Study Of The Active Faults Using Remote Sensing And Activity Analysis

Dangxiong area totally NE trending in Tibet is located in the middle of the Tibet plateau and develops the Yangbajing-Dangxiong-Gulu faulted basin which is an important part of the Yadong-Gulu-Naqu rift system. Nyenchen Tonglha Mountains runs through the middle of this area and the northwest and southeast part is mountains landform. Nyenchen tanglha southeast foothill fault zone is one of the biggest faults in this area. It is not only an important conversion tectonic belt but also a board line in tectonic and landform between the east and west Tibet. Magma and seismic activity is very intensive and frequent because of the strong tectonic movement.Based on the remote sensing,geology and seismic data, we use high resolution remote sensing image extracting the typical active structure landforms such as fault scarps, fault escarpments, river turning and offset ridges. The crust deformation features are discussed according to the PS-InSAR results. The results show that the uplifting rate on the edge of the basin is about 1.7mm/a and the maximum rate is nearly 3.34mm/year. This deformation trend is probably caused by the nearly E-W crust stretching deformation in the middle of the Tibet plateau. DEM data is used to extract river system and calculate water density. Rivers develop intensive within the study area and showing distribution of grid. Main tributaries and small tributaries arrange parallel to each other and often show right angle bends. The development was clear ly controlled by strong structure. Water density map reflects uplift and subsidence features of new structure. Water density gradient zone represents the transfer of structural parts of uplift and subsidence. It is usually the distribution zones of active faults. The density is low in Nyainqentanglha Mountain area and spread overall NNE-NE-NNE direction from south to north. It shows that there is still relatively strong uplift and subsidence in the region. Finally, we analyse the seismic data and the 2008 Dangxiong earthquake InSAR processing results and discuss the seismic activity features. The results show that the seismic activity in this region is periodic. Ms6.0-6.9 earthquakes generally appear in the period of 18 years. There is a seismically quiet period between 1960 and 1980 and only occurs a small 4.0 earthquake. This is probably due to the Ms 7.5-magnitude earthquake occurred in the west of Gulu graben.This earthquake releases the cumulative strain energy and results in a seismically quiet period after 1952. Since 1980, the earthquake magnitude in this area is about 4.0-5.0. The largest earthquake is 2008 Dangxiong Ms 6.6. The continuous small earthquakes release most strain energy and it suggests that the possibility of strong earthquakes reduces.