Dynamic analysis of water level in the Wanquan Well and the precursory anomalies of earthquakes

According to the characteristics of frequent water level step-variation in the Wanquan Well, the step-variationfrequency change on the time axis can be regarded as a sequence of step-variation. A study of the relationshipbetween the process of development and evolution of the sequential step-variation and the regional seismicityindicated that the sequential step-variation anomalies are rather better in coincidence with the time, magnitude andfrequency of regional seismic activities, which may predict the seismicity trend in months. Furthermore, on thisbasis, if the water level changes in a characteristic manner, the seismic regime during the time period from severaldays to 20 days or more may be evaluated. By using the method presented in this paper we had a prediction aboutthe Baotou ML=6.6 earthquake on May 3, 1996. This event occurred within the predicted time span but with a lessmagnitude and a little location deviation.