Detecting Deep Tectonic Tremor in Taiwan with a Dense Array
Detecting Deep Tectonic Tremor in Taiwan with a Dense Array
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用密集阵列探测台湾深部构造震动
DOI：
10.1785/0120140258
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发表时间：
2015
影响因子：
3
通讯作者：
K. Chao
中科院分区：
文献类型：
--
作者：
Wei;Zhigang Peng;Cheng‐Horng Lin;K. Chao
摘要：本文利用密集的小孔径地震阵列对台湾中部山脉南部的深部构造震动进行了系统的探测。自2011年2月部署以来，该阵列几乎连续记录了134天的构造震动，包括2011年日本东北9.0级地震引发的震动。我们使用宽带频率波数波束形成和移动窗口网格搜索方法来计算所有连续数据的阵列参数，并将震颤识别为深入射角的相干非脉冲地震信号。得到的阵列参数与用波形包络相关聚类（WECC）方法定位的重新定位的局部地震和触发的地震爆发参数吻合较好，表明了阵列技术的鲁棒性。在134天的研究期间，我们检测了44天的震颤，总持续时间为1481分钟，是WECC方法检测震颤时间的三到六倍。我们发现在2011年东北- Oki地震后的20天里，周围的地震活动相对平静，这表明来自遥远主震的动态应力触发了大多数接近失败的地震，导致暂时缺乏地震活动。在某些情况下，我们观察到以40-50公里/小时的速度快速移动的地震，这与日本和卡斯卡迪亚地区沿倾斜的窄条快速移动的速度相似。我们的研究结果表明，密集阵列技术能够捕捉台湾南部震颤行为的详细时空演变。在线资料：台站坐标和地震事件参数表，移动窗口网格搜索试验图，局部地震，2011年东北大地震引发的地震，以及检测到的环境地震的附加示例。
Abstract We perform a systematic detection of deep tectonic tremor beneath the southern Central Range in Taiwan using a dense, small‐aperture seismic array. Deployed in February 2011, the array has been recording tectonic tremor nearly continuously for 134 days, including tremor triggered by the 2011 M w 9.0 Tohoku‐Oki earthquake. We use broadband frequency–wavenumber beamforming and moving‐window grid‐search methods to compute array parameters for all continuous data and identify tremor as coherent nonimpulsive seismic signals with deep incidence angles. The obtained array parameters closely match with those of relocated local earthquakes and triggered tremor bursts located by the waveform envelope correlation and clustering (WECC) method, indicating the robustness of our array technique. During the 134‐day study period, we detect tremor for 44 days, with a total duration of 1481 min, three to six times as long as the detection of tremor by the WECC method. We find a relative quiescence in ambient tremor activity for about 20 days following the 2011 Tohoku‐Oki earthquake, suggesting that dynamic stresses from the distant mainshock triggered most tremor close to failure, resulting in a temporary lack of tremor activity. In some cases, we observe rapid tremor migration with a speed at the order of 40–50 km/hr that is similar to the speed of fast tremor migration along dip on narrow streaks in Japan and Cascadia. Our results suggest that dense array techniques are capable of capturing detailed spatiotemporal evolutions of tremor behaviors in southern Taiwan. Online Material: Tables of station coordinates and tremor event parameters, and figures of the moving‐window grid‐search test with local earthquakes, tremor triggered by the 2011 Tohoku‐Oki earthquake, and additional examples of detected ambient tremors.