Study Of Key Technologies In Earthquake Early Warning System

As a new and effective way of earthquake hazards mitigation, EarthquakeEarly Warning (EEW) system has drawn more and more attentions. Severalcountries and regions have already built their own EEW system or still test on it.In this paper, we focus on some key technologies that used in EEW system andmade research of them. Such as continuous earthquake location method,earthquake magnitude estimation method, reliability of EEW information, warninginformation release scheme are all include in this paper. Based on seismic recordsof great Wenchuan earthquake, Chi-Chi earthquake and the2011off the Pacificcoast of Tohoku earthquake in Japan, the feasibility and applicability of ourmethod was verified and analyzed. The contents are summarized as follows:(1) A continuous earthquake location method was developed in this paper.The location method make a full use of limited information and the epicenter ofthe earthquake can be constrained with just one station triggered, the possibleregion of the epicenter will gradually reduced with time increase. When3or morestations triggered, we can get more accurate result by take the location formulaproposed in this paper. By taking the location error estimation formula deduced inthis paper, we can make a prejudgment of the location quality, the accuracy andreliability of the location results will be improved in this way. We test our methodby using some actual observation records in Fujian seismic monitoring networks,results show that our method have certain precision and meet the highly timelinessrequirements of EEW system.(2) By analysis of the earthquake magnitude estimation method used inEEW system, we recommend the cand Pdmethod as the two priority methodsused in earthquake magnitude estimation. We obtain the magnitude estimationformulas of these two parameters based on several earthquake records. In addition,we expand the Pdmethod, and trace the peak ground motion of displacement sincestation triggered, and then the earthquake magnitude can be continuous updating.Meanwhile, the peak ground motion of velocity (PGV) can be estimate moreaccurate by taking the Pdparameter. Due to different epicenter distance ofdifferent stations, available information at each station will be different, then theprecision of magnitude results calculate at each station will be different too, weproposed4weighting approach to calculate the comprehensive earthquakemagnitude.(3) According to the highly accuracy requirement of the EEW system, wecombined different characteristics of different parameters, and test the reliabilityof information through several different ways, such as signal to noise ration,compatibility of parameters, coordinate of parameters and reliability of locationresult etc. We collect several seismic data recorded by Fujian seismic monitoring network to test our method, results show that by taking this method, we caneliminate the interference information effectively, and then the dependability ofthe EEW system will be improved.(4) Following the JMA instrumental seismic intensity method, combinedwith the main frequency range of building structure in our country (0.3Hz-3.0Hz),we proposed a complete set of instrumental seismic intensity calculation algorithm.The algorithm have a clear physic meaning, and made a reasonable consider ofamplitude, frequency and duration of ground motions, also it made full use of3components records. Based on this algorithm, we proposed an instrumentalseismic intensity standard, it reasonable inheritance and convergence of thecurrent Chinese seismic intensity standard. Take Wenchuan earthquake forexample, test results shows that the instrumental seismic intensity calculationresults consistant well with the seismic intensity field investigation results, whichfully indicated the applicability and reliability of our method.(5) Take Fujian province for example, combined with seismic stations andseismic activities data in this region, we studied and determined the warninginformation release scheme, and the contour maps of time needed for each reportcan be obtain according to this scheme. Based on historical earthquakes data andthe potential seismic source areas in Fujian region, we make an evaluation of theefficiency of EEW system.(6) By using seismic records of great Wenchuan earthquake, Chi-Chiearthquake, and the2011off the Pacific coast of Tohoku earthquake in Japan, thefeasibility and applicability of our method was verified and analyzed.