The short-term imminent precursors happened before many severe earthquakes in China may are summarized as follows:
1. The anomolies progressively migrated towards the epicenter from the outer boundaries.
2. The amplitudes of the anomolies alternatively fluctuated from high to low as they migrated to wards the epicenter.
These two points mentioned above, have the significance of predicting the earthquake immediately before it takes place, because they are very easy to be discovered.
Presented here are the mechanism of the short-term imminent earthquake precursors on the underground water, the animal, the geoelectricity, the earth light, the earth gas, etc, and that of the precursor phenomena on the rmall earthquake actions, the ground deformation, etc——"hydraulic fracturing" mechanism.Before the earthquake, the underground "hydraulic fracturing" phenomena had been indirectly proved by the fact that the levels of the oil in the oil wells and of the water in the deep wells enormously raise mously (differently from decades to thousands of metcrs) immediately before the earthquake. We suppose that the shortterm imminent anomlies are directiy under the influence of the shallow zone mechanism sather than the control of the seismic source.
Before the earthquake, the inerease of underground stress and the way of increase, the closed degree of the underground reservoir aquifer body can be regarded as the causes hwv the pore pressure ncreased up to "breakdown pressure". As the hydraulic fracturing phenomenon suddenly occurred and suddenly disppeared, the precursors Caused by it are in general, jumpy too.
Many coseismic phenomena and the anomolies after earthquakes Can also be cxplained by the theory of the "hydraulic fracturing" mechanism.