Based on seismic data from the regional network for the last 34 years, we analyzed the present fault behavior of major fault zones around the Mabian area, southern Sichuan, and identified the risky fault-segments for ...Based on seismic data from the regional network for the last 34 years, we analyzed the present fault behavior of major fault zones around the Mabian area, southern Sichuan, and identified the risky fault-segments for potential future. The method of analysis is a combination of activity background of historical strong earthquakes mainly show ~ （ 1 ） The spatial distribution of b-values strong and large earthquakes in the spatial distribution of b-values with and current seismicity. Our results indicates significant heterogeneity in the studied area, which reflects the spatial difference of cumulative stress levels along various fault zones and segments. （2） Three anomalously low b-value areas with different dimensions were identified along the Mabian-Yanjin fault zone. These anomalies can be asperities under relatively high cumulated stress levels. Two asperities are located in the north of Mabian county, in Lidian town in western Muchuan county, and near Yanjin at the south end of the fault zone. These two areas represent potential large earthquake seismogenic sites around the Mabian area in the near future. Besides them, the third relatively smaller asperity is identified at southern Suijiang, as another potential strong- earthquake source. （3） An asperity along the southwestern segment of the Longquanshan fault zone indicates the site of potential moderate-to-strong earthquakes. （4） The asperity along the segment between Huangmu town in Hanyuan county and Longchi town in Emeishan city on Jinkouhe-Meigu fault has potential for a moderate-strong earthquake.展开更多
In this paper,based on Gansu Digital Seismic Network data since 1990,we calculated b-value and ⊿ b-value of the neighborhood area before the 2013 Minxian-Zhangxian M_S6. 6,earthquake. The results show that the earthq...In this paper,based on Gansu Digital Seismic Network data since 1990,we calculated b-value and ⊿ b-value of the neighborhood area before the 2013 Minxian-Zhangxian M_S6. 6,earthquake. The results show that the earthquake occurred at the margin of the significantly lower b-value area in southeast of Gansu and before the earthquake the neighborhood area had an obviously abnormal ⊿ b-value. From the earthquake and the spatial distribution of low b-value, the region still has the possibility of generating dangerous strong earthquakes.展开更多
At some stage of a strong earthquake preparation, the focal mechanisms of small earthquakes have roughly the same direction with the tectonic stress field. According to this feature, we define the angle between P, B a...At some stage of a strong earthquake preparation, the focal mechanisms of small earthquakes have roughly the same direction with the tectonic stress field. According to this feature, we define the angle between P, B and T axis of focal mechanisms and the three stress axes of tectonic stress field as the consistency parameter a in studying the dynamic changes of stress fields in earthquake preparation areas. We mainly analyze the changes of the consistency parameter a of the Mw8. 3 Knril island arc earthquake and the Mw8. 4 Peru earthquake. Our study shows that before the strong earthquakes, the earthquake area saw a low consistency, and the focal mechanisms of a series of small earthquakes had small differences in the directions with the tectonic stress field, which means the foreshocks were under the control of the stress field. On the other hand, a higher consistency means the focal mechanisms of their aftershocks are scattered and have big differences in the directions with the tectonic field, which indicate that the control of background stress field starts weakening.展开更多
Two hours after the 2010 Yushu Earthquake, the shaking intensity distribution was obtained using the ShakeMap Rapid Generation System Based on Site Effects, developed by the author, which integrates the information of...Two hours after the 2010 Yushu Earthquake, the shaking intensity distribution was obtained using the ShakeMap Rapid Generation System Based on Site Effects, developed by the author, which integrates the information of tectonic settings, the strike and scale of causative faults, focal mechanism solutions, fault rupture process and attenuation relationship in Western China, as well as local site effects. The results are as follows： （1） The major axis of shaking intensity distribution is directed NW-SE, parallel to the Yushu fault; （2） The meizoseismal area reaches an intensity IX and covers 300km^2; （3） The intensity IX area is mainly distributed in the area 40km southeast and 15km northwest of the epicenter along the causative fault; （4） Due to local soil conditions, the northwestern part of the area with intensity IX on bedrock shows an intensity Ⅷ when converting from the bedrock to the soil; （5） Areas with intensity Ⅷ, VII, VI measure 3,000km^2, 8,000km^2, and 24,000km^2, respectively.展开更多
