The large earthquakes that struck southern California in July have caused the movement of a major fault that could potentially cause a magnitude 8 earthquake, according to a new study published on Science

The 6.4 and 7.1 magnitude earthquakes hit southern California over the summer caused not only significant building damages but also a rupture and an increased strain on a major fault called Garlock fault. 

Garlock fault runs east-west for 185 miles from the San Andreas Fault to Death Valley, it has been quiet for 500 years, and it has the capacity of causing an 8 magnitude earthquake. According to researchers from the California Institute of Technology along with NASA’s Jet Propulsion Laboratory, part of this fault has slipped 0.8 inches near its surface since being triggered by July earthquakes. This movement could seem tiny but was large enough length to be detected by the radar satellite in space. 

Zachary Ross, assistant professor of geophysics at Caltech and lead author of the paper, said: “It’s surprising. In California, we’ve been monitoring earthquakes for a long time. We think we have a pretty good sense of what typical behavior is over long timescales … and then when something happens that’s anomalous, that obviously stands out. We just don’t know what this could mean.”

The team emphasized that this unprecedented phenomenon doesn’t allow speculating what could mean for future hazards. These findings demand experts to rethink the previous earthquake model, which states that the rupture of one fault line causes large earthquakes; instead of a model where earthquakes are caused by “faults that, when they rupture, trigger one another like falling dominoes” should be considered. 

All earthquakes of magnitude 2.5 and greater in the Ridgecrest area July 4 to Aug. 15, 2019, are shown as gray circles. Red stars mark the two largest. The Garlock Fault south of the cluster of earthquakes has slipped almost an inch since July. Credit: USGS

All earthquakes of magnitude 2.5 and greater in the Ridgecrest area July 4 to Aug. 15, 2019, are shown as gray circles. Red stars mark the two largest. The Garlock Fault south of the cluster of earthquakes has slipped almost an inch since July. Credit: USGS

The study was published on the 30th anniversary of the Loma Prieta earthquake. Although, since that tragedy awareness about earthquakes has been deeply improved, new challenges like this require to keep ourselves informed and alert.

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Sources: 

Levin, S. (2019). California: July earthquake caused fault to move for first time on record. [online] the Guardian. Available at: https://www.theguardian.com/us-news/2019/oct/18/california-ridgecrest-earthquake-fault-strain-researchers

Gajanan, M. (2019). https://time.com. [online] Time. Available at: https://time.com/5705085/garlock-fault-ridgecrest-earthquake-california/

Jet Propulsion Laboratory
Calofnirnia Institute of Technology
NASA  https://www.jpl.nasa.gov/news/news.php?feature=7520

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