We investigated correlation of the slope of the initial part of P-wave envelope, hypocenter depth and plate boundaries by B-Δ method, which is used to determine epicentral distances in the Japan Meteorological Agency...We investigated correlation of the slope of the initial part of P-wave envelope, hypocenter depth and plate boundaries by B-Δ method, which is used to determine epicentral distances in the Japan Meteorological Agency and Japan Railway Company earthquake early warning(EEW) systems. The Tohoku region was chosen as the study region. 19,899 strong motion data for 265 events with magnitudes in the range from 5.0 to 7.6 from KiK-net(Kiban Kyoshin network) had been collected. The coefficient c to investigate is obtained from the linear relation between log B and log Δ. Compared to the hypocenter depth, the coefficients c of events is more likely to decide by the spatial correlation of the plate boundaries. The differences are likely to be due to earthquake characteristics, since deeper events in the subducting slabs the structural effects are likely to be larger than or comparable to those for shallow crust events.展开更多
After the establishment of the seismic observation network of southern Okinawa in August,1988 by the JMA(Japan Meteorological Agency),many hypocenters of earthquakes have been located.However,due to the small number o...After the establishment of the seismic observation network of southern Okinawa in August,1988 by the JMA(Japan Meteorological Agency),many hypocenters of earthquakes have been located.However,due to the small number of observation stations and narrow configuration of the array,the hypocenters lo-cated contain some systematic errors.Numerical experiments on the extent of the errors and the reliabilityof the JMA seismic observation network showed that the obtained hypocenters deeper than 100 km werereliable,but that for the obtained hypocenters shallower than 100 km,only the epicenters were reliable.展开更多
It is accepted as a well-known fact that in different places on the Earth’s crust,a similar anthropogenic impact causes a dissimilar response.Seismic zoning maps are not designed to predict such geodynamic hazards as...It is accepted as a well-known fact that in different places on the Earth’s crust,a similar anthropogenic impact causes a dissimilar response.Seismic zoning maps are not designed to predict such geodynamic hazards as rock bursts,induced earthquakes,reactivation of tectonic faults,etc.,and therefore require careful adjustments in places of intense impact on the subsurface strata.In this regard,we consider the classification of the Earth’s crustal areas according to the degree of geodynamic hazard,i.e.its potential geodynamic response to anthropogenic intervention.This classification is based on the concept that there exists a critically stressed layer within the Earth’s crust.It is believed that such a critically stressed layer within the Earth’s crust extends from the Earth’s surface to a certain depth,and each point depends on the nature of the interaction between crustal blocks of different hierarchical levels.From this perspective,anthropogenic impact,such as mining operations,represents a direct impact upon the critically stressed zone.We recognize the hypothesis that the thicker the critical stressed rock layer,the stronger the response might be to anthropogenic intervention,as it has more accumulated energy.Four categories of geodynamic threat have been found and mapped.To verify this classification,the manifestations of the geodynamic hazards were studied.The intensity of geodynamic hazard increased from the first area to the fourth area.The phenomenon of large induced seismic events with hypocenters at great depths is explained on the basis of this theory,and could be associated with anthropogenic impacts from the surface directly on the regional zone of the critically stressed rock massif.The approach can be used to assess the geodynamic consequences of human exposure to the Earth’s crust.展开更多
In order to improve reliability of probabilistic seismic hazard analysis, shallow earthquake (depth <70 km) data, recorded with orientation precision grades 1 and 2 by modern instrument and containing depth informa...In order to improve reliability of probabilistic seismic hazard analysis, shallow earthquake (depth <70 km) data, recorded with orientation precision grades 1 and 2 by modern instrument and containing depth information after 1970, are selected as statistical samples, meanwhile, North China seismic region, Central China seismic region, South China seismic region, Xinjiang seismic region and Qinghai-Xizang Plateau seismic region are chosen as statistical units to study the depth distribution characteristics of shallow earthquakes. Considering the differences of depth distribution characteristics of earthquakes with different magnitudes, the following magnitude intervals are adopted to analyze earthquakes with different magnitude scales, respectively: M S=2.0～2.9, M S=3.0～3.9, M S=4.0～4.9, M S=5.0～5.9 and M S=6.0～6.9. The results show that hypocenter depths are normally distributed by and large around the mean depth of the corresponding seismic region. The probabilistic distribution curves of earthquake depth in West China are wider than those in East China. The probabilistic distribution deviation, σ, of West China is greater than those of East China, that is, earthquakes in West China have a wider range in terms of depth. There is also a tendency that the absolute value of mean hypocenter depth increases with the magnitude by and large.展开更多
The hypocentral depths of more than 200 Chinese earthquakes, of magnitudes from M 8.6 to M 3.0, are calculated from macroseismic data carried on earthquake catalogs, by using the formula for macroseismic hypocen...The hypocentral depths of more than 200 Chinese earthquakes, of magnitudes from M 8.6 to M 3.0, are calculated from macroseismic data carried on earthquake catalogs, by using the formula for macroseismic hypocentral depths and the formula for general solution of macroseismic hypocentral depths. The results are plotted on maps to show their geographical distribution. It can be seen that most Chinese earthquakes are shollow ones. Of the 200 earthquakes calculated, 162(81.0%) hypocenters are shallower than 9 km, of which 111 (55.5%) hypocenters are shallower than 5 km. Such shallow earthquakes are mostly distributed in the provinces near to the North South Earthquake Belt, while the rest are scattered in the other provinces(except Zhejiang province). Earthquakes of medium(between 10 and 20 km) depth are relatively few (32 in number, 15.0%); they are distributed along the North South Earthquake Belt, and the western part of Xinjiang Uygur Autonomous Region and in provinces Shaanxi, Shanxi and Shandong (along the Tanlu Fracture Zone, crossing the sea to northeast China). Deep earthquakes are rare, being scattered in south Yunnan and the east end of Inner Mongolia Uygur Autonomous Region.展开更多
基金supported by the Director Foundation of the Institute of Seismology,China Earthquake Administration,China(IS200756046)
文摘We investigated correlation of the slope of the initial part of P-wave envelope, hypocenter depth and plate boundaries by B-Δ method, which is used to determine epicentral distances in the Japan Meteorological Agency and Japan Railway Company earthquake early warning(EEW) systems. The Tohoku region was chosen as the study region. 19,899 strong motion data for 265 events with magnitudes in the range from 5.0 to 7.6 from KiK-net(Kiban Kyoshin network) had been collected. The coefficient c to investigate is obtained from the linear relation between log B and log Δ. Compared to the hypocenter depth, the coefficients c of events is more likely to decide by the spatial correlation of the plate boundaries. The differences are likely to be due to earthquake characteristics, since deeper events in the subducting slabs the structural effects are likely to be larger than or comparable to those for shallow crust events.