基金This research is supported by the National Key Basic Research 973 Project(Grant No.:2008CB425701)the Special Project M7.0~8.0 of China Earthquake Administration
文摘Based on seismic data from the regional network for the last 34 years, we analyzed the present fault behavior of major fault zones around the Mabian area, southern Sichuan, and identified the risky fault-segments for potential future. The method of analysis is a combination of activity background of historical strong earthquakes mainly show ~ （ 1 ） The spatial distribution of b-values strong and large earthquakes in the spatial distribution of b-values with and current seismicity. Our results indicates significant heterogeneity in the studied area, which reflects the spatial difference of cumulative stress levels along various fault zones and segments. （2） Three anomalously low b-value areas with different dimensions were identified along the Mabian-Yanjin fault zone. These anomalies can be asperities under relatively high cumulated stress levels. Two asperities are located in the north of Mabian county, in Lidian town in western Muchuan county, and near Yanjin at the south end of the fault zone. These two areas represent potential large earthquake seismogenic sites around the Mabian area in the near future. Besides them, the third relatively smaller asperity is identified at southern Suijiang, as another potential strong- earthquake source. （3） An asperity along the southwestern segment of the Longquanshan fault zone indicates the site of potential moderate-to-strong earthquakes. （4） The asperity along the segment between Huangmu town in Hanyuan county and Longchi town in Emeishan city on Jinkouhe-Meigu fault has potential for a moderate-strong earthquake.
基金jointly sponsored by the Technology Research and Development Program of Institute of Earthquake Science,CEA(XH14049,XH15042)the Science Research Fund Programs of Gansu Province(Grant No.145RJZA186)+1 种基金the National Natural Science Foundation(41304048)Special Fund for the Seismic Industry of China(20160107)
文摘In this paper,based on Gansu Digital Seismic Network data since 1990,we calculated b-value and ⊿ b-value of the neighborhood area before the 2013 Minxian-Zhangxian M_S6. 6,earthquake. The results show that the earthquake occurred at the margin of the significantly lower b-value area in southeast of Gansu and before the earthquake the neighborhood area had an obviously abnormal ⊿ b-value. From the earthquake and the spatial distribution of low b-value, the region still has the possibility of generating dangerous strong earthquakes.
基金sponsored by the Basic Science and Technology Programme of the Institute of Earthquake Science(0207690205),China Earth quake Administration
文摘At some stage of a strong earthquake preparation, the focal mechanisms of small earthquakes have roughly the same direction with the tectonic stress field. According to this feature, we define the angle between P, B and T axis of focal mechanisms and the three stress axes of tectonic stress field as the consistency parameter a in studying the dynamic changes of stress fields in earthquake preparation areas. We mainly analyze the changes of the consistency parameter a of the Mw8. 3 Knril island arc earthquake and the Mw8. 4 Peru earthquake. Our study shows that before the strong earthquakes, the earthquake area saw a low consistency, and the focal mechanisms of a series of small earthquakes had small differences in the directions with the tectonic stress field, which means the foreshocks were under the control of the stress field. On the other hand, a higher consistency means the focal mechanisms of their aftershocks are scattered and have big differences in the directions with the tectonic field, which indicate that the control of background stress field starts weakening.
文摘Two hours after the 2010 Yushu Earthquake, the shaking intensity distribution was obtained using the ShakeMap Rapid Generation System Based on Site Effects, developed by the author, which integrates the information of tectonic settings, the strike and scale of causative faults, focal mechanism solutions, fault rupture process and attenuation relationship in Western China, as well as local site effects. The results are as follows： （1） The major axis of shaking intensity distribution is directed NW-SE, parallel to the Yushu fault; （2） The meizoseismal area reaches an intensity IX and covers 300km^2; （3） The intensity IX area is mainly distributed in the area 40km southeast and 15km northwest of the epicenter along the causative fault; （4） Due to local soil conditions, the northwestern part of the area with intensity IX on bedrock shows an intensity Ⅷ when converting from the bedrock to the soil; （5） Areas with intensity Ⅷ, VII, VI measure 3,000km^2, 8,000km^2, and 24,000km^2, respectively.
