The Japan Tohoku Tsunami of March 11, 2011

EERI Special Earthquake Report — November 2011

Learning from Earthquakes The Japan Tohoku Tsunami of March 11, 2011

This report summarizes the field Fukushima Prefecture because high US$300 billion, making it the most reconnaissance observations of radiation levels from the damaged costly natural disaster of all time the EERI team led by Lori Dengler, Fukushima Dai-Ichi nuclear power (VoA, 2011). Humboldt State University, and plant have prevented field teams from There is no question that the Megumi Sugimoto, Earthquake working there. Much of the informa- tsunami was responsible for the Research Institute, University of tion in this preliminary report may huge scale of the catastrophe. A Tokyo, who visited the hardest-hit change as more data and reports are preliminary report released in April areas of Miyagi and Iwate Prefec- released. 2011 summarizing autopsy results tures in April and May 2011. It also The publication of this report is showed 92% of the victims died as includes observations from two In- supported by EERI under National a result of drowning (SEEDS Asia, ternational Tsunami Survey Teams Science Foundation grant #CMMI- 2011). If it is assumed that most of (ITSTs) deployed to study tsunami 1142058. the missing were washed to sea or deposits. The first team visited the deposited in accessible areas by Sendai area in May and was made Introduction the tsunami, the tsunami casualty up of Kazuhisa Goto, Chiba Insti- contribution increases to over 96%. tute of Technology; Shigehiro Fuji- The Mw 9.0 earthquake produced no, University of Tsukuba; Witek a great tsunami that killed nearly This report summarizes field recon- Szczuciski, Adam Mickiewicz Uni- 20,000 people and wreaked destruc- naissance efforts and reports, em- versity, Poland; Yuichi Nishimura, tion along the Tohoku (eastern) phasizing factors that exacerbated Hokkaido University; Daisuke Su- coast of Japan. The tsunami traveled impacts; it considers factors that gawara, Tohoku University; Eko across the Pacific basin, triggering promoted or hindered successful Yulianto, Indonesian Institute of evacuations and causing some dam- evacuation. Refer to the compan- Science; Rob Witter, Oregon De- age in many countries; one person ion LFE report, The Japan Tohoku partment of Geology and Mineral was killed in California. The earth- Tsunami of March 11, 2011: Effects Industries; Catherine Chagué-Goff, quake struck at 2:46 University of New South Wales, p.m. local time in Australia; Masaki Yamada, Uni- Japan, and the shak- versity of Tsukuba; Dave Tappin, ing lasted for about British Geological Survey; Bruce three minutes (USGS, Richmond, U.S. Geological Survey 2011). Located on (USGS); and Bruce Jaffe, USGS. the subduction zone In August, Rick Wilson, California interface off the coast Geological Survey; Robert Weiss, of the Tohoku Region, Virginia Tech University; James it ruptured a 300 km- Goff, University of New South long fault extending Wales, Australia; and Yong Wei, from near the south- NOAA Pacific Marine Environmen- ern end of Ibaraki tal Laboratory, joined Nishimara, Prefecture to central Sugawara, Goto, Fujino and Jaffe Iwate Prefecture from the first ITST, and revisited (Figure 1). It was the Sendai as well as the Kuji and the largest magnitude Miyako areas in Iwate Prefecture. earthquake recorded Also included here is information in Japan in historic compiled by Masahiro Yamamoto time, and the com- for UNESCO’s International Ocean- bined impacts of the ographic Commission (IOC) and earthquake and tsu- material from other field and gov- nami left 15,749 dead Figure 1. Location map of the March 11 main shock ernment reports, as noted in the and 3,962 missing and March 9 foreshock. Outlined area shows the ap- text. This report focuses on the (IOC/UNESCO, 2011). proximate source dimensions (after Kanamori, 2011). tsunami impacts in Miyagi and Associated economic The three shaded prefectures, Iwate, Miyagi, and Iwate Prefectures; it does not cover losses may approach Fukushima, were the most affected by the tsunami (USGS, 2011).

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yellow area) and was characterized by normal rupture velocities and moderate slip (Kanamori, 2011). It produced strong ground shaking in much of the Tohoku region. Af- ter about 75 seconds, the rupture moved updip of the hypocenter into the much weaker rocks of the megathrust accretionary prism. This rupture (Figure 2, pink area) was characteristic of a “tsunami earthquake”: relatively slow rupture velocity with weak ground shaking and very large slip. Some models (Ozawa et al., 2011; Pollitz et al., 2011) suggest the peak slip may have exceeded 50 m in some areas of this zone. This second phase of the earthquake likely accounted for the majority of the tsunami gen- Figure 2. Source characteristics of the March 11 earthquake. Left: March 11 eration. epicenter and rupture area. Also shown is the aftershock region and the source areas of previous historical earthquake (adapted from Kanamori, 2011). Elastic rebound associated with Right: simplified cartoon of the rupture sequence and tsunami generation. the rupture produced permanent Yellow zone shows the initial rupture downdip of the epicenter (2). After about changes in the land surface. 75 seconds, the rupture migrated updip of the epicenter (pink zone). The Japan’s dense network of GPS second phase of rupture propagated slowly and produced very large slip (3). instruments documented both hori-

on Structures, by the ASCE/EERI team, for an overview of impacts on the built environment in Japan.

