|Strain Partitioning Across Metropolitan Los Angeles|
Andrea Donnellan, Ann Blythe, Louise Kellogg, Maggi Glasscoe
Geodetic data indicate that after northern Metropolitan Los Angeles is shortening at a rate of about 6 mm/yr between downtown Los Angeles and the San Gabriel Mountains. Fission track thermochronology indicates that the San Gabriel Mountains are undergoing bedrock uplift at a rate of 1 mm/yr. Assuming that the shortening crust is isostatically compensated the total crustal thickening of the San Gabriel block is 4.5-5.5 mm/yr. We assume that all of the uplift of the San Gabriels is due to the major frontal fault system (e.g. the Sierra Madre fault) yielding a total slip on the system of 5.5 mm/yr. This leaves 2.8 mm/yr of shortening to be accommodated by faults to the south, near downtown Los Angeles. By using strain rates and observed stress drops for typical southern California earthquake we estimate that earthquakes should occur at intervals of 700-1600 years on fault segments within the belt.
| PDF (78KB) |