Susceptibility to Deep-Seated Landslides in California

-->This map shows the relative likelihood of deep-seated landsliding based on regional estimates of rock strength and steepness of slopes. On the most basic level, weak rocks and steep slopes are most likely to generate landslides. The map uses detailed information on the location of past landslides, the location and relative strength of rock units, and steepness of slope to estimate susceptibility to deep-seated landsliding. This landslide susceptibility map is intended to provide infrastructure owners, emergency planners, and the public with a general overview of where landslides are more likely to occur. It is not appropriate for evaluation of landslide potential at any specific site.-->

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The Susceptibility to Deep-Seated Landslides map covers the entire state of California and was originally published in May of 2011 as CGS Map Sheet 58. It made use of several data layers of varying scales and formats, such as Landslide Inventory, Geology, Rock Strength, and Slope. For the statewide analysis of landslide susceptibility, the methodology of Wilson and Keefer (1985) was used in combining the rock strength and slope data layers as implemented by Ponti, el al. (2008) to create classes of landslide susceptibility (0 to 10, low to high). These classes express the generalization that on very low slopes, landslide susceptibility is low even in weak materials, and that landslide susceptibility increases with slope and in weak rocks.

The landslide susceptibility matrix, based on Rock Strength (RS) and Slope Steepness (SS) in degrees, is described below. Roman numerals may also be used to indcate class assignment (e.g., class 5 (V)):

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