Pervasive cracking of the northern Chilean Coastal Cordillera: New evidence for forearc extension
Pervasive cracking of the northern Chilean Coastal Cordillera: New evidence for forearc extension
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智利北部海岸科迪勒拉山脉普遍破裂：弧前延伸的新证据
DOI：
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发表时间：
2005
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影响因子：
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通讯作者：
D. Carrizo
中科院分区：
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作者：
J. Loveless;G. Hoke;R. Allmendinger;G. González;B. Isacks;D. Carrizo
尽管南美洲板块和纳斯卡板块之间的强耦合发震界面辐合，但智利北部弧前的主要新构造特征是弧正伸展。我们使用1米分辨率的IKONOS卫星图像在Salar Grande（21°S）附近500平方公里的区域内绘制了近37,000个裂缝。这些特征在无处不在的石膏表层中保存得最好，它们既有非构造起源，也有构造起源。然而，它们垂直于板块辐合矢量的强烈优先取向表明，它们的形成主要是由于与板块边界过程（如震间载荷、同震和震后应变）以及俯冲侵蚀引起的长期不稳定有关的近似东西向伸展。类似的结构在1995年发生在Salar Grande南部Antofagasta市附近的8.0级地震期间或之后不久形成，并与2001年发生在秘鲁阿雷基帕的8.2-8.4级地震同时发生。像这样的裂缝可能会在其他前缘形成，但由于植被覆盖或明显的河流侵蚀，这些裂缝大部分没有暴露出来，而智利北部由于极度干旱的气候而没有这些因素。
Despite convergence across the strongly coupled seismogenic interface between the South American and Nazca plates, the dominant neotectonic signature in the forearc of northern Chile is arc-normal extension. We have used 1 m resolution IKONOS satellite imagery to map nearly 37,000 cracks over an area of 500 km2 near the Salar Grande (21°S). These features, which are best preserved in a ubiquitous gypcrete surface layer, have both nontectonic and tectonic origins. However, their strong preferred orientation perpendicular to the plate convergence vector suggests that the majority owe their formation to approximate east-west extension associated with plate boundary processes such as interseismic loading, coseismic and postseismic strain, and long-term instability resulting from subduction erosion. Similar structures were formed during or shortly after the 1995 Mw = 8.0 earthquake near the city of Antofagasta, south of Salar Grande, and in conjunction with the 2001 Mw = 8.2–8.4 Arequipa, Peru, event. Cracks such as these may form in other forearcs but remain largely unexposed because of vegetative cover or marked fluvial erosion—factors that are absent in northern Chile as a result of its hyperarid climate.