Multichannel Seismic Study of Eastern Sunda Forearc, Indonesia

增生楔体的支承在楔体发育的演化过程中起着至关重要的作用，但对于支承体的意义和基本结构，无论支承体是向楔体的趾部倾斜还是远离楔形体的趾部倾斜，目前还没有一致的看法。没有一个区域的成像足够好，可以令人满意地回答这个基本问题。我们建议对印度尼西亚东巽他弧的弧前和弧后区域进行大来源、多通道的研究，在那里我们发现了弧前和弧后逆冲的证据。对逆冲构造（Sumba岛附近的Sawu逆冲构造）和逆冲构造的成像将对以下方面具有重要意义：a)确定逆冲构造期间弧前盆地地层在楔体后部的构造合并；B)识别楔形最早的增生产物，从而引发俯冲增生；c)确定弧陆碰撞带逆冲与弧后逆冲的相对时间关系。后者将需要一个钻井计划，而多通道研究将为这样一个计划提供一个框架。这些问题也将在沿弧后逆冲带发育的一个小型增生楔中得到解决，在那里我们可以完整地成像楔下的支承和下板块的结构。此外，我们建议在班达海进行为期8天的数字单通道地震剖面分析，使用1000立方英寸调谐源阵列。目的是进行区域地震地层学，为1988年的钻探做准备。

Backstops of accretionary wedges must play a critical role in the evolution of wedge development, but no agreement exists as to their significance or fundamental structure, whether backstops dip toward or away from the toe of the wedge. No region is sufficiently well imaged to answer this fundamental question satisfactorily. We propose a large source, multichannel study of the forearc and backarc areas of the eastern Sunda arc, Indonesia, where we have found evidence of backthrusting in the forearc and backarc thrusting in the backarc. Imaging the backthrust (the Sawu thrust near Sumba Island) and backstop geometry will have significant implications for: a) defining the tectonic incorporation of forearc basin strata into the rear of the wedge during backthrusting; b) identifying the earliest accretionary products of the wedge, and thus initiation of subduction accretions; and c) determining relative timing relations between backthrusting and back arc thrusting in a zone of arc-continent collision. The latter will require a program of drilling, and the multichannel study will provide a framework for such a program. These questions will also be addressed in a small accretionary wedge developed along the zone of backarc thrusting, where we can completely image the structure of the backstop and lower plate beneath the wedge. In addition, we propose to carry out 8 days of digital single-channel seismic profiling within the Banda Sea, using a 1,000 cubic inch tuned source array. The objective will be regional seismic stratigraphy in preparation for drilling in l988.