Collision of the Burma Arc Accretionary Prism and Foldbelt with the Ganges-Brahmaputra Delta in Bangladesh

在孟加拉国，2004年12月毁灭性地震和海啸的源头-苏美尔俯冲带与世界上最大的恒河-雅鲁藏布江三角洲相遇。 这两条大河流经喜马拉雅山脉的80%，向孟加拉国排放了超过10亿吨的沉积物。 这有一个巨大的沉积物堆，已经覆盖了300多公里的大陆边缘，到可能的洋壳上，进入俯冲带，用沉积物堵塞它，并建立一个巨大的陆上增生棱镜，一个长达300公里宽的折叠和断层沉积带从三角洲刮下来。 孟加拉国的缅甸弧褶皱带是一个罕见的海洋增生棱柱体暴露在陆地上的例子。 它也是大陆边缘沉积物进入俯冲带时大陆碰撞最早阶段的代表。 它是超压的，并具有最低的斜率的任何加积prism.Despite不寻常的发生陆上加积prism.But的沉积物和地壳结构的恒河雅鲁藏布江三角洲和缅甸弧褶皱带知之甚少。 由于没有可靠的大地震历史记录，地震危险性尚不清楚。 在这个项目中，哥伦比亚大学的一个研究小组与达卡大学的科学家合作，正在对褶皱带的结构及其运动学进行基本的一级理解。 正在三角洲和褶皱带部署地震仪网络。 地震学研究将利用地震来阐明褶皱带中活动断层的几何形状以及三角洲和褶皱带的沉积物和地壳结构。 从恒河-雅鲁藏布江三角洲到褶皱带的全球定位系统部署将收集关于整个区域的表面速度和变形的关键数据，并将与缅甸的全球定位系统调查相结合，以获得整个板块边界区总缩短量的初步估计。 地震和大地测量数据集将得到结构较浅部分的工业地震和钻井数据的补充。 总之，这些数据将提供前所未有的详细资料，在前面的一个活跃的海洋增生棱镜，是窒息与沉积物。 该项目将有助于确定三角洲、增生棱柱体和褶皱带的几何形状和运动，并对缅甸弧中发生的变形量和变形方式进行估计。 它将提供超压增生棱镜的力学信息。为了安全和具有成本效益的开发，迫切需要更好地了解孟加拉国正在进行的构造。 在苏美尔海沟的这个延伸部分，俯冲的速度有多快？ 两个板块之间的斜向运动是如何在褶皱带的不同结构之间分裂的？ 这个被巨大的沉积物堆积物堵塞的俯冲带能承受大地震吗？ 无论是地震滑动还是未来大地震的建设，都对地球上人口最稠密的地区之一的地震危险有着巨大的影响。 这项研究将帮助孟加拉国发展关键的基础设施和所使用的技术，并为评估地震危险提供基础。 该项目将支助哥伦比亚大学的两名孟加拉国研究生，他们将有望加强孟加拉国的基础设施。 Bangledeshi科学家将在一系列讲习班中接受GPS和地震学方法的培训。该奖项由NSF国际科学与工程办公室共同资助。

In Bangladesh, the Sumatran subduction zone, source of the devastating December 2004 earthquake and tsunami, encounters the Ganges-Brahmaputra Delta, the world's largest. These two great rivers, which drain 80 percent of the Himalayan mountain range, discharge over 1 Gigaton of sediments into Bangladesh. This has an enormous sediment pile that has prograded the continental margin over 300 km, onto likely oceanic crust and enters the subduction zone, clogging it with sediment and building a huge, subaerial accretionary prism, an up to 300 km wide belt of folded and faulted sediments offscraped from the delta. The Burma Arc foldbelt in Bangladesh is a rare instance of an oceanic accretionary prism exposed on land. It also is representative of the earliest stage of continental collision as the sediments of a continental margin enter the subduction zone. It is overpressured and has the lowest slope of any accretionary prism.Despite the unusual occurrence of an onshore accretionary prism, the sediment and crustal structure of both the Ganges-Brahmaputra Delta and Burma Arc foldbelt are poorly known. With no reliable historical record of large earthquakes, the seismic hazard is unclear. In this project, a Columbia University research team working in collaboration with scientists from Dhaka University are developing a basic first-order understanding of the structure of the foldbelt and its kinematics. A seismometer network in the delta and foldbelt is being deployed. Seismological studies will use earthquakes to illuminate the geometry of active faults in the foldbelt and the sediment and crustal structure of the delta and foldbelt. A GPS deployment from the Ganges-Brahmaputra Delta to the foldbelt will gather critical data on the surface velocities and deformation across the region and will be tied to GPS surveys in Myanmar to obtain the first estimate of total shortening across the plate boundary zone. The seismological and geodetic data sets will be supplemented by industry seismic and well data for the shallower parts of the structure. Together, these data will provide unprecedented detail on the tectonics at the front of an active oceanic accretionary prism that is being choked with sediments. This project will help define the geometry and motions of the delta, the accretionary prism and the foldbelt, providing estimates of the amount and style of deformation taking place in the Burma Arc. It will provide information of the mechanics of overpressured accretionary prisms.A better understanding of the ongoing tectonics in Bangladesh is critically needed for safe and cost-effective development. How fast is the subduction at this continuation of the Sumatran trench? How does the oblique motion between the two plates split between different structures in the foldbelt? Does this subduction zone, choked by an enormous sediment pile sustain large earthquakes? Whether it is sliding aseismically or building toward a future large earthquake has enormous implications for the seismic hazard of one of the most densely populated regions on the earth. This study will help Bangladesh develop critical infrastructure and in the technologies used, and provide the basis for assessing earthquake hazard. This project will support two Bangladeshi graduate students at Columbia University, who will then hopefully strengthen the infrastructure in Bangladesh. Bangledeshi scientists will be trained in GPS and seismological methods in a series of workshops.This award was co-funded by NSF's Office of International Science and Engineering.