The 1971 San Fernando earthquake: A double event?
The 1971 San Fernando earthquake: A double event?
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1971 年圣费尔南多地震：双重事件？
DOI：
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发表时间：
1982
影响因子：
3
通讯作者：
T. Heaton
中科院分区：
文献类型：
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作者：
T. Heaton
证据表明，1971年圣费尔南多地震可能是一个双重事件，发生在两个独立的，近平行的逆冲断层。据推测，最初的事件发生在马德雷山脉断层带的深处，该断层带沿着圣加布里埃尔山脉的底部。据推测，破裂发生在约15公里至约3公里的深度。第二个事件被认为是在大约4秒后在另一个陡倾的逆冲断层上开始的，该断层位于马德雷山脉断层带以南大约4公里处。该断层的地表痕迹与圣费尔南多断层带相吻合，圣费尔南多断层带是与地表破裂有关的主要断层。据推测，破裂从8公里的深度传播到自由表面。第一次和第二次事件的磁矩分别约为0.7 × 10^（26）达因-厘米和1.0 × 10^（26）达因-厘米。该模型被发现解释的组合数据集的强地面运动，EQUESTOP-S波形，和静态偏移比以前的模型，其中包括一个单一的断层面或一个平面的倾角变浅，随着深度的减小。尽管如此，观测到的运动的许多特征仍然无法解释，并且关于圣费尔南多地震的断层历史仍然存在相当大的不确定性。
Evidence is presented which suggest that the 1971 San Fernando earthquake may have been a double event that occurred on two separate, subparallel thrust faults. It is postulated that the initial event took place at depth on the Sierra Madre fault zone which runs along the base of the San Gabriel Mountains. Rupture is postulated to have occurred from a depth of about 15 km to a depth of about 3 km. A second event is thought to have initiated about 4 sec later on another steeply dipping thrust fault which is located about 4 km south of the Sierra Madre fault zone. The surface trace of this fault coincides with the San Fernando fault zone which was the principal fault associated with surface rupture. It is postulated that rupture propagated from a depth of 8 km to the free surface. The moments of the first and second events are approximately 0.7 × 10^(26) dyne-cm and 1.0 × 10^(26) dyne-cm, respectively. This model is found to explain the combined data sets of strong ground motions, teleseismic P and S waveforms, and static offsets better than previous models, which consist of either a single fault plane or a plane having a dip angle which shallows with decreasing depth. Nevertheless, many features of the observed motions remain unexplained, and considerable uncertainty still exists regarding the faulting history of the San Fernando earthquake.