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タイトル: The Gutenberg-Richter Relationship vs. the Characteristic Earthquake Model: Effects of different sampling methods
著者: Ishibe, Takeo
Shimazaki, Kunihiko
キーワード: the Characteristic Earthquake Model
the Gutenberg-Richter relationship
Late Quaternary fault
active fault
発行日: 2008年
出版者: 東京大学地震研究所
掲載誌情報: 地震研究所彙報. 第83号第1冊, 2008, pp. 131-151
抄録: The Gutenberg-Richter (G-R) relationship log n=a-bM has been used to describe regional seismicity. However, a number of studies report that the Gutenberg-Richer relationship does not hold for seismicity around late Quaternary faults or active faults during the entire seismic cycle. In this paper, we first report our study on the influences of different catalog intervals on seismicity analyses around six major strike-slip faults in southwest Japan studied by Stirling et al. in 1996. As a result, we find no essential differences between two observed annual occurrence rates estimated from the different catalog intervals, with the exception of the Tanna fault where the characteristic earthquake, i.e., the Kita-Izu earthquake (M=7.3), occurred in 1930. The results obtained after excluding all events in 1930 show much lower seismicity than that predicted by the G-R relationship. If the G-R relationship holds for one complete earthquake cycle, seismicity during a time-interval including occurrence time of the characteristic earthquake and its series of aftershocks should show much higher seismicity than that predicted by the G-R relationship, because the highest activity during a seismic cycle occurs in that period. However, the actual seismicity over 60 years including the 1930 occurrence shows, at most, activity equal to that predicted by the G-R relationship for the Tanna fault. We also discuss the bias caused by different spatial sampling methods. We propose a new method, which is applicable not only to strike-slip but also to dip-slip faults, to extract seismicity around active faults and for application to the six strike-slip fault systems using the unified Japan Meteorological Agency catalog and fault data that have been improved in recent years. The results show that the observed seismicity is lower than that predicted by the G-R relationship for all fault systems including the Yamasaki fault system, which showed higher seismicity than predicted by the previous study. These results hold even if the sampling volume is doubled.
URI: http://hdl.handle.net/2261/16683
ISSN: 00408972


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