Characterization of weak layers in the Southwestern slope of Ulleung Basin with seismic data merging and inversion

Failure at steep slopes and areas covered by a landslide can be controlled by laterally extended weak layers within the slope stratigraphy. Seismic data are essential in slope stability studies for identifying and tracking failure planes and the spatial extent of weak layers since weak layers often develop in decimeters and are buried together under 10–100 m sediment and water. Although seismic reflection profiles must be used to characterize weak layers at depths, it is challenging to visually characterize thin weak layers accurately due to the low vertical resolution. This study presents a method of merging 2D seismic data with different source resolutions on the same track to generate high-resolution broadband seismic data and perform seismic inversion to facilitate the tracing of thin weak layers. The resultant profile is a high-resolution acoustic impedance profile, which can track weak layers whose attributes are difficult to characterize using conventional methods. We also confirm the extension of the weak layer based on the porosity profile derived from the acoustic impedance of borehole 19ESDP-103 located on the seismic line used in the present study. Glide-planes, previously considered single or double layers due to their limited resolution, were further subdivided, tracked, and characterized in terms of lateral changes.