Extracting high-frequency anomaly information from fluid observational data: a case study of the Wenchuan Ms8.0 earthquake of 2008

With improvement of underground fluid observation technology, the sampling frequency of data has been obviously improved, especially after the digital transformation. There is a great deal of tectonic information in high-frequency observational data. It is a key problem how to extract the useful high-frequency information from theses data. We introduced the PDF (probability density distribution) method, and analyzed the observed fluid data of water level and water temperature at 72 stations in the area of the north-south seismic zone before the Wenchuan M(s)8.0 earthquake on 12 May, 2008. The analysis results show that 16 water level and 14 water temperature data had the high-frequency anomalies before the M(s)8.0 earthquake, and the points with abnormal information were concentrated in the tectonic belts of southwest Yunnan. The high-frequency anomalies appeared from south to north over time. On the basis of these results we considered that the PDF method has certain reliability and applicability to extract the high frequency anomaly information from observational data of fluid. It can provide a reference for information extraction of high-frequency digital observation.