The Tsunami Source The March 11 earthquake ruptured an area roughly 300 km long and 200 km wide on the boundary between the subducting Pacific plate and the overriding North American plate (USGS, 2011). This region of Japan has a well-documented his- tory of earthquakes, including at least 32 ranging from 7 to mid-magnitude 8 since 1900 (NGDC, 2011). The Tohoku sequence began on March 9 with a magnitude 7.3 earthquake that was widely felt. The Japan Meteorological Agency (JMA) issued a tsunami warning for the Miyagi and Iwate coasts, projecting water heights of 3 m. Tide gauges recorded a 0.5-m tsunami in Ofu- nato, but no damage was reported. Figure 3. Left: vertical displacement field of the Tohoku earthquake from GPS The main shock initiated about 43 measurements provided by the Geospatial Institute of Japan (2011). All coast- km WSW of the March 9 foreshock. al areas from Iwate to Chiba subsided during the earthquake. In this prelimi- The initial zone of rupture was down- nary map, the peak vertical displacement (1.2 m) was in the Oshika district of dip of the hypocenter (Figure 2, Miyagi Prefecture near Onagawa City. Right: Google Earth images taken before and after the earthquake show the impacts of subsidence at Ishinomaki.

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Figure 4. Mea- Miyagi prefectures. On the broad sured tsunami plain that characterizes the coast of water heights as Miyagi Prefecture south of Sendai, a function of peak water heights averaged 8-10 latitude from m. There were significant tsunami post-tsunami impacts as far south as Chiba Pre- surveys, as fecture. compiled by the Table 1 summarizes the character- NGDC (2011). istics of the tsunami at selected lo- The gap in mea- cations along the Tohoku coast, with surement in Fu- data from IOC/UNESCO bulletins kushima Pre- (2011), the NGDC, and Mori et al., fecture is due to 2011. Although peak water heights access restric- are higher in Iwate and northern tions associated Miyagi Prefectures, the inundation with the Fuku- areas are smaller, as the coast is shima Dai-ichi rugged and inundation is limited to nuclear power the low areas near river mouths. plant (shown by In most coastal communities, the the x). zontal and vertical changes (Gra- Table 1. Tsunami Characteristics and Impacts at Selected Locations penthin and Freymueller, 2011). There was subsidence along the Tohoku coast after the earthquake, with some areas dropping down more than a meter (Figure 3a). As a result, some low-lying areas are now below sea level (Figure 3b) and parts of the region are more susceptible to tsunami inundation. The Tsunami in Japan Over 5,400 water level measurements have been collected along 2,000 km of the Japanese coastline as of the time of this report (Tohoku Earthquake Tsunami Joint Survey Group, 2011), making this the largest collection of tsunami height measurements for a single tsunami event. The data have been summarized in reports of the IOC/ UNESCO intergovernmental commission on tsunamis (2011) and have also been posted at NOAA’s National Geophysical Data Center (NGDC) Tsunami Data Base (2011). Figure 4 shows the NGDC water height compilation. The highest water levels (38.9 m) at Aneyoshi Bay south of Miyako City in Iwate Prefecture were the maximum ever measured in a Japan tsunami. Wat- er heights were close to or exceeded 20 m in most populated coastal communities in Iwate and northern * Totals included in the Sendai numbers (source: summarized from IOC/UNESCO bulletins).

