107n=107 25%25% 25%25% n=5n=5 1010 n=176n=176 n=3n=3 n=2n=2 n=8n=8 n=0n=0 n=0n=0 n=0n=0 0 n=12n=12 7.57.5 7.77.7 7.97 . 9 8.18.1 8.38.3 8.58.5 8.78.7 8.98.9 9.19.1 99.3.3 9.59.5 Mw:Mw: EqualEqual ttoo oorr GGreaterreater ThanThan

Figure 9. Binned in 0.5-Mw-wide columns, the relative occurrence percent of highest magnitude megathrust that ruptured adjacent to 21 thick-sediment and 28 thin-sediment trench sectors (see Table 3).

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OccurrenceOccurrence OccurrenceOccurrence 100100 Thick-SedimentThick-Sediment TrenchesTrenches 100100 100%100% 100%100% 100%100% 100%100% 9090 Sediment-ThickSedime>1.0>n1t-.T0h kmkicmk TrenchesTrenches 100%100% 100%100% 9090 74%74% 75%75% 75%75% 75%75% n=3n=3 n=3n=3 n=1n=1 n=1n=1 72%72% 77%77% 78%78% n=3n=3 n=1n=1 8080 n=21n=21 n=11n=11 n=10n=1n=9n0=9 n=7n=7n=6n=6 8080 n=30n=30 67%67% 62%62% 59%59% 62%62% 60%60% 7070 57%57% n=11n=11 n=4n=4 7070 56%56% n=43n=43 n=28n=28 n=19n=19 n=3n=3 n=61n=656%516% 20112011 TohokuTohoku Mw9.0Mw9.0 6060 n=79n=79 51%51% 6060 20112011 TohokuTo19521h9ok5u2 Mw9.0MKamchatkaKwa9m.c0hatka MMw9.0w9.0 %% n=46n=46 50505050 19521952 KamchatkaKamchatka Mw9.0Mw9.0 49%49% 40404040 n=43n=43 28%28% 44%44%44%44% 43%43% 41%426%216%% n=12nn=21n==1221 25%25% 25%25% 30303030 n=47n=4n=61n7=61 38%3n=89n8=%89 n=13nn=8n==183 38%3n=4n8=%4 n=3n=3 40%40% n=26n=26 n=49n=49 n=7n=7 33%33%n=2n=2 2020 n=140n=140 n=32n=32 n=2n=2 2020 n=108n=108 n=69n=69 n=42n=42 22%22% n=29n=29 n=18n=18 23%23% 25%25% n=6n=6 1010 n=15n=15 n=3n=n=12n3=12 n=2n=2n=2n=2 1010 Thin-SedimentThin-Sediment TrenchesTrenches n=5n=5 SediSedimment-Thinent-Thin TrenchesTrenches n=13n=13 n=9n=9 0 <1.0<1.0 km n=8n=8 n=0n=0 n=0n=0 n=0n=0 0 7.57.5 7.7.7 7.97 . 9 8.18.1 8.8.3 8.8.5 8.8.7 8.8.9 9.19.1 9.39.3 9.59.5 7.7.5 7.7.7 7.7 . 9 88.1.1 8.8.3 8.8.5 8.8.7 8.8.9 99.1.1 99.3.3 99.5.5 Mw:MMw:Mww:: EqualEquuaal ltot otto oorr oroGreaterGrr eGreaterGatreera ThanTthearn ThanThan

Figure 10. Relative occurrence percent of ≥Mw7.5 instrumental megathrusts, but at thin-sediment sectors, the number of earthquakes Mw7.5 through 8.4 reduced by 41% (from 112 to 46) to compensate in this Mw range for the much greater occurrence length of thin versus thick sectors (~19,000 versus 7800 km).

DISCUSSION beneath the rock framework of the convergent ruptured the south-central Chile SZ (Table 2; margin (von Huene and Scholl, 1991; Clift and Fig. 3), trench sediment is thicker (~2.5 km) and Background Van nucchi, 2004; Scholl and von Huene, 2007). more laterally continuous (~750 km). Beneath This process of sediment subduction is shown the margin, the estimated long-term (~5 Myr) The tabulated, plotted, and statistically ana- on Figure 2C for the Ecuadorian SZ. Here the volume rate of sediment subduction is ~150 lyzed data presented in Tables 1, 2, and 3 were thickness of sediment entering the subduc- km3/Myr/km of convergent margin (Scholl and compiled to test with modern data sets the tion channel below the base of the overlying von Huene, 2007; Table 2). At an orthogonal validity of the posit by Ruff (1989) that excess plate is ~1 km. Farther to the south (33–45°S), convergent rate of ~75 km/Myr, transport of this sediment entering a subduction zone (SZ) favors where the super giant 1960 Mw9.5 megathrust volume requires an average thickness of sedi- nucleation of higher-magnitude megathrust or IPT (interplate thrust) earthquakes. This conjecture reasons that the entrance of an “excess” OccurrenceOccurrence thickness (i.e., thick enough to form a frontal 100100 prism by sediment accretion) of sediment into Thick-SedimentThick-Sediment TrenchesTrenches 100%100% n=3n=3 100%100% 100%100% 9090 n=3n=3 the SZ works to strengthen and smooth the lat- >1.0>1.0 kmkm 75%75% 75%75% n=1n=1 n=6n=6 n=1n=1 eral distribution of interplate coupling—thus 8080 65%65% n=9n=9 favoring the continuation of along-trench ruptur- 61%61% n=11n=11 60%60% 7070 56%56% n=14n=14 n=3n=3 ing and the generation of high-Mw earthquakes. n=21n=21 53%53% 56%56% 20112011 TohokuTohoku Mw9.0Mw9.0 At the time of his surmise, the notion of 6060 n=20n=20 n=15n=15 % 19521952 KamchatkaKamchatka Mw9.0Mw9.0 sediment subduction was little recognized as 5050 a signiﬁ cant tectonic process or that a subduction channel ﬁ lled with sediment and tectoni- 4040 47%47% 44%44% 44%44% n=18n=18 n=12n=12 cally eroded debris separated the underthrusting 3030 n=27n=27 39%39% 40%40% n=9n=9 oceanic plate from the rock framework of the n=38n=38 n=27n=27 35%35% n=2n=2 2020 n=48n=48 n=23n=23 n=6n=6 overlying convergent margin (Scholl et al., 1980; 25%25% 25%25% n=n=5 Cloos and Shreve 1988a, 1988b; von Huene 1010 Thin-SedimentThin-Sediment TrenchesTrenches n=17n=17 n=3n=3 n=2n=2 <1.0<1.0 km n=n=8 n=0n=0 n=0n=0 n=0n=0 and Scholl, 1991). Since the early 1980s, geo- 0 n=12n=12 physical, drilling, and geologic investigations 7.57.5 7.77.7 7.97 . 9 88.1.1 8.38.3 8.58.5 8.78.7 8.98.9 99.1.1 99.3.3 99.5.5 of the submerged forearc documented that at most (75–80%) convergent margins over a long Mw:Mw: EEqualqual ttoo oror GreaterGreater ThanThan period of time (i.e., 5–10 Myr) the greater part (75% or higher) of the incoming sediment enters Figure 11. Plot of relative occurrence percent of highest magnitude instrumental earth- the subduction channel and continues landward quake recorded at thick- (n = 21) and thin- (n = 27) sediment trench sectors.

