Submarine slope failures along the convergent continental margin of the Middle America Trench
Submarine slope failures along the convergent continental margin of the Middle America Trench
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DOI：
10.1029/2010gc003401
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发表时间：
2011-06-24
影响因子：
3.5
通讯作者：
Behrmann, Jan H.
中科院分区：
文献类型：
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作者：
Harders, Rieka;Ranero, Cesar R.;Behrmann, Jan H.
我们提出了第一个全面的研究质量消耗过程中的大陆斜坡的会聚边缘的俯冲带的构造过程是由俯冲侵蚀为主。我们使用了多波束测深沿着类似的中美洲俯冲带的中美洲海沟和深拖侧扫声纳数据的1300公里。我们发现了大量的证据，大规模的斜坡故障，大多是以前未映射。这些特征被分类为各种斜坡破坏类型，创建了147个斜坡破坏结构的清单。它们的类型、分布和丰度将大陆坡划分为六个部分。由于沉积物的物理性质的变化、天然气水合物的存在/不存在或水文地质系统的明显变化，边坡稳定过程中的分割似乎与边坡预处理无关。分割似乎是更好地解释了由于构造过程的变化，在斜坡预处理的变化。该区域是研究与俯冲侵蚀强度变化和俯冲板块地形变化有关的构造过程如何影响大陆坡物质耗损过程的最佳环境。最大的边坡破坏发生在哥斯达黎加近海。在那里，俯冲脊和海山产生的断层有数百米高的端壁，滑脱面深入大陆边，有时甚至到达板块边界。哥斯达黎加北方近海，平坦的大洋海底逆冲断层下是扰动最小的大陆坡。尼加拉瓜近海的海洋板块上分布着较小的海山以及强度不等的地垒和地堑地形。在这里，大量的消耗结构相对较小，但当它们结合在一起时，它们会影响大部分的边缘部分。再往北，在萨尔瓦多和危地马拉近海，下行板块没有大型海山，但有明显的地垒和地堑地形。萨尔瓦多外海的边坡破坏最不发达，主要发生在峡谷壁的最高大陆坡。在危地马拉海域，大量的物质流失可能与斜坡上的正断层作用有关。在俯冲洋板块地形的尾流中的崩塌是一个可能的崩塌触发器。俯冲地形上方的快速过陡可能会触发哥斯达黎加斜坡中部的平移滑动。地震震动可能是一个触发器，但我们解释说，边坡破坏率低于该地区大地震的复发时间。一般来说，我们的分析表明，质量消耗过程的重要性，在俯冲侵蚀占主导地位的边缘和沉积动力学的作用的演变可能被低估了。
We present the first comprehensive study of mass wasting processes in the continental slope of a convergent margin of a subduction zone where tectonic processes are dominated by subduction erosion. We have used multibeam bathymetry along similar to 1300 km of the Middle America Trench of the Central America Subduction Zone and deep-towed side-scan sonar data. We found abundant evidence of large-scale slope failures that were mostly previously unmapped. The features are classified into a variety of slope failure types, creating an inventory of 147 slope failure structures. Their type distribution and abundance define a segmentation of the continental slope in six sectors. The segmentation in slope stability processes does not appear to be related to slope preconditioning due to changes in physical properties of sediment, presence/absence of gas hydrates, or apparent changes in the hydrogeological system. The segmentation appears to be better explained by changes in slope preconditioning due to variations in tectonic processes. The region is an optimal setting to study how tectonic processes related to variations in intensity of subduction erosion and changes in relief of the underthrusting plate affect mass wasting processes of the continental slope. The largest slope failures occur offshore Costa Rica. There, subducting ridges and seamounts produce failures with up to hundreds of meters high headwalls, with detachment planes that penetrate deep into the continental margin, in some cases reaching the plate boundary. Offshore northern Costa Rica a smooth oceanic seafloor underthrusts the least disturbed continental slope. Offshore Nicaragua, the ocean plate is ornamented with smaller seamounts and horst and graben topography of variable intensity. Here mass wasting structures are numerous and comparatively smaller, but when combined, they affect a large part of the margin segment. Farther north, offshore El Salvador and Guatemala the downgoing plate has no large seamounts but well-defined horst and graben topography. Off El Salvador slope failure is least developed and mainly occurs in the uppermost continental slope at canyon walls. Off Guatemala mass wasting is abundant and possibly related to normal faulting across the slope. Collapse in the wake of subducting ocean plate topography is a likely failure trigger of slumps. Rapid oversteepening above subducting relief may trigger translational slides in the middle Nicaraguan upper Costa Rican slope. Earthquake shaking may be a trigger, but we interpret that slope failure rate is lower than recurrence time of large earthquakes in the region. Generally, our analysis indicates that the importance of mass wasting processes in the evolution of margins dominated by subduction erosion and its role in sediment dynamics may have been previously underestimated.