Ground movements affecting Westline Drive, the residence along Westline, and the utilities beneath Westline Drive appeared to be related to two distinct landslide complexes. The predominant landslide appeared to include # 28 and #30, along the northern side of Westline Drive, and #33 through # 77 on the southern side. The landslide toe coincided with the topographic break-in-slope bordering the level open space to the north. Based on the slide morphology and bedding structure in the Merced Formation, the mechanism of landsliding could be characterized by a block slide-earth flow complex involving oblique slip along bedding surfaces in the Merced Formation. The sliding appeared oriented at about N20ºW, and estimated maximum depth and volume of slide material is on the order of 80 feet and 400,000 cubic yards.
The second landslide scarp appears to project into the 90-degree bend in Westline Drive, where it is truncated by ground cracks associated with Landslide # 1. The predominate direction of sliding appeared oriented to about N60° W, and the estimated maximum depth and total volume of slide material is on order of 75 feet and 300,000 cubic yards. The main landslide mechanism may involve wedge sliding or slumping. The secondary slide mass may represent a geologically youthful slide that has developed in response to more extensive bordering slope movements (Jacobs Associates).