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OccurrenceOccurrence OccurrenceOccurrence 100100 100100 100%100% Thin-SedimentThin-Sediment Thick-SedimentThick-Sediment 100%100% Thick-SedimentThick-Sediment TrenchesTrenches n=2n=2 9090 9090 TrenchesTrenches TrenchesTrenches n=2n=2 >1.0>1.0 KMKM 8080 (<1.0(<1.0 km)km) (>1.0(>1.0 km)km) 8080 67%67% 64%64% n=6n=6 7070 7070 58%58% n=7n=7 n=7n=7 50%50% 6060 67%67% 6060 50%50% n=2n=2 n=3n=3 n=2n=2 % 5050 57%57% % 5050 n=2n=2 n=4n=4 50%50% 50%50% 4040 43%43% 4040 n=2n=2 n=3n=3 42%42% n=3n=3 3030 3030 33%33% n=5n=5 36%36% n=4n=4 n=1n=1 n=4n=4 33%33% n=6n=6 0%0% 2020 2020 n=12n=12 n=3n=3 n=11n=11 n=0n=0 n=3n=3 n=7n=7 n=2n=2 Thin-SedimentThin-Sediment TrenchesTrenches 1010 1010 n=9n=9 0%0% <1<1..00 KMKM 0 n=0n=0 0 8.08.0 8.48.4 8.58.5 88.9.9 9.09.0 9.49.4 8.08.0 8.28.2 8.48.4 8.68.6 8.88.8 9.09.0 MwMw Mw:Mw: EEqualqual ttoo oorr GGreaterreater ThanThan

Figure 12. Relative occurrence percent of pre-instrumental mega- Figure 13. Plot of the relative occurrence of pre-instrumental era thrust earthquakes (n = 12) listed on Table 4 (see also Table 6) for (1700–1898) interplate thrust earthquakes (n = 12) estimated to have thick- and thin-sediment trenches binned in ﬁ ve, 0.5-Mw-wide cate- rupture magnitudes ≥Mw8.0 that nucleated at or above a threshold gories ranging from Mw8.0 through 8.4–9.0 through 9.5. magnitude at thin- and thick-sediment trench sectors (Tables 4 and 6).

ment in the subduction channel of ~2.0 km (see TABLE 7. RESULTS OF BINOMIAL TEST USING GLOBAL LENGTHS fi g. 1 of Melnick et al., 2006). OF THICK- AND THIN-SEDIMENT TRENCHES ≥M N N RRN p p Farther south still (50–57°S), along the w tot thick 0 0-thick 1side 2side 7.5 176 61 0.35 0.39 68.6 0.900 0.250 southern sector of the Chile Trench (Fig. 3), 7.7 107 43 0.40 0.39 41.7 0.440 0.840 the thickness of sediment entering the subduc- 7.9 59 29 0.49 0.39 23 0.072 0.111 tion channel is ~3 km (Polonia et al., 2007). The 8.1 39 21 0.54 0.39 15.2 0.043* 0.070 8.3 20 11 0.55 0.39 7.8 0.110 0.170 trench fi ll is thick enough to completely bury 8.5 12 9 0.75 0.39 4.7 0.013* 0.015 2–3-km-high seamounts entering the SZ (Fig. 8.7 8 6 0.75 0.39 3.1 0.044* 0.063 14). Burial of this relief effects “smoothing” 8.9 5 3 0.60 0.39 2 0.300 0.380 Note: M —moment magnitude; N —total number of observed interplate thrust (IPT) earthquakes; N — of interplate roughness that Ruff (1989) argues w tot thick number of observed IPT earthquakes occurring in thick- sediment trenches; R—observed proportion of Nthick promotes rupture continuation and the genera- earthquakes; R0 —proportion of thick-sediment IPT earthquakes under the null hypothesis; N0-thick—number of thick- sediment IPT earthquakes expected under the null hypothesis; p —one-sided p value used for hypothesis tion of megathrusts of high magnitude. Arguing 1side testing; p2side —two-sided p value. in principal similarly, Wang and Bilek (2014) *p value less than critical value of 0.05. Alternative Ruff hypothesis accepted. observe that underthrust relief favors fault creep and either rupture termination or signifi cant changes in the rupture process. TABLE 8. RESULTS OF BINOMIAL TEST USING CUMULATIVE LENGTHS OF THICK- AND THIN-SEDIMENT SECTORS WHERE MW7.4–8.5 EARTHQUAKES HAVE OCCURRED The plotted data of Figures 5–7 and 9–11 ≥ Mw Ntot Nthick RR0 N0-thick p1side p2side also document that great and giant IPT earth- 7.5 176 61 0.35 0.29 51 0.060 0.110+ quakes nucleate in absence of a thick layer of 7.7 107 43 0.40 0.29 31 0.008* 0.014 subducting sediment. Accepting the statistically 7.9 59 29 0.49 0.29 17.1 0.001* 0.001 8.1 39 21 0.54 0.29 11.3 0.001* 0.001 supported correctness of the Ruff conjecture, 8.3 20 11 0.55 0.29 5.8 0.013* 0.023 this observation implies that lateral coupling 8.5 12 9 0.75 0.29 3.5 0.001* 0.001 smoothness favoring rupture continuation can 8.7 8 6 0.75 0.29 2.3 0.009* 0.009 8.9 5 3 0.60 0.29 1.5 0.150 0.150 also be effected where seafl oor of low average Note: Mw —moment magnitude; Ntot —total number of observed interplate thrust (IPT) earthquakes; Nthick — bathymetric relief underthrust the margin and number of observed IPT earthquakes occurring in thick- sediment trenches; R—observed proportion Nthick where the added tectonic debris of basal and earthquakes; R0 —proportion of thick-sediment IPT earthquakes under the null hypothesis; N0-thick—number of thick- sediment IPT earthquakes expected under the null hypothesis; p —one-sided p value used for hypothesis frontal subduction erosion signifi cantly thickens 1side testing; p2side —two-sided p value. the subduction channel (Figs. 15 and 16; von *p value less than critical value of 0.05. Alternative Ruff hypothesis accepted. Huene et al., 1994; Kopp, 2013).

Sediment Input and Earthquake less than Mw7.7–7.9. Both plots document an above any threshold magnitude are higher for Magnitude—Prominent Trends expected progressive decrease in number of sediment-rich trenches than for sediment-poor earthquakes occurring at increasingly higher trenches. Interplate thrust magnitudes exceed- The plots of Figures 4 and 8 show that for magnitudes. Of the 61 earthquakes that nucle- ing Mw9.0 are unknown for sediment-thin both thin- and thick-sediment trenches, most IPT ated at thick-sediment and 115 at thin-sediment sectors, whereas three super giant earthquakes earthquakes ≥Mw7.5 ruptured at magnitudes SZs, the occurrence number and percent at and (1960 Chile Mw9.5, 1964 Alaska Mw9.2, and

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0 0

2 2

4 4

6 6

8 8 km km 20 km

VE = ~3.75 km

SW Madre de Dios Basin NE 0 0 Buried Seamount 2 Southern Chile 2 Trench 4 ? 4 Décollement Basement 3.0 km 6 6

8 Line 251 8 ~ 15 km/ Myr km Subducted Sediment km After Polonia et al. (2007) Polonia et al.(2007) TECTONICS

Figure 14. Multichannel seismic proﬁ le across the southern sector of the Chile Trench revealing a fully buried 2.0+ km-high seamount poised to enter the subduction channel in ~1 Myr.

2004 Sumatra Mw9.2) nucleated at thickly sedi- ≥Mw8.3, occurring at both thick (n = 11) and Although few in number (n = 12), occurrence- mented SZs (Tables 2 and 3). thin (n = 9) trenches (Fig. 9; Tables 1 and 2). magnitude plots of pre-instrumental IPT earth- It seems signifi cant, as shown by the separate The combined or relative occurrence plots quakes also reveal a trend of increasing number thin- and thick-sediment plots of Figures 4 and of earthquakes binned on Figures 5–7, and as of higher-magnitude earthquakes rupturing at 8, and also the combined or relative occurrence continuous threshold diagrams on Figures 9–11, thick-sediment trench sectors (Figs. 12 and 13). plots for all recorded earthquakes (n = 176) display a pronounced overall trend of increasing shown on Figures 9–11, that ruptures >Mw9.0 relative occurrence of higher-magnitude earth- Trend Reversals have only been recorded at well-sedimented SZs quakes at thick-sediment trenches. Correspond- (see also Heuret et al., 2012). For higher-magni- ingly, at thin-sediment trenches, the overall At thin-sediment SZs, the overall trend of tude earthquakes, in particular for ≥Mw8.3, the relative number of earthquakes decreases with decreasing relative earthquake occurrence number of earthquakes is small (n = 20), and the increasing magnitude. These prominent trends reverses at ~Mw9.0. Trend reversal to a peak of signifi cance of the statistics of small numbers are equally apparent on threshold occurrence 50% is displayed by the binned data of Figures becomes a statistical concern (see Summary and plots of just the highest magnitude earthquakes 5–7. At the continuous threshold plots of Figures Conclusions). This circumstance, about which at thin- (n = 27) and thick- (n = 21) sediment 9–11, the occurrence peak (40%) is at ≥Mw8.9, nothing can be done, is true for IPT earthquakes trenches (Figs. 7 and 11). refl ecting the circumstance that data points are