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the Kesen River in southern Iwate Prefecture. The tsunami reached heights of 19 meters, reaching the fifth floor elevation in much of the central part of the city, destroying all structures in this area except for two large reinforced concrete buildings: the seven-story Capital Hotel and the adjacent tsunami evacuation building (Figure 5). The evacuation building featured a unique design, with exterior stairs leading up to a series of concrete seat plat- forms. The structure survived even though water heights exceeded the design tsunami, and only the two or three uppermost rows were above the water height and provided life Tsunami evacuation building, Rikuzentakata. Measured water levels Figure 5. safety. were 19 m, shown by the yellow arrow (photos: L. Dengler). Rikuzentakata was typical of many dense city and town centers were sanriku Disaster Management Build- cities in the Tohoku region where very vulnerable, though much of the ing shows the structure fully engulfed forests of pine trees had been town or city land area was outside at 3:35 p.m., 48 minutes after the planted along the coast to provide of the inundation zone on the hill earthquake. Analysis of the volumi- protection from both storm waves slopes and farther inland. Commu- nous set of photographs and video and tsunami surges. The trees in nities on the low-lying areas of the imagery taken of the tsunami, and Rikuzentakata were mature, with Sendai plain, such as Wakabayashi more detailed study of tide gauge diameters of 25 to 40 cm. With one and Yuriage in Natori City, had little recordings, should provide better notable exception, all of the esti- higher ground, and a larger percen- constraints on the time of arrival. mated 70,000 trees on the Rikuzen- takata coast were destroyed by the tage of these communities was The impact of the tsunami on popu- tsunami (Figure 6). The one surviv- flooded. lated areas of the Tohoku coast was ing tree, called “the tree of hope,” The amount of time between the strongly dependent upon the local has become a national symbol of earthquake and the arrival of signif- setting. There are factors unique to resilience, featured in songs and icant surges varied along the Toho- each setting, and the following brief poems. Unfortunately, the tree is ku coast. The tide gauges show the descriptions illustrate many of them. showing signs of stress caused by first tsunami wave arriving 36 min- Rikuzentakata City (population the high levels of salt in the soil and utes after the earthquake at Hachi- 23,000) is located at the mouth of may not survive. nohe and 29 minutes post-quake in Okai Town in Chiba Prefecture. A webcam at the Sendai Airport in Natori City showed water arriving at 3:37 p.m., and the generators ceased to function at 4 p.m. This agrees with a series of time-stamped photographs in the Yuriage area of Natori City (see Figure 17) that show peak flooding at 4:11 p.m. Generators at the Fukushima Dai- Ichi Nuclear Plant stopped at 3:41 p.m., 55 minutes after the earthquake. Eyewitnesses in Northern Figure 6. Left: the sole surviving pine tree out of a forest of 70,000 trees Miyagi and Southern Iwate Prefec- planted to protect the Rikuzentakata coast from tsunamis and storm surge. tures generally reported 25-30 min- The towers on the left are part of the tsunami gates built to prevent tsunami utes between the earthquake and surges from flooding the Kesen River. Right: the remains of the pine forest. the tsunami. A time-stamped photo Mature pine tree trunks were 20-40 cm in diameter and typically snapped 1-2 taken from the top of the Minami- m above the ground (photos: L. Dengler).

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Kesennuma City (population 73,000) is located at the head of Kesennuma Bay and, before the tsunami, was a thriving commercial fishing port and the center of Jap- an’s shark fin trade. Many of the large packing plants along the harbor suffered damage due to lique- faction. Dozens of boats were torn from moorings, some of which were deposited inland, and others sank in the bay (Figure 7). The long-term ecological impacts of the fuel and other hazardous materials released Figure 7. The tsunami deposited boats in many areas of Kesennuma City and in the bay are difficult to predict. left others to burn or sink in Kesennuma Bay (photos: L. Dengler). Minamisanriku Town (population 17,000) had gained an international reputation for tsunami preparedness before the tsunami and was a featured field trip stop for tsunami experts. The three rivers flowing through the town featured tsunami gates that could be shut in 15 minutes to keep the tsunami from pen- etrating inland up the river channels. Figure 8 is an approximation of the inundation zone, showing that the tsunami extended nearly 3 km up the Hachiman River and nearly 2 km up the adjacent river valleys. Offi- cials successfully lowered the gates on March 11 (Figure 9), but the adjacent sea walls were overtopped and undermined, and did not prevent the city from being flooded. An estimated 31 of 80 designated tsunami evacuation buildings were Figure 8. The approximate inundation zone in Minimisanriku Town. The destroyed (Japan Times, 2011). At tsunami surges destroyed the town center and went up the narrow Hachiman the Disaster Management Center River (center) and the Sakura River (on left) and the Oretate River (on right). (Figure 10), more than 30 officials, Black arrow is 2 km long. (A) marks the location of the disaster management including the town mayor, gathered building shown in Figure 10 and (B) shows the tsunami evacuation building in on the rooftop during the tsunami Figure 26. The gates shown in Figure 9 are just to the right of B. The inunda- event, and twenty died (Asahi Shim- tion area shown here (and in Figures 12 and 15) is based on Google earth bun, 2011). Miki Ando, a municipal imagery and may change when data from field teams is included. official responsible for broadcasting emergency information to the public, remained at her post on the second floor of the building and continued broadcasting announce- ments; she was credited by many for saving their lives as they heeded her warnings to get to higher ground, but she did not survive. Figure 9. Left: gates on the Hachiman River, Minamisanriku, in April 2010 in Ishinomaki City (population the up position (photo courtesy of J. Bourgeois). Right: the same gates in May 164,000) is one of the largest ports 2011 after the tsunami. They closed before the tsunami struck, but failure of north of Sendai and is a center of the sea walls negated their effectiveness (photo: L. Dengler).

