Research And Application Of Methods For Rapid Processing Of Seismic Data

Rapid processing of earthquake data is an important indicator for evaluating a seismic network.The development of digital seismic networks all over the world and the research and application of technology for automatic processing have greatly improved the ability of rapid processing of earthquake data.In recent years,with the development of economy and society,peoples' consciousness of earthquake resistance and disaster mitigation has been increasing and earthquake early warning system has been paid attention to.After completion of the 10th five-year seismic observation network project,real-time seismic data from near 1000 stations have provided conditions for automatically processing earthquake data.The aim of this study is to speed Chinese earthquake processing and accumulate technique and experience for construction of earthquake early warning system.In order to realize the goal that an earthquake is processed quickly,we have applied and/or developed EDT(Equal Differential Time) curve intersection method,real-time simulation method,optimal first arrival combination method and rapid determination of M_w using initial P waveform method.We mainly investigated EDT curve intersection method and optimal first arrival combination method.By applying these four methods,we designed two systems to automatically process Chinese Mainland earthquakes and global large earthquakes respectively.The results produced by these two systems demonstrated that these two systems can process an earthquake quickly with higher precision.The major contents and conclusions of this paper are listed as follows.(1) In consideration of the demand of automatic location now,we simplified the MAXI(The Maximum Intersection Method) method and developed EDT curve intersection method.The result of research for EDT curve intersection method indicates that for an earthquake occurred in a seismic network this method can obtain the epicenter with higher precision,but for an earthquake occurred on the edge or out of a seismic network the result of location using this method is unstable.One advantage of this method is to clean out outliers that may exist in the first arrival data set,so this method is suitable for auto-location.(2) In order to meet the requirement for automatic location of a large earthquake occurred in the world,we proposed a location method called Optimal First Arrival Combination method,and determined the rule for selecting optimal first arrival combination.The procedure of picking out the optimal first arrival combination involves three steps,the first step is to select the locations whose total residual is less than a threshold,the second step is to choose those locations whose stations deployment is of the first class among the results of step one and the third step is to pick out a location whose total residual is the least among the results of step two.The results show that location results by using this method is stable.(3) We applied the real-time simulation method developed by Jin Xing et al.and rapid determination of M_w using initial P waveform method developed by Tsuboi et al. to determine magnitude for near and teleseismic events respectively,and we verified these two methods,showing that they are feasible.(4) By applying the achievements as above,we have accomplished two auto-process earthquake systems to focus on Chinese Mainland earthquakes and global large earthquakes respectively.These two auto-processing systems have produced a series of earthquake catalogs.By comparing the results produced by the auto-processing systems with the manual results and with NEIC(National Earthquake Information Center) catalogs,we can draw a conclusion that(a) It is fast to locate the earthquake occurred in Chinese Mainland automatically by using EDT curve intersection method,and the location results are precise;(b) We can get a good estimate of M_L by using real-time simulated DD-1 displacement from broad band instrument record;(c) We can obtain a good reference epicenter by using optimal first arrival combination method to locate a large earthquake occurred in the world.(d) After revision of M_wp,the difference between M_wp and M_w(NEIC catalog) is minute.The two auto-processing systems have greatly improved Chinese earthquake processing ability.The results of this study is beneficial for speeding earthquake information release,emergency response and disaster relief,information service to the public and the construction of an earthquake early warning system.