California Fault Capable of 8.0 Earthquake Begins Moving For First Time

James Marshall
October 19, 2019

On July 4, the largest natural disaster in recent memory, a 7.1 magnitude tremor, struck the area in the Mojave Desert. The Ridgecrest sequence calls for rethinking seismic hazard, as multifault ruptures are not usually considered when assessing seismic risk. The researchers noted that while major earthquakes are commonly thought to be caused by the rupture of a single long fault, seismologists have since been rethinking that model.

This was followed the next day by more than 100,000 aftershocks.

A series of major earthquakes shook Southern California in July and placed strain on a nearby fault that has been quiet for about 500 years, according to a new study. "Here, all of a sudden, it changed its behavior", the lead author of the study, Zachary Ross, assistant professor of geophysics at Caltech told the L.A. Times. "It becomes an nearly intractable problem to construct every possible scenario of these faults failing together-especially when you consider that the faults that ruptured during the Ridgecrest Sequence were unmapped in the first place", Ross said in the release.

The collaborative study depicts the sequence of an natural disaster is far more complex than expected.

The period of seismic quiescence in Southern California was rudely interrupted by the Ridgecrest natural disaster sequence in July 2019.

In the past, there was no record of movement on the Garlock fault, which lies on the northern edge of the Mojave Desert, producing even a slight natural disaster.

The Ridgecrest sequence involved about 20 previously undiscovered, smaller faults crisscrossing in a geometrically complex and geologically young fault zone.

"This is surprising, because we've never seen the Garlock fault do anything".

The complexity of the extraordinary quake is only beginning to be understood because of the multiple types of scientific instruments used to study it.

Satellites observed the surface ruptures and associated ground deformation extending more than 60 miles (100km) from the earthquake's epicentre. Red stars mark the two largest.

The Ridgecrest sequence not only set the Garlock fault in motion, it has also shaken up our idea of how major earthquakes typically occur, the authors said. The nearby disruption triggered movement along the fault, scientists reported October 17 in the journal Science.

The fault has slipped nearly an inch at the surface since July, the researchers revealed.

He further explains just how little we now understand about these natural phenomena.

"It's going to force people to think hard about how we quantify seismic hazard and whether our approach to defining faults needs to change", Ross said.

The large natural disaster that hit southern California over the summer has increased strain on a major nearby fault, causing it to move for the first time on record, researchers said on Thursday.

Other reports by Click Lancashire

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