1887

Abstract

Summary

Geophysical methods often struggle with the direct detection of a subsurface cavity, in advance of its collapse and the formation of a sinkhole, which poses a threat to humans and infrastructure. Fracture zones above the cavities can prevent shear waves from propagating through them and obscure reflections from the structures to be imaged. Therefore, seismic methods focus on secondary effects such as reduced seismic velocity or diffractions. In this study, we investigate, by means of seismic finite-difference simulations, under which conditions a SH-wave can propagate through a fractured zone. We assume a system of long fractures which are impervious to SH-waves. However, if we consider fractures as a collection of cracks, bridges provide a contact between both sides of a fracture and enable a small portion of the SH-waves to pass the fracture system. The SH-wave reaches the cavity. In the presented 2-D case, SH-wave reflections from the cavity become visible if at least 40% of the cross-section of the cracks is replaced by these bridges.

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/content/papers/10.3997/2214-4609.201802557
2018-09-09
2020-04-09
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