In 1996, a retrogressive landslide claimed four lives near the village of Finneidfjord, northern Norway. Since then, the area has been developed into a prime natural field laboratory for investigating submarine slope instabilities. Research activities adopt an integrated approach inwhichwe aim to characterize the slip planes involved in the landsliding and understanding the sedimentary processes contributing to failure, including human activity (e.g., road works), the presence of quick clay deposits in the near-shore area as well as shallow gas accumulations in the fjord. In this paper, we focus on the spatial variability of soil conditions in general and the slip plane in particular as evidenced from different vintages of seismic data (very-high-resolution 3D chirp data and multi-channel sparker and boomer data) tied with soil samples and 1D in situ geotechnical logs (CPTU) across the landslide complex and shallow gas accumulation zone. The slip planes correspond to composite, thin event beds characterized by subtle variations in lithology. These event beds demonstrate a laterally variable character across the landslide complex, both in the seismic data and particularly in the CPTU response. Through impedance inversion and modelling and using the geological and geotechnical data as calibration, we have developed methods to derive geotechnical properties (e.g., partial gas saturation, lithology, density) from the seismic data. The integrated approach can be used to investigate similar landslides in coastal areas.