A New Body-Wave Amplitude Ratio-Based Method for Imaging Shallow Crustal Structure and Its Application in the Sichuan Basin, Southwestern China

Shallow crustal velocity and Poisson's ratio structures are of key importance to understand rock properties and near-surface tectonic deformation and evolution. We propose a novel imaging method to acquire such information at individual stations by joint inversion of amplitude ratios between the horizontal and vertical components of both teleseismic P and S waves. Our synthetic experiments demonstrate the validity of the method in recovering subsurface structures up to similar to 8-10 km depth. We apply this method to construct the velocity and Poisson's ratio images along a NW-SE-trending seismic array within the Sichuan Basin, southwestern China. The results reveal well developed stratification and localized high Poisson's ratio anomalies, which reflect a long-term stable sedimentary environment and fault-related deformation in response to the Cenozoic Tibet-basin collision, consistent with geological observations. Our new method builds a bridge between fine-scale near-surface seismic exploration and large-scale deep passive-source imaging, especially for areas of weak seismicity.

Automated summary

The study introduces a novel seismic imaging method to acquire shallow crustal velocity and Poisson's ratio structures at individual stations, demonstrating its validity through synthetic experiments and field applications. Results from experiments in the Sichuan Basin, China, revealed underground structures and lithological features, reflecting stable sedimentary environments and geological processes related to tectonic deformation.