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150E 170E tinuous greater relative occurrence of higher- magnitude earthquakes at thick- (≥1 km) versus thin- (≤1 km) sediment sectors. Although much less numerically based, the same overall trend is observed in the plots of pre-instrumental era earthquakes on Figures 12 and 13. 19521952 KamchatkaKamchatka For all instrumental era earthquakes (n = 176) Mw 99.0.0 uncompensated for the disproportionally longer global length of thin-sediment trenches, the greater relative occurrence of higher-mag- 50N nitude megathrusts at thick-sediment trenches EmperorEmperor crosses over from less to greater than 50% at SeamountsSeamounts ~Mw8.0 (Fig. 9). For just the highest magnitude earthquakes recorded along thin- and thick-sediment trenches (n = 48), the crossover 22011011 to greater than 50% earthquake occurrence at Tohoku-okiTohoku-oki ErimoErimo SeamountSeamount GroupGroup sediment-thick sectors is similar at ~Mw7.8 (Fig. 11). This general observation was noted MwMw 99.0.0 by Ruff (1989). 40N Fig.Fig. 116,6, PPanelsanels B aandnd C For the length-compensated number of earth- Fig.Fig. 16,16, PanelPanel A quakes occurring in the magnitude range of Mw7.5–8.4, the greater relative occurrence of higher-magnitude earthquakes at thick-sediment DaiicDaiichhi-Kashimai-Kashima SeamountSeamount trenches begins at less than Mw7.5. Except for GroupGroup a reversing dip at ≥Mw8.9, the relative higher occurrence at thick-sediment trenches is effec- tively continuous to IPT earthquakes greater than Mw9.0 (Fig. 10). Equally prominent is a Figure 15. Occurrence settings of 1952 Kamchatka and 2011 reversal in this trend at approximately Mw8.9– Tohoku-Oki Mw9.0 interplate thrust earthquakes. The seafl oor 9.0. The reversal is shown by the binned data of entering these subduction zones is relatively smooth, exhibiting few Figures 5–7 and the continuous threshold plots large seamounts and underthrusting ridges and fracture zones (see of Figures 9–11). The turnaround is virtually Fig. 16A. See also Wang and Bilek [2014]). entirely due to the 1952 southern Kamchatka and 2011 northern Japan or Tohoku-Oki Mw9.0 IPT earthquakes. Both rupture areas are under- plotted at odd Mw magnitudes. Because few smooth, exhibiting only widely spaced sub- thrust by seafl oor of low relief and a landward earthquakes are involved, the statistically less ducting seamount groups, fracture zones, and thickening, roughness-smoothing subduction robust plot of pre-instrumental IPT earthquakes ridges. Figures 15 and 16 illustrate the gen- channel expanded by inclusion of tectonically on Figure 13 nonetheless displays the same eral smoothness of Pacifi c plate entering the eroded debris (Figs. 15 and 16; Klaeschen reversal trend of decreasing relative occur- southern Kamchatka and northern Japan SZs et al., 1994; von Huene et al., 1994; Hueret rence for higher Mw earthquakes (Table 4). The (see also Wang and Bilek, 2014). We infer that et al., 2012). reversal in trend is predominantly owing to the asperity smoothing is further enhanced at these Equally signifi cant for the tsunami-launching nucleation of giant IPT earthquakes off northern SZs because basal subduction erosion adds a consequence of the Tohoku-Oki earthquake are Chile and northern Peru—for example, in the landward thickening volume of eroded debris the stratigraphic fi ndings at International Ocean instrumental era, the recent 2014, Iquique Chile to the subduction channel (Klaeschen et al., Discovery Program (IODP) Site C0019, which Mw8.2 (not included in listed earthquakes on 1994; von Huene et al., 1994; von Huene and penetrated the frontal prism (Chester et al., Table 1) (Schurr et al., 2014). Ranero, 2003; Heuret et al., 2012). For northern 2013; Moore et al., 2013) and DSDP Site 436 For instrumental-era IPT earthquakes, the Japan, the surface of interplate slip beneath the located nearby but seaward of the Japan Trench prominent trend reversal at thin-sediment frontal prism was stratigraphically localized, a (Nakamura et al., 2013). These drilling sites trenches refl ects the nucleation of the 1952 circumstance that conditioned near-trench rup- determined that a ~5-m-thick layer of pelagic, Kamchatka Mw9.0 and, in 2011, the devastat- ture continuation and tsunamigenesis (Chester abyssal clay overlying chert stratigraphically ing Mw9.0 Tohoku-Oki megathrust off north- et al., 2013; Moore et al., 2013; Nakamura localized the surface of displacement beneath ern Japan (Table 1). Other, but lower magnitude et al., 2013; Moore et al., 2015) (see Summary the frontal prism and conditioned the 30–60 m great megathrusts (i.e., Mw8.2–8.5) ruptured and Conclusions below). of slip that launched the disastrous Tohoku-Oki the thin-sediment south Peru, northern Chile, tsunami. It is unknown if the same stratigraphi- and northern and southern Kuril SZs. Along SUMMARY AND CONCLUSIONS cally controlled surface extends deeper and these trench sectors, but in particular for landward beneath the submerged forearc, but the 1952 Kamchatka and 2011 Japan earth- For instrumental IPT earthquakes ≥w7.5, the it certainly could. If nothing else, with respect quakes, lengthy (>300–500 km) widths of the plots of Figures 4–11 of megathrust size versus to generating great megathrust earthquakes and underthrusting seafl oor are bathymetrically sediment thickness document a nearly con- high-magnitude near- and far-fi eld tsunamis,

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W E A 0 Japan Trench, “Smooth” Incoming Pacific Plate Tohoku Area 5

10 km 15 Tsuru et al., 2000 (JGR) 20 km 20 B W E 0 20 km Sediment Thickness 4 ca. 0.6 km km 8 ShellShell Line,Line, 12 P849.P849. von Huene et al., 1994 (JGR)

~DSDP 439 W E C 0 BeachBeach DDepositseposits ((ca.ca. 3300 Ma)Ma) 20 km Subduction Channel Frontal Thickens Landward 4 Prism km L.L. CCretaceousretaceous Wave-cuve-cut UnconfoUnco nforrmitymity 8 RRockock FrameworkFramework 12 von Huene et al., 1994 (JGR)

Figure 16. Interpreted multichannel profi les off northern Japan that cross the outer margin and trench ~100– 150 km north of the epicentral latitude (38.3°N) of the 2011 Tohoku-Oki Mw9.0 megathrust. (A) reveals a bathymetric smooth seafl oor underthrust this margin. (B) and (C) show that although the thickness of sediment entering the subduction channel is only ~0.4–0.5 km, the thickness of debris fi lling the subduction channel thickens landward beneath the outer margin to 1.5–2.0 km. The excess material is provided by subduction erosion of the frontal prism, constructed most likely of slope debris, and of the upper plate’s bedrock framework of lithifi ed, Late Cretaceous sediment (von Huene et al., 1994). See Figure 15 for line locations. DSDP—Deep Sea Drilling Project.

