2023年甘肃积石山MS 6.2地震数据产品

Data products of the 2023 MS 6.2 earthquake in Jishishan,Gansu Province,China

2023年12月18日,地处青藏高原东北缘的甘肃积石山发生MS6.2地震。地震发生后,中国地震台网中心立即启动应急响应,测震台网快速产出地震数据产品,为地震发震构造研究、震源区地震危险性评估提供基础数据。基于中国地震台网资料,采用gCAP方法获得主震震源机制解,结果显示,此次地震为1次逆冲型为主、兼有左旋分量的事件,矩心深度为11 km。采用双差定位方法对积石山地震及主震后27天内623次余震序列进行重新定位,定位结果显示,主震位置为35.75°N、102.83°E,震源深度为14 km,余震序列展布方向为NNW,长度约18 km,震源深度优势分布在5—17 km,断层面有略向东倾趋势。另外,基于研究所得地震定位和震源机制结果,采用PSGRN/PSCMP软件包,计算此次地震不同深度上的库仑应力分布,结果显示,主震发生使得主震周边区域进入应力卸载状态。最后,使用中国地震预警网数据计算此次地震仪器烈度,显示最大烈度值为Ⅸ度,烈度区域小,且主要集中在主震NNW方向。结合周边地质构造,认为甘肃积石山MS6.2地震事件为一次带有左旋走滑分量的逆冲型地震。

On December 18,2023,an MS 6.2 earthquake occurred in Jishishan County,Gansu Province,on the northeastern edge of the Qinghai-Xizang Plateau.After the earthquake,China Earthquake Networks Center(CENC)started the emergency response immediately,and the National Seismic Network Center carried out the output of rapid seismic data products to provide basic materials for the study of seismogenic tectonics and the assessment of seismic hazard.Based on the data from the China Seismic Networks,the gCAP method is used to obtain the focal mechanism solution of the mainshock,which shows that the earthquake is a predominantly thrust-type event with a left-lateral component,and the centroid depth is 11 km.The double-difference location method is used to relocate the Jishishan mainshock and the sequence of 623 aftershocks within 27 days,and the result shows that the location of the mainshock is(35.75°N,102.83°E),with a depth of 14 km,while the aftershock sequence spreads in the direction of NNW,with a length of about 18 km,whose dominant distribution is of 5-17 km in depths,with a slightly eastward-dipping trend on the fault plane.In addition,based on the results of the location and focal mechanism obtained in this study,the Coulomb stress distribution at different depths of this earthquake is calculated by using the PSGRN/PSCMP code,and the result shows that the occurrence of the mainshock causes the source area a stress unloading status.Finally,the instrumental intensity of this earthquake is calculated with the data from the China Earthquake Early Warning Network(CEWN),and shows that the maximum intensity value isⅨ,concentrated in a small region and mainly focused on the NNW direction.Combined with the neighboring geological structure,the MS 6.2 event in Jishishan,Gansu is considered to be an uplift-type earthquake with a left-later slip component.