We relocated 2098 earthquakes that occurred in Beijing area between 1980 and 2000 using a double-dif- ference (DD) earthquake location algorithm, and obtained the high-precision relative locations of 1825 events. b va...We relocated 2098 earthquakes that occurred in Beijing area between 1980 and 2000 using a double-dif- ference (DD) earthquake location algorithm, and obtained the high-precision relative locations of 1825 events. b values versus depth were investigated with the relocated hypocen- ters. The results show that the b values decrease with the increasing hypocentral depth systematically. A dramatic variation in b is observed around the depth of 8 km. It indi- cates that there are more smaller earthquakes at shallow depth (0―8 km), while more larger earthquakes at greater depth (8―25 km). The physical mechanism behind this phe- nomenon can be explained by the variations in material het- erogeneity and lithostatic stress condition. Large earth- quakes are more likely to nucleate at greater depth with more homogenous material and higher lithostatic stress. On the basis of the results, we suggest that future strong earth- quakes in Beijing area tend to occur below the depth of 8 km.展开更多
基金supported by the Nationa1 Development and Reform Commission Program(Grant No.2004-1138)the National Key Project of Basic Condition Platform(Grant No.2003DIA6N005)+1 种基金the Preliminary Special Project for Key Basic Research of Ministry of Science and Technology of China(Grant No.2003CCB00600)the National Natural Science Foundation of China(Grant No.40474067).
文摘We relocated 2098 earthquakes that occurred in Beijing area between 1980 and 2000 using a double-dif- ference (DD) earthquake location algorithm, and obtained the high-precision relative locations of 1825 events. b values versus depth were investigated with the relocated hypocen- ters. The results show that the b values decrease with the increasing hypocentral depth systematically. A dramatic variation in b is observed around the depth of 8 km. It indi- cates that there are more smaller earthquakes at shallow depth (0―8 km), while more larger earthquakes at greater depth (8―25 km). The physical mechanism behind this phe- nomenon can be explained by the variations in material het- erogeneity and lithostatic stress condition. Large earth- quakes are more likely to nucleate at greater depth with more homogenous material and higher lithostatic stress. On the basis of the results, we suggest that future strong earth- quakes in Beijing area tend to occur below the depth of 8 km.
