Hybrid non-invasive characterization of soil strata at sites with and without embedded lava rock layers in the South Iceland Seismic Zone

• Published in: Bulletin of Engineering Geology and the Environment
• Main Authors: Olafsdottir, Elin Asta, Erlingsson, Sigurdur, Bessason, Bjarni
• Other Authors: Umhverfis- og byggingarverkfræðideild (HÍ), Faculty of Civil and Environmental Engineering (UI), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Háskóli Íslands, University of Iceland
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2023
• Subjects: Shear wave velocity; Surface wave analysis; Rayleigh wave ellipticity; Velocity reversal; Embedded lava-rock layers; Iceland
• Online Access: https://hdl.handle.net/20.500.11815/4951; https://doi.org/10.1007/s10064-023-03136-0

The geological setting of Iceland is unusual, with highly jointed rock mass, loose sediments created in glacial outburst floods and eruptions, and layers of lava-rock embedded in or overlying soft sediments. This study aims to assess the feasibility of a composite analysis of dispersion and ellipticity curves for characterization of two of the primary classes of soil sites in the South Iceland Seismic Zone. Specifically, it seeks to develop a cost-effective workflow to identify and characterize sites where a layer of lava-rock is embedded in the sedimentary stratum at shallow depth, along with deep soil site characterization. Microtremor HVSR (horizontal-to-vertical spectral ratio) is found to be efficient to distinguish between sedimentary sites with and without an embedded lava-rock layer. The results further demonstrate the effectiveness of hybrid ellipticity and dispersion curve inversion to characterize soil sites with an embedded layer of lava-rock, which results in a strong velocity reversal with depth. Consistent with previous studies, the hybrid dispersion-ellipticity inversion is also found efficient for characterization of sites with a simpler structure. This work was supported by the Icelandic Research Fund (grant numbers 206793-053, 218149-051); the Icelandic Road and Coastal Administration; and the Energy Research Fund of the National Power Company of Iceland. Accepted manuscript (post-print)