Large Earthquakes: a Way of Formation and Prediction

Zhiyong Zhu

It is believed that the accumulation of small fractures (small earthquakes) in the crust is one of many ways for the formation of large fractures (large earthquakes). In such cases, the temporal variations in the accumulation number of small earthquakes can be used to predict future seismic activity in the region. To do so, a structural system of the crust is constructed using the logarithmic linear relationship between earthquake frequency and magnitude, and a relationship between earthquake accumulation and time is derived by assuming that the rate of earthquake accumulation is proportional to the q-th power of the existing number of earthquakes. Earthquake record from selected regions of China and Italy are fitted by the theory and the obtained fitting parameters are used to evaluate the future seismic activity. It is found that the extent of deviation of earthquake accumulation from the theoretical expectation can be a reasonable judgement of the local seismic dangerous level and q ≥ 1 can be considered a marker of local crust entering an accelerated fracturing phase. The proposed method made the physical evaluation of local seismic activity possible by simplifying the 3D (space-time-magnitude) problem into 2D (time-magnitude) problem in earthquake prediction.