The seismogenic zone in the Central Costa Rican Pacific margin: high-quality hypocentres from an amphibious network
The seismogenic zone in the Central Costa Rican Pacific margin: high-quality hypocentres from an amphibious network
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DOI：
10.1007/s00531-013-0955-8
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发表时间：
2014-10-01
影响因子：
2.3
通讯作者：
Flueh, Ernst R.
中科院分区：
文献类型：
--
作者：
Arroyo, Ivonne G.;Husen, Stephan;Flueh, Ernst R.
从正常洋壳俯冲到加厚洋壳的转变发生在哥斯达黎加边缘的中部，那里发生大型板间地震（中级类似于7）和丰富的震间地震活动与测深高点的俯冲有关。我们使用 3D P 波速度模型中的概率地震重定位，对陆上和海上组合地震网络在 6 个月内记录的 1,300 次地震进行了类似的重定位。大多数地震活动起源于板块边界的发震带，在大陆架下方 15 至 25-30 公里深度处呈现为 18 度倾斜的平面集群。星团内解决了几个反向焦点机制。这种震间板间地震活动的上限似乎主要受上覆板块厚度和相干性控制，而上覆板块厚度和相干性又受侵蚀过程以及沿板块边界温度低于 100 至 120 摄氏度的流体释放和逃逸控制。粘滑行为的下倾极限与大约 150 至 200 摄氏度的相对低温相结合，表明它是由地幔楔的蛇纹石化控制的。不同深度的俯冲海山的存在局部改变了震间板间地震活动的分布。与哥斯达黎加北部不同，过去二十年大地震的破裂似乎与震间板间地震活动所定义的区域一致。
Transition from subduction of normal to thickened oceanic crust occurs in the central portion of the Costa Rican margin, where large interplate earthquakes (M similar to 7) and abundant interseismic seismicity have been associated with subduction of bathymetric highs. We relocated similar to 1,300 earthquakes recorded for 6 months by a combined on-and offshore seismological network using probabilistic earthquake relocation in a 3D P-wave velocity model. Most of the seismicity originated at the seismogenic zone of the plate boundary, appearing as an 18 degrees dipping, planar cluster from 15 to 25-30 km depth, beneath the continental shelf. Several reverse focal mechanisms were resolved within the cluster. The upper limit of this interseismic interplate seismicity seems to be controlled primarily by the overlying-plate thickness and coherency, which in turn is governed by the erosional processes and fluid release and escape at temperatures lower than similar to 100 to 120 degrees C along the plate boundary. The downdip limit of the stick-slip behaviour collocates with relative low temperatures of similar to 150 to 200 degrees C, suggesting that it is controlled by serpentinization of the mantle wedge. The distribution of the interseismic interplate seismicity is locally modified by the presence of subducted seamounts at different depths. Unlike in northern Costa Rica, rupture of large earthquakes in the last two decades seems to coincide with the area defined by the interseismic interplate seismicity.