Academic Progress on the Mechanism and Forecast for Continental Strong Earthquake in the First Two Years
Zhang GuominCenter for Analysis and Prediction, China Seismological Bureau, Beijing 100036, ChinaZhang PeizhenGeology Institute, China Seismological Bureau, Beijing 100029, China
Based on characteristics of large earthquakes in continental China, the project proposes "active crustal block" hypothesis to describe mechanism of present day tectonic deformation, and to exploit mechanism and methods of predictions of large earthquakes. Active crustal blocks are geological units that have been cut and separated by major quaternary active faults. Each active crustal block moves coherently with very little, if any, internal deformation. Most of tectonic activity takes place along the bondaries of each block. Detachment or decoupled zone develop on the base of each block at different depth. Devastating earthquakes occur along boundaries of active crustal blocks. On the basis of seismicity, neotectonic history, lithospheric structure, crustal deformation, geophysical anomaly, andgeodynamic background, we have preliminarily divided continental China into 5 first order active crustal blocks and 19 second order blocks. Different active crustal blocks respond to different lithospheric structure. We obtained regional distinctions of lithospheric structures in corresponding to the pattern of active crustal block delineation, and studied several important active crustal blocks and their boundary zones in detail. GPS measurements indicate different crustal block move in different direction and with different rates. Progresses are made in the fields of earthquake clustering and blocks movements, formation and instability of shear faults, constitutive relationship of frictions of crustal rocks, brittle-ductile transition and rheology of crustal rocks, relationships of stress distribution, transfer, and earthquake clustering. We also exploit new methods in earthquake prediction and disaster reduction.