This paper introduces the geological structure background around the 2014 Yutian Ms7. 3 earthquake area, investigates and analyzes the regime of small earthquake activity and the characteristics of regional seismicity...This paper introduces the geological structure background around the 2014 Yutian Ms7. 3 earthquake area, investigates and analyzes the regime of small earthquake activity and the characteristics of regional seismicity pattern in Xinjiang before the earthquake, and compares the characteristics of the regional seismic activity with the 2008 Yutian Ms7.3 earthquake. The results show： ① 2 ~ 3 years before the 2014 Yutian Ms7. 3 earthquake, Xinjiang was in a seismic active state with strong earthquake occurring successively, and before the 2008 Ms 7. 3 earthquake, Xinjiang was in the quiet state of moderate-small earthquakes with M3. 0 ~ 4. 0. ② Before this Yutian Ms7. 3 earthquake, the regional seismic activity showed a short-term anomaly feature, that is, seismicity of M ≥ 5. 0 earthquakes significantly increased on the Altun seismic zone and in the source area three years before the Ms7.3 earthquake, while a five year long quiescence of seismicity of M ≥4. 0 earthquakes appeared on the east of the source area in a range of about 440kin. Six months before this M7. 3 earthquake, there existed seismic gap of M3. 0 ~ 4. 0 earthquakes and near-conjugate seismic belt magnitude 3. 0 and 4. 0 in the source area. ③ The state of strong earthquake activity and the seismicity pattern of small earthquakes before this Yutian Ms7. 3 earthquake were significantly different to that before the 2008 Yutian Ms7. 3 earthquake, and this may be related to the different seismogenic environments of the two Ms7. 3 earthquakes.展开更多
815 earthquakes recorded by 12 seismic stations of the Zipingpu reservoir seismic network in 2009 were relocated using the double difference algorithm to analyze the seismic activity of the Zipingpu reservoir.Relocati...815 earthquakes recorded by 12 seismic stations of the Zipingpu reservoir seismic network in 2009 were relocated using the double difference algorithm to analyze the seismic activity of the Zipingpu reservoir.Relocation results show that the earthquakes are concentrated relatively in three zones.The distribution characteristics of focal depth are obviously different among different concentration zones.This means earthquakes in different concentration zones may have different causes.Compared to relocation of earthquakes taking place before the Wenchuan earthquake done by other researchers,the seismic concentration zones in the reservoir area shifted obviously after the Wenchuan earthquake.These variations are related to local stress adjustment in the reservoir area and may also be related to the diffusion depth and range of increased pore pressure caused by rock failure in the course of Wenchuan earthquake.展开更多
Velocity structure beneath active faults in the Beijing area has been discussed,based on the digital crustal model of velocity from deep seismic sounding profiles and tomography imaging of P waves. We found that there...Velocity structure beneath active faults in the Beijing area has been discussed,based on the digital crustal model of velocity from deep seismic sounding profiles and tomography imaging of P waves. We found that there exists nearly vertical deep faults beneath the Shunyi Depression and the Machiko Depression,which are very likely to be seismogenic faults in the future. In the superficial crust,the north segment of the Shunyi-QianmenLiangxiang fault,the north segment of the Huangzhuang-Gaoliying fault and the Qinghe fault show a trend to converge but without intersecting with vertical deep faults. This kind of seismo-tectonic state has great potential to generate large earthquakes.展开更多
Age and nature of the Budate Group in the Hailar Basin are of great significance in studying the evolution of the Hailar Basin and the Xing'an-Mongolian Orogenic Belt(XMOB).Zircon U-Pb ages of eight volcanic rocks...Age and nature of the Budate Group in the Hailar Basin are of great significance in studying the evolution of the Hailar Basin and the Xing'an-Mongolian Orogenic Belt(XMOB).Zircon U-Pb ages of eight volcanic rocks from the Budate Group and two basement granites in the Hailar Basin were reported in this study.The dating results indicated that the formation of these volcanic rocks was consistent with the emplacement of Late Paleozoic basement granite in age(356-290 Ma),i.e.,Early Carboniferous to Early Permian rather than Early Mesozoic.Combined with regional geology,it was concluded that the Budate Group is the component of the basement of the Hailar Basin,and these volcanic rocks were formed at an active continental margin,which is related to the closure of the Hegen Mountains suture zone.The captured Neoproterozoic zircons(814-873 Ma) were probably derived from the Neoproterozoic basement materials in the Ergun Block,implying the close genetic relationships between the Ergun Block(including the Hailar Basin) and the Siberian Block.展开更多
