Direct tomography of S-wave structure using subarray surface wave dispersion data: Methodology and validation

ABSTRACT Surface wave imaging based on ambient noise, especially with the deployment of increasingly dense arrays (such as nodal seismometers and distributed acoustic sensing), became an effective tool for investigating subsurface velocity structures. Although segmenting dense arrays into subarrays emerged as a promising approach, traditional subarray surface wave imaging methods faced challenges in positioning the average phase velocity dispersion data of subarrays, leading to velocity jumps and poor lateral constraints. A novel subarray surface wave direct imaging (SSWDI) method was proposed, which established a sensitivity kernel between subarray average dispersion data and subsurface parameters. Numerical experiments and real-world applications demonstrated that SSWDI reduced velocity artifacts compared to traditional methods. The method’s key advantages included inherent spatial smoothing constraints and the ability to jointly use multiscale subarray dispersion data, providing more reliable constraints on subsurface S-wave velocity structures from shallow to deep depths. The SSWDI method showed broad application potential in the future.