On seismic strengthening area before strong and great shocks and its mechanism

By systematically studying seismic strengthening areas before 85 earthquakes with M≥6.0 in China, some results have been extracted. (1) Earthquake active strengthening area exists universally before strong shock or great earthquake; (2) The size of the strengthening area and its appearing time will increase when the earthquake magnitude increases; (3) The rate between the size of seismic strengthening area and the size of the source region decreases when earthquake magnitude increases; (4) The appearing time of the earthquake active strengthening region in the eastern part of China is longer than that in the western part of China. The above characteristics have been preliminarily explained qualitatively and half-quantitatively by applying the strong body earthquake generating model and the hard inclusion theory. Then applying the seismic strengthening area, we have obtained long-term predictions of 2 earthquakes, so the seismic strengthening area before strong earthquake or great earthquakes is a universal phenomenon, which has some mechanical base. This research was supported by the Chinese Joint Seismological Science Foundation (198085).