Fault slip in southern California
Fault slip in southern California
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南加州断层滑动
DOI：
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发表时间：
1985
期刊：
影响因子：
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通讯作者：
Stephen N. Cohn
中科院分区：
文献类型：
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作者：
J. Louie;C. R. Allen;David C. Johnson;P. Haase;Stephen N. Cohn
在过去的18年里，主要使用经纬仪对准阵列和双线伸缩仪对加州南部主要断层的滑动进行了测量。它们提供了断层痕迹几百米范围内的大地测量控制，这补充了其他技术在更远距离进行的测量。在Garlock断层的西南部、Coachella山谷的Banning和San Andreas断层、Coyote Creek断层、Superstition Hills断层和埃尔森特罗以西20公里处的一个未命名断层中，发现了几年来约为0.5至5 mm/年的恒定滑动速率。这些滑动速率通常比位移速率低一个数量级，而位移速率是在距离断层迹线较远的点之间通过大地测量测得的。测量了1979年帝王谷地震引起的水平和垂直方向上指数衰减的震后滑动。它与同震位移的大小相似。对滑动断层附近地震活动的分析表明，累积的地震矩不足以解释震后滑动的恒定或衰减。因此，运动机制可能不同于加州中部的滑动断层，后者的运动速率接近板块运动，并伴随着足够的地震矩。从南加州的滑动断层移走的地震活动可能驱动了它们相对平静的运动。
Measurements of slip on major faults in southern California have been performed over the past 18 yr using principally theodolite alignment arrays and tautwire extensometers. They provide geodetic control within a few hundred meters of the fault traces, which complements measurements made by other techniques at larger distances. Approximately constant slip rates of from 0.5 to 5 mm/yr over periods of several years have been found for the southwestern portion of the Garlock fault, the Banning and San Andreas faults in the Coachella Valley, the Coyote Creek fault, the Superstition Hills fault, and an unnamed fault 20 km west of El Centro. These slip rates are typically an order of magnitude below displacement rates that have been geodetically measured between points at greater distances from the fault traces. Exponentially decaying postseismic slip in the horizontal and vertical directions due to the 1979 Imperial Valley earthquake has been measured. It is similar in magnitude to the coseismic displacements. Analysis of seismic activity adjacent to slipping faults has shown that accumulated seismic moment is insufficient to explain either the constant or the decaying postseismic slip. Thus the mechanism of motion may differ from that of slipping faults in central California, which move at rates close to the plate motion and are accompanied by sufficient seismic moment. Seismic activity removed from the slipping faults in southern California may be driving their relatively aseismic motion.