The Analysis of Seismogenic Structure of Seismic Source Area of Qingzhou ML4.1 Earthquake in Shandong
The ML4.1 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 Digit-al 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 ML2.0.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 ori-entated 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.
Qingzhou earthquakeFocal mechanism solutionDouble difference relocationStress field
万方数据