the Tohoku-Oki drilling results demonstrate ing bathymetric relief, a circumstance favoring of southern Pakistan and Iran seems capable of the contributing importance of the stratigraphy interplate creep and rupture termination rather unleashing a giant (>Mw8.5) megathrust earth- and lithologic makeup of subducted sediment than continuation. quake (Byrne et al., 1992; Kopp et al., 2000; where laterally extensive seaﬂ oor of low aver- Smith et al., 2013). These worrisome sectors, age roughness enters the subduction zone. Implications for Thick-Sediment Trenches identiﬁ ed on Figure 1 by horizontally striped, As noted, the predominant occurrence of sediment-thick trench sectors, include the east- great megathrust earthquakes at sediment- The megathrust occurrence data of Tables ern Aleutian or Fox Island sector (Butler, 2012; charged SZs statistically supports the correct- 1 and 2 only list instrumental earthquakes of Ryan et al., 2012), the Andaman-Myanmar or ness of Ruff’s (1989) surmise. But, accord- magnitude Mw7.5 and greater that ruptured far-northern Sumatra sector (Moore et al., 1980; ingly, it can also be inferred that a condition at the numbered trench sectors shown on Fig- Steckler et al., 2008), the Lesser Antilles or of homogeneous coupling can be achieved at ure 1. Many other thin- and thick-trench sectors Barbados sector (Biju-Duval et al., 1982; West- poorly sedimented SZs that are erosive and exist at which no earthquake ≥Mw7.5 has been brook et al., 1988; Mascle and Moore, 1990), underthrust by low-relief ocean crust. If charged instrumentally recorded (see Fig. 3 and its cap- the Hellenic Trench (Taymaz et al., 1990), and stratigraphically with a weak stratigraphic hori- tion). For thick-sediment trench sectors 250– the Tierra del Fuego or southern sector of the zon, the potential up-dip slip beneath the lower 300 km in length that are not underthrust by Chile Trench (Polonia et al., 2007). Although trench slope can be dangerously high. These rupture-inhibiting ridges, plateaus, or seamount well sedimented, the Hikurangi (Scherwath observations also underwrite the validity of the chains, a concern must be stated that a future et al., 2010) and Manila Trenches (Hayes and argument of Wang and Bilek (2014) that lateral IPT of magnitude Mw8.0 or much higher is Lewis, 1984; Lewis and Hayes, 1984) are coupling evenness is disrupted by underthrust- plausible (Table 2). For example, the Makran SZ underthrust by uneven relief and character-

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ized by strain releasing creep; hence they seem ACKNOWLEDGMENTS Byrne, D.E., Sykes, L.R., and Davis, D.M., 1992, Great thrust earthquakes along the plate boundary of the unlikely to rupture in a great megathrust (Wang With gratitude and thanks we acknowledge the Makran subduction zone: Journal of Geophysical and Bilek, 2014). many conversational inputs and guidance provided by Research, v. 97, p. 449–478. the members of the USGS Tsunami Source Working Chester, F.M., Rowe, C., Ujiie, K., Kirkpatrick, J., Regalla, Group (TSWG), Menlo Park, CA. The TSWG, con- C., Remitti, F., Moore, J. C., Toy, V., Wolfson-Schwehr, A Concerning Look at the Aleutian M., Vse, S., Kameda, J., Mori, J. J., Brodsky, E., Egu- Subduction Zone vened in the wake of the 2004 Banda Aceh disaster, by chi, N., Toczko, S., and Expedition 343 and 343T the 2nd author and its fi rst chair, is presently guided by Scientists, 2013, Structure and composition of the our colleague and astute interlocutor Walter Mooney. plate-boundary slip zone for the 2011 Tohoku-Oki It has long been noticed that megathrusts Our understanding of the many factors involved in Earthquake: Science, v. 342, p. 1208–1211. ≥Mw8.0 uncommonly, if at all, occur along determining the occurrence areas of high magnitude Cifuentes, I., and Silver, P., 1989, Low-frequency source intra-oceanic arcs, for example the Izu-Bonin- megathrusts benefi ted greatly from discussions with characteristics of the Great 1960 Chilean earthquake: Kelin Wang, Roy Hyndman, Nathan Bangs, Jean- Journal of Geophysical Research, v. 94, p. 643–663, Mariana (IBM), Tonga-Kermadec, Solomon, Yves Collot, and other informed colleagues. We are doi: 10 .1029 /JB094iB01p00643 . and Vanuatu SZs (Fig. 1; Tables 1 and 3). These Cisternas, M., Atwater, B.F., Torrejon, F., Sawai, Y., especially grateful to Emile Okal and Willie Lee for Machuca, G., Lagos, M., Eipert, A., Youlton, C., Sal- SZs are fronted by thin-sediment trenches. many insightful deliberations that helped us certify gado, I., Kamataki, T., Shishikura, M., Rajendran, C.P., However, great and giant megathrust ruptures that the large instrumental and pre-instrumental era Malik, J.K., and Husni, M., 2005, Predecessors of the are characteristic of the intra-oceanic Aleutian earthquakes compiled in our tables have the most giant 1960 Chile earthquake: Nature, v. 437, p. 404– up-to-date magnitudes and are indeed megathrust 407, doi: 10 .1038 /nature03943. SZ. Three great megathrusts have nucleated ruptures. Discerning and knowledgeable reviews by Clift, P., and Vannucchi, P., 2004, Controls on tectonic accre- there since 1957—from west to east, the 1965 Casey Moore and an anonymous reader were critical tion versus erosion in subduction zones: Implications western Aleutian or Rat Island Mw8.7 and the to improving the science content, focus, and scholar- for the origin and recycling of the continental crust, ship of the fi nal manuscript. Reviews of Geophysics, v. 42, RG2001, 31 p., doi: 10 1957 Mw8.6 and 1986 Mw8.0 of the Andreanof .1029 /2003RG000127 . or central Aleutian Trench (Tables 2 and 3). It REFERENCES CITED Cloos, M., and Shreve, R.L., 1988a, Subduction-channel seems plausible that the frequent rupturing of model of prism accretion, mélange formation, sedi- Abe, K., 1972, Mechanisms and tectonic implications of the ment subduction, and subduction erosion at convergent great and giant Aleutian earthquakes refl ects the 1966 and 1970 Peru earthquakes: Physics of the Earth plate margins: 1. Background and description: Pure circumstance that the Aleutian Trench is fl ooded and Planetary Interiors, v. 5, p. 367–379, doi: 10 .1016 and Applied Geophysics, v. 128, p. 456–500. Cloos, M., and Shreve, R.L., 1988b, Subduction-channel with a ~2.0-km-thick wedge of turbidite beds /0031 -9201 (72)90108 -2 . Abe, K., 2002, Catalogue of large earthquakes, mostly larger model of prism accretion, mélange formation, sedi- (Fig. 2A) and widely spaced high bathymet- than 6.8, 1897–1980, in Engdahl, E.R., and Villasenor, ment subduction, and subduction erosion at convergent ric relief. The sediment body is sourced from A., Global seismicity: 1900–1999, in Lee, W.H.K., plate margins: 2. Implications and discussion: Pure and and Kanamori, H., eds., International Handbook of Applied Geophysics, v. 128, p. 501–545, doi:10 .1007 glaciated eastern Alaskan drainages (Scholl, Earthquake & Engineering Seismology: Amsterdam, /BF00874549 . 