Geodetically inferred coseismic and postseismic slip due to the M 5.4 31 October 2007 Alum Rock earthquake
Geodetically inferred coseismic and postseismic slip due to the M 5.4 31 October 2007 Alum Rock earthquake
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由大地测量学推断的 2007 年 10 月 31 日明矾岩 5.4 级地震引起的同震和震后滑移
DOI：
10.1785/0120090017
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发表时间：
2009
影响因子：
3
通讯作者：
R. Simpson
中科院分区：
文献类型：
--
作者：
J. Murray;R. Simpson
2007年10月31日，5.4级明矾岩地震发生在旧金山湾区海沃德和卡拉维拉斯断层交界处附近，10台连续运行的全球定位系统（GPS）仪器记录了地震的同震和震后位移。地震后4个月的累积震后位移与余震的累积次数呈线性关系，并且在震级上与同震位移相当。地震后信号表明，除了发震深度的余震外，Calaveras西南倾斜浅断层面上还发生了局部的右侧/反向滑动。通过反演GPS数据推断出的滑动空间分布与一个模型相一致，在这个模型中，中度Calaveras断层地震破裂锁定了被蠕变、余震和微震活动区域包围的地块（Oppenheimer et al., 1990）。如果这个模型和现有的卡拉维拉斯断层滑动率估计是正确的，那么2007年明矾岩破裂斑块上仍然存在滑动缺陷，可能由地震滑动或更大地震中的滑动弥补。最近的研究（例如，Manaker等人，2005年）表明，在海沃德断层和卡拉维拉斯断层的深处，通过一个由任务地震趋势（MST）照亮的简单连续表面连接起来，这意味着破坏性的地震破裂可能涉及两个断层（Graymer等人，2008年）。如果这种几何结构是正确的，那么我们对2007年明矾岩事件推断的同震和震后滑动的组合预测，在MST表面和明矾岩震源西北约5公里的Calaveras断层北部，静态库仑应力增加约0.6巴。
On 31 October 2007 the M 5.4 Alum Rock earthquake occurred near the junction between the Hayward and Calaveras faults in the San Francisco Bay Area, producing coseismic and postseismic displacements recorded by 10 continuously operating Global Positioning System (GPS) instruments. The cumulative postseismic displacements over the four months following the earthquake are linearly related to the cumulative number of aftershocks and are comparable in magnitude to the coseismic displacements. The postseismic signal suggests that, in addition to afterslip at seismogenic depths, localized right-lateral/reverse slip occurred on dipping shallow fault surfaces southwest of the Calaveras. The spatial distribution of slip inferred by inverting the GPS data is compatible with a model in which moderate Calaveras fault earthquakes rupture locked patches surrounded by areas of creep, afterslip, and microseismicity (Oppenheimer et al. , 1990). If this model and existing Calaveras fault slip rate estimates are correct, a slip deficit remains on the 2007 Alum Rock rupture patch that may be made up by aseismic slip or slip in larger earthquakes. Recent studies (e.g., Manaker et al. , 2005) suggest that at depth the Hayward and central Calaveras faults connect via a simple continuous surface illuminated by the Mission Seismic Trend (MST), implying that a damaging earthquake rupture could involve both faults (Graymer et al. , 2008). If this geometry is correct, the combined coseismic and postseismic slip we infer for the 2007 Alum Rock event predicts static Coulomb stress increases of ∼0.6 bar on the MST surface and on the northern Calaveras fault ∼5 km northwest of the Alum Rock hypocenter.