Strain accumulation on the northern San Andreas Fault Zone since 1906
Strain accumulation on the northern San Andreas Fault Zone since 1906
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1906 年以来圣安德烈亚斯断裂带北部的应变积累
DOI：
10.1029/jb080i035p04873
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发表时间：
1975
影响因子：
--
通讯作者：
W. Thatcher
中科院分区：
文献类型：
--
作者：
W. Thatcher
1906年后在旧金山弗朗西斯科大地震发生地区进行的大地测量提供了一些关于现在在37°和38°N之间发生在圣安德烈亚斯断层系统上的应变积累的模式和机制的细节。在1907-1963年期间，在旧金山弗朗西斯科湾周围1070公里宽的区域内，张量剪切应变率的平均值为0.3×10−6 yr−1。地震后对圣安德烈亚斯断层的影响自1906年以来持续了230年，可以解释大多数早期观测结果。然而，自1940年以来，也许更早，圣安德烈亚斯以东的断层在应变积累中发挥了重要作用。自1950年以来，在数据不确定性范围内，旧金山弗朗西斯科湾地区的剪切应变在圣安德烈亚斯以东80公里宽的区域内是均匀的。最大剪应变方向近似平行于卡拉韦拉斯断层，与圣安德烈亚斯断层的走向和局部相对板块运动方向明显不同。在圣弗朗西斯科西北约70公里处的雷耶斯角，剪切应变集中在圣安德烈亚斯断层和罗杰斯溪断层附近，并且明显小于东南方向观测到的应变，从雷耶斯角向东北延伸的70公里长的三角弧上的平均应变仅为0.17×10−1 yr−6（1938-1961）。总之，所有这些观察结果表明，在应变积累过程中，断层滑动在深度上的重要性，但也表明，圣安德烈亚斯板块边界可能会逐渐锁定在旧金山弗朗西斯科西北部。
Post-1906 geodetic surveys in the region of the great San Francisco earthquake have provided some details on the pattern and mechanism of the strain accumulation now occurring between 37° and 38°N on the San Andreas fault system. Tensor shear strain rates have averaged 0.3×10−6 yr−1 during 1907–1963 in a ∼70-km-wide region around San Francisco Bay. Postearthquake effects on the San Andreas fault persisting for ∼30 years following 1906 can account for most of the early observations. However, since ∼1940 and perhaps earlier, faults to the east of the San Andreas have played an important role in the strain accumulation. Since about 1950, shear straining in the San Francisco Bay area has within the data uncertainties been uniform across an 80-km-wide region immediately to the east of the San Andreas. The maximum shear strain direction is approximately parallel to the Calaveras fault and is distinctly different from both the strike of the San Andreas fault and the local direction of relative plate motion. At Point Reyes, ∼70 km northwest of San Francisco, shear strains are concentrated near the San Andreas and Rogers Creek faults and are significantly smaller than strains observed further southeast, averaging only 0.17×10−1 yr−6 (1938–1961) across a 70-km-long triangulation arc extending northeast from Point Reyes. Taken together, all of these observations indicate the importance of fault slip at depth in the strain accumulation process but also suggest that the San Andreas plate boundary may become progressively more locked northwest of San Francisco.