At least six large ruptures of the San Jacinto Fault Zone are known to have followed the 1857 Fort Tejon earthquake that ruptured the central segment of the San Andreas Fault . These events began with the 1899 San Jacinto earthquake and occurred at intermittent intervals culminating with the 1987 Superstition Hills and Elmore Ranch events . The 1857 rupture spanned a total of and terminated on the southeast end near the point where the San Jacinto Fault Zone branches away from the San Andreas Fault Zone at the Cajon Pass . In a paper published in the journal '' Science '' , Christopher Sanders plotted the earthquakes of the SJFZ by time and location and found that a uniform pattern became apparent . Moving southeastward from the Cajon Pass , the large SJFZ events appear on a line with a slope of 1.7 km per year and Sanders hypothesized that the 1857 earthquake introduced a strain pulse that migrated southeast and triggered large earthquakes as it traversed the SJFZ at that rate
1857 Fort Tejon earthquake
1857 Fort Tejon earthquake
San Jacinto Fault Zone