The 26 November 2005 Jiujiang-Ruichang, Jiangxi, Ms 5.7 earthquake occurred in a seismotectonic setting of moderate earthquake. The northwest-trending Xiangfan-Guangji fault （XFG） does not enter into the epicenter v...The 26 November 2005 Jiujiang-Ruichang, Jiangxi, Ms 5.7 earthquake occurred in a seismotectonic setting of moderate earthquake. The northwest-trending Xiangfan-Guangji fault （XFG） does not enter into the epicenter vicinity, but the northeast-trending Ruichang-Wuning fault （RWF） as a regional fault extends to the epicenter nearby, appearing as the Ruichang basin and its marginal faults. Tilting of the Ruichang Basin （RCB） in the Quaternary was controlled by the RCB southeast- marginal, buried fault （RSMBF）. Shallow geophysical survey reveals that the RSMBF caused an offset of the reflection layers. Drill hole columnar section demonstrates that there are about 10-12 m displacement in the lower section of the middle-Pleistocene Series along the RSMBF, but no disruption is found in the upper section of the middle-Pleistocene Series. The RSMBF not only has activity in the Quaternary, but also coincides with the nodal plane I from the focal mechanism of the Jiujiang- Ruichang Ms 5.7 earthquake. This evidence, including aftershock distribution and isoseismic lines, strongly suggests that the RSMBF might be the seismogenic tectonics. The RWF is discontinuous at the surface, and consists of three en echelon Quaternary basins, which are the Ruichang, Fanzhen and Wuning basins. Three moderate earthquakes, the Fanzhen ML 4.9 earthquake, the Yejiapu ML 4.1 earthquake and the Jiujiang-Ruichang Ms 5.7 earthquake, have happened in the basins since 1995. The seismogenic tectonics of the Jiujiang-Ruichang Ms 5.7 earthquake is not isolated, but may be controlled by the RWF at depth, the slip of which causes the accumulation of energy for earthquake occurrence.展开更多
The author has proved the presence of the NW-trending Hangzhou Bay deep fault by the gravity inversion of a constant density model, and subsequently further discovered through the integrated gravity-seismic inversion ...The author has proved the presence of the NW-trending Hangzhou Bay deep fault by the gravity inversion of a constant density model, and subsequently further discovered through the integrated gravity-seismic inversion of a multi-layered variable density model that this NW-trending tectonic belt is a transitional zone not only of the low-density layer展开更多
Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the foc...Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the focal mechanism of the main shock （MsS.7） and the probable seismo-tectonics. The precise relocation results indicate that the average horizontal error is 0.31kin in a EW direction and 0.40kin in a NS direction, and the average depth error is 0.48kin. The focal depths vary from 8kin to 14kin, with the predominant distribution at 10kin - 12kin. The epicenter of the main shock is relocated to be 29.69^oN, 115.74^oE and the focal depth is about 10.Skin. Combining the predominant distribution of the earthquake sequence, the focal mechanism of the main shock and the tectonic conditions of N-E- and NW-strike faults growth in the seismic region, we infer that the main shock of the earthquake sequence was caused by a NW striking buried fault in the Rnichang basin. The nature of seismic faults needs to be further explored.展开更多
Seismo-tectonic areas of historical strong earthquakes with MS(7 along Xianshuihe-Xiaojiang fault zone are divided, and their individual fault-pattern and tectonic geomorphology are analyzed. Those strong-earthquake a...Seismo-tectonic areas of historical strong earthquakes with MS(7 along Xianshuihe-Xiaojiang fault zone are divided, and their individual fault-pattern and tectonic geomorphology are analyzed. Those strong-earthquake areas are located in some special parts of the fault zone, where the major branch-faults of the fault zone form left stepping, parallel, and fork-like patterns. In the strong-earthquake areas structurally complicated basins are developed, such as pull-apart basins in fork-like area, in double stepping area, and in stepping and fork-like areas.展开更多
文摘The 26 November 2005 Jiujiang-Ruichang, Jiangxi, Ms 5.7 earthquake occurred in a seismotectonic setting of moderate earthquake. The northwest-trending Xiangfan-Guangji fault （XFG） does not enter into the epicenter vicinity, but the northeast-trending Ruichang-Wuning fault （RWF） as a regional fault extends to the epicenter nearby, appearing as the Ruichang basin and its marginal faults. Tilting of the Ruichang Basin （RCB） in the Quaternary was controlled by the RCB southeast- marginal, buried fault （RSMBF）. Shallow geophysical survey reveals that the RSMBF caused an offset of the reflection layers. Drill hole columnar section demonstrates that there are about 10-12 m displacement in the lower section of the middle-Pleistocene Series along the RSMBF, but no disruption is found in the upper section of the middle-Pleistocene Series. The RSMBF not only has activity in the Quaternary, but also coincides with the nodal plane I from the focal mechanism of the Jiujiang- Ruichang Ms 5.7 earthquake. This evidence, including aftershock distribution and isoseismic lines, strongly suggests that the RSMBF might be the seismogenic tectonics. The RWF is discontinuous at the surface, and consists of three en echelon Quaternary basins, which are the Ruichang, Fanzhen and Wuning basins. Three moderate earthquakes, the Fanzhen ML 4.9 earthquake, the Yejiapu ML 4.1 earthquake and the Jiujiang-Ruichang Ms 5.7 earthquake, have happened in the basins since 1995. The seismogenic tectonics of the Jiujiang-Ruichang Ms 5.7 earthquake is not isolated, but may be controlled by the RWF at depth, the slip of which causes the accumulation of energy for earthquake occurrence.
文摘The author has proved the presence of the NW-trending Hangzhou Bay deep fault by the gravity inversion of a constant density model, and subsequently further discovered through the integrated gravity-seismic inversion of a multi-layered variable density model that this NW-trending tectonic belt is a transitional zone not only of the low-density layer
基金This research was supported by the Joint Earthquake Science Foundation (A07124)the project of"Application of Digital Seismic Data to Short-impending Tracing"of China Earthquake Administration (120602-06-114)
文摘Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the focal mechanism of the main shock （MsS.7） and the probable seismo-tectonics. The precise relocation results indicate that the average horizontal error is 0.31kin in a EW direction and 0.40kin in a NS direction, and the average depth error is 0.48kin. The focal depths vary from 8kin to 14kin, with the predominant distribution at 10kin - 12kin. The epicenter of the main shock is relocated to be 29.69^oN, 115.74^oE and the focal depth is about 10.Skin. Combining the predominant distribution of the earthquake sequence, the focal mechanism of the main shock and the tectonic conditions of N-E- and NW-strike faults growth in the seismic region, we infer that the main shock of the earthquake sequence was caused by a NW striking buried fault in the Rnichang basin. The nature of seismic faults needs to be further explored.
基金Chinese Joint Seismological Science Foundation (9507424). Contribution No. 2001A003, Institute of Crustal Dynamics, China Seis
文摘Seismo-tectonic areas of historical strong earthquakes with MS(7 along Xianshuihe-Xiaojiang fault zone are divided, and their individual fault-pattern and tectonic geomorphology are analyzed. Those strong-earthquake areas are located in some special parts of the fault zone, where the major branch-faults of the fault zone form left stepping, parallel, and fork-like patterns. In the strong-earthquake areas structurally complicated basins are developed, such as pull-apart basins in fork-like area, in double stepping area, and in stepping and fork-like areas.
