景谷6.6级、鲁甸6.5级地震序列应力降变化对比研究

发布时间：2018-10-22 10:24

【摘要】：利用云南2014年10月7日景谷6.6级、8月3日鲁甸6.5级地震序列的波形与震相资料,消除区域地震波衰减与台站场地响应后,计算得到2次地震序列的应力降。结果显示,在研究所涉及的震级范围内,应力降呈现随震级增大而增大的趋势。为尽可能消除震级对应力降的影响,对比了相同震级档地震的应力降,结果显示,景谷地震序列的平均应力降明显高于鲁甸地震,这可能与2次6.5级左右地震后震源区的应力状态有关。从序列余震应力降的时、空变化对比来看,景谷6.6级地震后至2014年12月6日5.8、5.9级强余震发生前,应力降变化呈现先缓慢下降、进而转折升高并持续高值的变化过程;同时,高应力降地震在空间上主要集中于5.8级强余震区域。这表明,主震发生后经过一个较短期的调整之后,5.8级强余震震源区的应力环境可能持续增强。5.8、5.9级强余震发生后,地震序列应力降快速下降至相对稳定状态。研究表明,2次6级左右强余震发生后,震源附近区域应力得到一定程度的释放,应力环境降低,地震序列活动也趋于结束。对于后续没有强余震发生的鲁甸地震序列,余震应力降小于景谷地震序列相同震级档地震的平均应力降,同时,主震后余震序列的应力降在时间上几乎未发生太大的变化;结合主震能量释放特点推测,震源区的应力在主震破裂过程中已得到较多的释放,主震后震源区应力变化呈现逐渐恢复的过程,这可能是鲁甸地震余震活动明显较弱,后续亦未有较强余震发生的原因之一。
[Abstract]:Using the waveform and phase data of Yunnan Jinggu M = 6.6 earthquake sequence on October 7, 2014 and Ludian M = 6.5 earthquake sequence on August 3, 2014, the regional seismic wave attenuation and the site response of the station are eliminated, and the stress drop of the two earthquake sequences is calculated. The results show that the stress drop increases with the increase of magnitude. In order to eliminate the influence of magnitude on the stress drop as far as possible, the stress drop of the same magnitude earthquake is compared. The results show that the average stress drop of the Jinggu earthquake sequence is obviously higher than that of the Ludian earthquake. This may be related to the stress state in the focal area after two earthquakes with magnitude 6.5 or so. From the point of view of the stress drop of the sequence aftershocks, the variation of the stress drop after the Jinggu earthquake (M = 6.6) and before the aftershock with M = 5.890 M = 5.9 on December 6, 2014 shows a slow decrease, then a turning point and a continuous high value. The high stress drop earthquakes are mainly concentrated in the region of strong aftershocks with M = 5.8 in space. This indicates that after a relatively short period of adjustment after the occurrence of the main shock, the stress environment in the focal area of the strong aftershock with M = 5.8 may continue to strengthen. After the occurrence of the strong aftershock with M = 5.8 or M = 5.9, the stress drop of the earthquake sequence rapidly decreases to a relatively stable state. The results show that after two strong aftershocks with magnitude 6 or so, the regional stress near the earthquake source is released to a certain extent, the stress environment decreases, and the earthquake sequence activities tend to end. For the Ludian earthquake sequence with no strong aftershocks, the aftershock stress drop is smaller than the average stress drop of the same magnitude earthquake in Jinggu earthquake sequence, and the stress drop of the aftershock sequence after the main earthquake almost does not change much in time. Combined with the characteristics of the energy release of the main shock, it is inferred that the stress in the focal area has been released more during the rupture process of the main shock, and the stress variation in the focal area has gradually recovered after the main earthquake, which may be due to the obvious weakness of the aftershock activity of the Ludian earthquake. No strong aftershocks have occurred since then.
【作者单位】：中国地震局地震预测研究所;中国地震台网中心;
【基金】：中国地震局监测预报司2016年度任务性科技专项(1640401320716)资助
【分类号】：P315

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