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首页> 外文期刊>Geosphere >A 3700 yr paleoseismic record from the northern San Jacinto fault and implications for joint rupture of the San Jacinto and San Andreas faults
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A 3700 yr paleoseismic record from the northern San Jacinto fault and implications for joint rupture of the San Jacinto and San Andreas faults

机译：来自圣哈辛托北部断层的3700年古地震记录及其对圣哈辛托断层和圣安德烈亚斯断层的联合破裂的影响

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The San Andreas and San Jacinto faults are the primary plate-boundary structures in southern California and present a large earthquake hazard for the region. They approach each other in the Cajon Pass area between the San Gabriel and San Bernardino Mountains, where the northern end of the San Jacinto fault forms a 2-km-wide releasing step with the San Andreas fault. In this study, we used paleoseismic data from sites on the San Jacinto and San Andreas faults near their juncture to evaluate spatial and temporal patterns of surface rupture between these major structures of the North American–Pacific transform plate boundary. We present a new 3700 yr paleoseismic record from the northern San Jacinto fault at Mystic Lake, where trench excavations exposed evidence for at least 16 surface ruptures. A sedimentary gap in our trench exposures separates three ruptures in the oldest part of the record from 13 ruptures during the past 2000 yr. For the past 2000 yr, the mean recurrence times varied from 86 to 312 yr, with a mean recurrence interval of 160 yr. This rate of surface rupture is roughly equal to that of the southern San Andreas fault south of the Cajon Pass juncture, but it is half that of the San Andreas fault north of the juncture, indicating that coseismic strain on the San Andreas fault is split between the southern San Andreas and San Jacinto faults south of Cajon Pass. Comparison of the past 2000 yr of the Mystic Lake record to similar paleoseismic records from nearby sections of the San Andreas fault suggests that: (1) the current open interval on these two faults in the study area is longer than their average recurrence intervals, but that similar intervals of quiescence have occurred in the past 2000 yr; (2) the San Andreas and San Jacinto faults have probably ruptured together multiple times in the past 2000 yr; and (3) a joint rupture of the San Jacinto fault with the Mojave section of the San Andreas fault may be a more likely source of a major earthquake in southern California than a rupture on the San Andreas fault from the Mojave segment to the southern end of the fault.
机译：San Andreas和San Jacinto断层是加利福尼亚南部的主要板块边界构造，对该地区构成了巨大的地震危险。它们在圣加布里埃尔山脉和圣贝纳迪诺山脉之间的卡洪Pass口地区互相靠近，圣哈辛托断裂的北端与圣安德烈亚斯断裂形成了一个2公里宽的释放台阶。在这项研究中，我们使用了San Jacinto和San Andreas断裂附近交会处的古地震数据，以评估北美-太平洋转换板块边界这些主要结构之间的表面破裂时空格局。我们提供了Mystic Lake北部San Jacinto断层的3700年新的古地震记录，那里的沟槽开挖暴露了至少16个表面破裂的证据。在我们的沟渠中，沉积物上的沉积间隙使记录的最旧部分中的三个破裂与过去2000年中的13个破裂分开。在过去的2000年中，平均复发时间从86年到312年不等，平均复发间隔为160年。该表面破裂率大致等于Cajon Pass交接点以南的圣安德列斯断层南部，但是交接点以北的圣安地列斯断层的一半，这表明圣安德里亚斯断层的同震应变在Cajon Pass以南的San Andreas南部和San Jacinto断层。将Mystic Lake记录的过去2000年与圣安德烈亚斯断层附近断层的类似古地震记录进行比较表明：（1）研究区中这两个断层的当前开裂间隔长于其平均复发间隔，但是在过去的2000年中，出现了类似的静止间隔; （2）在过去的2000年中，圣安德烈亚斯和圣哈辛托断层可能一起破裂了多次; （3）San Jacinto断层与San Andreas断层的Mojave断面联合破裂可能是南加利福尼亚州发生大地震的原因，而不是从Mojave段到南端的San Andreas断层的破裂。故障。

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