Tomographic investigation of the upper crustal structure and seismotectonic envi—ronments in Yunnan Province

Investigation has been made for the upper crust structure and seismotectionic environments in Yunnan Province using the plentiful DSS data of the four profiles.The derived velocity model has a good relationship with the ex-posed basins,uplifts and faults.The low velocity anomaly corresponding to the volcano also has been revealed.There exits a prominent lateral inhomogeneity within the upper crust of Yunnan region.The depth of crystalline basement generally ranges from 0km to 5km,and the bedrocks are exposed on the ground directly in some places,nevertheless the thickness of sedimentary cover also can reack to 8km or even 12km at some targe depressions.Although the Changning-Shuangjiang fault is a boundary between two first class tectonic units,its incision depth within the crust maybe shallow.On the other hand,known as the plates‘seam,the Honghe fault has a distinct evi-dence of extending into the mid-lower crust.The widely spread activity of the volcanoes in the geological era has a close relationship with the earthquake‘s occurrence nowadays.Despite of the ceasing of the volcanoes in some places on the ground,the material in the mid-lower crst is still active,and there still exists strong upward stress-As the ceasing of the volcanoes on the surface,most parts of the power from the lower crust and the upper mantle cannot be released;therefore it accumulates at some appropriate tectonic locations.Moreover,the saturation of the water from the basin,the action of other fluids,and the effects of the outer stress maybe another direct reason ac-count for the strong earthquakes‘occurrence in Yunnan region.

Tomographic investigation of the upper crustal structure and seismotectonic environments in Yunnan Province

Investigation has been made for the upper crust structure and seismotectonic environments in Yunnan Province using the plentiful DSS data of the four profiles. The derived velocity model has a good relationship with the ex-posed basins, uplifts and faults. The low velocity anomaly corresponding to the volcano also has been revealed. There exists a prominent lateral inhomogeneity within the upper crust of Yunnan region. The depth of crystalline basement generally ranges from 0 km to 5 km, and the bedrocks are exposed on the ground directly in some places, nevertheless the thickness of sedimentary cover also can reach to 8 km or even 12 km at some large depressions. Although the Changning-Shuangjiang fault is a boundary between two first class tectonic units, its incision depth within the crust maybe shallow. On the other hand, known as the plates seam, the Honghe fault has a distinct evi-dence of extending into the mid-lower crust. The widely spread activity of the volcanoes in the geological era has a close relationship with the earthquakes occurrence nowadays. Despite of the ceasing of the volcanoes in some places on the ground, the material in the mid-lower crust is still active, and there still exists strong upward stress. As the ceasing of the volcanoes on the surface, most parts of the power from the lower crust and the upper mantle cannot be released; therefore it accumulates at some appropriate tectonic locations. Moreover, the saturation of the water from the basin, the action of other fluids, and the effects of the outer stress maybe another direct reason ac-count for the strong earthquakes occurrence in Yunnan region.