The Northe South Seismic Belt(NSSB) is a Chinese tectonic boundary with a very complex structure, showing a sharp change in several geophysical field characteristics. To study these characteristics and their relations...The Northe South Seismic Belt(NSSB) is a Chinese tectonic boundary with a very complex structure, showing a sharp change in several geophysical field characteristics. To study these characteristics and their relationship with the distribution of earthquakes and faults in the study area, we first analyze the spatial gravity anomaly to achieve the Bouguer gravity anomaly(EGM2008 BGA) and the regional gravity survey Bouguer gravity anomaly.Next, we ascertain the Moho depth and crustal thickness of the study area using interface inversion with the control points derived from the seismic and magnetotelluric sounding profiles achieved in recent years. In this paper, we summarize the relief, trend, Moho gradient, and crustal nature, in addition to their relationship with the distribution of earthquakes and faults in the study area. The findings show that earthquakes with magnitudes greater than Ms7.0 are mainly distributed in the Moho Bouguer anomaly variation belt and faults. The results of the study are important for future research on tectonic characteristics, geological and geophysical surveys, and seismicity patterns.展开更多
North China is a key region for studying geophysical progress. In this study, ground-based and Gravity Recovery and Climate Experiment（GRACE） gravity data from 2009 to 2013 are used to calculate the gravity change r...North China is a key region for studying geophysical progress. In this study, ground-based and Gravity Recovery and Climate Experiment（GRACE） gravity data from 2009 to 2013 are used to calculate the gravity change rate（GCR） using the polynomial fitting method. In general, the study area was divided into the Shanxi rift, Jing-Jin-Ji（Beijing-Tianjin-Hebei Province）, and Bohai Bay Basin（BBB） regions. Results of the distribution of the GCR determined from ground-based gravimetry show that the GCR appears to be ＂negativepositive-negative＂ from west to east, which indicates that different geophysical mechanisms are involved in the tectonic activities of these regions. However, GRACE solutions are conducted over a larger spatial scale and are able to show a difference between southern and northern areas and a mass redistribution of land water storage.展开更多
By using GPS and gravity data before and after the Wenchuan Ms8.0 earthquake and combining data from geological surveys and geophysical inversion studies, an initial coseismic fault model is constructed. The dip angle...By using GPS and gravity data before and after the Wenchuan Ms8.0 earthquake and combining data from geological surveys and geophysical inversion studies, an initial coseismic fault model is constructed. The dip angle changes of the fault slip distribution on the fault plane are inversed, and the inversion results show that the shape of the fault resembles a double-shovel. The Yingxiue Beichuan Fault is approximately 330 km long, the surface fault dip angle is 65.1, which gradually reduces with increasing depth to 0 at the detachment layer at a depth of 19.62 km. The Guanxiane Jiangyou Fault is approximately90 km long, and its dip angle at the surface is 55.3, which gradually reduces with increasing depth; the fault joins the Yingxiue Beichuan Fault at 13.75 km. Coseismic slip mainly occurs above a depth of 19 km. There are five concentrated rupture areas, Yingxiu,Wenchuan, Hanwang, Beichuan, and Pingwu, which are consistent with geological survey results and analyses of the aftershock distribution. The rupture mainly has a thrust component with a small dextral strikeeslip component. The maximum slip was more than10 m, which occurred near Beichuan and Hanwang. The seismic moment is 7.84 1020 Nm(Mw7.9), which is consistent with the seismological results.展开更多
In this study, we analyzed the gravity and, magnetic characteristics, and the occurrence of a fault zone and discussed the relationships between the two locations. The results reveal that the subsurface structures str...In this study, we analyzed the gravity and, magnetic characteristics, and the occurrence of a fault zone and discussed the relationships between the two locations. The results reveal that the subsurface structures strikes are different compared with those in the research region. In other words, the geophysical advantageous directions from the gravity and magnetic anomalies are not the same as those caused by the surface structures. The local horizontal gradient results from the gravity and magnetic anomalies show that the majority of earthquakes occur along an intense fault zone, which is a zone of abrupt gravity and negative magnetic change, where the shapes match very well. From the distribution of earthquakes in this area, we find that it has experienced more than 11 earthquake events with magnitude larger than Ms7.0. In addition, water development sites such as Jinshajiang, Lancangjiang, and the Red River and Pearl River watersheds have been hit ten times by earthquakes of this magnitude. It is observed that strong earthquakes occur frequently in the Holocene active fault zone.展开更多
基金supported by the China Earthquake Administration, Institute of Seismology Foundation (201326126)Institute of Seismology Foundation (201326128)Chinese earthquake scientific array exploration e northern section of North South seismic belt gravity profile Foundation (201308011)
文摘The Northe South Seismic Belt(NSSB) is a Chinese tectonic boundary with a very complex structure, showing a sharp change in several geophysical field characteristics. To study these characteristics and their relationship with the distribution of earthquakes and faults in the study area, we first analyze the spatial gravity anomaly to achieve the Bouguer gravity anomaly(EGM2008 BGA) and the regional gravity survey Bouguer gravity anomaly.Next, we ascertain the Moho depth and crustal thickness of the study area using interface inversion with the control points derived from the seismic and magnetotelluric sounding profiles achieved in recent years. In this paper, we summarize the relief, trend, Moho gradient, and crustal nature, in addition to their relationship with the distribution of earthquakes and faults in the study area. The findings show that earthquakes with magnitudes greater than Ms7.0 are mainly distributed in the Moho Bouguer anomaly variation belt and faults. The results of the study are important for future research on tectonic characteristics, geological and geophysical surveys, and seismicity patterns.
