2010年智利8.8级地震在北京房山岩体附近的动态触发活动

Remotely triggered seismicity around the Fangshan Pluton near Beijing following the 2010 M_w 8.8Chile earthquake

本文采用波形分析和β统计方法,基于首都圈地区数字测震台网和部分流动地震台的观测资料,对2010年2月27日Mw8.8智利大地震在北京房山岩体附近地区的动态触发活动进行了分析讨论.结果表明,在背景地震活动相对较弱的北京房山岩体附近,我们检测出至少5次小震活动事件在智利地震面波到达时发生.这些触发活动显著地改变了房山岩体地区这一地震活动相对平静地区的地震活动性,但是对北京地区地震活动性的影响并不明显.NKY地震台记录的智利地震触发活动的最大动态应力与之前的研究结果相比要小,约为7kPa.这可能与房山岩体附近地区的背景地震在智利地震前一直较为平静有关.此外,相对有利的面波入射方向,以及在对蹠点上的前两组面波叠加的效应等因素综合作用,使得本研究能在约2万公里极远处观测到远震触发小震活动.然而,在随后的多次面波叠加期间并没有观测到明显的触发地震活动.在智利地震10h前发生的琉球Mw7.0地震也未在房山地区触发相关的微震活动,这可能与它们引起的动态应力变化太过微弱有关.

Using seismic data collected by the Beijing metropolitan Digital Seismic Network （BDTSN） and our temporary seismic stations, we conduct a systematic search of dynamic triggering around the Fangshan Pluton near Beijing following the 2010/02/27 Mw8.8 Chile earthquake. Based on standard waveform processing and statistical analysis, we find at least 5 microearthquakes occurred during the direct surface waves of the Chile mainshock. Because ourstudy region is relatively stable with minor background seismicity, the observed seismicity change is statistically significant. However, their effects on the overall seismic activity around Beijing were negligible. The peak dynamic stress induced by the Chile mainshock recorded at station NKY is about 7 kPa, which is the smallest value among the other cases of triggering found in this region. This could be caused by a combination of relatively quiet background seismicity right before the Chile mainshock, favorable incident angle, and possible superposition of the first two groups of surface wave at near antipodal distances （-20000 km）. However, we did not find any evidence of triggered activity during multiple surface waves of the Chile mainshock that arrived later, and during the teleseismic waves of the MwT. 0 Ryukyu earthquake occurred 10 hours earlier. This is likely because of the relatively smaller amplitudes of the triggering waves.