1974; Scholl et al., 1983, 1987; McCarthy and Netherlands, Academic Press, p. 689. Collot, J.-Y., Charvis, P., Gutscher, M.A., and Operto, S., Scholl, 1985). Abe, K., and Kanamori, H., 1980, Magnitudes of great shal- 2002, Exploring the Ecuador-Colombia active margin low earthquakes from 1953 to 1977: Tectonophysics, and interplate seismogenic zone: Eos (Transactions, As emphasized by Butler (2012) and Ryan v. 62, p. 191–203, doi:10 .1016 /0040 -1951 (80)90192 -4 . American Geophysical Union), v. 83, no. 17, p. 185– et al. (2012), since Russian exploration began Atwater, B.F., and Yamaguchi, D.K., 1991, Sudden, probably 190, doi: 10 .1029 /2002EO000120 . Collot, J.-Y., Marcaillou, B., Sage, F., Michaud, F., Agudelo, in the mid-1700s, the ~700-km-long Fox Island coseismic submergence of Holocene trees and grass in coastal Washington State: Geology, v. 19, p. 706–709, W., Charvis, P., Graindorge, D., Gutscher, M.-A., or eastern sector of the Aleutian Trench has not doi: 10 .1130 /0091 -7613 (1991)019 <0706 :SPCSOH>2 .3 and George Spence, G., 2004, Are rupture zone lim- ruptured in a great earthquake. The Fox Island .CO;2 . its of great subduction earthquakes controlled by Atwater, B.F., Musumi-Rokkaku, S., Satake, K., Tsuji, Y., upper plate structures?: Evidence from multichannel sector lies between ~172.5°W and 162.5°W and Uyeda, K., and Yamaguchi, D., 2005, The Orphan Tsu- seismic refl ection data acquired across the northern separates the thick-sediment eastern Aleutian nami of 1700: U.S. Geological Survey Professional Ecuador–southwest Colombia margin: Journal of and western Alaska sectors (Fig. 1). Bathymetri- Paper 1707, p. 133. Geophysical Research, v. 109, p. B11103, doi:10 .1029 Béjar-Pizarro, M., Socquet, A., Armijo, R., Carrizo, D., Gen- /2004JB003060 . cally smooth ocean crust underthrusts the Fox rich, J., and Mark Simons, M., 2013, Andean structural Collot, J.-Y., Ribodetti, A., Agudelo, W., and Sage, F., 2011, Island sector. Progressive landward migration of control on interseismic coupling in the North Chile The South Ecuador subduction channel: Evidence for a dynamic mega-shear zone from 2D fi ne-scale seismic the arc magmatic front since ca. 45 Ma implies subduction zone: Nature Geoscience, v. 6, p. 462–467, doi: 10 .1038 /ngeo1802 . refl ection imaging and implications for material trans- that subduction erosion also provides thicken- Biju-Duval, B., Le Quellec, P., Mascle, A., Renard, V., and fer: Journal of Geophysics, v. 116, B11102, doi: 10 ing material to the subduction channel (Vallier Valery, P., 1982, Multibeam bathymetric survey and .1029 /2011JB008429 . high resolution seismic investigations on the Bar- Comte, D., and Pardo, M., 1991, Reappraisal of great his- et al., 1994). bados ridge complex (eastern Caribbean): A key to torical earthquakes in the northern Chile and southern These circumstances, and the implications of the knowledge and interpretation of an accretionary Peru seismic gaps: Natural Hazards, v. 4, p. 23–44, doi: the discovery of a massive paleotsunami deposit wedge: Tectonophysics, v. 86, p. 275–304, doi: 10 .1016 10 .1007 /BF00126557 . /0040 -1951 (82)90070 -1 . Conover, W.J., 1971, Practical Nonparametric Statistics: on the island of Kauai reported by Butler et al. Bilek, S.L., 2010, Seismicity along the South American sub- New York, John Wiley and Sons, Inc., 462 p. (2014), warn that in the coming decades the east- duction zone: Review of large earthquakes, tsu namis, Dorbath, L., Cisternas, A., and Dorbath, C., 1990, Assess- ern or Fox Island sector may well (again?) rup- and subduction zone complexity: Tectonophysics, ment of the size of large and great historical earth- v. 495, p. 2–14, doi: 10 .1016 /j .tecto .2009 .02 .037 . quakes in Peru: Bulletin of the Seismological Society ture in a great or giant megathrusts, as have all Bilek, S.L., Schwartz, S.Y., and DeShon, H.R., 2003, Con- of America, v. 80, p. 551–576. other well-sedimented Aleutian Trench sectors. trol of seafl oor roughness on earthquake rupture behav- Doser, D.I., 2006, Relocations of Earthquakes (1899–1917) ior: Geology, v. 31, p. 455–458, doi:10 .1130 /0091 in south-central Alaska: Pure and Applied Geo physics, The corresponding generation of a trans-oceanic -7613 (2003)031 <0455 :COSROE>2 .0 .CO;2 . v. 163, p. 1461–1476, doi: 10 .1007 /s00024 -006 -0085 -3 . tsunami similar to the ones launched by the 1957 Borrero, J.C., Sieh, K., Chlieh, M., Costas, E., and Syno- El Hariri, M., Bilek, S.L., DeShon, H.R., Engdahl, E.R., central Aleutian or Andreanof sector Mw8.6 and lakis, C.E., 2006, Tsunami Inundation Modeling for and Bisrat, S., 2013, Along-strike variability of rupture Western Sumatra: Proceedings of the National Acad- duration in subduction zone earthquakes: Journal of the 1946 western Alaska or Alaska Peninsula emy of Sciences, v. 103, p. 19,673–19,677. Geophysical Research. Solid Earth, v. 118, p. 646–664, Mw8.6 megathrusts (Tables 2 and 3) will target Butler, R., 2012, Re-examination of the potential for great doi: 10 .1029 /2012JB009548 . the Hawaiian Islands (Fryer et al., 2004; Lopez earthquakes along the Aleutian Island Arc with impli- Engdahl, E.R., and Villasenor, A., 2002, Global seismicity: cations for tsunami in Hawaii: Seismological Research 1900–1999, in Lee, W.H.K., and Kanamori, H., eds., and Okal, 2006; Butler et al., 2014; von Huene Letters v. 83, n. 1, p. 38. International Handbook of Earthquake & Engineer- et al., 2014). Considerable damage can also be Butler, R., Burney, D., and Walsh, D., 2014, Paleotsunami ing Seismology: Amsterdam, Netherlands, Academic evidence on Kaua‘i and numerical modeling of a great Press, p. 665–690. expected along the west coast of North America Aleutian tsunami: Geophysical Research Letters, v. 41, Engdahl, E.R.., van der Hilst, R., and Buland, R., 1998, and coastal and island communities to the south. doi: 10 .1002 /2014GL061232 . Global teleseismic earthquake relocation with