基金sponsored by the Special Fund for Earthquake Trend Tracing from Department of Monitoring and Prediction of China Earthquake Administration
文摘This paper introduces the geological structure background around the 2014 Yutian Ms7. 3 earthquake area, investigates and analyzes the regime of small earthquake activity and the characteristics of regional seismicity pattern in Xinjiang before the earthquake, and compares the characteristics of the regional seismic activity with the 2008 Yutian Ms7.3 earthquake. The results show： ① 2 ~ 3 years before the 2014 Yutian Ms7. 3 earthquake, Xinjiang was in a seismic active state with strong earthquake occurring successively, and before the 2008 Ms 7. 3 earthquake, Xinjiang was in the quiet state of moderate-small earthquakes with M3. 0 ~ 4. 0. ② Before this Yutian Ms7. 3 earthquake, the regional seismic activity showed a short-term anomaly feature, that is, seismicity of M ≥ 5. 0 earthquakes significantly increased on the Altun seismic zone and in the source area three years before the Ms7.3 earthquake, while a five year long quiescence of seismicity of M ≥4. 0 earthquakes appeared on the east of the source area in a range of about 440kin. Six months before this M7. 3 earthquake, there existed seismic gap of M3. 0 ~ 4. 0 earthquakes and near-conjugate seismic belt magnitude 3. 0 and 4. 0 in the source area. ③ The state of strong earthquake activity and the seismicity pattern of small earthquakes before this Yutian Ms7. 3 earthquake were significantly different to that before the 2008 Yutian Ms7. 3 earthquake, and this may be related to the different seismogenic environments of the two Ms7. 3 earthquakes.
基金funded jointly by National Science& Technology Pillar Program (Grant No. 2008BAC38B0401)special fund for basic scientific research of Institute of Geology,CEA (DF-IGCEA060828)
文摘815 earthquakes recorded by 12 seismic stations of the Zipingpu reservoir seismic network in 2009 were relocated using the double difference algorithm to analyze the seismic activity of the Zipingpu reservoir.Relocation results show that the earthquakes are concentrated relatively in three zones.The distribution characteristics of focal depth are obviously different among different concentration zones.This means earthquakes in different concentration zones may have different causes.Compared to relocation of earthquakes taking place before the Wenchuan earthquake done by other researchers,the seismic concentration zones in the reservoir area shifted obviously after the Wenchuan earthquake.These variations are related to local stress adjustment in the reservoir area and may also be related to the diffusion depth and range of increased pore pressure caused by rock failure in the course of Wenchuan earthquake.
基金sponsored by the National Science & Technology Pillar Program (2006BAC13B01-0203)the Specific Earthquake Scientific Research Program (200808008),China
文摘Velocity structure beneath active faults in the Beijing area has been discussed,based on the digital crustal model of velocity from deep seismic sounding profiles and tomography imaging of P waves. We found that there exists nearly vertical deep faults beneath the Shunyi Depression and the Machiko Depression,which are very likely to be seismogenic faults in the future. In the superficial crust,the north segment of the Shunyi-QianmenLiangxiang fault,the north segment of the Huangzhuang-Gaoliying fault and the Qinghe fault show a trend to converge but without intersecting with vertical deep faults. This kind of seismo-tectonic state has great potential to generate large earthquakes.
基金supported by the National Natural Science Foundation of China (Grant No. 40972041)
文摘Age and nature of the Budate Group in the Hailar Basin are of great significance in studying the evolution of the Hailar Basin and the Xing'an-Mongolian Orogenic Belt(XMOB).Zircon U-Pb ages of eight volcanic rocks from the Budate Group and two basement granites in the Hailar Basin were reported in this study.The dating results indicated that the formation of these volcanic rocks was consistent with the emplacement of Late Paleozoic basement granite in age(356-290 Ma),i.e.,Early Carboniferous to Early Permian rather than Early Mesozoic.Combined with regional geology,it was concluded that the Budate Group is the component of the basement of the Hailar Basin,and these volcanic rocks were formed at an active continental margin,which is related to the closure of the Hegen Mountains suture zone.The captured Neoproterozoic zircons(814-873 Ma) were probably derived from the Neoproterozoic basement materials in the Ergun Block,implying the close genetic relationships between the Ergun Block(including the Hailar Basin) and the Siberian Block.
