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攀西裂谷带及其邻区的现代构造应力场特征 总被引:1,自引:0,他引:1
本文主要根据近30多年来,发生在攀西裂谷地区地震的断层面解,辅以其它手段的资料,讨论该地区的现代构造应力场。结果表明,攀西裂谷带的受力状态已由过去的拉张变为现今的压扭,是一条消亡的古裂谷带。 相似文献
916.
Hideki Shimamura Morio Ino Hisayoshi Hikawa Takaya Iwasaki 《Pure and Applied Geophysics》1984,122(6):933-946
Microtemperature measurements of groundwater with a relative precision better than 1/1000°C have been made in several seismically active areas in Japan. The measured temperatures show clear coseismic signals as well as a correlation with atmospheric pressure. Simultaneous observations at various depths have shown that these temperature changes were not induced by simple groundwater level changes. Also, distinctive signals occurred before several earthquakes and seem to be caused by a different mechanism than the coseismic signals. The microtemperature at some observation sites shows excellent correlation with records of nearby sensitive borehole strainmeters. Simultaneous recording of microtemperature and strain has been initiated in some boreholes. 相似文献
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919.
Hongfei Zhang Zengqiu Zhong Shan Gao Benren Zhang Li Zhang Shenghong Hu Qingye Hou 《Lithos》2004,73(3-4):215-227
The Qinling–Dabie–Sulu belt is the world's largest ultrahigh pressure (UHP) metamorphic belt. The UHP metamorphism is well dated at 220–245 Ma in the Dabie–Sulu belt but at 507 Ma in the Qinling belt. The Tongbaishan is located between the Qinling orogenic belt to the west and the Dabie–Sulu UHP metamorphic belt to the east. It is the key area for studying the tectonic relation between the Qinling and Dabie–Sulu belts and the diachronous UHP metamorphism. The Jigongshan granitic pluton (t=128 Ma) with a total area of 1200 km2, composed of monzogranite, was mostly emplaced into the Tongbai complex, an exposed basement in the Tongbaishan. The Jigongshan granites have SiO2=69.85–72.35%, K2O/Na2O=0.87–1.13, A/CNK=0.91–1.03, Rb/Sr=0.14–0.25 and Th/U=3.3–12. Their REE compositions show strongly fractionated patterns with (La/Yb)N=14–58 and Eu*/Eu=0.79–1.05. The granites are characterized by low radiogenic Pb isotopic composition. The present-day whole-rock Pb isotopic ratios are 206Pb/204Pb=16.707–17.055, 207Pb/204Pb=15.239–15.326 and 208Pb/204Pb=37.587–37.853, which are similar to that of the continental lower crust. Their Nd(t) values range from −16 to −20, and depleted-mantle Nd model ages (TDM) from 1.8 to 2.2 Ga. The above evidence indicates that the magma of the Jigongshan granites was derived from the partial melting of the continental crust. The Pb and Nd isotopic compositions of the Jigongshan granites resemble those of the Dabie core complex in the Dabieshan but are distinct from those of the Tongbai complex in the Tongbaishan. Thus, the Dabie core complex would be the magma source of the Jigongshan granites. The result implies that the Dabie core complex is extended to the west and constitutes the unexposed basement underlaying the Tongbai complex in the Tongbaishan. 相似文献
920.
Yang Xiao-ping Li De-qing Zhao Cheng-bin Liu Bao-jin Sun Zhen-guo Zhao Jing-yao 《地震学报(英文版)》2004,17(1):94-102
Field experimental seismic sounding permitted us to obtain optimal shallow seismic reflection sounding parameters. In process
of data processing, we obtained a high-qualitative shallow seismic reflection sounding profile by using the techniques such
as filtering, edition surgical blanking, prediction deconvolution, fitting static correlation of first arrival time, and velocity
analysis. Comprehensive analysis on the information of reflection wave groups along the seismic sounding profile and the stratigraphic
and neogeochronological data obtained from many drills near the sounding line reveals that the upper termination of the detected
fault zone is located at depth of 75–80 m, in the Middle Pleistocene deposits dated to be about 220 ka BP. The continuity,
discontinuity, increasing and decreasing amount of reflection wave groups and change of their configurations, in combination
with geological columns of drills, permitted us to know that the width of upper termination of the fault zone is 100 m. It
can be inferred from the variation of number of reflection wave groups along the profile that the scarp of hidden fault is
200 m wide and the fault is a synsedimentary active fault in the Early Pleistocene and the early stage of Middle Pleistocene.
No tectonic movement, which offset the covering deposits, had occurred since the late stage of Middle Pleistocene.
Foundation item: A High-new Technique Project by State Development and Planning Commission of China (2001977). 相似文献