Imaging the source region of the 2003 San Simeon earthquake within the weak Franciscan subduction complex, central California
Imaging the source region of the 2003 San Simeon earthquake within the weak Franciscan subduction complex, central California
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对 2003 年圣西蒙地震的震源区域进行成像，该地震位于加利福尼亚州中部薄弱的方济会俯冲复合体内
DOI：
10.1029/2004gl021049
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发表时间：
2004
影响因子：
5.2
通讯作者：
T. Brocher
中科院分区：
文献类型：
--
作者：
E. Hauksson;D. Oppenheimer;T. Brocher
从2003年加州中部圣西蒙6.5级地震序列和1986年地震折射实验中收集的数据表明，弱方济各俯冲复合体在一个没有明显速度对比的区域内发生脆性破坏。重新定位的震源表明地震活动性和海洋断层之间的空间关系，虽然附近的未知断层上的盲断层也是一个同样合理的选择。余震体积夹在纳西米恩托和大洋断层之间，其特征是低压缩速度（Vp）的岩石，东部和西部被较高Vp的岩石包围。推测方济各会岩石的体积嵌在较大的圣露西亚背斜内。孔隙流体，其存在意味着提高Vp/Vs值，可能会局部降低正应力和限制余震的深度分布在3至10公里的上盘。沿主震破裂面沿着余震的缺乏可能反映了在主震破裂周围的低Vp或软弱的岩石基质中没有损伤区或几乎完全的应力下降。
Data collected from the 2003 Mw6.5 San Simeon earthquake sequence in central California and a 1986 seismic refraction experiment demonstrate that the weak Franciscan subduction complex suffered brittle failure in a region without significant velocity contrast across a slip plane. Relocated hypocenters suggest a spatial relationship between the seismicity and the Oceanic fault, although blind faulting on a nearby, unknown fault is an equally plausible alternative. The aftershock volume is sandwiched between the Nacimiento and Oceanic faults and is characterized by rocks of low compressional velocity (Vp) abutted to the east and west by rocks of higher Vp. This volume of inferred Franciscan rocks is embedded within the larger Santa Lucia anticline. Pore fluids, whose presence is implied by elevated Vp/Vs values, may locally decrease normal stress and limit the aftershock depth distribution between 3 to 10 km within the hanging wall. The paucity of aftershocks along the mainshock rupture surface may reflect either the absence of a damage zone or an almost complete stress drop within the low Vp or weak rock matrix surrounding the mainshock rupture.