Title Space‒Time Clustering of Large Thrust Earthquakes Along
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Kyoto University Research Information Repository Space‒Time Clustering of Large Thrust Earthquakes along the Title Mexican Subduction Zone: An Evidence of Source Stress Interaction Santoyo, Miguel A.; Singh, Shri K.; Mikumo, Takashi; Ordaz, Author(s) Mario Bulletin of the Seismological Society of America (2005), Citation 95(5): 1856-1864 Issue Date 2005-10 URL http://hdl.handle.net/2433/193414 Right © 2005 Bulletin of the Seismological Society of America Type Journal Article Textversion publisher Kyoto University Bulletin of the Seismological Society of America, Vol. 95, No. 5, pp. 1856–1864, October 2005, doi: 10.1785/0120040185 Space–Time Clustering of Large Thrust Earthquakes along the Mexican Subduction Zone: An Evidence of Source Stress Interaction by Miguel A. Santoyo, Shri K. Singh, Takeshi Mikumo, and Mario Ordaz Ն Abstract The spatiotemporal plot of epicenters of large (Ms 6.9) subduction earthquakes in Mexico (1900 to present day) suggests that these earthquakes cluster in space and time. In this work we test the hypothesis that the coseismic stress transfer may lead to this clustering. For the analysis we estimate the spatial extent of the coseismic Coulomb stress change for these large events and then perform a statistical analysis using the v2 goodness-of-fit test for the interevent time intervals. We find that there are, at least, two groups of time intervals where the observed frequencies are much higher than that expected from a Poisson model, indicating a bimodal pattern. For the first mode, the observed frequencies for the 0- to 5-year interval becomes about 2.1 times the expectation, with a probability of occurrence of about 30%. These results show that large thrust Mexican earthquakes between 1900 and 2003 are clustered in space and time probably due to stress interactions among them. The second mode includes the time interval of 30–50 years. In the interval of 30–40 years, the observed frequencies become about 1.7 times the expectation and about 1.2 times the expectation for the 40- to 50-year interval. This second mode could be associated with a reloading interval of tectonic stress due to the plate convergence and appears consistent with the long-term recurrence periods of large thrust earth- quakes in the Mexican subduction zone. Introduction A glance at the spatiotemporal plot of epicenters of large quake occurrence as our null hypothesis. For this purpose, subduction earthquakes in Mexico, which occurred during we analyze the Mexican earthquake catalog from 1900 to the last 103 years on the Pacific coast, suggests that these 2003. events are clustered in space and time (e.g., Singh et al., 1981; Nishenko and Singh, 1987a; Ward, 1991). Several au- Earthquake Data thors have reported a positive correlation between the co- seismic stress changes on the neighborhood of the source The Mexican earthquake catalog is complete from 1900 Ն region, and the occurrence in clusters of subsequent earth- to the present for events with magnitudes Ms 6.5 (Singh quakes with different magnitudes in the same area (e.g., et al., 1984; Kostoglodov and Pacheco, 1999). As our King et al., 1994; Stein et al., 1994; Deng and Sykes, 1997; method is based on the spatial relationship between large Freed and Lin, 1998; Gomberg et al., 1998; Harris, 1998, earthquakes, we only consider rupture areas greater than km), which is equivalent to events 25 ן Toda et al, 1998; Stein, 1999). Here, the term stress transfer 625 km2 (25 km Ն or earthquake interaction implies that given an earthquake, with Ms 6.9. The catalog for this period and magnitudes the time of occurrence of the following large events in its comprises 46 shallow thrust earthquakes (Table 1). close neighborhood is accelerated in time due to its coseis- mic stress increase outside the main slip region. Method of Analysis In this study, we test the hypothesis that the coseismic