西北区域自动地震速报系统定位结果评估

The Assessment of Positioning Result of Northwestern Regional Automatic Earthquake Rapid Report System

西北区域自动地震速报系统是中国地震局5大区域速报系统之一。分析了2009年7月1日至2011年8月31日该系统产出的149个天然地震与全国统一地震编目系统定位结果的匹配情况:97.3%的地震发震时刻偏差小于5s;96%的地震震中偏差分布在5～30km之间;94%的地震深度偏差不超过5km;68.5%的地震震级偏差不大于0.3。分析了7个非天然地震的匹配情况。并对未匹配地震及偏差较大地震作了进一步的分析。对自动地震速报系统的整合与完善提出了一些建议。

The northwestern regional automatic earthquake rapid-report system,the center of which is located in earthquake networks center of Shaanxi province,is one of five such systems under the China Earthquake Administration.The principal rapid-report range includes Shaanxi province,Gansu province,Ningxia Hui Autonomous Region,western Inner Mongolia Autonomous Region,and eastern Qinghai province.The system,which is based on software in a regional digital seismic network for a real-time earthquake rapid report system,relies on the network platform of the Earthquake Administration of Shaanxi province and accepts data from all seismic earthquake stations in Shaanxi,Gansu,Ningxia,and Qinghai,in addition to those west of Inner Mongolia.On July 1,2009,this system officially assumed primary responsibility for the northwestern regional automatic earthquake rapid report,by which northwestern region M≥3.0 earthquakes are automatically output and uploaded to the China earthquake networks center.This system can automatically analyze seismic phases of earthquakes on this region and neighbor areas and gives three elements of earthquake including origin time,earthquake magnitude,and earthquake epicenter.In addition,region M≥ 4.0 earthquakes are recorded by the automated rapid reporting mobile message service.This study selects 173 natural earthquakes and 11 non-natural earthquakes from the earthquake catalog,from July 1,2009,to August 31,2011.One hundred fifty-six earthquakes output from the northwestern regional automatic earthquake rapid report system correlate with earthquakes listed in the catalog,including 149 natural earthquakes（86.1%） and 7 non-natural earthquakes（63.6%）.This study has determined that 24 earthquake had been not detected by this automatic system,all of which occurred in western Gansu and the Qinghai-Tibet plateau area,where earthquake seismic the network layout is relatively sparse.Earthquakes occurring in areas in which seismic stations layout are relatively reasonable,such as Shaanxi,Ningxia,eastern Gansu province,western Inner Mongolia,and eastern Qinghai province,were all reported by this system.This study also analyzes the deviation and accuracy of positioning results of 149 natural and 7 non-natural earthquakes on the basis of correlation to the those listed in the earthquake catalog and northwestern regional automatic earthquake rapid report system.This paper shows that in 97.3% of natural earthquakes,the deviation of origin time is less than 5 s;in 96%,deviation of the earthquake epicenter is 5 to 30 km;in 94%,deviation of earthquake depth is less than 5 km;and in 68.5%,deviation of magnitude is less than 0.3.All 7 non-natural earthquakes were related to a coal mine collapse earthquake with deviation of origin times of less than 5 s.Therefore,the performance has achieved first-class competition status as outlined by the 2010 appraisal standard for rapid reporting.Moreover,4 achieved second-class for earthquake epicenter location accuracy;2 reached third-class,1 reached fourth-class in positioning accuracy.One earthquake had a magnitude deviation of 0.2;that of all other non-natural earthquakes was greater than or equal to 0.3.In addition,this paper analyzes the reasons why minor earthquakes are not recognized by system or are output with large deviation.According to the task of the northwestern regional automatic earthquake rapid-report system and research of the northwestern region seismic and seismic network layout,this study also provides suggestions for integration and improvement of the automatic earthquake rapid report system,which include relaxing the requirement for magnitude deviation;optimizing the layout of Qinghai networks;increasing the number of stations in mid-and western Qinghai and in northern Shaanxi;and optimizing existing processing software.