摘要:
2023年12月18日在中国甘肃省积石山县发生了Mw6.0地震，本文采用合成孔径雷达干涉测量技术（InSAR）处理了覆盖震源区域的Sentinel-1 A SAR影像，得到积石山地震的同震地表形变场，并联合余震精定位数据，基于小震断层面拟合方法和弹性半空间的位错模型建立了积石山地震断层几何参数，反演本次地震的滑动分布，继而通过计算断层面库仑应力变化评估了此次地震对周边断层的影响。结果表明：2023年积石山地震为逆冲兼具走滑分量类型的地震，并未破裂到地表，InSAR形变结果表明本次地震的升、降轨同震地表形变场均以抬升形变为主，升轨最大LOS向位移~7.0cm，降轨最大LOS向位移~6.8cm；联合小震断层面拟合与断层几何参数反演得到震源深度主要集中在6-15km，发震断层面倾向NE，走向为323°, 倾角50°; 破裂主要集中在地下4~8km深度范围内，最大滑移量0.2m，出现与地下5.7km处，滑动分布模型揭示此次地震是以逆冲为主的地震，矩震级为Mw5.8。此次地震发生在拉脊山南缘断裂上，静态库仑应力变化显示2023年积石山地震增加了拉脊山南缘断裂、拉脊山北缘断裂、倒淌河-临夏断裂东段的未来地震风险。
Abstract:
The Mw6.0 earthquake occurred in Jishishan County, Gansu Province, China, on December 18, 2023. Methods: The interferometric synthetic aperture radar (InSAR) technique was utilized to process Sentinel-1A radar images from both ascending and descending tracks to retrieve high resolution coseismic surface displacement maps for these Jishishan earthquakes. The coseismic surface displacements and the double difference relocation algorithm of the earthquake sequence were then inverted to determine the fault geometry parameters and the non-uniform fault slip distributions with a dislocation model in an elastic half-space. Results: The results show that the 2023 Jishishan earthquake was a reverse event on a buried fault with a maximum surface displacement of 7.0 cm and 6.8 cm on the ascending and descending tracks, respectively. The depth of the seismic source is mainly concentrated at 6-15 km, which is obtained by the joint small-seismic fault-plane fitting and the fault-geometry parameter inversion. The depth of the earthquake source is mainly concentrated in 6-15km, and the seismic fault tends to NE, strikes at 323°, and dips at 50°. the rupture is mainly concentrated in the depth range of 4-11km underground, and the maximum slip amount of 0.2m occurs at 5.7km underground, Conclusions: we prefer this eqrthquake occurred on Southern edge of Lajishan fault with a NNW-trending, east-dipping, thrust fault. By calculating the coulomb failure stress changes (ΔCFS), it indicates an increased seismic risk for the future in the southern margin of Laqishan Fault, the northern margin of Laqishan Fault, and the eastern segment of Daotanghe-Linxia Fault after the 2023 earthquake in Jishishan.
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