The earthquake cycle in the Los Angeles basin

< This animation shows the process of  elastic strain build-up and release by earthquakes on the faults cross-crossing the LA basin

During quiet times in between earthquakes (interseismic periods), the LA basin and the San Gabriel mountains are squeezed ,due to the bend along the San Andreas fault. The convergrence rate between the Catalina Islands, offshore LA, and the San Gqbriel mountains is about  9mm/yr (about 1/3d of inch per year).  This process is loading the faults criss-cossing the LA basin. There are places where these faults stick together (locked) and places where they don't (creeping). Stress build up on the locked patches until they fail in earthquakes. This process leads to recurring events  similar to the Northridge earthquake of 1994 which reached  magnitude 6.8

This "seismic cycle" recurs about every 250 years.

Credit: Jean-Philippe Avouac, Chris Rollins and Juan Vargas


California Institute of Technology
Last updated: March 5, 2019