Seismic refraction and electrical resistivity surveys were carried out to characterize a landslide that occurred near the Çanakkale-Lapseki-Bursa highway, in northwest Turkey. Hydrometer analyses were also performed to highlight the composition of the slip surface material. The combined interpretation of the methods yielded the mass of the landslide body and the possible subsurface nature of a basal slip plane. Sediment-size fraction maps show that the slip surface material contained an excessive amount of clay. The clay-rich slipping layer was observed to a maximum depth of 4–5 m marked by a low (2–4 ohm-m) resistivity zone, contrasting with the underlying sand-rich beds with relatively higher resistivities (>6 ohm-m). A velocity variation ranging between ∼1,250–1,500 m/s also characterized this water-saturated slipping zone. Results indicated a buried failure surface under the studied shallow slide mass, which appeared to be a prolongation of the long upward-concave slip surface of the old landslide area to the east. Thus, future reactivations can be expected along basal slip surfaces of both recent and old landslide areas, which may pose a risk for the road structure and vehicular traffic along the active Çanakkale-Lapseki-Bursa highway.