Researchers at the University of California, Riverside have described a new method for studying faults that could improve earthquake forecasting, shedding light on when earthquakes will initiate and propagate.
This method examines past earthquakes’ origins and directions, which is valuable information for modeling future earthquakes on major faults.
Like the tire marks left after a drift, earthquakes leave behind scratches on the fault plane. By studying these scratches, researchers can determine the direction of the earthquakes.
“Fault planes accumulate these curved scratch marks, which until now we didn’t know to look for or how to interpret,” explains the first author Nic Barth.
Several curved incisions were observed on fault surfaces following several historic ruptures, including the 2019 Ridgecrest earthquakes in California. Computer simulations confirmed the shape of the curvature indicates the direction from which the earthquake came.
The study, published in the journal Geology, demonstrates that this method can be applied to fingerprint the locations of prehistoric earthquakes. The novel method applies to faults worldwide, improving the global earthquake assessment and future possible earthquakes.
“The scratches indicate the direction and origin of a past earthquake, potentially giving us clues about where a future quake might start and where it will go. This is key for California, where anticipating the direction of a quake on faults like San Andreas or San Jacinto could mean a more accurate forecast of its impact,” Barth said.
A milestone for forecasting earthquake hazards
The start and the spread of an earthquake can have a big influence on the intensity of the shaking. For instance, a large earthquake originating on the San Andreas fault, near the Salton Sea, propagating to the north will direct more damaging energy into the Los Angeles region.
Such earthquakes could provide cellular alert systems to give Angelenos a warning about a minute before the shaking arrives.
New Zealand’s Alpine Fault is an ideal fault for studying earthquake behavior because of its regular timing. This fault is known to rupture every 250 years. By utilizing this technique on the Alpine Fault, researchers could state that the recent quake of 1717 traveled from south to north.
Interestingly, the study revealed that large earthquakes can start on both ends of the fault.
“We can now take the techniques and expertise we have developed on the Alpine Fault to examine faults in the rest of the world. Because there is a high probability of a large earthquake occurring in Southern California in the near term, looking for these curved marks on the San Andreas fault is an obvious goal,” Barth said.
The lead author and colleagues are keen to use this new technique to unravel the history of their faults.
“There is no doubt that this new knowledge will enhance our understanding and modeling of earthquake behavior in California and globally,” Barth concludes.
Journal Reference
- Nicolas C. Barth, Jesse R. Kearse, Timothy A. Little, Russ J. Van Dissen; Rupture direction of paleoearthquakes on the Alpine Fault, New Zealand, as recorded by curved slickenlines. Geology 2024; 52 (12): 917–921. DOI: 10.1130/G52543.1