Multichannel Seismic Study of Eastern Sunda Forearc, Indonesia

增长楔形支撑物必须在楔形发展的演变中发挥关键作用，但对于它们的意义或基本结构，无论支撑物是向楔形脚趾倾斜还是远离楔形脚趾，都没有一致意见。没有一个地区的形象足够好，无法令人满意地回答这个根本问题。我们建议对印度尼西亚东顺他弧弧前和弧后地区进行大规模震源、多道研究，在那里我们发现了弧前逆冲和弧后逆冲的证据。对背冲(松巴岛附近的萨乌逆冲)和支撑几何学的成像将对以下方面具有重要意义：a)确定在背冲期间弧前盆地地层在楔形后方的构造并入；b)识别楔形的最早的增生产物，从而开始俯冲；C)确定弧-陆碰撞带中背冲与弧后逆冲的相对时序关系。后者将需要一个钻探计划，而多通道研究将为这样的计划提供一个框架。这些问题也将在沿着弧后冲断带发展的一个小的吸积楔形中得到解决，在那里我们可以完全想象出楔形背板和下盘的结构。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，使用1,000立方英寸调谐震源阵列。目标将是区域地震地层学，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.