Shallow seismic structure of Kunlun fault zone in northern Tibetan Plateau, China: implications for the 2001 Ms8.1 Kunlun earthquake
Shallow seismic structure of Kunlun fault zone in northern Tibetan Plateau, China: implications for the 2001 Ms8.1 Kunlun earthquake
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DOI：
10.1111/j.1365-246x.2009.04049.x
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发表时间：
2009-06
影响因子：
2.8
通讯作者：
Chun-yong Wang;W. Mooney;Z. Ding;Jiansi Yang;Z. Yao;Hai Lou
中科院分区：
文献类型：
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作者：
Chun-yong Wang;W. Mooney;Z. Ding;Jiansi Yang;Z. Yao;Hai Lou
根据地震折射剖面和5次爆炸激发的地震陷波记录，联合反演了昆仑断裂带浅层地震速度结构。这些数据是在2001年青藏高原北方昆仑山口西8.1级地震后收集的。分析了沿断裂带沿着15公里范围内的26条共线记录剖面的震相，并利用地震折射法确定了断裂带内浅部地壳的一维P波和S波速度模型。16个地震台站沿着垂直于断裂带的离线剖面部署。用三维有限差分法模拟了断层陷波在记录剖面上的分布。对合成波形与实测波形相关系数的定量分析表明，昆仑断裂带宽度为300 m，断裂带内S波品质因子Q为15。值得注意的是，断层带内的横波速度从周围岩石到至少1-2公里的深度降低了30- 45%，而纵波速度降低了7- 20%，具有这种P波和S波低速度的断层带是高流体压力的指示，因为Vs比Vp受影响更大。KLFZ模型中的低速低Q带是2001年昆仑山口西Ms8.1地震沿断层轨迹沿着多次破裂的结果。
SUMMARY The shallow seismic velocity structure of the Kunlun fault zone (KLFZ) was jointly deduced from seismic refraction profiling and the records of trapped waves that were excited by five explosions. The data were collected after the 2001 Kunlun Ms8.1 earthquake in the northern Tibetan Plateau. Seismic phases for the in-line record sections (26 records up to a distance of 15 km) along the fault zone were analysed, and 1-D P- and S-wave velocity models of shallow crust within the fault zone were determined by using the seismic refraction method. Sixteen seismic stations were deployed along the off-line profile perpendicular to the fault zone. Fault-zone trapped waves appear clearly on the record sections, which were simulated with a 3-D finite difference algorithm. Quantitative analysis of the correlation coefficients of the synthetic and observed trapped waveforms indicates that the Kunlun fault-zone width is 300 m, and S-wave quality factor Q within the fault zone is 15. Significantly, S-wave velocities within the fault zone are reduced by 30–45 per cent from surrounding rocks to a depth of at least 1–2 km, while P-wave velocities are reduced by 7–20 per cent. A fault-zone with such Pand S-low velocities is an indication of high fluid pressure because Vs is affected more than Vp. The low-velocity and low-Q zone in the KLFZ model is the effect of multiple ruptures along the fault trace of the 2001 Ms8.1 Kunlun earthquake.