广西测震台网台站地方性震级偏差分析

Study on the deviation of local magnitude in Guangxi Seismic Network

选用广西数字化测震台网2008—2020年记录的广西及邻区1251个M_(L)≥2.0地震事件震相资料,采用震级残差统计方法,获取广西51个地震台单台震级与台网平均震级的平均偏差和标准差,分析观测仪器类型、台基场地响应和震中距等因素对震级偏差的影响,进而提出台基校正值,修正区域量规函数。结果发现,南宁、天等、北海等15个地震台站的震级偏大,桂林、贺州、天峨等16个地震台站的震级偏小,崇左、灵山、平果等20个地震台站震级适中;在单台震级共14784个样本中,震级偏差集中在-0.4—0.4,呈正态分布;震级偏差受台基场地响应和震中距因素影响明显,当场地响应值大于1.0时震级偏大,小于1.0时震级偏小,等于1.0时震级较为适合,当震中距在70 km范围内时单台震级偏小,当震中距在70—300 km时单台震级较为适合,当震中距在300—550 km时,单台震级稍有偏大。修正后的区域量规函数和台基校正值,可有效提高广西测震台网测定震级的准确性。

Based on the seismic data of 1251 M_(L)≥2.0 earthquakes in Guangxi and adjacent areas recorded by the Guangxi Digital Seismic Network from 2008 to 2020,using the magnitude residual statistical method,the station magnitudes of 51 seismic stations and the average magnitudes of the network were obtained.The average and standard deviation of the magnitude deviations are analyzed.The influences of factors such as the instrument type,the site response of the station base,and the epicentral distance on the magnitude deviation are analyzed,and then the correction values for the stations are proposed to correct the regional calibration functions.The results showed that the magnitudes of 15 seismic stations,including NNS,TDX,and BHS,et al.,were larger,16 seismic stations,such as GUL,HZS,and TE,et al.,were smaller,and 20 seismic stations,such as CZS,LNS and PGX,et al.,were moderate;in a total of 14784 samples of station magnitudes,the magnitude deviations are concentrated in-0.4—0.4,with a normal distribution;the magnitude deviations are significantly affected by the site response of the station base site and the epicentral distance.When the base site response value is greater than 1.0,the magnitude is larger.When it is less than 1.0,the magnitude is smaller.When it is equal to 1.0,the magnitude is suitable.When the epicentral distance is smaller than 70 km,the station magnitude is relatively small.When it is between 300 km and 550 km,the station magnitude is slightly larger.The revised regional calibration function and the base correction value can effectively improve the accuracy of the Guangxi Digital Seismic Network in determining the magnitude.