Abstract: The recognition and extraction of seismic precursory anomalies are important tasks for earthquake prediction research, and they are also the bottleneck of development of earthquake prediction. In this paper, combined with the results of Ludian earthquake research, its high-frequency abnormalities of the fixed-point deformation by the methods of S-transform and overrun rate are extracted. Then, the abnormal morphological characteristics are summarized and its regularities of distribution are analyzed. Finally, the precursory mechanism of high-frequency abnormal are dissected. According to the analysis, the signal components of high-frequency anomalies are mainly composed of several minutes to several hours of signal with a wide frequency band and a good cluster. It begun 4~5 days before the earthquake and disappeared in a week, which was accompanied by the kick and step abnormalities of the curve. The distribution of anomalies was along with the NW-SE tectonic block boundary, which was consistent with the direction of regional stress and the seismogenic fault trend. It could be a record of slip and instantaneous rupture between different rates of tectonic block, and its formation also related to the stability of the crustal medium near the station.

Key words: Ludian M_S6.5 earthquake, High-frequency information anomalies, S transformation, Overrun Rate Analysis(ORA), Precursor mechanism