Creep on the Sargent Fault over the Past 50 Yr from Alignment Arrays with Implications for Slip Transfer between the Calaveras and San Andreas Faults, California
Creep on the Sargent Fault over the Past 50 Yr from Alignment Arrays with Implications for Slip Transfer between the Calaveras and San Andreas Faults, California
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过去 50 年萨金特断层的蠕变，来自对准阵列，对加利福尼亚州卡拉维拉斯断层和圣安德烈亚斯断层之间的滑移转移具有影响
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
B. Philibosian
中科院分区：
文献类型：
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作者：
Daniel D. Mongovin;B. Philibosian
55 公里长的萨金特断层穿过加利福尼亚州吉尔罗伊以西的圣克鲁斯山脉，将蠕动的卡拉维拉斯断层与锁定的圣安德烈亚斯断层连接起来。这两个断层之间的萨金特断层的位置可能对蠕变断层和闭锁断层之间的滑动传递和应变积累有影响。萨金特断层蠕变的检测和测量将表明震间应变在这些邻近断层附近累积的位置。 1969 年，在萨金特断层中部安装了两个相距 3.7 公里的对准阵列，以研究潜在的蠕变。这些阵列于 1970 年和 1975 年进行了测量，通过比较这些测量结果，北部阵列中两条断层带的蠕变率为 3.4 ± 0.6 毫米/年；南部阵列的结果从未公布。 2019 年和 2020 年，我们使用全站仪重新勘察了两个阵列，并分析结果以确定累积的断层蠕变。我们的结果表明，在 1970 年至 2020 年（49.3 年）期间，北部阵列在 1970 年代活跃的两条断层带上向右偏移了 164 ± 25 毫米，产生的平均蠕变率为 3.3 ± 1.3 毫米/年。因此，该地点的 5 年和 50 年蠕变率似乎相似。南部阵列可能不会跨越整个断层带，但在 1970 年至 2019 年间，在两条断层带上向右偏移了 84 ± 13 毫米，在 48.9 年间产生的平均蠕变率为 1.7 ± 0.8 毫米/年。这些最近的调查记录了萨金特断层的持续蠕变，这可能会减少地震应变积累，从而减少地震危险。然而，该断层上持续的抗震滑动可能会导致应力和应变重新分布到邻近的断层上，应该成为继续研究的领域。
The 55-km-long Sargent fault connects the creeping Calaveras fault with the locked San Andreas fault through the Santa Cruz Mountains west of Gilroy, California. The position of the Sargent fault between these two faults may have implications for slip transfer and strain accumulation between a creeping and locked fault. The detection and measurement of creep on the Sargent fault would indicate where interseismic strain is accumulating adjacent to these neighboring faults. In 1969, two alignment arrays separated by 3.7 km were installed across the central section of the Sargent fault to investigate potential creep. These arrays were measured in 1970 and 1975, and comparison of these measurements yielded a creep rate of 3.4 ± 0.6 mm/yr across two fault strands in the northern array; results from the southern array were never published. In 2019 and 2020, we resurveyed both arrays using a total station and analyzed the results to determine accumulated fault creep. Our results show that between 1970 and 2020, a period of 49.3 yr, the northern array was dextrally offset 164 ± 25 mm across the same two fault strands that were active in the 1970s, yielding an average creep rate of 3.3 ± 1.3 mm/yr. Thus, it appears that the 5 and 50 yr creep rates at this site are similar. The southern array, which may not span the entire fault zone, was dextrally offset 84 ± 13 mm across two fault strands between 1970 and 2019, yielding an average creep rate of 1.7 ± 0.8 mm/yr over 48.9 yr. These recent surveys document continued creep on the Sargent fault, which may reduce seismic strain accumulation and therefore seismic hazard. However, continued aseismic slip on this fault may result in the redistribution of stress and strain to adjacent faults and should be an area of continued study.