区域宽频地震波形反演所揭示的2022年青海门源M_(S)6.9地震震源破裂过程  

Rupture process of the 2022 M_S6.9 Menyuan,Qinghai earthquake revealed by inversion of regional broadband seismograms

作　　者：朱音杰 罗艳[2] 赵里 Zhu Yinjie;Luo Yan;Zhao Li(Hebei Hongshan National Observatory on Thick Sediments and Seismic Hazards,Hebei Xingtai 054000,China;Key Laboratory of Earthquake Prediction,Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China;Hebei Earthquake Agency,Shijiazhuang 050021,China;School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China)

机构地区：[1]河北红山巨厚沉积与地震灾害国家野外科学观测研究站,河北邢台054000 [2]中国地震局地震预测研究所地震预测重点实验室,北京100036 [3]北京大学地球与空间科学学院,北京100871 [4]河北省地震局,石家庄050021 [5]中国科学技术大学地球和空间科学学院,合肥230026

出　　处：《地震学报》2023年第5期781-796,共16页Acta Seismologica Sinica

基　　金：国家自然科学基金面上项目(41974063);地震科学联合基金(U1939202);河北省地震科技星火计划攻关项目(DZ202108090110)联合资助。

摘　　要：基于有限断层模型反演方法,利用区域宽频带数据反演了2022年1月青海门源M_(S)6.9地震的震源破裂过程,并结合地质构造与地震重定位结果判断发震断层走向.综合反演结果表明:此次地震的发震断层走向为WNW向,主要以走滑为主;破裂主要发生在震源两侧,可能存在着双侧破裂,在震后2 s和9 s出现破裂极大值,最大错动量约为1.5 m,位于深度约6km处,发生明显破裂的深度约为16 km,地表破裂长度约20 km;此次地震释放的标量地震矩为1.23×10^(19)N·m,相当于矩震级M_(W)6.7,地震能量主要在前15 s释放;发震断层面的倾角为84.6°,接近于垂直,由于破裂范围较大,所以发生明显错动分布的地表投影也长达34 km.Finite fault inversion is an effective method commonly used to study the rupture process of earthquakes and has been widely applied to seismic source rupture process research.In this study,we utilized the method to investigate the rupture process of the M_S6.9 Menyuan,Qinghai earthquake in 2022 using regional broadband seismic waveform data.Considering the quality and distribution of the network data,we selected 20 regional seismic stations with high signal-to-noise ratio and epicentral distances less than 500 km.We preprocessed the observed waveforms by removing instrument response,demeaning,detrending,and filtering.We also calculated the near-field Green's functions using the frequency-wavenumber(f-k)method.First,synthesize the waveforms using the Green's function synthesis theory and compare them with corresponding observed waveforms.Then,perform fault model inversion where the displacement response of each sub-fault at any station can be represented as a function of the sub-fault's slip,direction,rise time,and rupture velocity.Additionally,in the process of reducing errors,we use wavelet transform to establish the objective function and use simulated annealing(SA)to search for the global optimal solution of each sub-fault parameter,so that the waveform residual can be minimized in the wavelet domain,ultimately obtaining the best spatio-temporal distribution model of the source fault slip.In this study,high frequency signal of regional network is used.Low-frequency information constrains the overall characteristics of the earthquake source,but is less sensitive to detailed rupture features such as rupture rise time or rupture velocity changes.However,sudden changes in slip amplitude or rupture velocity will radiate intense seismic signals with higherfrequency.Therefore,using higher-frequency signals for finite fault inversion can effectively improve spatial and temporal resolution,and fully utilize the wide-band information of seismic waves to better understand the earthquake source rupture process.The followi

关 键 词：2022年门源地震 有限断层 错动分布 震源破裂过程 青藏高原东北缘 

分 类 号：P315.2[天文地球—地震学]