Three-dimensional S-wave velocity structure of the crust and upper mantle for the normal fault system beneath the Yinchuan Basin from joint inversion of receiver function and surface wave
Three-dimensional S-wave velocity structure of the crust and upper mantle for the normal fault system beneath the Yinchuan Basin from joint inversion of receiver function and surface wave
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DOI：
10.1007/s11430-022-1059-y
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发表时间：
2023-03
期刊：
影响因子：
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通讯作者：
Weilai Wang;Guangyao Cai;Guijuan Lai;Xianwei Zeng;J. Bao;Long Zhang;Jun Su;Mingfei Chen
中科院分区：
文献类型：
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作者：
Weilai Wang;Guangyao Cai;Guijuan Lai;Xianwei Zeng;J. Bao;Long Zhang;Jun Su;Mingfei Chen
贺兰山-银川盆地构造带分布着一系列平行正断层，历史上曾发生过8.0级地震。在大陆的正断层系统中发生如此大的地震是罕见的。为深入了解正断层系统的精细结构，在正断层系统附近布设了104个宽带临时台站，采集了附近永久台站和其他临时台站的资料，通过接收函数和面波联合反演，获得了206个台站下方高精度的三维横波速度结构。银川盆地具有典型的地堑中地堑的特征，由四条主要断裂组成。分析了正断层系统的地震活动性，发现盆地南部存在一条地震条带，其沉积厚度变化明显，推测为正断层系统的南部边界。贺兰山-银川盆地边界两侧地壳厚度和速度结构存在明显差异，边界之下的上地幔存在低速带，这可能与贺兰山-银川盆地构造带位于阿拉善地块和鄂尔多斯地块之间有关。银川-平罗8.0级地震发生在银川盆地四条主要断裂交汇处，位于盆山边界速度过渡带附近的高速带上。该边界下的上地幔低速带可能促进了这次地震的成核。根据地质钻探、微震活动、区域应力场和速度模型等证据，推断贺兰山东麓皮埃蒙特断裂带是1739年银川-平罗8.0级地震的发震断裂。
A series of parallel normal faults are distributed in the Helan Mountain-Yinchuan Basin tectonic belt, where a historical M8.0 earthquake occurred. It is rare that such a great earthquake occurs in a normal fault system within the continent. To deeply understand the fine structure of the normal fault system, we deployed 104 broadband temporary stations near the system, collected data from permanent stations and other temporary stations nearby, and obtained the high-precision three-dimensional S-wave velocity structure beneath 206 stations via joint inversion of receiver function and surface wave. A typical graben-in-graben feature bounded by four major faults was identified in the Yinchuan Basin. We analyzed the seismicity in the normal fault system and found a seismic strip in the southern part of the basin, where there are significant changes in the sedimentary thickness, which is speculated to be the southern boundary of the normal fault system. There are significant differences in the crustal thickness and velocity structure in the crust on both sides of the boundary between the Helan Mountain and the Yinchuan Basin, and a low-velocity zone was identified in the upper mantle beneath this boundary, which could be related to the fact that the Helan Mountain-Yinchuan Basin tectonic belt is located between the Alxa Block and the Ordos Block. TheM8.0 Yinchuan-Pingluo earthquake occurred at the junction of four major faults in the Yinchuan Basin, which was located in the high-velocity zone near the velocity transition zone at the basin-mountain boundary. The low-velocity zone in the upper mantle beneath this boundary may have promoted the nucleation of this earthquake. Based on evidence from geological drilling, microseismicity, the regional stress field, and the velocity models obtained in this study, it is inferred that the eastern piedmont fault zone of the Helan Mountain was the seismogenic fault of the 1739M8.0 Yinchuan-Pingluo earthquake.