Collaborative Research: Earthquake Geology of the Pakistani Himalaya: Characterizing Slip Rates and Recurrence of Potentially Devastating Earthquake Sources

2005年10月8日发生的克什米尔7.6级地震造成7.3万多人死亡，是印度次大陆地震中生命损失最大的一次。这也是巴基斯坦所有自然灾害中最严重的一次，给巴基斯坦和印度政府敲响了警钟，因为两国都生活在地震活跃、城市人口日益增加的喜马拉雅地区。喜马拉雅地区毁灭性的大地震被认为与喜马拉雅基底滑脱有关，也就是印度-亚洲板块的边界。在过去的两个世纪里，历史性的地震使这条断层破裂，但还没有到达喜马拉雅逆冲前缘的地表。相比之下，逆冲前缘的地表破裂确实发生在大约900年前的尼泊尔和600年前的印度西北部。在巴基斯坦喜马拉雅西北部，尚不清楚板块边界地震期间逆冲前缘是否发生破裂。2005年克什米尔地震发生在造山带内的断层上，而不是在逆冲前缘，这表明巴基斯坦境内的印度-亚洲汇聚部分被内部断层吸收。第二个主要的未知数是应变和会聚如何在内部断层和前缘逆冲断层系统之间分配。俄勒冈州立大学和加州州立大学北岭分校的研究小组正在进行一项为期三年的研究项目，目的是约束巴基斯坦的印度-亚洲板块边界地震周期，以便对地震复发和活动构造的滑移率提供第一个约束。这些数据代表了对威胁主要人口中心(伊斯兰堡、拉瓦尔品第和白沙瓦的总人口约为600万人)的断层进行地震危险性表征的迫切需要的第一步。喜马拉雅地区的板块边界地震威胁着整个地区不断增加的人口，该地区很可能受到下一次喜马拉雅大地震的广泛影响。喜马拉雅以南的恒河平原上居住着4000多万人，喜马拉雅山脚下散布着许多城市，人口从大约50万到200多万不等。巴基斯坦2005年克什米尔地震造成近8万人死亡，突显了与喜马拉雅地震有关的危险的严重性。尽管巴基斯坦发生了历史性的毁灭性地震(1935年奎达，35000人死亡)，但该国整体上对未来的事件基本上没有做好准备，也没有一支受过地震地质学培训的科学家队伍。在这个项目中，科学团队将确定巴基斯坦主要活动断裂的地震历史，同时培训巴基斯坦科学家掌握世界各地广泛使用的在该领域限制地震危险的技术。该项目的科学贡献将是对印度-亚洲碰撞是如何通过喜马拉雅西北部的地震表现出来的新的理解。该项目的社会遗产将是关于威胁到一些主要人口中心的大地震的概率预测的新信息，从而改进建筑规范和灾害预防，并使新一代科学家接受现代地震科学技术培训。这些巴基斯坦地球科学家将有能力在未来对巴基斯坦活动断裂的地震危险性和地震历史进行系统的描述。该奖项由美国国家科学基金会国际科学与工程办公室共同资助。

The magnitude 7.6 Kashmir earthquake of October 8, 2005 caused the deaths of more than 73,000 people, the greatest loss of life of any earthquake in the Indian subcontinent. It also was Pakistan's worst natural disaster of any kind, a source of alarm to the governments of Pakistan and India because both countries share the seismically-active and increasingly urban-populated Himalaya. Large, devastating earthquakes in the Himalaya are thought to be associated with the Himalayan basal decollement, the India-Asia plate boundary. Historic earthquakes in the past two centuries have ruptured this fault but have not reached the surface at the Himalayan thrust front. In contrast, surface rupture at the thrust front did occur in Nepal and northwest India approximately 900 and 600 years ago, respectively. In the northwestern Himalaya of Pakistan, it is unknown whether ruptures occur at the thrust front during plate-boundary earthquakes. The 2005 Kashmir earthquake occurred on a fault within the orogenic belt and not at the thrust front, which indicates that some of the India-Asia convergence in Pakistan is absorbed by internal faults. A second major unknown is how strain and convergence are partitioned between the internal faults and the frontal thrust fault systems. The Oregon State University and California State University, Northridge, research team are conducting a three-year research project with the goal of constraining the India-Asia plate boundary earthquake cycle in Pakistan in order to provide the first constraints on the earthquake recurrence and slip rate of active structures. These data represent a much-needed first step in seismic hazard characterization of faults threatening major population centers (Islamabad, Rawalpindi, and Peshawar have a combined population of approximately 6,000,000).Plate boundary earthquakes in the Himalaya threaten an ever-increasing population across a region in harm's way that is likely to be widely affected by the next great Himalayan earthquake. Over forty million people live in the Ganges plain south of the Himalaya, and the Himalayan foothills are dotted by numerous cities ranging in size from about 500,000 to more than 2 million people. The nearly 80,000 deaths in Pakistan during the 2005 Kashmir earthquake emphasize the magnitude of the hazard associated with Himalayan earthquakes. Although Pakistan has had historic devastating earthquakes (1935 Quetta, 35,000 killed), the country as a whole is largely unprepared for future events and does not have a cadre of scientists trained in earthquake geology. In this project, the scientific team will determine the earthquake history of key active faults in Pakistan and simultaneously train Pakistani scientists in the techniques used widely around the world to constrain earthquake hazard in the field. The scientific contribution of this project will be a new understanding of how the India-Asia collision is manifested by earthquakes in the northwest Himalaya. The societal legacy of this project will be new information on probabilistic forecasting of large earthquakes threatening some of the major population centers, leading to improved building codes and disaster prevention, and a new generation of scientists trained in the modern techniques of earthquake science. These Pakistani earth scientists will be equipped to carry forward into the future a systematic characterization of seismic hazards and earthquake history of active faults in Pakistan.This award was co-funded by NSF's Office of International Science and Engineering.