Long-range and long-term fault interactions in Southern California
Long-range and long-term fault interactions in Southern California
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DOI：
10.1130/g23789a.1
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发表时间：
2007-09-01
期刊：
影响因子：
5.8
通讯作者：
Sammis, Charles G.
中科院分区：
文献类型：
--
作者：
Dolan, James F.;Bowman, David D.;Sammis, Charles G.
古地震学资料表明，在过去的12,000年里，洛杉矶地区发生了四次地震矩释放爆发。这段历史时期似乎是持续了大约1000年的持续平静的一部分。洛杉矶地区的这些快速地震位移时期发生在莫哈韦沙漠中加州东部剪切带上观察到的类似活动爆发之间的平静期，该剪切带现在是地震活跃的。一个运动学模型，其中的断层大圣安德烈亚斯系统抑制活动的断层在东加州剪切带，反之亦然，可以解释两个断层网络之间的活动明显切换。结合短期大地测量速率和长期地质速率在南加州主要断层系统上共同变化的观察，这表明要么（1）上地壳断层上地震位移的时间集群增加了其向下延伸的韧性变形，要么（2）断层下方下地壳的快速韧性滑动加载上地壳，驱动地震集群。我们认为，交替周期的快速地震位移可能是预期的地震活动模式时，两个断层系统容纳相同的板块边界运动，并在一个系统上的滑动抑制滑动的其他。
Paleoseismologicall data suggest the occurrence of four bursts of seismic moment release in the Los Angeles region during the past 12,000 yr. The historic period appears to be part of an ongoing lull that has persisted for about the past 1000 yr. These periods of rapid seismic displacement in the Los Angeles region have occurred during the lulls between similar bursts of activity observed on the eastern California shear zone in the Mojave Desert, which is now seismically active. A kinematic model in which the faults of the greater San Andreas system suppress activity on faults in the eastern California shear zone, and vice versa, can explain the apparent switching of activity between the two fault networks. Combined with the observation that short-term geodetic and longer-term geologic rates co-vary on major southern California fault systems, this suggests that either (1) a temporal cluster of seismic displacements on upper-crustal faults increases ductile deformation on their downward extensions, or (2) rapid ductile slip in the lower crust beneath faults loads the upper crust, driving a seismic cluster. We suggest that alternating periods of rapid seismic displacement may be the expected mode of seismicity when two fault systems accommodate the same plate-boundary motion, and slip on one system suppresses slip on the other.