The comprehensive variation analysis of digital Observational records of sand layer strain

The sand layer strain with digital records are a new-style strain data with some physical basis and prediction significance, whose measure principle is based on granular media theory and whose observational instruments have been installed in the sand layer with very fine particles. The evolution characteristics of sand layer strain observational data and the abnormal forms of earthquake precursory at different distances at Changping and Tongzhou stations have been systematically analyzed to consider that the sand layer strain records are a comprehensive strain response in the crust at different distance, and including the change compositions with extremely complex and meaningful information with very rich. The clear precursor change features and impending information were remarkably demonstrated be-fore some earthquakes with different epicentral distances and magnitudes. Specifically, there were some unloading variations with large-scales and large amplitudes, and can reflect the pre-cursor images of seismogenic processes to the large earthquakes, which may reveal certain physical models and precursor evidences of seismogenic processes. Accordingly, it is possible to achieve some successful predictions for the devastating earth-quakes, rather than the unpredictability of the earthquakes. According to the above reasons and facts, the sand layer strain with the novelty, the unique physical property and certain precursory significance have obvious differences with the other traditional strain. Therefore, there will be the exploring significance in earthquake prediction used by the sand layer strain data.