New geodetic constraints on southern San Andreas fault-slip rates, San Gorgonio Pass, California
New geodetic constraints on southern San Andreas fault-slip rates, San Gorgonio Pass, California
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DOI：
10.1130/ges02239.1
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发表时间：
2021-02-01
期刊：
影响因子：
2.5
通讯作者：
McGill, Sally F.
中科院分区：
文献类型：
--
作者：
Guns, Katherine A.;Bennett, Richard A.;McGill, Sally F.
评估扩散板块边界系统（如加州南部的圣安德烈亚斯断层）的断层滑动速率对于表征地震危险性和了解不同断层链如何共同作用以适应板块边界运动至关重要。在圣戈尔戈尼奥山口这样的地方，在一个小区域内相互作用的众多断层链的几何复杂性为理解每个断层的破裂潜力和行为增加了额外的障碍。为了更好地了解该地区断层滑动速率的划分，我们建立了一套新的弹性断块模型，测试了该地区16个不同的模型断层几何形状。这些模型建立在以前的研究，将更新的运动GPS测量从圣贝纳迪诺山脉和东部横向范围到一个新计算的GPS速度场，已被删除的长期和短期震后位移从12个过去的大规模地震，以估计模型断层滑动率。使用这个震后减少GPS速度场产生一个最佳拟合的模型几何形状，解决了长期存在的地质-大地滑动率差异在东加州剪切带时，考虑到断层外变形，产生的总滑动率为7.2 +/- 2.8毫米/年。我们的模型表明，两个活跃的链的圣安德烈亚斯系统在圣戈尔戈尼奥通行证需要产生足够低的大地向右滑动率，以配合地质观测。最后，结果表明，震后变形可能有更多的作用，发挥在影响加载的断层在南加州比以前认为的。
Assessing fault-slip rates in diffuse plate boundary systems such as the San Andreas fault in southern California is critical both to characterize seismic hazards and to understand how different fault strands work together to accommodate plate boundary motion. In places such as San Gorgonio Pass, the geometric complexity of numerous fault strands interacting in a small area adds an extra obstacle to understanding the rupture potential and behavior of each individual fault. To better understand partitioning of fault-slip rates in this region, we build a new set of elastic fault-block models that test 16 different model fault geometries for the area. These models build on previous studies by incorporating updated campaign GPS measurements from the San Bernardino Mountains and Eastern Transverse Ranges into a newly calculated GPS velocity field that has been removed of long- and short-term postseismic displacements from 12 past large-magnitude earthquakes to estimate model fault-slip rates. Using this postseismic-reduced GPS velocity field produces a best-fitting model geometry that resolves the long-standing geologic-geodetic slip-rate discrepancy in the Eastern California shear zone when off-fault deformation is taken into account, yielding a summed slip rate of 7.2 +/- 2.8 mm/yr. Our models indicate that two active strands of the San Andreas system in San Gorgonio Pass are needed to produce sufficiently low geodetic dextral slip rates to match geologic observations. Lastly, results suggest that postseismic deformation may have more of a role to play in affecting the loading of faults in southern California than previously thought.