Observation‐Constrained Multicycle Dynamic Models of the Southern San Andreas and the Northern San Jacinto Faults: Addressing Complexity in Paleoearthquake Extent and Recurrence With Realistic 2D Fault Geometry
Observation‐Constrained Multicycle Dynamic Models of the Southern San Andreas and the Northern San Jacinto Faults: Addressing Complexity in Paleoearthquake Extent and Recurrence With Realistic 2D Fault Geometry
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DOI：
10.1029/2021jb023420
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发表时间：
2022-02
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影响因子：
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通讯作者：
Dunyu Liu;B. Duan;K. Scharer;D. Yule
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作者：
Dunyu Liu;B. Duan;K. Scharer;D. Yule
了解导致地震复杂性的力学条件对地震危险性分析很重要。在这项研究中，我们模拟了基于物理的圣安德烈斯断层（卡里佐通过圣贝纳迪诺部分）和圣哈辛托断层（克莱蒙和克拉克链）的多源动力学模型。我们专注于一个复杂的断层几何形状的基础上，南加州地震中心社区断层模型和它的影响，在多个地震周期。使用大地测量得出的应变率，我们验证模型对地质滑动率和复发间隔在不同的古地震网站。我们发现，断层几何形状，动态破裂和震间应力积累之间的相互作用产生的应力不均匀性，导致破裂分段和地震复发的变化。我们的模型产生的地震破裂程度类似于最近的综合古地震目录。大弯和卡洪山口的“地震门”偶尔会阻止动态破裂。压缩角是从局部断层走向中减去最大剪切应变率方向，可以更好地确定抑制弯曲对动态破裂的阻抗的可能性。由于大弯的压缩角为20°，因此穿越大弯的破裂（如1857年特洪堡地震）比基于经验关系的预期更频繁，经验关系预测40°的限制弯曲终止大多数破裂。我们的模型表明，大破裂往往开始北部的大弯和向南传播，类似于1857年的地震，提供了关键信息，在该地区的地面震动评估。
Understanding mechanical conditions that lead to complexity in earthquakes is important to seismic hazard analysis. In this study, we simulate physics‐based multicycle dynamic models of the San Andreas fault (Carrizo through San Bernardino sections) and the San Jacinto fault (Claremont and Clark strands). We focus on a complex fault geometry based on the Southern California Earthquake Center Community Fault Model and its effect over multiple earthquake cycles. Using geodetically derived strain rates, we validate the models against geologic slip rates and recurrence intervals at various paleoseismic sites. We find that the interactions among fault geometry, dynamic rupture and interseismic stress accumulation produce stress heterogeneities, leading to rupture segmentation and variability in earthquake recurrence. Our models produce earthquakes with rupture extents similar to a recent comprehensive paleoseismic catalog. The “earthquake gates” of the Big Bend and the Cajon Pass occasionally impede dynamic ruptures. The angle of compression, which is the subtraction of the maximum shear strain rate direction from the local fault strike, can better determine the likelihood of the impedance of restraining bends to dynamic ruptures. Because the Big Bend has an angle of compression of ∼20°, ruptures that traverse the Big Bend, like the 1857 Fort Tejon earthquake, are more frequent than expected based on empirical relations which predict the ∼40° restraining bend to terminate most ruptures. Our models indicate that large ruptures tend to initiate north of the Big Bend and propagate southwards, similar to the 1857 earthquake, providing critical information for ground shaking assessment in the region.