Aftershock Activities for Two Days after the 1923 Kanto Earthquake ( M =7.9) Inferred from Seismograms at Gifu Observatory: ―岐阜測候所の今村式二倍強震計記録の解析―
Aftershock Activities for Two Days after the 1923 Kanto Earthquake ( M =7.9) Inferred from Seismograms at Gifu Observatory: ―岐阜測候所の今村式二倍強震計記録の解析―
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1923年关东地震（M=7.9）后两天的余震活动，根据岐阜县气象台的地震图推断：“岐阜气象站今村型双强震仪记录的分析”
DOI：
10.4294/zisin1948.46.4_439
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
M. Takemura
中科院分区：
文献类型：
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作者：
M. Takemura
本文根据岐阜地震台新测得的S-P时间、最大振幅及其周期等资料，重新研究了1923年关东大地震后两天的余震活动。34次余震，震级从5. 0到7。五是记录在案。由S-P时间推断的余震震中位置表明，大震多集中在主震破裂区的西端或东端附近。9月1日12：00左右，主震发生后，西部地区立即开始了第一次余震活动，其中包括两次7级地震，其震级是根据这些记录的垂直分量最大振幅重新确定的。12时40分左右，东部地区开始发生余震。下一场活动13时再次在西部地区拉开帷幕。9月1日17时至2日11时，活动静悄悄。最大的余震M=7。5及其相关事件发生在东部地区后，这一平静。随后，21时左右，活动再次回到西部地区。它被发现，M？6次余震是两天内的16次，这比日本及其周边地区的其他M=8级地震要大得多。垂直分量的固有周期约为1 s，水平分量的固有周期约为5s。因此，垂直分量的最大振幅与水平分量的最大振幅之比y被用作表示来自每个余震的地震波的频率特性的参数。东部地区的余震都具有低频特征，与西部地区相比，东部地区的余震具有较小的y值。我们还发现了一些余震，其波形与最近发生在同一地区的事件相似。这些结果表明，余震活动包括相同的类型的事件，我们可以发现在最近的地震活动，并建议在本研究中推断的余震震中位置是正确的。
Aftershock activities for two days after the 1923 Kanto earthquake is reinvestigated from the data of S-P time, maximum amplitude, and its period, which are newly measured on the records at the Gifu observatory. 34 aftershocks with magnitude M from 5. 0 to 7. 5 are identified on the records. According to locations of epicenters of aftershocks inferred from the S-P times, most of large events concentrated in the vicinities of western or eastern ends of the rupture area of the main shock. The first aftershock activity started in the western region immediately after the main shock at about 12 : 00 on the 1st of September and included two M=7 class events, whose magnitudes are newly determined from maximum amplitudes in vertical component of these records. At about 12:40, aftershocks began to occur in the eastern region. The next activity began at 13: 00 in the western region again. From 17:00 on the 1st to 11: 00 on the 2nd of September, the activity was quiet. The largest aftershock of M=7. 5 and its related events occurred in the eastern region after this quietness. Then, the activity returned to the western region again at about 21: 00. It is found that the number of M? 6 aftershocks is 16 for two days, which is meaningfully larger than that for the other M=8 class events in and around Japan. The natural period of the vertical component of the seismograph was about 1 s, while those of the horizontal components were about 5 s. Therefore, the ratio y of maximum amplitude in vertical component to those in horizontal components is used as a parameter which show a frequency characteristic of seismic waves from each aftershock. All the aftershocks in the eastern region have low-frequency characteristics, which show smaller y values, comparing with those in the western region. We also found some aftershocks of which wave forms are similar to those of recent events occurring in the same region. These results indicate that the aftershock activities included the same type events as we can find in the recent seismicity and suggest that the locations of epicenters of the aftershocks inferred in the present study are proper.