Relation Between The Abnormal Infrasound Signals And The Earthquakes

A long term observation shows that abnormal infrasound signals often appear few days before magnitude M≥7 worldwide earthquakes, which reveals that the abnormal infrasound signal is one of important and effective methods for conducting the imminent earthquake prediction. This thesis research work examines the correlation between abnormal infrasound signals and large earthquakes, and temporal characteristics of the signals.Worldwide M≥7 earthquakes in 2002 ~ 2009 are extracted from the catalog of the United States Geological Survey, and the abnormal infrasound signals are recorded by Institute of Earthquake Prediction at Beijing University of Technology. The relationship between the maximum magnitude, starting time, duration, or epicenter distance to the observation station and the associated earthquakes are investigated. To understand the characteristics of the abnormal infrasound signals in the time and frequency domain, Cohen distribution method is applied on the time-frequency analysis of the abnormal infrasound signals before the earthquakes. The abnormal infrasound signals of four areas in Japan, Indonesia, China Mainland and Taiwan Island are utilized to find differences and types among them.Finally to locate the epicenter of a forthcoming earthquake, two arrays formed by 8 observation stations have been set up in Beijing and Taiwan. A time delay method is employed to predict the epicenters of forthcoming earthquakes since 2008.