WHAT’S BEING CLAIMED:
- A new study found that the wave of powerful earthquakes that rocked Southern California in July caused a nearby fault in motion.
- The study reports that the surface of the Garlock fault has significantly moved to about 0.8 inches.
- It also noted that a rupture triggered the first quake setting off shocks through a system of faults nearby.
A new research reports that the July quakes that shook Southern California have placed a huge strain on a fault nearby that has been quiescent for around 500 years, possibly triggering a magnitude 7.8 temblor.
Collectively known as the Ridgecrest earthquake sequence, the major earthquakes last July had shaken the earth after ruptures along several small faults in the region occurred.
Scientists reported in the journal Science that the Garlock fault has significantly moved an estimated 0.8 inches (2 centimeters) at the surface since July. The fault marks the northern boundary of the Mojave Desert and runs about 186 miles (300 kilometers) across Southern California.
According to study statements, the strongest shaking during the Ridgecrest sequence occurred on July 4 around 124 miles (200 km) north of Los Angeles, with a magnitude of 6.4. This was even followed by a more powerful quake at magnitude 7.1 about 34 hours later. The NASA Earth Observatory recorded over 100,000 aftershocks in the region over the following weeks.
CalTech assistant geophysics professor and study co-author Zachary Ross said that the very first rupture that triggered the first quake set off a wave of slips and shocks coursing through a criss-crossing system of nearby faults. Prior to the event, the authors discovered twenty faults caught in the domino effect.
“We actually see that the magnitude-6.4 quake simultaneously broke faults at right angles to each other, which is surprising because standard models of rock friction view this as unlikely,” explained Ross.
Ross added that the Ridgecrest sequence not only set the Garlock fault moving but has also reversed previously held assumptions on how major earthquakes take place.
Scientists have always thought that a 7.0 magnitude quake was most probably caused by a break of a single long fault with a maximum magnitude restricted by the length of the fault. However, Ross said the Ridgecrest sequence illustrates an opposite scenario: small faults can join up creating a complex network and stir up powerful earthquakes.
“Over the last century, the largest earthquakes in California have probably looked more like Ridgecrest than the 1906 San Francisco earthquake, which was along a single fault,” said Ross.
“It becomes an almost 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.”
Overall, the Ridgecrest event ended up being one of the best-documented earthquake sequences in history. In a statement, Ross said that people will be compelled to think about how we quantify seismic hazard and whether we need to change our approach to defining faults.
Source: Live Science