TY - JOUR
T1 - Similarities and differences in the rupture process of the M ~ 4.8 repeating-earthquake sequence off Kamaishi, northeast Japan
T2 - Comparison between the 2001 and 2008 events
AU - Shimamura, Kouhei
AU - Matsuzawa, Toru
AU - Okada, Tomomi
AU - Uchida, Naoki
AU - Kono, Toshio
AU - Hasegawa, Akira
PY - 2011/10/1
Y1 - 2011/10/1
N2 - Earthquakes of M ~ 5 have repeatedly occurred at the same location on the plate boundary off Kamaishi, northeast Japan, with a mean recurrence interval of about 5.5 years. The latest two events (M 4.8 on 13 November 2001, and M 4.7 on 11 January 2008) were successfully observed by the broadband seismic network of Tohoku University covering the Tohoku District of northeast Japan. We estimated the source processes of the 2001 and 2008 events by carefully picking the onsets of P and S waves and by inverting seismic waveforms recorded by the network. The results show that both events were caused by the rupture of the same asperity patch (diameter, ~1 km). As the previous 1995 event was also reported to have ruptured the source area of the 2001 event, at least the last three events (1995, 2001, and 2008) in this earthquake sequence are thought to have been caused by repeated ruptures of the same asperity. A closer examination, however, reveals a small discrepancy in the slip distribution between the last two events, which explains the difference in the highfrequency components of the seismograms. The regions in which slip was smaller during the 2001 event than during the 2008 event nearly coincide with the source areas of the smaller repeating earthquakes that occurred just before the 2001 event. This finding suggests that the activity of smaller events immediately before the mainshock can influence the slip distribution of the mainshock.
AB - Earthquakes of M ~ 5 have repeatedly occurred at the same location on the plate boundary off Kamaishi, northeast Japan, with a mean recurrence interval of about 5.5 years. The latest two events (M 4.8 on 13 November 2001, and M 4.7 on 11 January 2008) were successfully observed by the broadband seismic network of Tohoku University covering the Tohoku District of northeast Japan. We estimated the source processes of the 2001 and 2008 events by carefully picking the onsets of P and S waves and by inverting seismic waveforms recorded by the network. The results show that both events were caused by the rupture of the same asperity patch (diameter, ~1 km). As the previous 1995 event was also reported to have ruptured the source area of the 2001 event, at least the last three events (1995, 2001, and 2008) in this earthquake sequence are thought to have been caused by repeated ruptures of the same asperity. A closer examination, however, reveals a small discrepancy in the slip distribution between the last two events, which explains the difference in the highfrequency components of the seismograms. The regions in which slip was smaller during the 2001 event than during the 2008 event nearly coincide with the source areas of the smaller repeating earthquakes that occurred just before the 2001 event. This finding suggests that the activity of smaller events immediately before the mainshock can influence the slip distribution of the mainshock.
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U2 - 10.1785/0120100295
DO - 10.1785/0120100295
M3 - Article
AN - SCOPUS:80053176458
VL - 101
SP - 2355
EP - 2368
JO - Bulletin of the Seismological Society of America
JF - Bulletin of the Seismological Society of America
SN - 0037-1106
IS - 5
ER -