Active tectonics and seismic hazard assessment in Shaanxi, Gansu, and Ningxia Provinces, China

陕西、甘肃和宁夏三省位于鄂尔多斯地块的南部和西部边缘和青藏高原东北部。该地区的人口约为7000万，其中约一半居住在大城市内，大城市近年来迅速发展，位于历史上曾被地震摧毁的小得多的城市的核心周围。其余的人口是农村人，住在非常脆弱的建筑里。该地区经历了有记录以来最致命的三次地震；1556年的华县地震造成80多万人死亡，其他历史上的地震已知已造成10多万人死亡。该项目旨在显著改善该地区的地震危险性评估，而且特别及时，因为研究区域覆盖了丝绸之路经济带中国一端人口最稠密的部分，计划投资数千亿美元，将改变整个欧亚大陆的通信、交通和贸易。与太平洋沿岸国家不同，在地震频繁发生的国家，地震发生在众所周知的断层上，中国暴露在一个广泛分布的断层系统上的地震危险中，这些断层的位置鲜为人知--或者在地震发生之前根本不知道。这种地震灾害的中心方面是，同一断层上连续发生的地震之间的间隔是几千年。因此，为了准确地刻画一个地区的形变特征，我们需要确定该地区过去1万至10万年来活动断裂的分布、速率和作用。我们将通过野外地质、地球物理、卫星测图以及利用GPS和卫星雷达测量地球表面形变的技术来实现这一点。我们将把这些观测结果结合成一幅连贯的区域形变图，用来绘制一张比现有图更准确、更详细的新的区域地震危险性图。

The provinces of Sha'anxi, Gansu, and Ningxia lie between the southern and western margins ofthe Ordos block and the northeastern Tibetan plateau. The population of the region is about 70million, of whom approximately half live within large cities, which have grown rapidly and recentlyaround the nuclei of much smaller cities that are known to have been destroyed by earthquakesin the historical past. The remainder of the population is rural, and live in highly vulnerable buildings.The region has suffered three of the most deadly earthquakes in recorded history; the 1556 Huaxianearthquake was responsible for the deaths of over 800,000 people, and other historical earthquakesare known to have killed over 100,000 people. This project aims to make a significant improvement in the assessment of seismic hazard in the region,and is particularly timely because the study area covers the most populous part of the Chinese end of the Silk Road Economic Belt, a planned investment of hundreds of billions of dollars that will transform communications, transport and trade across Eurasia.Unlike countries around the Pacific Rim, where earthquakes occur quite frequently, on faults whose locations are well known, China is exposed to hazards from earthquakes that occur on a widelydistributed system of faults, whose locations are poorly known -- or not known at all until an earthquake occurs. The central aspect of this earthquake hazard is that the intervals between successiveearthquakes on the same section of fault are thousands of years. In order to characterize accuratelythe deformation of a region, therefore, we need to determine the distribution, rate, and roleof the active faults across the region over the past 10,000 to 100,000 years.We shall shall achieve this by combining techniques of field geology, geophysics, satellite-based mapping,and measurements of the deformation of the Earth' surface using GPS and satellite radar. We shall combine these observations into a coherent picture of the deformation of the region, which will be usedto make a new map of seismic hazard of the region that is both more accurate and more detailed than existing maps.