SF Gate by Rong-Gong Lin II 11/14/2019
When an earthquake strikes, the instinct of many Californians is to ask: Which fault ruptured — the Newport-Inglewood, the Hayward, the mighty San Andreas?
But scientists are increasingly saying it's not that simple.
New research shows that the Ridgecrest earthquakes that began in July ruptured at least two dozen faults. It's just the latest evidence of how small faults can join together to produce a large earthquake, and how they can cover a wider area than many might expect.
The findings are important in helping understand how earthquakes can grow in the seconds after a fault ruptures, when two blocks of earth move away from each other. In areas blanketed by a crisscross pattern of faults, an earthquake on a smaller fault can destabilize bigger ones, beginning a process that leads to a much stronger earthquake.
In the case of Ridgecrest, some follow-up earthquakes came seconds later; the largest one came 34 hours later.
It has only been in recent decades that earthquake scientists have understood how smaller faults in California join together to create a more powerful earthquake.
More:
https://www.sfgate.com/news/article/Biggest-California-earthquake-in-two-decades-14836129.php
