3D S-wave velocity imaging of a subsurface disturbed by mining using ambient seismic noise

Abstract

Seismic interferometry based on ambient seismic noise was used to image the 3D S-wave velocity field of a subsurface disturbed by mining under the geological conditions at the KGHM Rudna copper mine in southwestern Poland. We recorded ambient seismic noise data for 3 months using 11 surface-mounted broadband seismometers located across the mining area. We used ambient-noise cross-correlation techniques to create a three-dimensional S-wave velocity model of the Cenozoic and Triassic formations up to a depth of 500 m. Cross-correlation functions (CCFs) indicate the Rayleigh and Love waves; however, only the Love waves in the 0.19–0.4 Hz frequency range were reliable, based on the symmetry of the CCFs in the positive and negative conditions. Imaging using the Love waves indicated that the changes in the S-wave velocity field in the model may be explained by the subsidence processes occurring above the mined area. The S-wave velocity decreased above the areas of the current mining operations. However, the S-wave velocity increased above older mined areas, probably due to suppression of the subsidence process and progressive consolidation of the geological medium over time. We also observed low-velocity anomalies in the intersection zones of the larger faults, with high energy seismic events. This could be caused by fault activation by current mining operations and a reduction in the stiffness of the layers in the fault intersection zone. This study presents the possibility of imaging the subsurface layers in a mining area using ambient seismic noise. It also has the potential to give a broader insight into how a geological medium responds to mining in terms of protecting the terrain surface and developing mining technologies.