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Figure 11. The inundation level in this area of Ishinomaki City was at the base of the second floor, but large objects in the water such as the boat shown caused extensive damage above the flow depth (photo: L. Dengler). Figure 10. The disaster management headquarters for ure 12). Parts of three-story building and the upper the town of Minamisanriku. About 30 officials gathered the city south of floors were above the inundation on the upper floor and roof on March 11. The tsunami the Tona Canal zone; however, it was not used completely flooded the structure and only 11 people sur- had no direct for vertical evacuation, perhaps vived. Note the location of high ground in the background access to high because the stairways were inside (photo: L. Dengler). ground. One the building and would not have of the designated evacuation sites been accessible if the building were the rice trade. The main port facilities (Figure 13) was the multipurpose closed. An estimated 200 people are located to the southwest of the room adjacent to an elementary gathered in the multipurpose room population center and experienced school. The elementary school was a after the earthquake, but it did not water heights in the 4.5 to 5 meter range (PARI, 2011). Warehouses and reinforced concrete buildings suffered some damage but did not collapse. The port was nearly fully operational in May. Much of the rest of the city was very badly damaged and, because of the large exposed population, had the highest casualty total of any community in the Tohoku region. The large amount of debris in the water, including boats, caused some areas to be damaged that were above the inundation level (Figure 11). Higashimatsushima City (population 34,000) is located in the tran- sitional zone between the much steeper terrain to the north and the broad, low-lying Sendai plain to the south. This city was particularly vulnerable, as tsunami surges attacked it from four different sources: the Figure 12. Approximate inundation area in the west area of Higashimatsushi- coast, the Naruse River, the Tona ma City. This region was particularly vulnerable because the tsunami attacked Canal, and Matsushima Bay (Fig- from several directions. The star marks the location of the evacuation building shown in Figure 13. Note its proximity to higher ground on the hillside.

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Figure 14. Tsunami evacuation route signs in Matsu- shima Town (photo: L. Dengler).

an easy visual a much larger areal extent was guide (Figure 14). inundated (see Table 1). Much of Figure 13. The multipurpose room of the Higashimatsu- the inundation zone was agricultural shima elementary school, where 200 people gathered Natori City and the population density was low, after the earthquake. The site was flooded to the base of (population but there were two notable excep- the windows and most of the evacuees did not survive. 73,000), to the tions in the city limits: the Sendai The floor was used as morgue after the tsunami (photo: south of Sendai, Airport area and Yuriage, close to L. Dengler). is situated simi- larly to other towns and cities on the the Natori River. provide protection as the water Sendai plain. Landward of the coastal Located within 800 m of the coast, level reached the base of the win- dunes and sea walls, the land eleva- most of Yuriage was inundated. Like dows, and only a few people were tion is close to sea level for more than Higashimatsushima, Yuriage was able to get to safety on the ledge 4 km. Once the walls were over- attacked from several directions: next to the windows. This site was topped, the tsunami, unconfined to the coast, the river, and a canal that located at the base of a hill where river valleys, spread out over the land cut off the most exposed area of the everyone could have reached high surface (Figure15). Although the peak community from ready access to ground had they walked a few more water heights on the Sendai plain higher ground (Figure 16), and few minutes. One family of survivors were less than those farther north, structures exceeded three stories lived close to the evacuation site, but they had only recently moved to the area and weren’t aware of the designated building. Instead, they headed up the hillside behind their house after the earthquake and were able to see the waves approaching and to move up the hill when it became clear that the tsunami was very large. Matsushima Town (population 4,000) overlooks Matsushima Bay and is considered to have one of Japan’s most famous views. The bay protected the town from the brunt of the tsunami, and water heights reached only 2.5 m, with flooding extending into the ground floors of buildings near the water- front. Because of the large tourist Figure 15. Approximate inundation area in Sendai, Natori, and Iwanuma population, the town has numerous Cities. Pins mark the locations of Wakabayashi, Yuriage, and the Sendai tsunami evacuation route signs, Airport, discussed in the text. The tsunami deposits transect is close to the some painted on the sidewalk for black arrow where the tsunami penetrated about 5 km.

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This school, like many other evacuation sites in the Tohoku area, was not equipped to serve the needs of people stranded for many days. Neither food nor water was stored on the premises, nor were blankets or bedding; there were no sanitary facilities and no access to first aid or emergency medical care. After the earthquake, winter temperatures were close to 0° C in much of the Tohoku region. Some elderly and Figure 16. View from the top of the Yuriage memorial hill shown in Figure 15 injured tsunami survivors succumbed (photo: L. Dengler). to the difficult conditions after ex- in elevation. The junior high and access by students, staff, and com- tended time at such evacuation sites. elementary schools had been des- munity members. Sendai Airport served as a vertical ignated as vertical evacuation sites. After the tsunami, the gymnasium at evacuation site for passengers, Figure 17A shows the elementary the elementary school was cleaned staff, and nearby neighbors (Figure school with several hundred people and became a “Memory Hall.” Mem- 18). Although a security guard told assembled on the roof at the peak bers of the Japanese Civil Defense employees that a tsunami was ex- of inundation about an hour and 25 Force, who were first to enter the re- pected within 30 minutes, many be- minutes after the earthquake. Many gions after the disaster, collected pho- lieved there was no tsunami hazard schools like the Yuriage Elementary tographs and other surviving items at the site, although it is located School were designed with external from the surrounding neighborhood, within the mapped tsunami inunda- stairways (Figure 17B) for easy and volunteers organized them on tion zone. walls and The earthquake caused nonstruc- stands by tural damage at the airport, and, ini- location tially, security personnel attempted for sur- to assign people to floors, with those vivors to on the first floor not allowed on the claim and upper floors. It took two days before friends helicopters evacuated stranded and rel- passengers and neighborhood resi- atives dents, and at least some of the staff to view walked out of the inundation zone (Figure through standing water more than 17D). half a meter deep in some places.

