Precursory anomalies inSichuanregion before 2008 Wenchuan MS8.0 earthquake and their statistical analysis

Various observation anomalies in Sichuan region before the 12 May 2008 Wenchuan MS8.0 earthquake were studied. The abnormal items against all of observation items (or observation stations, measuring platforms, sites, well points, spring points) are the ratio of abnormal items (points), following are similar. On the mobile short leveling, the site and item ratios of existing medium to long-erm trend anomalies are 0.28 and 0.20 respectively. On the mobile short baseline, the site and item ratios of existing medium-erm trend anomalies are 0.13 and 0.13 respectively. On the ground tilt measurement, the station ratio of medium-erm trend anomalies is 0.17, the abnormal item ratio is 0.13. On the groundwater level observation, the well point ratio of medium-erm trend anomalies is 0.20. On the hot spring observation, the spring point ratio of short-erm anomalies is 0.15. On the hot spring water-as radon observation, the station and point ratio of short-erm anomalies is 0.08, the abnormal item ratio is 0.04. On the well water quality component observation, the station and point ratio of short-erm anomalies is 0.02, the abnormal item ratio is 0.04. On the apparent resistivity, the station and items ratios of medium-erm anomalies are 0.17 and 0.06 respectively. There have various observation means in the same station or site, we calculate the station or site number. There are 172 various stations or sites in Sichuan area before the Wenchuan MS8.0 earthquake, and abnormal stations or sites ratio is 0.14, the site ratios of appearing medium-erm and short-erm anomalies are 0.08 and 0.03 respectively. The total of various observation items are 335, the ratio of abnormal items is 0.09. The ratios of medium-erm and short-erm abnormal items are 0.06 and 0.01 respectively. It is clear that there are not obvious anomalies recorded by station or observation items before the earthquake. As for other observation means and data of observation items which are not involved in this paper, after researching, there have no abnormal items.