Structural Properties of the San Jacinto Fault Zone at Blackburn Saddle from Seismic Data of a Dense Linear Array
Structural Properties of the San Jacinto Fault Zone at Blackburn Saddle from Seismic Data of a Dense Linear Array
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DOI：
10.1007/s00024-018-1988-5
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发表时间：
2018-09
影响因子：
2
通讯作者：
P. Share;A. Allam;Y. Ben‐Zion;F. Lin;F. Vernon
中科院分区：
文献类型：
--
作者：
P. Share;A. Allam;Y. Ben‐Zion;F. Lin;F. Vernon
我们对布莱克本鞍座的圣哈辛托断裂带进行了成像，使用的地震波形是由一个约2公里的断层线性阵列记录的，其中108个三分量传感器间隔约10-30米。阵列的长度和时空采样使我们能够获得具有空间范围的内部断裂带结构的高分辨率信息，这些信息可以与区域层析模型合并。远震p波的极化、振幅和到达时间的跨断层变化表明，在断层表面轨迹附近（传感器BS55）和东北方向约270 m处（传感器BS34）的地下结构发生了突变。对局部事件产生的断裂带头波的分析表明，存在一个深层双物质界面，该界面从阵列向东南方向延伸至少50公里，其部分速度对比为bb0 ~ 10%。这一分析也证实了远震结果，表明主要在断层东北方向有一个广泛的破坏带，在BS34附近有一个浅层双物质界面，并与深部界面合并。局部事件产生的love型断裂带圈闭波探测和波形反演表明，在宽约150 m、速度比围岩降低约55%、深度约2 km的较宽破坏区内存在圈闭构造。所进行的分析对主要发震断层的地下位置以及主要双材料界面和损伤结构的性质提供了一致的结果。成像断裂带的性质与地震破裂在西北方向的首选传播方向一致。
We image the San Jacinto fault zone at Blackburn Saddle using earthquake waveforms recorded by a ~ 2-km across-fault linear array with 108 three-component sensors separated by ~ 10–30 m. The length and spatiotemporal sampling of the array allow us to derive high-resolution information on the internal fault zone structure with spatial extent that can be merged with regional tomography models. Across-fault variations in polarization, amplitude, and arrival time of teleseismicPwaves indicate abrupt changes in subsurface structure near the surface trace of the fault (sensor BS55) and ~ 270 m to the northeast (sensor BS34). Analysis of fault zone head waves from local events reveals the existence of a deep bimaterial interface that extends from the array to at least 50 km southeast and has a section with > 10% velocity contrast. This analysis also corroborates the teleseismic results and indicates a broad damage zone primarily northeast of the fault bounded by a shallow bimaterial interface near BS34 that merges with the deep interface. Detection and waveform inversions of Love-type fault zone trapped waves generated by local events indicate a trapping structure within the broader damage zone with width of ~ 150 m, velocity reduction of ~ 55% from the surrounding rock and depth extent of ~ 2 km. The performed analyses provide consistent results on the subsurface location of the main seismogenic fault and properties of a major bimaterial interface and damage structure. The imaged fault zone properties are consistent with preferred propagation direction of earthquake ruptures in the area to the northwest.