潍坊青州M_(L)4.1地震震源区发震构造分析

The Analysis of Seismogenic Structure of Seismic Source Area of Qingzhou M_(L)4.1 Earthquake in Shandong

2022年5月2日7时53分山东潍坊青州发生M_(L)4.1地震,基于中国地震台网中心的地震观测报告和山东数字化台网的波形资料,采用双差定位法对潍坊青州地震序列进行重新精定位,利用P波初动方法对其中11个M_(L)2.0以上的地震求震源机制解。利用阻尼时空应力反演方法和MSATSI软件包反演震源区局部应力场特征。经过分析得到以下结论:青州地震序列往SN向展布、倾向N。主震震源机制显示为正断,其节面Ⅰ走向263°、倾角31°、滑动角-109°,节面Ⅱ走向106°、倾角61°、滑动角-78°,局部应力场最佳主压应力轴呈NWW-SEE向(-92.19°)低倾角(16.09°)挤压,最优主张应力轴呈SSE-NNW向(0.26°)近水平(8.45°)拉张。本文推断发震断层为走向EW的隐伏断裂。

The M_(L)4.1 earthquake occurred in Qingzhou,Weifang,Shandong province,at 7:53 a.m.,on May 2,2022.Based on the earthquake observation reports from the China Earthquake Networks Center and the digitized waveform data from the Shandong Digital Network,the double-difference localization method was used to relocate the earthquake sequence in Qingzhou,Weifang,and the P-wave initial motion method was used to determine the source mechanism solutions for 11 of the earthquakes with magnitude above M_(L)2.0.The damped spatial-temporal stress inversion method and MSATSI software package were used to invert the local stress field characteristics in the source area.The following conclusions were obtained from the analysis.The Qingzhou earthquake sequence is orientated in the SN direction tending to the North.The focal mechanism of mainshock shows a rupture in normal type with a 263°strike,31°dip,and−109°rake for node I,and a 106°strike,61°dip,and−78°rake for node II.The principal compressive stress axis is in the direction of the SSE-NNW(−92.19°)with a low plunge(16.09°),and the optimal extensional stress axis is the direction of the SSE-NNW(0.26°)with a horizontal plunge(8.45°).In this paper,we concluded that the seismogenic fault is a blind fault which is trended in the direction of the E-W.