stress transfer leads to clustering of large thrust earthquakes Rupture Areas in the Mexican subduction zone. For this purpose, we define The rupture areas for each earthquake are estimated a criterion to obtain the interoccurrence times, taking into from their aftershock areas when they are known. The after- account the spatial extent of the changes of the Coulomb shock areas have been mapped for only 24 out of the 46 failure stress due to the coseismic slips of each earthquake. events (Fig. 1, Table 1). For the remaining events, we esti- ס (The analysis is performed with the aid of the Pearson v2 mate the rupture area from an empirical relation: log(S מ statistical test, with reference to a Poisson model of earth- Ms 4.1 (e.g., Utsu and Seki, 1954; Purcaru and Berck- 1856 Space–Time Clustering of Large Thrust Earthquakes along the Mexican Subduction Zone 1857 Table 1 Ն Catalog of Shallow Thrust Mexican Earthquakes with Magnitudes Ms 6.9 (1900–2003) Location* Location* Event Date Event Date No. (yr/dd/mm) Lat. Lon. M† L‡ No. (yr/dd/mm) Lat. Lon. M† L‡ 112.33 1(7.9) 102.941מ 18.85 1941/4/15 24 79.53 2(7.6) 105.01מ 20.0 1900/1/20 1 89.23 1(7.7) 101.151מ 17.62 1943/2/22 25 44.73 2(7.1) 105.01מ 20.0 1900/5/16 2 58.24 7.37 4[98.82מ] [16.61] 1950/12/14 26 150.64 7.94 4[99.2מ] [16.62] 1907/4/15 3 92.04 7.87 4[99.41מ] [16.59] 1957/7/28 27 100.13 2(7.8) 99.25מ 16.7 1908/3/26 4 40.09 7.19 9[99.99מ] [16.93] 1962/5/11 28 50.23 2(7.2) 101.05מ 17.0 1908/3/27 5 35.09 7.09 9[99.92מ] [16.85] 1962/5/19 29 35.53 5(6.9) 102.05מ 18 1908/10/13 6 108.510 7.57 10[96.02מ] [15.58] 1965/8/23 30 70.93 2(7.5) 99.91מ 16.8 1909/7/30 7 70.010 7.37 10[98.01מ] [16.01] 1968/8/2 31 44.73 2(7.1) 99.451מ 16.62 1909/7/31 8 90.011 7.711 11[103.41מ] [18.29] 1973/1/30 32 35.53 2(6.9) 101.11מ 17.1 1909/10/31 9 84.010 7.812 10[97.05מ] [15.75] 1978/11/29 33 112.33 6(7.9) 102.56מ 17.5 1911/6/7 10 95.013 7.412 13[101.45מ] [17.46] 1979/3/14 34 79.53 2(7.6) 100.71מ 17 1911/12/16 11 48.014 7.212 14[102.25מ] [17.75] 1981/10/25 35 70.93 6(7.5) 96.17מ 15.67 1928/3/22 12 53.015 6.912 15[98.37מ] [16.35] 1–1982/6/7 36 100.13 6(7.8) 96.91מ 15.8 1928/6/17 13 57.015 6.912 15[98.54מ] [16.4] 2–1982/6/7 37 63.23 6(7.4) 97.41מ 16.1 1928/8/4 14 180.016 8.112 16[102.51מ] [17.79] 1985/9/19 38 79.53 6(7.6) 97.31מ 16.3 1928/10/9 15 80.016 7.512 16[101.82מ] [17.62] 1985/9/21 39 222.08 8.07 8[105.4מ] [19.8] 1932/6/3 16 55.016 6.912 16[102.49מ] [18.42] 1986/4/30 40 71.08 7.97 8[104.6מ] [18.99] 1932/6/18 17 35.017 6.912 17[99.46מ] [16.58] 1989/4/25 41 35.53 8(6.9) 104.688מ 18.74 1932/6/22 18 45.018 7.312 18[98.76מ] [16.48] 1995/9/14 42 35.53 8(6.9) 103.938מ 18.87 1932/7/25 19 175.019 8.012 19[104.90מ] [19.1] 1995/10/9 43 35.53 1(6.9) 101.01מ 17.5 1933/5/8 20 68.020 7.112 20[98.26מ] [15.78] 1996/2/25 44 39.93 8(7.0) 105.318מ 19 1934/11/30 21 35.53 3(6.9) 102.6621מ 17.99 2000/8/9 45 35.53 8(6.9) 103.58מ 18.75 1935/6/29 22 72.022 7.612 22[104.20מ] [18.7] 2003/1/22 46 61.24 7.57 4[98.61מ] [16.39] 1937/12/23 23 *Bracketed numbers indicate the location of the center of the rupture area. ס ס † M Ms if in parenthesis, otherwise M Mw. ‡L indicate the lengths of the faults along the coast (see text). מ ס Numbers shown as superscripts indicate references: 1, Singh et al. (1984); 2, Nishenko and Singh (1987a); 3, L from log(S) Ms 4.1; 4, Nishenko and Singh (1987b); 5, Singh et al. (1981); 6, Anderson et al. (1989); 7, Singh and Mortera (1991); 8, Singh et al. (1985); 9, Ortiz et al. (2000); 10, Singh et al. (1980); 11, Reyes et al. (1979); 12, Harvard CMT catalog; 13, Valde´s and Novelo (1998); 14, Havskov et al. (1983); 15, Astiz and Kanamori (1984); 16, UNAM seismology group (1986); 17, Zun˜iga (1993); 18, Courboulex et al. (1997); 19, Pacheco et al. (1997); 20, Santoyo and Islas, unpublished report; 21, SSN catalog; 22, Singh et al., 2003. hemer, 1978; Wells and Coopersmith, 1994), where S is the for the time interval between two earthquakes that could be 2 source area in km , and Ms is the surface-wave magnitude.