Upper plate contraction north of the migrating Mendocino triple junction, northern California: Implications for partitioning of strain
Upper plate contraction north of the migrating Mendocino triple junction, northern California: Implications for partitioning of strain
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加利福尼亚州北部迁移的门多西诺三联点以北的上板块收缩：对应变分配的影响
DOI：
10.1029/1999tc001177
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发表时间：
2000
期刊：
影响因子：
4.2
通讯作者：
P. A. McCrory
中科院分区：
文献类型：
--
作者：
P. A. McCrory
对卡斯卡迪亚俯冲边缘永久收缩的地质测量限制了沿会聚板块边界的构造变形的一个组成部分，这一组成部分对于地壳断层的地震危险性评估至关重要。对卡斯卡迪亚俯冲带南端陆上俯冲边缘岩石中活动断层的综合调查表明，这些逆冲断层每年可容纳约 10 毫米的 020°–045° 方向的汇聚。俯冲带的地震构造模型通常将上部板块应变分配给巨型逆冲断层上的地震滑移的估计。大地测量模型将这种永久地壳应变纳入对巨型逆冲断层弹性应变累积的估计中。两种类型的模型都低估了与地壳断层相关的地震危险。从板块收敛速度（40-50 毫米/年；方向 040°-055°）中减去观测到的收缩，剩下 30-40 毫米/年的收敛，可分为巨型逆冲断层上的滑移、南胡安德富卡板块内的收缩和俯冲复杂岩石外的地壳收缩。这种滑移划分的简单估计忽略了门多西诺三联结附近板块收敛和收缩方向之间的差异。
Geologic measurement of permanent contraction across the Cascadia subduction margin constrains one component of the tectonic deformation along the convergent plate boundary, the component critical for the seismic hazard assessment of crustal faults. A comprehensive survey of active faults in onshore subduction margin rocks at the southern end of the Cascadia subduction zone indicates that these thrust faults accommodate ∼10 mm/yr of convergence oriented 020°–045°. Seismotectonic models of subduction zones typically assign this upper plate strain to the estimate of aseismic slip on the megathrust. Geodetic models include this permanent crustal strain within estimates of elastic strain accumulation on the megathrust. Both types of models underestimate the seismic hazard associated with crustal faults. Subtracting the observed contraction from the plate convergence rate (40–50 mm/yr; directed 040°–055°) leaves 30–40 mm/yr of convergence to be partitioned between slip on the megathrust, contraction within the southern Juan de Fuca plate, and crustal contraction outside the subduction complex rocks. This simple estimate of slip partitioning neglects the discrepancy between the plate convergence and contraction directions in the vicinity of the Mendocino triple junction.