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北京西部房山岩体多次发现动态触发事件,但之前的研究都受限于台站分布稀疏的影响。本文系统地分析了2011年3月11日日本东北近海MW9.1地震和2012年4月14日印度洋MW8.6地震之前和之后各40天内固定台站和流动台站记录的连续波形。首先,本文采用短时平均比长时平均的检测方法构建模板数据库;其次,本文运用波形模板匹配滤波技术对连续波形进行互相关来检测地震事件。最后,本文分别检测得到日本东北近海地震主震后和印度洋地震主震后1 956个和950个地震事件。多数检测到的地震属于浅源(<5km)地震并群集出现在北京西部房山岩体北岭向斜构造,这个地区邻近一个正在运行的煤矿。从两次主震的强振幅面波中分别检测出7个和10个地震事件,但对应的强前震和余震波形中则没有检测到类似的多事件爆发模式。多种统计检验表明两次主震后短时爆发事件是动态触发事件。本文认为采矿相关的活动可能扰动了地下应力环境,从而使该地区比其他地区更容易被动态应力触发。
Dynamic triggering events were found many times in Fangshan granite in western Beijing, but previous studies were limited by the sparse distribution of stations. This paper systematically analyzes the continuous waveforms recorded by stationary and mobile stations in the offshore northeast of Japan on March 11, 2011 and the 40 days before and after the MW8.6 earthquake on April 14, 2012 in Japan. First of all, this paper uses the short-term average than the long-time average detection method to build a template database; secondly, this paper uses waveform template matching filter technology to cross-correlation continuous waveforms to detect seismic events. Finally, we detected 1 956 and 950 earthquakes respectively after the main offshore earthquake in northeastern Japan and after the main Indian Ocean earthquake in Japan. Most of the earthquakes detected belong to the shallow source (<5km) earthquakes and cluster in the Northling syncline of the Fangshan pluton in western Beijing, adjacent to a running coal mine. Seven and ten earthquake events were detected from the strong amplitude surface waves of the two main shocks respectively, but no similar multi-event explosion pattern was detected in the corresponding strong and aftershock waveforms. A variety of statistical tests show that the short-term burst events after two main shocks are dynamic trigger events. This paper argues that mining-related activities may disturb the subsurface stress environment, making the area more susceptible to dynamic stress triggering than other areas.