| The uplift of the Tibetan plateau caused by the collision between India and Asia is one of the most important geological events for millions of years. In these series of tectonic movements, the most controversial and conspicuous is undoubtedly Himalaya-Tibetan orogeny. For the past few years, many scholars used observed surface deformation from space geodetic to study fault relative dislocation, as the basis of the earthquake simulation and prediction, which had a significant practical impact on earthquake disaster mitigation.This article used GPS measurement technology as a means, with the goal of studying crustal deformation characteristics in the Himalayan region, combining with part of the mathematical and physical mode. For the regional crustal structure deformation characteristics and fault three-dimensional activity, this article’s research contents are as follows:(1) This article collected and integrated multiple sets of GPS deformation data in Himalaya region, and established the GPS velocity field which base on ITRF2000 reference frame and the Eurasian plate.In the central Himalaya, the total rate of extension in theN100°E direction between 80°E and 93°E is about 23.0±4.0mm/yr. When crossed Thakkola graben and Yadong-Gulu fault, GPS velocity component appeared obvious gradient, which illustrated the crust extension rate is not uniform in the Himalayas from west to east direction.And this point further verified the conclusions of previous studies. Meanwhile, there were slight right lateral strike slip tendency in Himalayan main boundary faults.(2)The current locking strength and slip deficit of main Himalayan thrust fault were inverted by the negative dislocation inversion theory. Then this study found that the locking depth of MHT in most areas is about 18 km, the corresponding locking width is about 103 km. But near Thakkola graben, the fault locking depth and the slip deficit average have significant changes. And in the eastern part of the fault, with the increase of longitude, the locking depth gradually deepened, and the slip deficit rate gradually increased. The high value region of slip deficit corresponded to the frequent seismic activity. At the same time, there was a wide area of about 46~52km next to the locked area. In this region, the strength of the locking was decreased rapidly, and the seismic activity was also obvious.(3)According to the slip deficit rate, MHT seismic moment deficit was about194.0′10 Nm/ yr, its value was equivalent to a Mw7.01 earthquake occurred every year.(4) According to the results of GPS velocity and least square collocation method, the strain rate field was calculated. Meanwhile, the article pointed out that the central crust of Himalayan tectonic belt was severe compression, and the eastern crustal compression strength gradually weakened. With Yadong-Gulu fault as a dividing line, crustal compression strain rate significantly weakened and the direction showed a characteristic of disperse changes. And from south to north, crustal compression decreased gradually, too. Similarly, with Yarlung-Zangbo fault as a dividing line, the surface expansion gradient changed significantly. And maximum shear strain appeared in the east-central part of the main Himalayan boundary fault. The distribution of shear strain gradient belt was from west to east along the main Himalayan boundary fault, then, it was blocked in geometric features intersections between Yadong-Gulu fault and the main boundary fault.(5)Finally, according to the fault vertical slip deficit rate in MHT, and combining with the maximum horizontal slip in the Nepal earthquake which was given by USGS, the recurrence period of the regional MW7.8 earthquake was estimated about 270 years. And this area still belongs to the earthquake-prone areas. |
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