An Improved Two‐Station Surface Wave Method and Its Application in Lithospheric Tomography Beneath the Chinese Mainland

Abstract The two‐station surface wave method has been widely applied in seismic tomography, providing high‐resolution lithospheric‐scale velocity structures without the influence of source‐phase uncertainty. However, due to limitations in the dominant frequency content and poor signal‐to‐noise ratio (SNR) of individual earthquake events, the phase velocity dispersion curves derived from single events often exhibit limited reliable frequency bands. When only a limited number of events are available or the SNR is low, the stacked dispersion curve may exhibit discontinuities. In this study, we propose an improved two‐station method that enhances the SNR of surface wave by stacking the cross‐correlation results of multiple teleseismic events within the stationary phase zone. Dispersion information is then extracted from the post‐stacking cross‐correlation function, yielding smoother and more robust dispersion curves. We apply this method to the dense China Digital Seismic Network (CDSN) and extract broadband Rayleigh wave phase velocity dispersion data in the period range of 10–120 s. The resulting shear‐wave velocity model of the lithosphere shows strong consistency with geological units, demonstrating the reliability of our phase velocity measurements and providing important insights into the evolution of the lithosphere in mainland China and its intrinsic relationship with seismic activity.