Active tectonics and intracontinental earthquakes in China; the kinematics and geodynamics
Active tectonics and intracontinental earthquakes in China; the kinematics and geodynamics (in Continental intraplate earthquakes; science, hazard, and policy issues, Seth Stein (editor) and Stephane Mazzotti (editor))
Special Paper - Geological Society of America (2007) 425: 299-318
China is a country of intense intracontinental seismicity. Most earthquakes in western China occur within the diffuse Indo-Eurasian plate-boundary zone, which extends thousands of kilometers into Asia. Earthquakes in eastern China mainly occur within the North China block, which is part of the Archean Sino-Korean craton that has been thermally rejuvenated since late Mesozoic. Here, we summarize neotectonic and geodetic results of crustal kinematics and explore their implications for geodynamics and seismicity using numerical modeling. Quaternary fault movements and global positioning system (GPS) measurements indicate a strong influence of the Indo-Asian collision on crustal motion in continental China. Using a spherical three-dimensional (3-D) finite-element model, we show that the effects of the collisional plate-boundary force are largely limited to western China, whereas gravitational spreading of the Tibetan Plateau has a broad impact on crustal deformation in much of Asia. The intense seismicity in the North China block, and the lack of seismicity in the South China block, may be explained primarily by the tectonic boundary conditions that produce high deviatoric stresses within the North China block but allow the South China block to move coherently as a rigid block. Within the North China block, seismicity is concentrated in the circum-Ordos rifts, reflecting the control of lithospheric heterogeneity. Finally, we calculated the change of Coulomb stresses associated with 49 major (M> or =6.5) earthquakes in the North China block since 1303. The results show that approximately 80% of these events occurred in regions of increasing Coulomb stresses caused by previous events.