On a new map produced by the United States and California Geological Surveys, a stretch of orange and red extends on the coastal range from Los Angeles to Oregon and patches of Orange can also be seen in the Sierra and in Tehama County.
These are the areas where the slopes are steepest and the rock strength is weakest. Tim McCrink with the CGS says this is the first map they have produced that combines the two as they try to better predict where slides will occur..
"We do plan to take this map into the next stage where we look at the triggering mechanisms for landslides…both rainfall levels and earthquake shaking levels."
McCrink says the Sierra presents an interesting dynamic as it has plenty of granite…which is strong but also has plenty of earthquake activity, rainfall, steep slopes and weaker rock mixed in.
The map is available online: http://www.conservation.ca.gov/cgs/information/publications/ms/Documents/MS58.pdf