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The San Andreas Fault is part of a giant "Z" of faults; the top of the "Z" consists of the Ridgecrest Fault, the middle is the Garlock Fault and the bottom is the southern part of the famous San Andreas. If the "top-of-the-Z" Ridgecrest Fault were to have a really big earthquake (at least a magnitude 7.5), that could trigger an earthquake on the "middle-of-the-Z" Garlock Fault, which, in turn, could cause a massive earthquake along the "bottom-of-the-Z" San Andreas, a new study finds. These successive earthquakes wouldn't necessarily happen all at once, but over a period of time (perhaps...

The study, published in the Bulletin of the Seismological Society of America on Monday, says there is now a 2.3% chance of an earthquake of magnitude 7.5 or greater in the next 12 months on a section of the 160-mile-long Garlock fault, which runs along the northern edge of the Mojave Desert. That increased likelihood, in turn, would cause there to be a 1.15% chance of a large earthquake on the San Andreas fault in the next year.

In the modern historical record, the 160-mile-long Garlock fault on the northern edge of the Mojave Desert has never been observed to produce either a strong earthquake or to even creep — the slow movement between earthquakes that causes a visible scar on the ground surface. But new satellite radar images now show that the fault has started to move, causing a bulging of land that can be viewed from space. “This is surprising, because we’ve never seen the Garlock fault do anything. Here, all of a sudden, it changed its behavior,” said the lead author of the study, Zachary...