The focal depths of the 2008 Panzhihua earthquake sequence and the stress field in the source region
The focal depths of the 2008 Panzhihua earthquake sequence and the stress field in the source region
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2008年攀枝花地震序列震源深度及震源区应力场
DOI：
10.1007/s11430-018-9441-6
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发表时间：
2019-10-17
影响因子：
5.7
通讯作者：
Tian, Jianhui
中科院分区：
文献类型：
--
作者：
Luo, Yan;Zhao, Li;Tian, Jianhui
研究了2008年攀枝花6.1级地震序列的震源深度和震源区构造应力场。利用地震深度相位sPL确定了攀枝花地震序列中M ≥ 3.0级的24个地震的震源深度，并利用P波和S波三分量波形拟合方法测定了232个地震的震源深度。主震震源深度约为12 km。大多数震级M >= 3.0的余震发生在12-18 km深度范围内的脆性上地壳中。进一步对攀枝花地震震源区周边232个地震的震源机制进行了研究，结果表明：滇中地块内的地震以走滑机制为主，而滇中地块边界外和边界附近的地震则表现出震源机制的复杂性。将本研究中的232个地震机制与全球质心矩张量（GCMT）目录中的解相结合，得到二维应力场。反演结果表明，滇中地块主要为走滑断裂体制，最大主压应力σ（1）方向为北西-东南向。其分布与GPS速度场基本一致。而滇中地块外围和附近的主应力轴方向和断裂类型发生了变化。结果表明，研究区构造应力场主要受滇中地块东南向水平运动和顺时针旋转的控制，这是藏东地块东移与古老而坚硬的华南地块（SCB）相遇的结果。攀枝花地震破裂深度约为12 km，构造应力场为SE向水平挤压、NE向水平拉张。
Focal depths of the 2008 M(S)6.1 Panzhihua earthquake sequence and tectonic stress field in the source area are investigated. Source depths of 24 earthquakes in Panzhihua earthquake sequence with a magnitude M >= 3.0 were determined using the seismic depth phase sPL; additionally, the focal depths of 232 earthquakes were measured by fitting the three-component waveforms of the P and S waves. The source depth of the main shock is similar to 12 km. The majority of the aftershocks with magnitude M >= 3.0 occurred in the brittle upper crust at the depths range of 12-18 km. Further, the Source mechanisms of the 232 events around the Panzhihua earthquake source area were determined, and the results show that the earthquakes have predominantly strike-slip mechanisms in the Dianzhong Block, but display complexity of the focal mechanisms outside and near the boundary of the Dianzhong block. The 232 earthquake mechanisms from this study are combined with the solutions from the Global Centroid Moment Tensor (GCMT) catalog to derive 2D stress field. The inversion results show that the Dianzhong block is predominantly under a strike slip faulting regime and the direction of the maximum principal compression sigma(1) is northwest-southeast (NW-SE)-trending. The distribution is coincide with GPS velocity field. However, orientations of principal stress axes as well as the faulting types change outside and near the Dianzhong block. The results show that the tectonic stress field in the study area is predominantly controlled by the southeast (SE)-trending horizontal movement and clockwise rotation of the Dianzhong block as a result of the eastward movement of eastern Tibetan meeting the old and rigid South China block (SCB). The Panzhihua earthquake ruptured at similar to 12 km depth where the tectonic stress regime is under the SE-direction horizontal compression and the NE-direction horizontal extension.