This study used the double-difference seismic tomography method to obtain the upper crustal velocity structure in Laizhou Bay and its adjacent areas (LBAA). We found that the horizontal and vertical distributions of the earthquakes after relocation in earthquake swarms are more concentrative than that before relocation. The lateral heterogeneity of crustal velocity structure near the surface in the LBAA is weak, and the low-velocity sedimentary caprocks are developed in most areas except for the Jiaobei uplift. The velocity structure in 5–25 km depth range is highly heterogeneity, which is closely related to different tectonic units. The local uplift tectonic units in Jiyang depression show high-velocity anomalies and should have deep crustal media properties. The high-velocity anomalies under the crust of Tancheng–Lujiang fault zone and the northern Laizhou Bay indicate the properties of upwelling mantle material media. Earthquake swarms activity in the study area are mainly concentrated in the high-velocity interlayer of the upper crust and its periphery. Compared with the relatively stable high-velocity body at the bottom crust, the location of high-velocity interlayer in the study area is more prone to earthquakes under the combined action of gravity and tectonic stress.

中文翻译：

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莱州湾及其附近地区上地壳速度结构及其与地震群活动的关系

本研究利用双差地震层析成像方法获得了莱州湾及其邻近地区（LBAA）的上地壳速度结构。我们发现，地震群中搬迁后的地震的水平和垂直分布比搬迁前的集中。LBAA地表附近地壳速度结构的横向非均质性较弱，除胶北隆起以外，大多数地区都发育了低速沉积盖层。5–25 km深度范围内的速度结构具有高度的非均质性，这与不同的构造单元密切相关。济阳depression陷的局部隆升构造单元表现出高速度异常，应具有较深的地壳介质特征。Tan城—庐江断裂带和莱州湾北部地壳下的高速异常表明上地幔物质介质的特征。研究区的地震群活动主要集中在上地壳及其外围的高速夹层中。与底部地壳相对稳定的高速体相比，研究区高速夹层的位置在重力和构造应力共同作用下更容易发生地震。