In-mine seismics provide a better resolution and spatial coverage than surface exploration methods such as 2D or 3D seismics, enhancing the exploration around underground facilities. Over the past decades, seismic exploration techniques have been developed to address challenges in exploring ahead and around tunnels and mines. Methods such as reflection seismics and tomography are applied, taking into account the constraints on resolution and exploration range due to the distribution, accessibility, and shape of in-ground cavities.
The major challenges for the application of underground seismic exploration include avoiding cost-intensive downtimes of construction and production, as well as minimizing risks to underground facilities for safety reasons. The Integrated Seismic Imaging System (ISIS) largely integrates seismic exploration into the workflow of tunnel construction. ISIS has been improved to 3D underground seismics within the Helmholtz Innovation Lab 3D-Underground Seismics. For a detailed seismic exploration, seismic sources and receivers are used in all accessible underground spaces. The exploration capabilities were enhanced with a seismic borehole tool for exploration ahead, a borehole receiver chain, and a borehole source in exploration boreholes.
With efficient impact hammers or magnetostrictive vibrators as sources and three-component receivers, our 3D underground seismics can resolve and image 3D structures in underground with reconnaissance depths up to several hundred meters and resolutions of dm to m. Especially for exploration in clay-bearing salt reservoirs 3D underground seismics is an alternative to the established GPR. We present the components of our 3D-underground seismics and discuss their applications based on case studies in various salt mines.