广东测震台站的场地响应以及对震级确定的影响分析

Site Response of Guangdong Seismic Stations and Its Influence on Determination of Earthquake Magnitude

认识台站场地响应对提高台网产出数据的准确性具有重要的意义。分析了广东台网72个测震台站的地脉动记录数据,利用谱比法计算得到各台站0.1~20Hz的场地响应。结果表明有32个台站场地响应曲线平缓,无明显频率放大点;有32个台站的场地响应曲线在部分频率范围表现出较高值;还有4个台站场地响应曲线表现轻微场地缩小作用和4个台站场地响应曲线呈起伏剧烈的形态。综合台基岩性分析,发现台站的基岩硬度越大、结构越致密,场地放大作用越小。进一步利用2011年1月至2019年10月广东台网记录到的852次地震事件(ML≥2),分析了台站场地响应对单台震级的影响,结果发现大部分台站的震级偏差结果与场地响应具有一定关系,考虑场地响应的单台震级校正值能够在一定程度上减小单台震级偏差,提高单台震级的准确性。

Researching the site response of the stations is of great significance to improve the accuracy of the output data of the seismic network.The paper processed the microtremors noise data recorded by 72 stations of Guangdong Seismic Network,and calculated the site response of each station at 0.1-20 Hz based on horizontalto-vertical(H/V)spectral ratio method.The results show that the site response curves of 32 stations are flat,and there were no obvious frequency amplification points.The site response curves of 32 stations showed higher values in some frequency ranges.In addition,there were 4 stations showing slight site reduction and 4 stations with sharply fluctuating response curves.Based on comprehensive lithology analysis of the platform,it is found that the greater the hardness of the bedrock and the denser the structure,the smaller the site amplification effect.This paper further uses the 852 earthquake events with ML≥2 recorded by the Guangdong Station Network from January 2011 to October 2019 to analyze the effect of the station site response on the magnitude of a single station.As a result,the magnitude deviation of most stations has a certain relationship with the site response.The single magnitude correction value obtained from the site response can reduce the deviation between the single magnitude and the average magnitude of the network to a certain extent and improve the accuracy of the single station magnitude.