Figure 17. The Yuriage Elementary School evacuation site. Clockwise from upper left: A) photo taken at 4:11 p.m. during the peak of inundation (photo from the Memory Hall); B) detail of the exterior stairs; C) classroom that was used as a sleeping place Figure 18. View out the third floor windows of the for evacuees; D) the Memory Hall in the elementary gymnasium Sendai Airport during the tsunami (photo from (photos: L. Dengler). Sendai Airport display).

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earlier deposits (Figure 19). Arche- ologists studying early human habit- ation on the Sendai plain have excavated a trench about 4 km inland of Arahama and 10 km north of the Airport. That trench shows a similar stratigraphy to the gouge cores. A large deposit dated to about 150 BCE may have been responsible for a temporary hiatus in rice cultivation in the region (Wilson, 2011). Con- sidering the tsunamis in historic time, the paleotsunami deposits, and an older tsunami deposit found in some locales dating back about Figure 19. Wall of excavated trench from the line north of the Sendai Airport. 3,000 years before the present, the Rectangular markers on right show locations where sediment samples were average recurrence of great tsuna- collected for further analysis (left photo: B. Jaffe; right photo: R. Wilson). mis on the Sendai plain appears to be on the order of 1,000 years (Min- Tsunami Deposits inland than the 2011 tsunami. The oura et al., 2001; Sawai et al., 2008). sedimentary evidence of the 2011 Two International Tsunami Survey tsunami was complicated by liquefac- Teams studied tsunami deposits on The Tsunami in the Pacific tion of some coastal-plain sediment Basin the Sendai plain. The first team during the earthquake and an exten- (Jaffe et al., 2011; Chagué-Goff et sive canal system that affected the The earthquake generated a tsunami al., 2011; Sugawara et al., 2011) movement of the tsunami waves and that affected the entire Pacific basin visited the area in May 2011 and the sediment they carried. (Figure 20). Tsunami warnings and made careful observations along a advisories were issued by the Pacif- The second team (Wilson, 2011) visit- line just north of the Sendai Airport ic Tsunami Warning Center (PTWC), ed the area in August and examined in Natori City (near the arrow in the West Coast Alaska Tsunami the deposits in the vicinity of the first Figure 15). They measured water Warning Center (WCATWC), and team’s line to see how they had levels, flow directions, topography, other national warning centers. The changed in the intervening four sediment thickness, grain size and largest water heights outside of Ja- months. To identify other possible pa- sedimentary structures, and col- pan were recorded in Crescent City, leotsunamis, they also took a number lected sediment samples for other California (2.49 m recorded on a of gouge core samples along the line analyses (Figure 19) to examine tide gauge, 3 m from eye witness that the May team studied. The cores how the tsunami characteristics accounts). Two other tide gauges showed several pre-2011 sand layers varied with tsunami speed and flow on the U.S. West Coast recorded interpreted as possible tsunami can- depth, topography, distance from heights in excess of 2 m. Similar didates, including the Jogan and two the coast, urban and rural settings, water heights were recorded at subsidence, and other aspects of the landscape. New sand deposits >0.5 cm thick were observed up to 2.8 km inland. The team also identified paleotsunami deposits as far inland as 3 km that were likely deposited by the 869 CE Jogan tsunami, an event (described by Abe et al., 1990) that has attracted considerable interest in the past decade from both paleo- seismologists and modelers (Min- oura, 2001; Satake et al., 2008; Sawai, 2008; Sawai et al., 2008; Figure 20. Left: computed maximum tsunami amplitudes throughout the Namegaya et al., 2010). At this Pacific (from NOAA PMEL). Note higher amplitude peak directed to northern location, the Jogan event apparent- California and southern Oregon. Right: tsunami travel times and measured ly extended at least 200 m farther water heights (NGDC, 2011).

