Abstract: Based on the characteristics of the observed data of volume strain tides, a time-domain mathematical model is proposed to process the observed data of volum estrain tides. In the model, tidal factor, barometrical coefficient, no n-tidal strain rate and acceleration are simultaneously considered and computed in the process. The observed da ta a reprocessed separately in time domain and frequency domain. It is found that anomalies of different amplitudes and duration times in the above-mentioned parameters appeared before 1989 Datong M^6.1 earthquake sequence. These parameters seem to have definite physical meanings when used as indicators for medium- and short-term earthquake prediction.

Key words: Volume strain, Solid earthquake tides, Information extraction, Medium and short-term prediction