为深度剖析2023年山东平原M5.5地震对周围区域的影响,首先结合不同震源机制结果确定了本次地震的震源机制中心解: 节面Ⅰ走向124.02°、倾角72.37°、滑动角-19.54°,节面 Ⅱ 走向220.16°、倾角71.41°、滑动角-161.36°,该地震的震源机制与当地的应力场较为符合,是在当地构造应力场作用下的一次正常能量释放,并且节面 Ⅱ 的相对剪应力和正应力的结果比节面 Ⅰ 更容易破裂,再结合该地震断层走向判断节面 Ⅱ 为本次地震的发震断层面。然后基于本次地震的破裂模型及均匀弹性半空间模型,计算此次地震对周围地区产生的地表同震位移场及水平应变场,发现震中北侧和南侧的物质向外涌出,而西侧的物质涌入震中,在发震断层附近呈现明显的走滑机制; 震中南北两侧隆升,西侧沉降; 震中西侧的面应变分布呈现压缩,南北侧呈现伸张。最后计算该地震在周围主要活动断层上产生的库伦应力变化,结果表明平原M5.5地震对沧东断裂北段、聊城—兰考断裂北段、高唐断裂、徐黑西断裂和埕西—丰二庄断裂的库伦应力变化不明显,对齐河—广饶断裂西段和临邑断裂的最大应力卸载量达到了千Pa量级,对夏口断裂和陵县—阳信断裂的库伦应力最大增加量达到百Pa量级,对沧东断裂中段的库伦应力最大增加量和卸载量均达到千Pa量级,应注意沧东断裂中段库伦应力变化较高区域的地震活动性。

In order to comprehensively analyze the impact of the 2023 Pingyuan,Shandong,M5.5 earthquake on the surrounding area,we first determined the central focal mechanism of the earthquake based on different focal mechanism results:nodal plane I:strike 124.02°,dip 72.37°,slip -19.54°;nodal plane Ⅱ:strike 220.16°,dip 71.41°,slip -161.36°. The earthquake's focal mechanism aligns with the local stress field,indicating a normal energy release under the local tectonic stress field. Moreover,the relative shear stress and normal stress on nodal plane II exceed those on nodal plane I. Considering the NE-SW orientation of the active faults around the epicenter,it is inferred that nodal plane II is the seismogenic fault. Subsequently,based on the rupture model of the earthquake and a homogeneous elastic half-space model,we calculated the surface co-seismic displacement field,horizontal principal strain,and areal strain generated by the earthquake in the surrounding area. Our observations reveal that material to the north and south of the epicenter experienced uplift,while material to the west side subsided,indicating a distinct strike-slip mechanism close to the seismogenic fault. Compressional areal strain distribution was evident on the west side of the epicenter,whereas extensional strain distribution prevailed on the north and south sides. Finally,we computed the Coulomb stress changes on the main active faults around the earthquake. The results indicate insignificant Coulomb stress changes on the northern segment of the Cangdong fault,Liaocheng-Lankao fault's northern segment,the Gaotang fault,the Xuheixi fault,and the Chengxi-Fengerzhuang fault. However,the Coulomb stress unloading amount reached a significant magnitude of 1,000 Pa on the western section of the Qihe-Guangrao fault and the Linyi fault. The Xiakou Fault and the Lingxian-Yangxin fault exhibited the most significant increase in Coulomb stress,with a magnitude of 100 Pa,while the middle section of the Cangdong fault experienced both a maximum increase and reduction in Coulomb stress,reaching a high magnitude of 1,000 Pa. The area with substantial Coulomb stress modification in the middle section of the Cangdong fault warrants special attention regarding seismic activity.

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中央高校科研业务费专项(ZY20215117)、国家自然科学基金(42174074、41674055)、河北省高等学校自然科学技术项目(ZD2022160)和河北省地震动力学重点实验室开放基金(FZ212105)共同资助