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Table 2. Tohoku tsunami heights exceeding 2 meters outside of Japan mouth of the Klamath River to photograph the tsunami; all were swept into the water, but two man- aged to get back to land. The body of the third was recovered three weeks later near the mouth of the Columbia River in Oregon, about 500 km to the north. Other people were swept into the water in the Port Orford and Gold Beach areas of Oregon and at Ocean Beach in southern California, but were rescued. The impacts on the West Coast of the U.S. were reduced by the ambient tidal conditions. In California and Oregon, the strongest tsunami surges coincided with a low neap tide and ambient water levels close to zero. The highest absolute water levels in the Crescent City area coincided with the highest tide, nearly 24 hours after the onset of Source: NGDC, 2011; data in bold from tide gauge recordings the tsunami when the tide was 2 m and the tsunami still had amplitudes four locations in Chile as well as in Maui and Oahu. At the Keehi Lagoon over 1 m. Had the largest surges the Galapagos Islands and Maui, marina on Oahu, floating docks broke coincided with high tides, there Hawaii (Table 2). loose and sank an estimated 25 would have been significant on- The tsunami caused damage on boats and damaged 200 others. Eco- land flooding at a number of West Midway Island and in California, Or- nomic losses in Hawaii were exac- Coast locations. The impacts were egon, and Hawaii, portions of which erbated by the cancellations of large also reduced by the effectiveness were declared federal disaster areas. numbers of Japanese tourists. of tsunami warning systems that The California Geological Survey Brookings Harbor in southern Oregon allowed commercial fishermen in activated a post-tsunami clearing- was badly damaged by the strong both Crescent City and Brookings house after the event and organized currents caused by the tsunami. Docks to move most of the commercial teams of scientists and engineers broke loose and several boats sank, fleet out of the harbors before the that examined or received reports causing an estimated $6.7 million in tsunami arrived. about every port and harbor facility damage. Damage to docks was also In South America the largest am- in the state. Two harbors (Santa reported in Depoe Bay and Coos Bay. plitude tsunami waves coincided Cruz and Crescent City) had major The only life lost outside of Japan with high tide. Damage was report- damage (Figure 21), and less seri- was in northern California, where ed in Chile and the Galapagos Is- ous impacts were observed at 22 three young men had gone to the lands. At Tongoy, in Chile’s Co- other locations in California. All the damage was attributed to strong currents, which were measured at speeds of up to 10 knots (Wilson et al., 2011). Losses in California were estimated at over $50 million. In Hawaii, the most serious damage was at Kealakekua Bay and in Kai- lua-Kona, where one house floated to sea and 26 were damaged. A number of hotels were damaged, including the landmark Kona Village Resort, which remains closed to Figure 21. Crescent City, California. Left: the inner boat basin during the date. Damage was also reported on tsunami. Right: damaged docks and boats (photos: R. Hiser).

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Figure 23. Evacuation and inundation map of Unosumai Town near Kamaishi. The orange line shows the evacuation area, the red line is the approximate inundation from the 1896 and 1933 tsunamis, and the blue line is the 2011 inundation (source: Mainichi Newspaper).

1) Hazard assess- is possible to identify conditions ments that un- that constrain or permit such derestimated “overslip.” the size of the The rich historic record of major earthquake tsunamis in Japan and sophisti- and tsunami. cated numerical modeling had The basis for produced consensus about the evacuation relation between earthquake planning is an source characteristics and the accurate as- expected tsunami size. In par- Figure 22. Historic tsunami water heights along the To- sessment of ticular, the tsunami events from hoku coast. Water heights from the 1896 Meiji tsunami hazard, and 1896, 1933, and 1960 (Figure 22) (red), 1933 Showa tsunami (yellow), and 1960 Chilean Japanese sci- had provided a basis for tsunami tsunami (green) are superimposed on the 2011 water entists and gov- planning. Consensus about the levels (data from NGDC). ernment agen- hazard based on these relatively cies have made detailed assess- recent historic events informed quimbo region, strong currents dis- ments of the capability of identified such hazard reduction efforts as placed concrete blocks and dam- fault systems to produce significant seawall construction, evacuation aged the shellfish industry (Le- earthquakes. An earthquake hazard zone mapping, designation of grande, 2011); in the Galapagos on map published in 2008 (Headquar- evacuation sites, the warning sys- Santa Cruz Island, a hotel and the ters for Earthquake Research Pro- tem, and outreach and education Biomar Building at the Charles Dar- motion) identified a number of pos- efforts. Potentially larger events win Research Station were serious- sible sources of earthquakes in the had been recognized in much ly damaged (Lopez, 2011). Tohoku region likely to produce earlier historical records by paleo- earthquakes in the magnitude 7-8.2 seismologists (Abe et al., 1990; Recommendations for range. The Tohoku earthquake was Minoura et al., 2001; Sawai et not only larger than most of the Further Research al., 2008) but they had not been scientific community expected, but incorporated into hazard assess- Failure to evacuate was the primary it also may have produced the larg- ment efforts. The Tohoku tsunami cause of the high casualty rate in est fault slip ever observed. The raises fundamental questions the Tohoku tsunami. A number of earthquake has prompted a recon- about hazard assessment, the factors, each discussed below, sideration of why the magnitude inclusion of paleoseismic data in contributed to the evacuation fail- was unexpected (Stein and Okal, the assessment, and planning for ures and should be studied in more 2011), of the relationship between rare but potentially catastrophic detail. magnitude and slip, and whether it events.

