中国东北的深源地震波形匹配检测及定位

中国东北珲春周边地区位于环太平洋地震带上，也是中国唯一存在的深源地震带.较大地震发生后常会有若干震级较小的余震发生，但在相同的地震震级情况下深源地震的余震一般比浅源地震的余震数量要少1~3个数量级，且在全球不同深震区的深震余震数量也存在显著差异.针对国际地震中心（ISC）2010年7月至2014年12月目录中给出的中国东北附近27次震源深度超过300 km的深源地震，我们首先利用区域固定地震台及NECsaids流动地震台阵的连续波形数据，选取已知地震事件作为模板，采用Match&Locate及Matched Filter方法进行波形互相关叠加分析来检测微小深震事件；然后对1966至2017年ISC目录中的东北地区深源地震进行双差重定位以提高震源位置的准确性，进一步分析深震活动与俯冲板片的关系.研究结果显示除ISC目录中给出的深震事件，我们未能检测出作为模板的深源地震的前震或余震活动，证明东北深源地震余震活动较少并不是由于台站分布有限而造成的漏检结果；重定位后震源延伸的角度与西太平洋板片在410~660 km地幔转换带内的俯冲角度较为一致，并且大部分深震震源位置位于俯冲板片中的亚稳态橄榄岩楔形区内部.结合双差定位结果、b值分析及前人研究成果，我们认为东北深源地震应不属于与俯冲非直接相关的"孤立地震"，而是与西太平洋板块俯冲直接相关.

Waveform detection and location of deep earthquakes in the subduction zone beneath Northeast China

Along the Japan trench, the West Pacific plate is subducting beneath the Eurasian plate, reaching about 600 km depth below near the Hunchun area, Northeast China, as evidenced by deep earthquakes (with focal depth more than 300 km) observed. These quakes are notable for producing very few aftershocks in comparison with shallow earthquakes. There are 27 earthquakes deeper than 300 km in Northeast China reported by the International Seismological Centre (ISC) from August 2010 to December 2014. However, few foreshocks or aftershocks before and after these earthquakes are documented in the ISC catalog, which is unclear that whether this is due to detection threshold by limited station distribution or different mechanisms between the deep and shallow earthquakes. In this study, we employ continuous waveform data from August 2010 to December 2014 recorded by the dense NECsaids Array (Northeast China Seismic Array to Investigate Deep Subduction) and Jilin and Heilongjiang Seismic Networks to detect the aftershock productivity of deep earthquakes by using Match & Locate (M&L) and Matched Filter methods. The well recorded waveforms for the 27 deep earthquakes in the ISC catalogue are chosen as template waveforms, meanwhile the continuous waveforms recorded by the same seismic stations are used to detect their foreshocks or aftershocks. The 27 ISC-listed deep earthquakes are self-detected successfully with maximum CC (Cross-Correlation)≈1.0. However, we don't detect any more foreshocks or aftershocks before and after the deep template earthquakes. We also relocate the deep earthquakes in Northeast China from 1966 to 2017 based on the ISC bulletin data and our phase picking data, and almost all the double-difference relocated deep earthquakes occurred within the Metastable Olivine Wedge (MOW). The about 5 km depth difference within nearby hypocenters and about 0.5 b-value for the deep earthquakes in Northeast China may indicate that these deep events are directly related to the subducting Pacific slab.