Deformation, Fragmentation and Seismic Hazards on the Western Edge of India

2005年克什米尔Mw7.6级地震（死亡人数85，000人）是地震学家预测的几次地震之一，因为喜马拉雅山的地震危险性在过去1000年中发生了类似的破坏性地震。 那里的地震是由印度以每年2英寸的速度向北移动到亚洲引起的。 出于同样的原因，地震也发生在印度板块的西部和东部边缘的沿着。 东部最大的地震是2004年苏门答腊/安达曼Mw9.1地震（死亡人数30万）。 最近在印度板块西部边缘的巴基斯坦没有发生大地震，但有充分的理由认为它们应该发生。 巴基斯坦西南部的地震可能会使拥有1200万人口的巴基斯坦最大城市卡拉奇陷入瘫痪，就像1935年奎达被Mw7.7地震摧毁一样（死亡人数35,000人）。 摧毁卡拉奇对巴基斯坦的经济将是灾难性的。 和洛杉矶一样，卡拉奇在250年前还是一个渔村，在过去的50年里才取得了特大城市的地位。 不像洛杉矶，没有抗震措施，也没有破坏性地震的历史。 该项目的一个目的是查明历史上没有地震是否是因为没有地震发生，或者正如我们所怀疑的那样，这是因为它们的间隔太长，以至于无法记录其200年的殖民历史。印度板块的边缘，从南部的卡拉奇以西的海岸，到北部喀布尔以东的阿富汗和巴基斯坦之间的山脉，它可能是锁定的，为未来的地震做准备，它可能是抗震滑动的（就像加州中部的部分地区，或者它可能是一个旋转地质块的广阔区域，就像滚珠轴承一样允许板块相互滑动。 我们计划进行一系列全球定位系统（GPS）测量，以区分这三种可能性。 这些测量将告诉我们板块边缘的相对速度、变形带的宽度以及两个板块锁定的深度--这些信息将用于量化该地区的地震生产力，并确定未来破坏性地震最有可能发生的位置。这些信息对该地区的地震工程师至关重要，并将决定未来30年的建筑政策。 这些测量还将对应力的物理和性质提供重要的限制，这些应力允许大陆转换板块边界，如圣安德烈亚斯断层，随着时间的推移而滑动和演变。 实地调查是与来自三所巴基斯坦大学和两所印度大学的科学家和工程师密切合作进行的，因此建立了国际联系，这对美国在这些发展中国家的形象大有裨益。 由于该项目的国际性质，这项工作是由地球物理方案和国际科学与工程办公室共同资助的。

The 2005 catastrophic Mw7.6 earthquake in Kashmir (death toll 85,000) was one of several earthquakes that were anticipated by seismologists because of the known seismic hazard of the Himalaya where similar damaging earthquakes have occurred throughout the past 1000 years. The earthquakes there are caused by the northward movement of India towards Asia at a rate of 2 inches/year. For the same reasons earthquakes also occur along the western and eastern edges of the Indian plate. The largest in the east was the Mw9.1 Sumatra/Andaman earthquake of 2004 (death toll 300,000). No great earthquakes have occurred recently on the western edge of the Indian plate in Pakistan, yet there are good reasons to suppose that they should. An earthquake in SW Pakistan could cripple Karachi, Pakistan's largest city with 12 million people, just as Quetta was destroyed in 1935 by an Mw7.7 earthquake (death toll 35,000). The destruction of Karachi would be catastrophic to the economy of Pakistan. Like Los Angeles, Karachi is a city that was a fishing village 250 years ago and has only in the past 50 years achieved megacity status. Unlike Los Angeles no earthquake resistance is in place, and no history of damaging earthquakes has survived. One aim of the project is to find out whether the historical absence of earthquakes is because no earthquakes occur, or whether, as we suspect, it is because they recur at intervals too long to be recorded by its 200 year colonial history.The edge of the Indian plate, which passes from the coast west of Karachi in the south, to the mountains that separate Afghanistan from Pakistan east of Kabul in the north, could be locked, preparing for a future earthquake, it could be sliding aseismically (like parts of central California, or it could be a wide region of rotating geological blocks, that act like ball-bearings permitting the plates to slide past each other. We plan a series of Global Positioning System (GPS) measurements that will uniquely distinguish between these three possibilities. The measurements will tell us the relative velocities at the edge of the plate, and the width of the zone of deformation, and the depth at which the two plates are locked - information that will be used to quantify the seismic productivity of the region, and identify the most probable future location of future damaging earthquakes. This information is of fundamental importance to earthquake engineers in the region, and will dictate building policies for the next 30 years. The measurements will also provide important constraints on the physics and nature of the stresses that permit continental transform plate boundaries, like the San Andreas fault, to slip and evolve with time. The field investigations are being undertaken in close collaboration with scientists and engineers from three Pakistan, and two Indian Universities, and as such forge international ties that are of great benefit to the image of the United States in these developing nations. Because of the international nature of the project, this work is jointly funded by the Geophysics Program and the Office of International Science and Engineering.