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Table 3. Japan Meteorological Agency Tsunami Bulletins their plans when they saw the surges heading into the community. They changed plans twice before finally running to the hills (green circle). Professor Katada at Gunma University had served as an advisor to the Unosumai school disaster planning effort and had emphasized that children should be taught to head to high ground, to evaluate the situation with their own eyes, and to assist others. 3) Changing official warning information. The Japanese Me- teorological Agency (JMA) has the responsibility for issuing tsunami warnings in Japan. On March 11, the JMA issued a series of bulletins assessing the likely tsunami hazard posed by the earthquake (Table 3). The initial bulletin issued three minutes after the earthquake estimated a magnitude of 7.9 and forecast 3-m surges along the Iwate and Fukushima coasts, and waves as high as 6 m in Miyagi. This information was dis- seminated to emergency officials and to the public via television, Source: http://www.jma.go.jp/en/tsunami/info_04_20110311145026.html (Ozaki, 2011). radio, and cell phones. Succeed- ing bulletins expanded the warn- 485 deaths in Unosumai, 419 of 2) Limitations of published haz- ing areas and increased the ex- which (86%) had residences within ard maps. All coastal communi- pected water height; however, ties used the tsunami hazard the 2011 inundation area, but out- it took nearly four hours before assessment to develop inunda- side of the mapped hazard area. the designated warning areas tion and evacuation maps. Fig- In Unosumai, over 500 students stopped changing. JMA recently ure 23 shows the evacuation from the junior high and elemen- changed its protocol for very map for Unosumai Town located tary schools successfully made it large earthquakes because of near Kamaishi City. The 1896 to high ground (Asahi Shimbun, the underestimation on March and 1933 tsunamis flooded the 2011b). Both schools were located 11. For earthquakes of magni- town to the red line. Seawalls just outside of the mapped hazard tude 8 or larger, anticipated and large river dikes had been zone, and the students in the ele- water heights will no longer be constructed since 1933 and mentary school had been taught to announced; instead, the warn- were believed to be able to pre- go to the building’s third floor after ing will focus on “the possibility vent the level of flooding seen an earthquake. At the adjacent ju- of a huge tsunami” (Cyranoski, previously. The hazard map, in- nior high school, students and staff 2011). An important research cluding the mitigating effect of had been taught to evacuate. When question is how officials and the the seawall, is shown by the the elementary students saw the public responded to the chang- orange line. The actual inunda- older students evacuating, they ing hazard assessment and tion in 2011 (blue line) exceeded joined them, the older students what level of detail is sufficient to both the historic inundation and assisting the younger ones. The motivate people to evacuate. the mapped hazard areas. A group first headed to a location 4) Importance and effectiveness study done by Mainichi Newspa- well outside of the mapped zone of visual inundation markers. per (Sugimoto, 2011) reported (red circle Figure 23), but changed Many communities featured vis-

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Figure 25. Tsunami evacuation building in Manamisanriku (B on map, Figure 8). The building is adjacent to the seawall (white arrow on the left). The tsunami left debris on the fourth floor windows (red arrow) (photo: L. Dengler).

A number of me- 5) Reliance on evacuation build- dia stories have ings. Tsunami evacuation plan- described tsu- ning in most coastal areas of nami stones that Japan involves designating build- mark safe areas ings thought to be safe and based on past teaching residents to go to those tsunami heights buildings after an earthquake. (Fackler, 2011). The buildings are generally three Figure 24D shows or more stories in elevation and the tsunami stone usually feature exterior stairs to in Aneyoshi Bay, facilitate access. Towns and cities reputed to have had designated tens to hundreds been erected of structures as evacuation build- after the 1896 ings; there were 80 in Minamisan- Figure 24. Water height markers. A) Marker commemo- Meiji tsunami, riku alone. Unfortunately, many rating the 2.6 m height of the 1960 Chilean tsunami at directing people of the buildings were either over- Minamisanriku Town (2010 photo courtesy of J. Bour- to build houses topped or destroyed by the tsu- geois). B) The same marker in May 2011 (photo: L. Deng- above its eleva- nami; preliminary reports are ler). Water height at this location was over 15 m. C) Pole tion. Although that over 100 evacuation build- with expected 2 m tsunami height in Kesennuma City Aneyoshi Bay had ings failed to provide life safety (photo: L. Dengler). Tsunami height reached the 3rd floor the highest runup (Japan Times, 2011). Even when of the evacuation building in the background. D) Tsunami (38.9 m) in the buildings survived, they created stone commemorating the height of the 1896 tsunami in 2011 tsunami, the other problems for the people Aneyoshi Bay (photo: B. Jaffe). stone was about sheltering there. In many cases, ual reminders of the height of 10 m above the inundation zone, the buildings were located close past tsunamis or the expected and no houses in Aneyoshi Village to the coast (Figure 25), where highest water level (Figure 24). were flooded. More than two doz- they could be quickly cut off from At Minamisanriku, a series of en tsunami stones have been high ground. Once people had monuments and statues com- identified in the Tohoku region, gone to a building, it was impos- memorates the 1960 Chilean and preliminary reconnaissance sible to make another decision tsunami (Figure 24A). The 2011 suggests that about 20% were as the situation evolved. The tsunami exceeded the 1960 flooded in 2011 (Sugimoto, 2011). water heights, trapping of water, water levels by more than 12 m Unraveling the stories behind the level of damage and permanent (Figure 24B). At Kesennuma, stones will require careful investi- subsidence isolated people in the modeled tsunami height was gation, as the original intent of the these structures for several days printed on light poles as a visual stone is not always clear, nor is without adequate supplies or reminder of the hazard (Figure whether it is still located in its access to emergency care. While 24C). The actual tsunami at this original position, or how people vertical evacuation may provide location was about 10 m higher. understood its meaning. the only life safety in areas where

