Geophysical pre‐investigation for a Stockholm tunnel project: joint inversion and interpretation of geoelectric and seismic refraction data in an urban environment

Abstract

Underground constructions for public traffic purposes are becoming increasingly important for urban areas in order to use the limited space more efficiently. Several electric resistivity tomography and seismic refraction tomography measurements were performed crossing a water passage near Stockholm during the pre‐investigation phase of a tunnel building project. The objective was to determine the bedrock interface and qualitatively assess the rock quality. The scope of this study is to present a field case in an urban environment and show improvements of geophysical results due to additional model constraints by a joint inversion. Results of individual inversions show a large transition zone below the seabed from electric resistivity tomography. Some parts of the seismic refraction tomography have a low model resolution, due to gas‐bearing sediments with a low velocity together with a high noise level, which leads to insufficient investigation depth that makes it difficult to determine the bedrock interface. However, the bedrock interface could be reconstructed in the resistivity model by performing a joint inversion, using the seismic velocity model to constrain the electric resistivity tomography model and vice versa. Adjacent geotechnical soundings support the joint inversion results. A vertical low resistive zone could be identified as a dominant fracture zone in the southern part of the investigated area. In general, the joint inversion approach significantly improved the electric resistivity tomography results and provided a more reliable bedrock estimation.

Near‐shore geophysical and geotechnical investigations in support of the Trieste Marine Terminal extension

“…Anderson and Ringis ; Shtivelman ; Masoli et al . ; Ronczka, Wisen and Dahlin ). S‐wave data are preferred because they are strictly related to the geotechnical parameters, but generation and recording of S‐wave at the sea bottom is not a trivial issue.…”

Joint inversion of seismic and electrical data in saturated porous media

“…In near‐surface geophysics, which does not benefit from the same abundance of dedicated rock‐physics studies as for hydrocarbon exploration, the structural coupling only is more common (Hellman et al ., 2017; Ronczka et al ., 2018; Senkaya et al ., 2020) than the introduction of physical couplings between formations into inversion process. Some examples of physical joint inversion can be found in Dal Moro (2008) and Boiero and Socco (2014), who introduced the Poisson's ratio, which describes the deformation of a material in the perpendicular direction of the applied stress in terms of negative of the ratio between transverse strain and axial strain, as constraint between S‐wave and P‐wave velocities in a joint inversion of surface wave and P‐wave refraction data.…”

Temporal filtering and time-lapse inversion of geoelectrical data for long-term monitoring with application to a chlorinated hydrocarbon contaminated site

“…Geophysical monitoring can provide a valuable tool to interpolate the sparse and point information from the groundwater and soil samples and monitor more effectively the changes in the subsurface, both in space and time (Mishra et al 2019). Geophysical methods can also be used as a base for designing a drilling and sampling program that is as representative as possible, or to identify spots where an existing sampling program needs to be augmented (Danielsen & Dahlin 2009Ronczka et al 2018).…”