Geosphere, April 2015 263

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/2/236/3333818/236.pdf by guest on 30 September 2021 Scholl et al.

improved travel times and procedures for depth deter- Klaeschen, D., Belykh, I., Gnibidenko, H., Patrikeyev, S., before the 2010 earthquake: Nature Geoscience, v. 7, mination: Bulletin of the Seismological Society of and von Huene, R., 1994, Structure of Kuril Trench p. 292–296, doi: 10 .1038 /ngeo2102 . America, v. 88, p. 722–743. from seismic refl ection records: Journal of Geophysi- Nakamura, Y., Kodaira, S., Miura, S., Regalla, C., and Taka- Estabrook, C., Jacob, K.H., and Sykes, L.R., 1994, Body wave cal Research, v. 99, B12, p. 24,173–24, 188. hashi, N., 2013, High-resolution seismic imaging in the and surface wave analysis of large and great earthquakes Kodaira, S., Takahashi, N., Nakanishi, A., Miura, S., and Japan Trench axis area off Miyagi, northeastern Japan: along the eastern Aleutian arc, 1923–1989: Implications Kaneda, Y., 2000, Subducted seamount imaged in the Geophysical Research Letters, v. 40, p. 1713–1718, for future events: Journal of Geophysical Research, rupture zone of the 1946 Nankaido earthquake: Sci- doi: 10 .1002 /grl .50364 . v. 99, p. 11643–11662, doi: 10 .1029 /93JB03124 . ence, v. 289, p. 104–106, doi: 10 .1126 /science .289 Natawidjaja, D.H., Sieh, K., Chlieh, M., Galetzka, J., Franke, D., Schnabel, M., Ladage, S., Tappin, D.R., Neben, .5476 .104 . Suwargadi, B.W., Cheng, H., Edwards, R.L., Avouac, S., Djajadihardja, Y.S., Müller, C., Kopp, H., and Kopp, C., Fruehn, J., Flueh, E.R., Reichert, C. Kukowski J-P., and Ward, S.N., 2006, Source parameters of Gaedicke, C., 2008, The great Sumatra–Andaman N., Bialasa, J.D., and Klaeschen, D., 2000, Structure the great Sumatran megathrust earthquakes of 1797 earthquakes—Imaging the boundary between the rup- of the Makran subduction zone from wide-angle and and 1833 inferred from coral microatolls: Journal of tures of the great 2004 and 2005 earthquakes: Earth reflection seismic data: The control of subduction Geophysical Research, v. 111, B06403, doi: 10 .1029 and Planetary Science Letters, v. 269, p. 118–130, doi: zone structural complexity and geometry on margin /2005JB004025 . 10 .1016 /j .epsl .2008 .01 .047 . segmentation and seismicity: Tectonophysics, v. 329, Newcomb, K.R., and McCann, W.R., 1987, Seismic His- Fryer, G., Watts, J.P., and Pratson, L.F., 2004, Source of the p. 171–170. tory and Seismotectonics of the Sunda Arc: Journal of great tsunami of 1 April 1946: A landslide in the upper Kopp, C.L., 2013, The control of subduction zone structural Geophysical Research, v. 92, p. 421–439, doi:10 .1029 Aleutian forearc: Marine Geology, v. 203, p. 201–218, complexity and geometry on margin segmentation and /JB092iB01p00421 . doi: 10 .1016 /S0025 -3227 (03)00305 -0 . seismicity: Tectonophysics, v. 589, p. 1–6, doi: 10 .1016 Okal, E.A., 1992, Use of mantle magnitude Mm for the Fukao, Y., and Furumoto, M., 1979, Stress drops wave /j .tecto .2012 .12 .037 . reassessment of moment of historical earthquakes I: spectra and recurrence intervals of great earthquakes: Lewis, S.D., and Hayes, D.E., 1984, A geophysical study Shallow events: Pure and Applied Geophysics, v. 139, Implications of the Etorofu Earthquake of 1958 of the Manilla Trench, Luzon, Philippines: 2. Fore-arc p. 17–57, doi: 10 .1007 /BF00876825 . November 6: Geophysical Journal of the Royal Astro- basin structural and stratigraphic evolution: Journal of Okal, E.A., 1999, Historical seismicity and seismotectonic nomical Society, v. 57, p. 23–40, doi:10 .1111 /j .1365 Geophysical Research, v. 89, p. 9196–9214, doi:10 context of the great 1979 Yapen and 1996 Biak, Irian -246X .1979 .tb03769 .x . .1029 /JB089iB11p09196 . Jaya earthquakes: Pure and Applied Geophysics, Gutenberg, B., and Richter, C.F., 1954, Seismicity of the Lomnitz, C., 2004, Major Earthquakes of Chile: A Historical v. 154, p. 633–675, doi: 10 .1007 /s000240050247 . Earth and Associated Phenomena (second edition): Survey 1535–1960: Seismological Research Letters, Okal, E.A., 2005, A re-evaluation of the great Aleutian and Princeton, New Jersey, Princeton University Press, v. 75, p. 368–378, doi: 10 .1785 /gssrl .75 .3 .368 . Chilean earthquakes of 1906 August 17: Geophysical 310 p. Lopez, A.M., and Okal, E.A., 2006, A seismological re assess- Journal International, v. 161, p. 268–282, doi:10 .1111 Gutscher, M.-A., Malod, J., Rehault, J.-P., Klingelhoefer, F., ment of the source of the 1946 Aleutian “tsunami” /j .1365 -246X .2005 .02582 .x . Mendes-Victor, L., and Spakman, W., 2002, Evidence earthquake: Geophysical Journal International, v. 165, Okal, E.A., 2011a, Tsunamigenic earthquakes: Past and for active subduction beneath Gibraltar: Geology, p. 835–849, doi: 10 .1111 /j .1365 -246X .2006 .02899 .x . present milestones: Pure and Applied Geophysics, v. 30, no. 12, p. 1071–1074, doi: 10 .1130 /0091 -7613 Mascle, A., and Moore, J.C., 1990, ODP Leg 110: Tectonic v. 168, p. 969–995, doi: 10 .1007 /s00024 -010 -0215 -9 . (2002)030 <1071 :EFASBG>2.0 .CO;2 . and hydrologic synthesis, in Moore, J.C., Mascle, A., Okal, E.A., 2011b, Earthquake, focal mechanism, in Gupta, Hatori, T., 1981, Field investigation of the Nankaido tsu- et al., eds., Proceedings of the Ocean Drilling Program, H., ed., Encyclopedia. Solid Earth Geophysics: Berlin, namis of 1707 and 1854 along the southwest coast of Scientifi c Results: College Station, Texas, Ocean Drill- Springer, p. 194–199. Shikoku: Bulletin of Earthquake Research Institute, ing Program, v. 110, p. 409–425. Okal, E.A., and Synolakis, C.E., 2008, Far fi eld tsunami haz- v. 56, p. 547–570 (in Japanese). McCarthy, J., and Scholl, D.W., 1985, Mechanisms of subduc- ard from megathrust earthquakes in the Indian Ocean: Hayes, D.E., and Lewis, S.D., 1984, A geophysical study tion accretion along the central Aleutian Trench: Geo- Geophysical Journal International, v. 172, no. 3, of the Manilla Trench, Luzon, Philippines: 1. Crustal logical Society of America Bulletin, v. 96, p. 691–701, p. 995–1015, doi: 10 .1111 /j .1365 -246X .2007 .03674 .x . structure, gravity, and regional tectonic evolution: doi: 10 .1130 /0016 -7606 (1985)96 <691 :MOSAAT>2 .0 Okal, E.A., Synolakis, C.E., Fryer, G.J., Heinrich, P., Bor- Journal of Geophysical Research, v. 89, p. 9171–9195, .CO;2 . rero, J.C., Ruscher, C., Arcas, D., Guille, G., and Rous- doi: 10 .1029 /JB089iB11p09171 . Melnick, D., Bookhagen, B., Echtler, H.P., Manfred, M.R., seau, D., 2002, A fi eld survey of the 1946 Aleutian tsu- Heuret, A., Conrad, C.P., Funiciello, F., Lallemand, S., and and Strecker, R., 2006, Coastal deformation and great nami in the far fi eld: Seismological Research Letters, Sandri, L., 2012, Relation between subduction mega- subduction earthquakes, Isa Santa Maria, Chile (37°S): v. 73, p. 490–503, doi: 10 .1785 /gssrl .73 .4 .490 . thrust earthquakes, trench sediment thickness and Geological Society of America Bulletin, v. 118, Okal, E.A., Plafker, G., Synolakis, C.E., and Borrero, J.C., upper plate strain: Geophysical Research Letters, v. 39, no. 11/12, p. 1463–1480, doi: 10 .1130 /B25865 .1 . 2003, Near-fi eld survey of the 1946 Aleutian tsunami L05304, doi: 10 .1029 /2011GL050712 . Miyazawa, M., and Mori, J., 2009, Test of Seismic Hazard on Unimak and Sanak Islands: Bulletin of the Seismo- Johnson, J.M., Tanioka, Y., Ruff, L.J., Satake, K., Kanamori, Map from 500 years of Recorded Intensity Data in logical Society of America, v. 93, p. 1226–1234, doi: 10 H., and Sykes, L.R., 1994, The 1957 great Aleutian Japan: Bulletin of the Seismological Society of Amer- .1785 /0120020198 . earthquake: Pure and Applied Geophysics, v. 142, ica, v. 99, p. 3140–3149, doi: 10 .1785 /0120080262 . Okal, E.A., Borrero, J.C., and Synolakis, C.E., 2004, The p. 3–28, doi: 10 .1007 /BF00875966 . Mochizuki, K., Yamada, T., Shinohara, M., Yamanaka, Y., earthquake and tsunami of 17 November 1865: Evi- Kanamori, H., 1970, Synthesis of long-period surface waves and Kanazawa, T., 2008, Weak interplate coupling by dence for far-fi eld tsunami hazard from Tonga: Geo- and its application to earthquake source studies: Kurile seamounts and repeating M ~ 7 earthquakes: Science, physical Journal International, v. 157, p. 164–174, doi: Islands Earthquake of October 13, 1963: Journal of v. 321, p. 1194–1197, doi: 10 .1126 /science .1160250 . 10 .1111 /j .1365 -246X .2004 .02177 .x . Geophysical Research, v. 75, p. 5011–5027, doi:10 Moore, G.F., Curray, J.R., Moore, D.G., and Karig, D.E., Okal, E.A., Borrero, J.C., and Synolakis, C.E., Evaluation of .1029 /JB075i026p05011 . 1980, Variations in geologic structure along the Sunda tsunami risk from regional earthquakes at Pisco, Peru: Kanamori, H., 1972, Tectonic implications of the 1944 fore arc, northeastern Indian Ocean, in Hayes D.E., Bulletin of the Seismological Society of America, Tonakai and the 1946 Nankaido earthquakes: Physics ed., The Tectonic and Geologic Evolution of Southeast v. 96, p. 1634–1648. of the Earth and Planetary Interiors, v. 5, p. 129–139, Asian Seas and Islands: American Geophysical Union Pacheco, J.F., and Sykes, L.R., 1992, Seismic moment cata- doi: 10 .1016 /0031 -9201 (72)90082 -9 . Geophysical Monograph Series. v. 23, p. 145–160. log of large shallow earthquakes, 1900 to 1989: Bul- Kanamori, H., 1976, Re-examination of the Earth’s free Moore, G.F., Bangs, N.L., Taira, A., Kuramoto, S., Pang- letin of the Seismological Society of America, v. 82, oscillations excited by the Kamchatka earthquake of born, E., Tobin, H.J., 2007, Three-dimensional splay p. 1306–1349. November 4, 1952: Physics of the Earth and Planetary fault geometry and implications for tsunami genera- Plafker, G., and Thatcher, W., 2008, Geological and geo- Interiors, v. 11, p. 216–226, doi:10 .1016 /0031 -9201 tion: Science, v. 318, p. 1128–1131. physical evaluation of the mechanisms of the great (76)90066 -2 . Moore, J.C., Chester, F.M., Plank, T.A., Polissar, P.J., and 1899 Yakutat Bay earthquakes, in Freymueller, J.T., Kanamori, H., 1977, The energy release in great earthquakes: Savage, H.M., 2013, The Décollement of the 2011 Haeussler, P.J., Wesson, R.L., and Ekström, G., eds., Journal of Geophysical Research, v. 82, p. 2981–2987, Great Tohoku Earthquake: Oceanographic Provenance Active Tectonics and Seismic Potential of Alaska: doi: 10 .1029 /JB082i020p02981 . and a Potential Model for Tsunami Earthquake Produc- American Geophysical Union Geophysical Mono- Kanamori, H., Rivera, L. and Lee, W.H.K., 2010. Historical tion: San Francisco, American Geophysical Union, Fall graph, v. 179, p. 215–236, doi: 10 .1029 /179GM12 . seismograms for unravelling a mysterious earthquake: 2013 Meeting, abstract T41F-01, http:// abstractsearch Polet, J., and Kanamori, H., 2009, Tsunami Earthquakes, in The 1907 Sumatra Earthquake: Geophysical Journal .agu .org /meetings /2013 /FM /sections /T /sessions /T41F Meyers, R.A., ed., Encyclopedia of Complexity and International, v. 183, p. 358–374, doi:10 .1111 /j .1365 /abstracts/T41F -01 .html. Systems Science: Springer-Verlag, p. 9577–9592. -246X .2010 .04731 .x . Moore, J.C., Plank, T.A., Chester, F.M., Polissar, P.J., and Polonia, A., Torelli, L., Brancolini, G., and Loreto, M.-F., Keating, B.H., Helsley, C.E., Wanink, M., and Walker, D., Savage, H.M., 2015, Sediment provenance and con- 2007, Tectonic accretion versus erosion along the 2011, Tsunami deposit research: Fidelity of the tsu- trols on slip propagation: Lessons learned from the southern Chile trench: Oblique subduction and margin nami record, ephemeral nature, tsunami deposits char- 2011 Tohoko and other earthquakes of the subduct- segmentation: Tectonics, v. 26, TC3005, doi: 10 .1029 acteristics, remobilization of sediment by later waves, ing NW pacifi c plate: Geosphere, v. 11, doi:10 .1130 /2006TC001983 . and boulder movements, in Mörner N.A., ed., The /GES01099 .1 (in press) . Quittmeyer, R.C., and Jacob, K.H., 1979, Historical and Tsunami Threat—Research and Technology: Intech, Moreno, M., Haberland, C., Oncken, O., Rietbrock, A., modern seismicity of Pakistan, Afghanistan, North- p. 389–422 (http://www .intechopen .com /books /the Angiboust, S., and Heidbach, O., 2014, Locking of western India, and Southeastern Iran: Bulletin of the -tsunami -threat -research-and -technology). the Chile subduction zone controlled by fl uid pressure Seismological Society of America, v. 69, p. 773–823.

