Magnetotelluric (MT) and the passive seismic Horizontal to Vertical Spectral Ratio (HVSR) methods are commonly used to characterize cover thickness. While MT is sensitive to resistivity contrasts in the subsurface, the MT data inversion process is affected by non-uniqueness, noise, and sometimes sparsely sampled data, all which tend to increase uncertainty in the inverted models. Likewise, HVSR models are also affected by uncertainty. In this study, we test a new approach to exploit the complementarity between HVSR and MT modelling, using structural information from HSVR to reduce the uncertainty on the cover thickness recovered using MT data inversion. To this end, we adjust the roughness constraints applied to MT inversion using the depth range predicted by the HVSR method. New approach can recover sharp resistivity contrasts at the cover-basement interface and the cover depth estimation uncertainty could be reduced to 5%.

Open-Access Online Publication: March 03, 2023