Three‐dimensional seismic imaging of the Costa Rica accretionary prism: Structural diversity in a small volume of the lower slope
Three‐dimensional seismic imaging of the Costa Rica accretionary prism: Structural diversity in a small volume of the lower slope
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哥斯达黎加增生棱柱的三维地震成像：下坡小体积内的结构多样性
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
P. Stoffa
中科院分区：
文献类型：
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作者：
T. Shipley;K. Mcintosh;E. Silver;P. Stoffa
传统的二维地震反射调查通常依赖于提供大到中等规模的结构特征的加积棱镜的图像。我们进行了三维地震反射调查的一小部分的棱镜拱的中美洲海沟关闭哥斯达黎加更正确的图像结构和使用改进的结构信息来检查的过程中的增生。该调查揭示了数百米尺寸的小特征，同时还定义了横向范围数千米的特征，这两者在同一地区的传统二维数据中都未得到充分重视。我们已经对海沟的活动刮擦以及海沟弧向几公里处的断层和无序断层进行了成像。断层间距和反射体几何形状在几百米的空间内变化很大。其中一些变化与下面的海洋基底形态的可见变化有关，但其他变化则不容易记录。断层表面反射定义了一种可以控制通过棱镜的总流体运动的结构。这种构造显然是由断层活动和无序断层活动形成的，并通过某些无序断层的周期性运动得以维持。斜坡沉积扇记录了多期变形。丰富的小偏移逆断层破坏了海底，并表明最近缩短了一个广泛的地区的基础棱镜。本次调查的主要结果是赞赏的结构多样性跨越一个小宽度的增生棱柱。
Conventional two-dimensional seismic reflection investigations have been generally relied upon to provide images of large to medium scale structural features in accretionary prisms. We undertook a three-dimensional seismic reflection survey of a small part of a prism arcward of the Middle America Trench off Costa Rica to more correctly image structure and to use the improved structural information to examine the processes of accretion. This survey reveals small features, with dimensions of hundreds of meters, while also defining features thousands of meters in lateral extent, both of which were underappreciated in conventional two-dimensional data from the same area. We have imaged active off scraping at the trench and both duplexing and out-of-sequence faulting a few kilometers arcward of the trench. Fault spacing and reflector geometry vary dramatically over a space of several hundred meters. Some of these variations are related to visible changes in morphology of the underlying oceanic basement, but others are not so easily documented. Fault surface reflections define an architecture which may control gross fluid motion through the prism. This architecture is apparently formed by duplexing and out-of-sequence faulting and has been maintained by periodic motion on some of the out-of-sequence faults. The slope sediment apron records multiple phases of deformation. Abundant small offset reverse faults break the seafloor and indicate recent shortening of a broad region of the underlying prism. A primary result of this survey is appreciation of the structural diversity across a small width of an accretionary prism.