报告时间：2012年2月12日（周日）10:00
地 点：三楼会议室
报告题目：Intraplate earthquakes: Spatiotemporal migration and hazard assessment
报告摘要：
Most earthquakes occur along tectonic plate boundaries, and the relative plate motion provides the basic prediction for their general spatiotemporal patterns . In contrast, intraplate earthquakes are much more irregular in time and space, and their causes are poorly understood. One example is earthquakes in the New Madrid Seismic Zone (NMSZ) in central United States, where three large earthuqaukes shaked central and eastern US two hundred years ago. Paleoseismic evidence indicates at least two similar events around AD 900 and 1400, giving an apparent recurrance interval of ~500 years. Consequently, the US Geological Survey has assigned NMSZ a hazard level as high as that in California (i.e., the plate boundary zones). However, GPS measurements in the past two decades have shown no strain accumulation in the NMSZ. Many of these puzzles of the NMSZ earthequakes may be better understood in an emerging model of intraplate earthquakes as a complex system. This system is illustrated by the 2000-year record from North China, which shows migration of large earthquakes between fault systems spread over a large region, and no large earthquake repeated on the same fault segment during this 2000-year time window. The spatial migration of these earthquakes, however, is not entirely random, because the seismic moment release between fault systems are complementary, indicating that these systems are mechanically coupled. Such spatiotemporal pattern of earthquakes is common in mid-continents, where slow tectonic loading is accommodated collectively by a complex system of interacting faults, each of which can be active for a short period after long dormancy. The resulting large earthquakes are episodic and spatially migrating. Preliminary results of numerical simulations of interacting faults in a complex system indicate that the apparent spatiotemporal patterns of intracontinental earthquakes may vary significantly with the size of the time window, thus calling for caution when assess earthquake hazards based on available earthquake records, which are incomplete in most intracontinental regions.
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引力中心
2012年2月9日