基金supported by the National Natural Science Foundation of China(41304060)the national key basic research and development plan(2013CB733304)
文摘North China is a key region for studying geophysical progress. In this study, ground-based and Gravity Recovery and Climate Experiment（GRACE） gravity data from 2009 to 2013 are used to calculate the gravity change rate（GCR） using the polynomial fitting method. In general, the study area was divided into the Shanxi rift, Jing-Jin-Ji（Beijing-Tianjin-Hebei Province）, and Bohai Bay Basin（BBB） regions. Results of the distribution of the GCR determined from ground-based gravimetry show that the GCR appears to be ＂negativepositive-negative＂ from west to east, which indicates that different geophysical mechanisms are involved in the tectonic activities of these regions. However, GRACE solutions are conducted over a larger spatial scale and are able to show a difference between southern and northern areas and a mass redistribution of land water storage.
基金supported by the China Earthquake Administration, Institute of Seismology Foundation (IS201226003, IS201326128)the National Natural Science Foundation of China (41104049)the National Basic Research Program of China (2013CB733304-2)
文摘By using GPS and gravity data before and after the Wenchuan Ms8.0 earthquake and combining data from geological surveys and geophysical inversion studies, an initial coseismic fault model is constructed. The dip angle changes of the fault slip distribution on the fault plane are inversed, and the inversion results show that the shape of the fault resembles a double-shovel. The Yingxiue Beichuan Fault is approximately 330 km long, the surface fault dip angle is 65.1, which gradually reduces with increasing depth to 0 at the detachment layer at a depth of 19.62 km. The Guanxiane Jiangyou Fault is approximately90 km long, and its dip angle at the surface is 55.3, which gradually reduces with increasing depth; the fault joins the Yingxiue Beichuan Fault at 13.75 km. Coseismic slip mainly occurs above a depth of 19 km. There are five concentrated rupture areas, Yingxiu,Wenchuan, Hanwang, Beichuan, and Pingwu, which are consistent with geological survey results and analyses of the aftershock distribution. The rupture mainly has a thrust component with a small dextral strikeeslip component. The maximum slip was more than10 m, which occurred near Beichuan and Hanwang. The seismic moment is 7.84 1020 Nm(Mw7.9), which is consistent with the seismological results.
基金supported by the Chinese Earthquake Administration,Institute of Seismology Foundation(IS201326126)Chinese earthquake scientific array exploration northern section of North South Seismic Belt gravity profile Foundation(201308011)
文摘In this study, we analyzed the gravity and, magnetic characteristics, and the occurrence of a fault zone and discussed the relationships between the two locations. The results reveal that the subsurface structures strikes are different compared with those in the research region. In other words, the geophysical advantageous directions from the gravity and magnetic anomalies are not the same as those caused by the surface structures. The local horizontal gradient results from the gravity and magnetic anomalies show that the majority of earthquakes occur along an intense fault zone, which is a zone of abrupt gravity and negative magnetic change, where the shapes match very well. From the distribution of earthquakes in this area, we find that it has experienced more than 11 earthquake events with magnitude larger than Ms7.0. In addition, water development sites such as Jinshajiang, Lancangjiang, and the Red River and Pearl River watersheds have been hit ten times by earthquakes of this magnitude. It is observed that strong earthquakes occur frequently in the Holocene active fault zone.
