An effective method for small event detection: match and locate (M&L)
An effective method for small event detection: match and locate (M&L)
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小事件检测的有效方法：匹配定位（M
DOI：
10.1093/gji/ggu466
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发表时间：
2015-03-01
影响因子：
2.8
通讯作者：
Wen, Lianxing
中科院分区：
文献类型：
--
作者：
Zhang, Miao;Wen, Lianxing
李晓明，李晓明，李晓宇。低震级地震的探测是地震学研究的关键和难点。本文提出了一种新的小事件检测方法——匹配定位法（M&L）。M&L方法采用一些模板事件，通过叠加模板事件波形与多个台站和分量的连续波形中潜在小事件信号之间的交叉积分图来检测小事件，但叠加是在模板事件和潜在小事件扫描模板周围三维区域的相对位置进行相对走时校正后进行的。与当前的小事件检测方法相比，M&L方法将事件检测置于较低的级别，并扩展了检测与模板有较大距离分离的小事件的能力。该方法对所用速度模型的精度依赖较小，同时能提供探测到的小震级地震的高精度定位信息。我们通过2011年日本9.0级地震前的前震检测和日本岛的按比例缩小的地震实例，证明了M&L方法的有效性及其相对于匹配滤波方法的优势。在前震检测中，M&L方法检测到的事件（1427）比模板多四倍，在相同的检测阈值下，比匹配的过滤器多9%（134）。在探测到的事件中，高达41%（580）的事件没有位于最大距离为9.4公里的模板位置。基于已识别的前震，我们观察到mw9.0主震沿平行海沟方向向震中方向的5个前震迁移序列。
S U M M A R Y Detection of low magnitude event is critical and challenging in seismology. We develop a new method, named the match and locate (M&L) method, for small event detection. The M&L method employs some template events and detects small events through stacking crosscorrelograms between waveforms of the template events and potential small event signals in the continuous waveforms over multiple stations and components, but the stacking is performed after making relative traveltime corrections based on the relative locations of the template event and potential small event scanning through a 3-D region around the template. Compared to the current methods of small event detection, the M&L method places event detection to a lower magnitude level and extends the capability of detecting small events that have large distance separations from the template. The method has little dependence on the accuracy of the velocity models used, and, at the same time, provides high-precision location information of the detected small-magnitude events. We demonstrate the effectiveness of the M&L method and its advantage over the matched filter method using examples of scaled-down earthquakes occurring in the Japan Island and foreshock detection before the 2011 Mw 9.0 Tohoku earthquake. In the foreshock detection, the M&L method detects four times more events (1427) than the templates and 9 per cent (134) more than the matched filter under the same detection threshold. Up to 41 per cent (580) of the detected events are not located at the template locations with the largest separation of 9.4 km. Based on the identified foreshocks, we observe five sequences of foreshock migration along the trench-parallel direction toward the epicentre of the Mw 9.0 main shock.