STUDY ON FAULT LOCKING CHARACTERISTIC AROUND THE DALIANGSHAN SUB-BLOCK

doi:10.3969/j.issn.0253-4967.2014.04.016

Abstract

Abstract:

GPS campaign observations can monitor dynamic characteristic of crustal deformation near the fault zone effectively. Dynamic characteristic of crustal deformation is the manifestation of the dynamic action of the faults in deep and shallow structures. The locking and movement state of faults in deep and shallow structures can be an objective characterization of strain accumulation in seismogenic fault. So we can use dynamic GPS observations to invert fault locking and fault slip deficit rate by some models, and then judge the mid- to long-term seismic potential of the faults. Research about the faults around the Daliangshan sub-block is relatively poor, and the moderate-strong earthquakes increased significantly around the sub-block over the past decade, which makes fault locking and seismic potential around the sub-block be the problem to be urgently studied. Therefore, by using the GPS horizontal velocity field of 1999-2007, 2009-2013 and the negative dislocation model of DEFNODE, we inverted for spatial fault locking and fault slip deficit rate in the Daliangshan sub-block which contains three major fault zones, named Daliangshan, Mabian-Yanjin and Huize-Yiliang, before and after the Wenchuan earthquake. We analyzed the seismic potential characteristic of the three faults combining with the seismic gap and the spatial distribution of b value. The results show that the locking state of the three faults was basically same before and after the Wenchuan earthquake, which indicates that the earthquake probably has a very weak influence on the faults. The inversion results of two periods show that the southern segment of Daliangshan, Mabian-Yanjin and Huize-Yiliang Faults are basically completely locked except the southwestern segment of Huize-Yiliang Fault. The slip deficit rates of the three faults are not huge before and after the earthquake. Daliangshan Fault is mainly of a sinistral strike-slip deficit, Mabian-Yanjin Fault has a little amount of sinistral strike-slip and compressional deficit which was slightly enhanced after the earthquake, and Huize-Yiliang Fault is characteristic of compressional deficit with a small amount of dextral strike-slip deficit, which reduced to about zero after the earthquake. Combining with some other results, we conclude that current seismic potential for strong or major earthquakes exists on the three faults.

Key words: Daliangshan sub-block, negative dislocation inversion of DEFNODE, fault locking, slip deficit rate

摘要：

利用1999—2007期和2009—2013期中国大陆GPS速度场数据, 采用DEFNODE负位错反演程序估算了大凉山次级块体周边断层——大凉山断裂、马边-盐津断裂、会泽-彝良断裂在汶川地震前后的断层闭锁程度和滑动亏损空间分布动态变化特征, 并结合地震空区和b值空间分布等结果分析了这几条断裂带的强震危险性.结果表明, 汶川地震对这3条断裂带的影响可能较弱, 它们在地震前后闭锁程度基本一致, 两期结果均显示大凉山断裂南段、马边-盐津断裂、会泽-彝良断裂(西南端除外)基本为完全闭锁;汶川地震前后3条断裂带的滑动亏损速率均较小, 大凉山断裂以左旋滑动亏损为主, 马边-盐津断裂具有很弱的左旋和挤压滑动亏损分量并在震后均稍有增强, 会泽-彝良断裂以挤压滑动亏损为主、兼有右旋滑动亏损, 汶川地震后其右旋分量消失.结合其他方法的研究结果, 认为目前这3条断裂带仍具有较大地震发生的危险性.

关键词: 大凉山次级块体, DEFNODE负位错反演, 断层闭锁, 滑动亏损

CLC Number:

P315.2

ZHAO Jing, LIU Jie, NIU An-fu, YAN Wei. STUDY ON FAULT LOCKING CHARACTERISTIC AROUND THE DALIANGSHAN SUB-BLOCK[J]. SEISMOLOGY AND GEOLOGY, 2014, 36(4): 1135-1144.

赵静, 刘杰, 牛安福, 闫伟. 大凉山次级块体周边断层的闭锁特征[J]. 地震地质, 2014, 36(4): 1135-1144.

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