Imaging subsurface structures in the San Jacinto fault zone with high-frequency noise recorded by dense linear arrays
Imaging subsurface structures in the San Jacinto fault zone with high-frequency noise recorded by dense linear arrays
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DOI：
10.1093/gji/ggz069
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发表时间：
2019-02
影响因子：
2.8
通讯作者：
D. Zigone;Y. Ben‐Zion;M. Lehujeur;M. Campillo;G. Hillers;F. Vernon
中科院分区：
文献类型：
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作者：
D. Zigone;Y. Ben‐Zion;M. Lehujeur;M. Campillo;G. Hillers;F. Vernon
利用南加州圣哈辛托断裂带(SJFZ)三个线性阵列记录的2-35 Hz环境地震噪声的互相关，推导出阵列位置地壳顶部50-90m的高分辨率横波速度模型。对相干瑞利面波进行了反演，得到了S−1在0.2~0.6公里范围内的二维群速度图。利用马尔科夫链蒙特卡罗方法，将这些图反演出为断层周围的剪切波速度。结果表明，在顶部20-30m处有明显的低速带，速度减幅达35%，浅层fl构造的深度小于50m，所得到的速度、低速带相对于主地表轨迹的位置以及随深度的形状与同一地点或附近的钻孔测量和以前的SJFZ深部成像基本一致。成像技术只需要30天的∼数据(90%的信噪比是在15天内获得的)，它弥合了地表地质和没有最高100米分辨率的典型层析成像研究之间的观测差距。
Cross-correlations of 2–35 Hz ambient seismic noise recorded by three linear arrays across the San Jacinto Fault Zone (SJFZ) in Southern California are used to derive high-resolution shear wave velocity models for the top 50–90 m of the crust at the array locations. Coherent Rayleigh surface waves are inverted to construct 2-D maps of group velocities in the range 0.2–0.6 km s − 1 . These maps are inverted to shear wave velocities around the fault using a Markov Chain Monte Carlo approach. The results show marked low-velocity zones in the top 20–30 m with velocity reduction up to 35 per cent and shallow flower structures at depth shallower than 50 m. The derived velocities, location of low-velocity zone with respect to main surface traces and shape with depth are generally consistent with borehole measurements and previous imaging of deeper sections of the SJFZ at the same sites or nearby. The imaging technique requires only ∼ 30 d of data (90 per cent of the signal-to-noise ratio is obtained in 15 d) and it bridges an observational gap between surface geology and typical tomography studies with no resolution in the top 100 m.