文摘After the establishment of the seismic observation network of southern Okinawa in August,1988 by the JMA(Japan Meteorological Agency),many hypocenters of earthquakes have been located.However,due to the small number of observation stations and narrow configuration of the array,the hypocenters lo-cated contain some systematic errors.Numerical experiments on the extent of the errors and the reliabilityof the JMA seismic observation network showed that the obtained hypocenters deeper than 100 km werereliable,but that for the obtained hypocenters shallower than 100 km,only the epicenters were reliable.
基金partially used the materials obtained during grant implementation No.GК-1406(2009)of the Russian Ministry of Science and Education
文摘It is accepted as a well-known fact that in different places on the Earth’s crust,a similar anthropogenic impact causes a dissimilar response.Seismic zoning maps are not designed to predict such geodynamic hazards as rock bursts,induced earthquakes,reactivation of tectonic faults,etc.,and therefore require careful adjustments in places of intense impact on the subsurface strata.In this regard,we consider the classification of the Earth’s crustal areas according to the degree of geodynamic hazard,i.e.its potential geodynamic response to anthropogenic intervention.This classification is based on the concept that there exists a critically stressed layer within the Earth’s crust.It is believed that such a critically stressed layer within the Earth’s crust extends from the Earth’s surface to a certain depth,and each point depends on the nature of the interaction between crustal blocks of different hierarchical levels.From this perspective,anthropogenic impact,such as mining operations,represents a direct impact upon the critically stressed zone.We recognize the hypothesis that the thicker the critical stressed rock layer,the stronger the response might be to anthropogenic intervention,as it has more accumulated energy.Four categories of geodynamic threat have been found and mapped.To verify this classification,the manifestations of the geodynamic hazards were studied.The intensity of geodynamic hazard increased from the first area to the fourth area.The phenomenon of large induced seismic events with hypocenters at great depths is explained on the basis of this theory,and could be associated with anthropogenic impacts from the surface directly on the regional zone of the critically stressed rock massif.The approach can be used to assess the geodynamic consequences of human exposure to the Earth’s crust.
文摘In order to improve reliability of probabilistic seismic hazard analysis, shallow earthquake (depth <70 km) data, recorded with orientation precision grades 1 and 2 by modern instrument and containing depth information after 1970, are selected as statistical samples, meanwhile, North China seismic region, Central China seismic region, South China seismic region, Xinjiang seismic region and Qinghai-Xizang Plateau seismic region are chosen as statistical units to study the depth distribution characteristics of shallow earthquakes. Considering the differences of depth distribution characteristics of earthquakes with different magnitudes, the following magnitude intervals are adopted to analyze earthquakes with different magnitude scales, respectively: M S=2.0～2.9, M S=3.0～3.9, M S=4.0～4.9, M S=5.0～5.9 and M S=6.0～6.9. The results show that hypocenter depths are normally distributed by and large around the mean depth of the corresponding seismic region. The probabilistic distribution curves of earthquake depth in West China are wider than those in East China. The probabilistic distribution deviation, σ, of West China is greater than those of East China, that is, earthquakes in West China have a wider range in terms of depth. There is also a tendency that the absolute value of mean hypocenter depth increases with the magnitude by and large.
文摘The hypocentral depths of more than 200 Chinese earthquakes, of magnitudes from M 8.6 to M 3.0, are calculated from macroseismic data carried on earthquake catalogs, by using the formula for macroseismic hypocentral depths and the formula for general solution of macroseismic hypocentral depths. The results are plotted on maps to show their geographical distribution. It can be seen that most Chinese earthquakes are shollow ones. Of the 200 earthquakes calculated, 162(81.0%) hypocenters are shallower than 9 km, of which 111 (55.5%) hypocenters are shallower than 5 km. Such shallow earthquakes are mostly distributed in the provinces near to the North South Earthquake Belt, while the rest are scattered in the other provinces(except Zhejiang province). Earthquakes of medium(between 10 and 20 km) depth are relatively few (32 in number, 15.0%); they are distributed along the North South Earthquake Belt, and the western part of Xinjiang Uygur Autonomous Region and in provinces Shaanxi, Shanxi and Shandong (along the Tanlu Fracture Zone, crossing the sea to northeast China). Deep earthquakes are rare, being scattered in south Yunnan and the east end of Inner Mongolia Uygur Autonomous Region.
