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Calibration of the Tibetan Plateau using regional seismic waveforms

机译：利用区域地震波形对青藏高原进行标定

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摘要

We use the recordings from 51 earthquakes produced by a PASSCAL deployment in Tibet to develop a two-layer crustal model for the region. Starting with their ISC locations, we iteratively fit the P-arrival times to relocate the earthquakes and estimate mantle and crustal seismic parameters. An average crustal P velocity of 6.2-6.3 km/s is obtained for a crustal thickness of 65 km while the P velocity of the uppermost mantle is 8.1 km/s. The upper layer of the model is further fine-tuned by obtaining the best synthetic SH waveform match to an observed waveform for a well-located event. Green's functions from this model are then used to estimate the source parameters for those events using a grid search procedure. Average event relocation relative to the ISC locations, excluding two poorly located earthquakes, is 16 km. All but one earthquake are determined by the waveform inversion to be at depths between 5 and 15 km. This is 15 km shallower, on average, than depths reported by the ISC. The shallow seismicity cut-off depth and low crustal velocities suggest high temperatures in the lower crust. Thrust faulting source mechanisms dominate at the margins of the plateau. Within the plateau, at locations with surface elevations less than 5 km, source mechanisms are a mixture of strike-slip and thrust. Most events occurring in the high plateau where elevations are above 5 km show normal faulting. This indicates that a large portion of the plateau is under EW extension.
机译：我们使用西藏PASSCAL部署产生的51次地震的记录来开发该地区的两层地壳模型。从其ISC位置开始，我们迭代拟合P到达时间以重新定位地震并估计地幔和地壳地震参数。对于65 km的地壳厚度，平均地壳P速度为6.2-6.3 km / s，而最高地幔的P速度为8.1 km / s。通过获得最佳合成的SH波形与观测到的波形的最佳位置，可以进一步微调模型的上层。然后使用网格搜索过程，使用该模型的Green函数来估计这些事件的源参数。相对于ISC地点的平均事件重定位（不包括两次地震的位置不佳）为16 km。除一次地震外，所有地震都通过波形反演确定在5至15 km之间。平均而言，这比ISC报告的深度浅15公里。浅的地震活动截止深度和低的地壳速度表明下地壳温度较高。推力断层源机制在高原边缘占主导地位。在高原内，在表面高度小于5 km的位置，源机制是走滑和推力的混合。高海拔超过5 km的高原地区发生的大多数事件都表明是正常断层。这表明高原的很大一部分处于EW扩展之下。

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