A Study Of The Direction Of Infrasonic Origin On Earthquake Forecast

Imminent prediction of earthquake is a difficult task in the world. At the present time earthquake forecast focus on various phenomena of earthquake such as seismic-electricity, geo-stress, electromagnetic wave, etc. Earthquake forecast based on anomalous infrasound is one of important methods because of the good corresponding relationship between the anomalous infrasound and earthquake. Using the infrasound method to predict the initial time and scale of the earthquake is effective. At present time, the infrasound method stays the stage of using recorders to record the infrasound wave continuously for 24 hours. Automatically data acquisition and computerized analysis is not available. Furthermore, the above recording data limited to a single point is not valid to predict the epicenter. In this thesis, seismic infrasound is profoundly studied.hi this thesis, the technique of detector array is used to obtain the location of anomalous infrasound, it is the basic of the study of prediction of earthquake. To derive useful information by using spectrum analysis on infrasonic signal. Then combing with other methods a forecast could be made.Firstly, a system was developed in functions to collect infrasound data, to transform analog voltage signal from detector into discrete signal by A/D card and to process the data by using methods of Digital Signal Process.Secondly an infrasonic array was constructed. The array is made up of three detectors with about 1 kilometer distance between each other. The three detectors are connected with telephone line. Their locations were correctly arranged. With the correlation technique, direction and speed of the infrasound can be calculated by computing the time delay of each detector and by using geometric knowledge. The epicenter can be determined by calculating the intercross point of two or more directions of detectors.An infrasound detecting software was developed in Visual C++. It is a real-time infrasonic data acquisition and analysis program of 3-point array. The program includes the infrasonic signal data acquisition of three channels, 3-D dynamic spectrum analysis, correlation analysis of 3 channel infrasonic signals, the calculation of wave direction, the wave speed, the spectrum analysis at any length and a real-time infrasonic gravity wave pressure-time (P-T) curve.