东昆仑断裂带东段微震检测与构造分析

Microearthquake Detection and Its Tectonic Implications in the Eastern Segment of the East Kunlun Fault Zone

本文整理了一套包括微震检测、地震去噪、震相拾取和地震定位的构建高精度地震目录数据的处理流程。收集了青海省内东昆仑断裂带东段20个数字地震台站记录的2009−2018年的连续地震数据,并应用该流程进行微震检测、去噪和定位。首先,从台网中心提供的3198个地震事件目录中筛选出1200个信噪比高且震相较为明显的地震事件作为模板事件,利用基于图像处理器加速的模板匹配定位方法(GPU-M&L)进行遗漏地震的检测与识别,然后利用基于神经网络的地震波形去噪方法进行去噪处理,再结合基于深度学习的震相拾取技术和双差定位方法对去噪后的地震事件进行震相拾取和定位。使用GPU-M&L共检测出13318个地震事件,约为台网地震目录事件数量的4.2倍;去噪后得到7514个地震事件,约为台网地震目录事件数量的2.3倍,完备震级从台网目录的ML 1.5降低至ML 0.9。定位后共获得7247个地震事件,精定位结果显示,东昆仑断裂带东段的地震以中小震为主,在空间上呈窄条带状或簇状分布,震源深度的优势分布深度为0~15 km;在101°E附近地震的空间展布发生变化,主要沿阿万仓断裂带向东南展布;在玛沁-玛曲段可能存在地震空区。本研究的微震结果为研究东昆仑断裂带东段地震活动性、发震断层的深部构造等提供了重要的数据基础。

To comprehensively analyze the seismic activity of the East Kunlun Fault Zone from 2009 to 2018,we developed a procedure encompassing microearthquake detection,seismic denoising,seismic phase picking,and seismic location to construct a seismic catalog.We collected continuous waveforms recorded by 20 stations in the eastern segment of the East Kunlun Fault Zone from January 2009 to December 2018.From the 3198 seismic events listed in the China Earthquake Networks Center(CENC)catalog,we selected 1200 events with clear seismic phases and high signal-to-noise ratios as template events.Using the Graphics Processing Unit-based Match and Locate(GPU-M&L)method,we detected a total of 13,318 earthquake events,including the template events,which is roughly 4.2 times the number of events in the CENC catalog.Next,we employed the neural network-based seismic waveform denoising technique(DeepDenoiser)to extract seismic signals from the noise.By examining the time-domain and frequency-domain charac-teristics of noise and seismic signals,we further identified and confirmed 7514 seismic events,approximately 2.3 times the number reported by the CENC.The complete magnitude of the detected catalog decreased from ML 1.5,as given by the CENC,to ML 0.9 in this study.Subsequently,we applied the deep neural network-based seismic arrival-time picking algorithm(PhaseNet)to pick the seismic phases.Finally,using the double-difference localization method(hypoDD),we finely located 7247 events.The results show that earthquakes in the eastern segment of the East Kunlun Fault Zone are linearly distributed or clustered,with focal depths predominantly ranging from 0 to 15 km.East of 101°E,the spatial distribution of earthquakes mainly spreads southeastward along the Awancang Fault Zone.Additionally,our results indicate a possible seismic gap in the Maqin-Maqu segment.This study provides an important database for further research on seismic activity and deep seismogenic faults in the eastern segment of the East Kunlun Fault Zone.