There has been a lot of research on how a big earthquake like Sylmar '71 leads to Northridge '94 (study below says the former accelerated the latter by a factor of decades).

This study at the link below analyzes the degree to which the 1933 Long Beach quake triggered the 1952 Kern County quake which triggered the 1971 San Fernanco/Sylmar quake and, in turn, the 1994 Northridge quake. Each quake increased stress on the fault lines which slipped in these subsequent quakes.

I'm not sure "triggered" is the most apt term but I'm on my first cup of coffee....

https://profile.usgs.gov/myscience/uploa...cience_1994.pdf


"A model of stress transfer implies that earthquakes in 1933 and 1952 increased the Coulomb stress at the site of the 1971 San Fernando earthquake. The 1971 earthquake in turn raised stress and produced aftershocks at the site of the 1987 Whittier Narrows and 1994 Northridge ruptures. The Northridge main shock raised stress in areas where its aftershocks and surface faulting occurred. Together, M>=6 earthquakes near Los Angeles since 1933 have stressed parts of the Oak Ridge, Sierra Madre, Santa Monica Mountains, Elysian Park, and Newport- Inglewood faults by >1 bar.

"While too small to cause earthquakes, these stress changes can trigger events if the crust is already near failure, or advance future earthquake occurrence if it is not."



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