Research On Earthquake Location Using Single Station For Earthquake Early Warning

The paper is focused on earthquake location using single station for earthquake early warning. The main content of the research includes how to pick up P wave and to determine azimuth and epicentral distance of an earthquake quickly using information contained in the first few seconds of acceleration records.The following research has been carried out in the paper:1. Determination of P wave arrival time is the foundation of earthquake location using single station for early warning. The combination of STA/LTA and AIC is used to pick up P waveform and to decide the arrival time.2. There are three steps to calculate epicentral distance using the B-Δ method based on P waveform in the initial three-second vertical component of accelegrams. The first step is to deduce the recursion formula and the general term formula of envelope curves. Aimed at the fitting method of envelope, the conversion formula which transfers curve fitting into linear fitting has been obtained. And then the method of obtaining B value for the fitting function is explained. The second step is to get the regression function applying the linear method on the basis of B value and epicentral distances of earthquakes acceleration records, including near and distant earthquakes. And the last step is to using the regression function to calculate epicentrial distances of each earthquake as B is recognized as a known value. The explanation for deviation between the real and calculated epicentral distances is elaborated.3. P wave information contained within the first0.6seconds of three-component acceleration recording data is applied to calculating azimuth. Reasons for errors between the real values and calculated ones are analysed. Based on this analysis, window length and date type to get optimal accuracy of the results are put forward. Two methods to calculate azimuth using single station, the project method and the smoothing method are introduced basically. And calculated results from those two methods are compared with application of acceleration records. Then the polarization analysis methods is placed emphasis on calculating azimuth attempting different window lengths. Advantages and disadvantages are analysed and compared by using acceleration, velocity and displacement records. The deviation of those computed results are calculated, and the possible reasons for the deviation are presented.4. On the basis of above research,12earthquakes’ epicenters are located. Then what causes errors of location is explained. And the level of errors is evaluated.