13 EERI Special Earthquake Report — November 2011

no high ground is nearby, re- Outside of Japan, risk perception Data Center for providing informa- search should assess its effec- also posed a problem. While evac- tion on tsunami impacts outside tiveness in areas where there uation efforts on the U.S. West Japan, and Brian Atwater of the are other options. Coast were more successful than USGS for his insights and critical review of the manuscript. We also 6) Effectiveness of seawalls as a in the past (Dengler et al., 2011), thank all of the kind people in Japan mitigation measure. It is not the a significant number of people purpose of this report to assess headed to the coast to watch the who spoke with us and told us their the engineering issues associat- event. There continue to be prob- stories, in spite of how painful and ed with seawalls, but an impor- lems with warning message com- difficult it was to do so. tant research issue is the rela- prehension, especially for non- tive effectiveness of seawalls English speaking communities References compared to other mitigation (Wilson et al., 2011). A high-priority research effort would be to exam- Abe, H., Y. Sugeno and A. Chigama, measures, such as land use 1990. “Estimation of the height of planning, and education. This ine the primary influences on in- dividual perception of risk, and the Sanriku Jogan 11 earthquake- discussion has already begun in tsunami (A.D. 869) in the Sendai how those perceptions informed the media (Yomiuri Shimbun, Plain,” Zisin [Earthquakes], Vol. 43, 2011), and can be seen in great- evacuation behavior. pp. 513-525. er detail in the companion LFE Asahi Shimbun, 2011a. POINT OF report, “The Japan Tohoku Tsu- Acknowledgments VIEW by Jin Sato: “Government nami of March 11, 2011: Effects The teams whose work is included in should provide lending to rebuild on Structures,” by the ASCE/ this report were supported by a num- homes in quake-hit town,” March 24. EERI team. ber of organizations, including EERI; http://ajw.asahi.com/article/ the U.S. Geological Survey; the Na- 0311disaster/quake_tsunami/ 7) Perception of risk. A recurring AJ201103211750 chorus among the people inter- tional Tsunami Hazard Mitigation Pro- viewed during this and other gram; the California Geological Sur- Asahi Shimbun, 2011b. “Tsunami drills vey; Humboldt State University; the paid off for hundreds of children,” field reconnaissance trips is that March 23. http://ajw.asahi.com/ Science and Technology Research they did not perceive themselves article/0311disaster/life_and_death/ to be at risk. An NHK survey of Partnership for Sustainable Develop- AJ201103233378 tsunami survivors found that over ment (SATREPS) of the Japan Sci- ence and Technology Agency (JST); Chagué-Goff , Catherine, et al., 2011. half did not think they were in an “Preliminary Results of a Geological the Japan International Cooperation inundation area (Sugimoto, Field Survey in the Sendai Plain after 2011). For a significant number Agency (JICA); the Overseas Intern- the 11 March 2011 Tohoku Tsunami,” of people, the earthquake was a ship Program for Outstanding Young Proceedings, IUGG Melbourne 2011, trigger — not to head to higher Earth and Planetary Researchers, Paper # 6074. Department of Earth and Planetary ground, but rather to go into Cyranoski, David, 2011. “Japan’s hazard zones where they lived, Science, University of Tokyo; the tsunami warning system retreats,” either to rescue a relative or to Indonesian Ministry of Research and NatureNews, August 11. http://www. retrieve belongings. Although Technology (RISTEK); and the Indo- nature.com/news/2011/110811/full/ taught to evacuate on foot, most nesian Institute of Sciences (LIPI). news.2011.477.html?s=news_rss people relied on cars; this made We thank Kenji Satake, Teruyuki Kato Dengler, Lori et al., 2011. “The 2011 it difficult for them to assess the and Yoshinobu Tsuji of ERI at the Tohoku-oki tsunami on the Northern situation around them and caused University of Tokyo for discussions California and Southern Oregon massive traffic jams that hindered and logistical assistance; Laura Kong Coast,” Proceedings, IUGG Mel- bourne 2011, Paper # 6078. evacuation (Japan Times, 2011b). of the International Tsunami Informa- A number of factors may have tion Center for coordinating ITST Fackler, Martin, 2011. “Tsunami Warn- contributed to the reduced sense efforts; Masahiro Yamamoto of IOC/ ings, Written in Stone,” The New York of risk: the perceived safety of UNESCO for compiling the Tohoku Times, April 20. http://www.nytimes. seawalls, previous events that com/2011/04/21/world/asia/21stones. tsunami reports, Jose Borrero of ASR html?pagewanted=all had failed to produce significant Limited, New Zealand, for information tsunamis (warnings had been is- on California impacts, Jody Bourgeois Grapenthin, Ronni, and J. T. Freym- ueller, 2011. “The dynamics of a sued for the 2010 Chilean quake of the University of Washington for and the March 9 foreshock), con- seismic wave field: Animation and allowing us to use her 2010 photos analysis of kinematic GPS data fusion over or misinterpretation of Minamisanriku; Kumi Watanabe- recorded during the 2011 Tohoku-oki of tsunami warning bulletins, and Shock of Humboldt State University earthquake, Japan,” Geophysical the failure of education efforts to for translation assistance; Paula Research Letters, Vol. 38, L18308, reach people. Dunbar of the National Geophysical doi:10.1029/2011GL048405

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