Effects of Low‐Velocity Fault Damage Zones on Long‐Term Earthquake Behaviors on Mature Strike‐Slip Faults
Effects of Low‐Velocity Fault Damage Zones on Long‐Term Earthquake Behaviors on Mature Strike‐Slip Faults
复制标题
低速断层损伤带对成熟走向滑断层长期地震行为的影响
DOI：
10.1029/2020jb019587
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Kaneko, Yoshihiro
中科院分区：
文献类型：
--
作者：
Thakur, Prithvi;Huang, Yihe;Kaneko, Yoshihiro
成熟的走滑断层通常被狭窄的受损岩石带包围，其特征是地震波速度低。对这些断层沿着地震的观测表明，地震活动高度集中在这个断层破坏带内。然而，断层破坏带对完整地震周期的长期影响，即几年到几个世纪，还没有得到很好的理解。我们模拟了一个垂直走滑断层上的非稳态滑动和动态地震破裂，该断层周围有一个断层破坏带，时间尺度为一千年，使用断层带材料特性和几何形状，这些特性和几何形状是由沿着主要走滑断层的观测结果激发的。断层损伤区近似为剪切波速低于围岩的弹性层。我们发现，动力波反射对断层的应力历史有显着影响，其特征强烈依赖于断层损伤区的宽度和刚度对比。弹性损伤的存在可以部分地解释沿着单一断层的地震规模和震源位置的变化，其随断层损伤带的深度、宽度和与寄主岩石的刚度对比而变化。断层破坏带的深度范围对震源位置有明显的影响，浅断层破坏带有利于浅震源，地震活动沿深度沿着呈双峰分布。我们的研究结果还表明，当断层破坏带穿透到地震的成核地点时，震源分布可能受到岩性（材料）和流变（摩擦）边界的影响。
Mature strike‐slip faults are usually surrounded by a narrow zone of damaged rocks characterized by low seismic wave velocities. Observations of earthquakes along such faults indicate that seismicity is highly concentrated within this fault damage zone. However, the long‐term influence of the fault damage zone on complete earthquake cycles, that is, years to centuries, is not well understood. We simulate aseismic slip and dynamic earthquake rupture on a vertical strike‐slip fault surrounded by a fault damage zone for a thousand‐year timescale using fault zone material properties and geometries motivated by observations along major strike‐slip faults. The fault damage zone is approximated asan elastic layer with lower shear wave velocity than the surrounding rock. We find that dynamic wave reflections, whose characteristics are strongly dependent on the width and the rigidity contrast of the fault damage zone, have a prominent effect on the stressing history of the fault. The presence of elastic damage can partially explain the variability in the earthquake sizes and hypocenter locations along a single fault, which vary with fault damage zone depth, width and rigidity contrast from the host rock. The depth extent of the fault damage zone has a pronounced effect on the earthquake hypocenter locations, and shallower fault damage zones favor shallower hypocenters with a bimodal distribution of seismicity along depth. Our findings also suggest significant effects on the hypocenter distribution when the fault damage zone penetrates to the nucleation sites of earthquakes, likely being influenced by both lithological (material) and rheological (frictional) boundaries.
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