天津地区场地响应和震源参数联合反演

Joint Inversion of Ground Response and Seismic Source Parameter in Tianjin Region

根据天津数字地震台网记录的发生在天津地区的中小地震波形资料,采用Moya方法,反演天津地区39个地震的震源谱低频水平、拐角频率和28个台站的场地响应,计算了参与反演的地震矩、拐角频率、应力降和震源半径等参数,并讨论了它们之间的关系。结果表明:27个井下台的场地响应曲线形态基本一致,低频有不同程度的放大,高频衰减较快;蓟县地表基岩台的场地响应低频基本在1附近变化,高频也有明显衰减。地震矩与震级及震源谱拐角频率的关系密切;拐角频率随震级的增大,有明显的下降;对于3级以上的地震,应力降、震源半径随地震震级的增大有明显的增大。

Based on wave form data of medium and micro earthquakes, recorded by the Tianjin Digital Seismic Network, seismic source spectrum level at low frequency and turning frequency of 39 earthquakes, and ground response of 28 stations in Tianjin region in are inversed by using Moya method. Some parameters （seismic moment, turning frequency, stress drop and source radius） of earthquakes involved in the inversions are calculated. Meanwhile, the relationship between them is discussed. The ground response curve of 27 downhole stations are basically consistent, with magnifications of different degree at low frequency and rather rapid attenuation at high frequency. Ground response of Jixian Station, located on bedrock, changes around 1 for its low frequency band and attenuates obviously at high frequency. The seismic moment is closely related to the magnitudes and the turning frequency of source spectrum. With the increasing of magnitude, the turning frequency obviously declines. For earthquakes of ML〉3, with the increasing of magnitude, stress drop and source radius increase distinctly.