远震相对走时数据快速计算方法及应用

A fast method for calculating relative residuals of teleseismic data and its application

远震层析成像技术已成为研究地球深部速度结构最为主要的方法,而其所用数据通常为初至震相的相对走时残差值.本文针对信噪比差的远震波形资料提出一种计算远震相对走时残差数据的快速方法,整个计算过程全部由计算机自动完成.该方法主要有两大特点:(1)利用互相关方法计算波形间的偏移时间时引入波形相位信息,有效压制噪声,增强有用震相的识别;(2)改进常规方法中计算相对走时残差的理论公式,避免求解超定方程组,提高计算精度.为验证新方法的可行性和实用性,以长江中下游地区远震波形资料为例,采用常规方法和新方法分别计算相对走时残差数据,对比结果显示:新方法比常规方法的工作效率和数据精度都高.

Teleseismic tomography has been the most important method to study the deep velocity structure in the Earth and it generally uses the relative residuals of first arrival phases.In this study,a fast method is proposed to calculate the relative residuals of teleseismic data with lower ratio of signal/noise,in which all works can be automatically finished by the computer.There are two special characters：（1） the phase information is used to calculate the offset time between two waveforms by using the cross-correlation method,which can effectively suppress the noise and improve the identification of valid phases;（2） the formula of regular method to calculate the relative residual is modified to avoid the inversion of overdetermined equations,which improve the calculation precision.To verify the feasibility and practicability of our new method,we chose the teleseismic waveform data from the middle-lower Yangtze River as an example and respectively used the regular method and our new method to calculate the relative residual.The comparison result shows that the efficiency and precision of our new method is better than that of the regular method.