264 Geosphere, April 2015

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/2/236/3333818/236.pdf by guest on 30 September 2021 Megathrust earthquakes and sediment subduction

Ruff, L.J., 1989, Do trench sediments affect great earth- sediment flux and mantle melting in subduction Toczko, S., and Expedition 343 and 343T Scientists, quake occurrence in subduction zones?: Pure and zones?: Trace element evidence from Aleutian arc 2013, Low coseismic shear stress on the Tohoku-Oki Applied Geophysics, v. 129, p. 263–282, doi:10 .1007 basalt, in Bebout, G.E., Scholl, D.W., Kirby, S.H., and megathrust determined from laboratory experiments: /BF00874629 . Pratt, J.P., eds., Subduction Top to Bottom: Washing- Science, v. 342, p. 1211–1214, doi: 10 .1126 /science Ryan, H., von Huene, R., Scholl, D.W., and Kirby, S, 2012: ton, D.C., American Geophysical Union, Geophysical .1243485 . Tsunami hazards to U.S. coasts from giant earthquakes Monograph Series, v. 96, p. 285–291. Utsu, T., 2002, A list of deadly earthquakes in the World: in Alaska Alaskan-Aleutian earthquakes: Eos (Trans- Singer, B.S., Jicha, B.R., Leeman, W.P., Rogers, N.W., 1500–2000, in Lee, W.K., Kanamori, H., Jennings, actions, American Geophysical Union), v. 93, no. 19, Thirlwall, M.F., Ryan, J., Kirsten, E., and Nicolaysen, P.C., and Kisslinger, C., eds., International Handbook p. 185–186. K.E., 2007, Along-strike trace element and isotopic of Earthquake and Engineering Seismology Part A: Satake, K., Hirata, K., Yamaki, S., and Tanioka, Y., 2006, Re- variation in Aleutian Island arc basalt: Subduction San Diego, Academic Press, p. 691–717. estimation of tsunami source of the 1952 Tokachi-oki melts sediments and dehydrates serpentine: Journal of Vallier, T.L., Scholl, D.W., Fisher, M.A., Bruns, T., Wilson, earthquake, Earth Planets Space, v. 58, p. 535–542. Geophysical Research, v. 112, B06206, doi:10 .1029 F.H., von Huene, R., and Stevenson, A.J., 1994, Scherwath, M., Kopp, H., Flueh, E.R., Henrys, S.A., Suther- /2006JB004897 . Geologic framework of the Aleutian arc, Alaska, in land, R., Stagpoole, V.M., Barker, D.H.N., Reyners, Singh, S.C., Hananto, N., Mukti, M., Robinson, D.P., Das, Plafker G., and Berg, H.C., eds., The Geology of M.E., Bassett, D.G., Planert, L., and Dannowski, A., S., Chauhan, A., Carton, H., Gratacos, B., Midnet, S., Alaska: The Geology of North America, v. G-1: Boul- 2010, Fore-arc deformation and underplating at the Djajadihardja, Y., and Harjono, H., 2011, Aseismic der, Colorado, The Geological Society of America, northern Hikurangi margin, New Zealand: Journal of zone and earthquake segmentation associated with a p. 367–388. Geophysical Research, v. 115, B06408, doi:10 .1029 deep subducted seamount in Sumatra: Nature Geo- von Huene, R., and Ranero, C.R., 2003, Subduction erosion /2009JB006645 . science, v. 4, p. 308–311, doi: 10 .1038 /ngeo1119 . and basal friction along the sediment starved conver- Scholl, D.W., 1974, Sedimentary sequences in North Pacifi c Smith, G.L., McNeill, L.C., Wang, K., He, J., and Henstock, gent margin off Antofagasta, Chile: Journal of Geo- Trenches, in Burk, C.A. and Drake, C., eds., The Geol- T.J., 2013, Thermal structure and megathrust seismo- physical Research, v. 108, B2, p. 2079, doi:10 .1029 ogy of Continental Margins: New York, Springer- genic potential of the Makran subduction zone: Geo- /2001JB001569. Verlag , p. 493–504. physical Research Letters, v. 40, 1–6, doi: 10 .1002 /grl von Huene, R., and Scholl, D.W., 1991, Observations at con- Scholl, D.W., and von Huene, R., 2007, Crustal recycling at .50374, 201 . vergent margins concerning sediment subduction, sub- modern subduction zones applied to the past—Issues Sparkes, R., Tilmann, F., Hovius, N., and Hillier, J., 2010, duction erosion, and the growth of continental crust: of growth and preservation of continental basement, Subducted seafloor relief stops rupture in South Reviews of Geophysics, v. 29, p. 279–316, doi: 10 .1029 mantle geochemistry, and supercontinent reconstruc- American great earthquakes: Implications for rupture /91RG00969 . tion, in Hatcher, R.D., Jr., Carlson, M.P., McBride, behavior in the 2010 Maule, Chile earthquake: Earth von Huene, R., Klaeschen, D., Cropp, D.B., and Miller, J., J.H., and Martíne-Catalán, J.R., eds., The 4D Frame- and Planetary Science Letters, v. 298, p. 89–94, doi:10 1994, Tectonic structure across the accretionary and work of Continental Crust: Geological Society of .1016 /j .epsl .2010 .07 .029 . erosional parts of the Japan Trench margin: Journal of America Memoir 200, p. 9–32. Steckler, M.S., Akhter, S.H., and Seeber, L., 2008, Collision Geophysics, v. 99, no. B11, p. 22,349–22,361, doi:10 Scholl, D.W., von Huene, R., Vallier, T.L., and Howell, of the Ganges–Brahmaputra Delta with the Burma Arc: .1029 /94JB01198 . D.G., 1980, Sedimentary masses and concepts about Implications for earthquake hazard: Earth and Plane- von Huene, R., Miller, J. J., and Weinrebe, W., 2012, Sub- tectonic processes at underthrust ocean margins: Geol- tary Science Letters, v. 273, p. 367–378, doi:10 .1016 ducting plate geology in three great earthquakes rup- ogy, v. 8, p. 564–568, doi:10 .1130 /0091 -7613 (1980)8 /j .epsl.2008 .07 .009 . tures of the western Alaska margin, Kodiak to Unimak: <564:SMACAT>2 .0 .CO;2 . Strasser, M., Kölling, M., dos Santos Ferreira, C., Fink, Geosphere, v. 8, no. 3, doi: 10 .1130 /GES00715 .1 . Scholl, D.W., Vallier, T.L., and Stevenson, A.J., 1983, Arc, H.G., Fujiwara, T., Henkel, S., Ikehara, K., Kanamatsu, von Huene, R., Kirby, S., Miller, J., and Dartnell, P., 2014, fore-arc, and trench sedimentation and tectonics: T., Kawamura, K., Kodaira, S., Römer, M., Wefer, G., The destructive 1946 Unimak near-field tsunami: Amlia corridor of the Aleutian Ridge, in Watkins, J. and the R/V Sonne Cruise SO219A and JAMSTEC New evidence for a submarine slide source from and Drake, C.L., eds., Hedberg Symposium Volume on Cruise MR12-E01 scientists, 2013, A slump in the re processed marine geophysical data: Geophysical Continental Margin Processes: American Association trench: Tracking the impact of the 2011 Tohoku-Oki Research Letters, v. 41, no. 19, p. 6811–6818, doi: 10 of Petroleum Geologists Memoir 34, p. 413–439. earthquake: Geology, v. 41, no. 8, p. 935–938, doi: 10 .1002 /2014GL061759 . Scholl, D.W., Vallier, T.L., and Stevenson, A.J., 1987, Geo- .1130 /G34477 .1 . Wang, K., and Bilek, S.L., 2011, Do subducting seamounts logic evolution and petroleum geology of the Aleutian Suarez, G., and Albini, P., 2009, Evidence for great tsunami- generate or stop large earthquakes?: Geology, v. 39, Ridge, in Scholl, D.W., Grantz, A., and Vedder, J.G., genic earthquakes (Mw8.6) along the Mexican subduc- no. 9, p. 819–822, doi: 10 .1130 /G31856 .1 . eds., Geology and Resource Potential of the Continental tion zone: Bulletin of the Seismological Society of Amer- Wang, K., and Bilek, S.L., 2014, Fault creep caused by Margin of Western North America and adjacent ocean ica, v. 99, no. 2A, p. 892–896, doi: 10 .1785 /0120080201 . subduction of rough seafl oor relief: Tectonophysics, basins—Beaufort Sea to Baja California: Houston, Tanioka, Y., and Satake, K., 2001, Coseismic slip distribu- v. 610, p. 1–24. Texas, Circum-Pacifi c Council for Energy and Mineral tion of the 1946 Nankai earthquake and aseismic slips Wang, S.C., 1981, Tectonic implications of global seismicity Resources, Earth Science Series, v. 6, p. 124–155. caused by the earthquake: Earth, Planets and Space, studies [Ph.D. thesis]: Stanford, California, Stanford Scholl, D.W., Kirby, S.H., von Huene, R., and Wells, R., v. 53, p. 235–241, doi: 10 .1186 /BF03352380 . University. 2011, Exploring a link between great and giant mega- Taymaz, T., Jackson, J., and Westaway, R., 1990, Earthquake Westbrook, G.K., Ladd, J.W., Bruhl, P., Bangs, N., and Tiley, thrust earthquakes and relative thickness of sediment mechanisms in the Hellenic Trench near Crete: Geo- G.J., 1988, Cross section of an accretionary wedge: and eroded debris in the subduction channel to rough- physical Journal International, v. 102, no. 3, p. 695– Barbados Ridge complex: Geology, v. 16, p. 631–635, ness of subducted relief: San Francisco, California, 731, doi: 10 .1111 /j .1365 -246X .1990 .tb04590 .x . doi: 10 .1130 /0091 -7613 (1988)016 <0631 :CSOAAW>2 Fall Meeting, American Geophysical Union, abstract Thiebot, E., and Gutscher, M.-A., 2006, The Gibraltar Arc .3 .CO;2 . T14B-01. seismogenic zone (part 1): Constraints on a shallow Wu, F., and Kanamori, H., 1973, Source mechanism of Feb- Schurr, B., Asch, G., Hainz, S., Bedford, J., Hoechner, A., east dipping fault plane source for the 1755 Lisbon ruary 4, 1965, Rat Island earthquake: Journal of Geo- Palo, M., Wang, R., Moreno, M., Bartsch, M., Zhang, earthquake provided by seismic data, gravity and ther- physical Research, v. 78, p. 6082–6092, doi: 10 .1029 Y., Oncken, O., Tilmann, F., Dahm, T., Victor, P., Bar- mal modeling: Tectonophysics, v. 426, p. 135–152. /JB078i026p06082 . rientos, S., and Vilotte, J.-P., 2014, Gradual unlocking Trehu, A.M., Blakely, R.J., and Williams, M.C., 2012, Sub- Zachariasen, J., Sieh, K., Taylor, F.W., Edwards, R.L., and of plate boundary controlled initiation of the 2014 ducted seamounts and recent earthquakes beneath the Hatoro, W.S., 1999, Submergence and uplift associated Iquique earthquake: Nature, v. 512, p. 299–302, doi: central Cascadia forearc: Geology, v. 40, no. 2, p. 103– with the giant 1833 Sumatran subduction earthquake: 101038 /nature13681 . 106, doi: 10 .1130 /G32460 .1 . Evidence from coral microatolls: Journal of Geo- Singer, B.S., Leeman, W.P., Thirlwall, M.F., and Rogers, Ujiie, K., Tanaka, H., Saito, T., Tsutsumi, A., Mori, J. J., physical Research, v. 104, p. 895–919, doi:10 .1029 N.W., 1996, Does fracture zone subduction increase Kameda, J., Brodsky, E. E., Chester, F. M., Eguchi, N., /1998JB900050.

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