New research uncovers a surprising clue in earthquake forecasting: tiny curved scratches on fault planes.
These marks reveal where past earthquakes started and how they spread, offering a new tool to predict future seismic activity. The technique is now being applied to major fault lines worldwide, including California’s earthquake-prone zones.
A Breakthrough in Earthquake Forecasting
Scientists have developed a new technique to study faults, which could improve earthquake forecasting by revealing where quakes begin, how they spread, and where they might cause the most damage.
A recent study published in Geology introduces this method, which helps identify the starting points and movement patterns of past earthquakes. Understanding these details is crucial for predicting how future quakes might unfold along major fault lines.
Curved Scratches: Nature’s Earthquake Fingerprints
Researchers found that earthquakes leave behind subtle curved scratches on fault planes — similar to tire marks after a high-speed turn. By analyzing these markings, scientists can determine the direction from which an earthquake traveled to a specific location.
“Fault planes accumulate these curved scratch marks, which until now we didn’t know to look for or how to interpret,” explained UC Riverside geologist and paper first author Nic Barth.
A Game-Changer for Global Fault Studies
These curved scratches have been observed on fault surfaces after several major earthquakes, including the 2019 Ridgecrest earthquakes in California. Computer modeling confirmed that the shape and orientation of these marks reveal the direction in which the earthquake moved.
This study is the first to demonstrate that this method can be applied to fingerprint the locations of prehistoric earthquakes. It can be applied to faults worldwide, helping to forecast the effects of possible future earthquakes and improve hazard assessments globally.
Forecasting Future Earthquakes with Precision
“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.
Where an earthquake starts and where it goes can have a big influence on the intensity of shaking and the amount of time before people feel it. For example, scientists have shown that a large earthquake originating on the San Andreas fault near the Salton Sea that propagates to the north will direct more damaging energy into the Los Angeles region than a closer San Andreas earthquake that travels away from LA.
More optimistically, such an earthquake that starts further away could allow cellular alert systems to give Angelenos a warning of about a minute before the shaking arrives, which could save lives.
A Glimpse into the Future with New Zealand’s Alpine Fault
New Zealand’s Alpine Fault is known for its regular timing of large earthquakes, which makes it a more straightforward choice for studying fault behavior. The fault is known to rupture at almost metronomic intervals of about 250 years.
This study provides two valuable insights for the Alpine Fault. First, that the most recent quake in 1717 traveled from south to north, a scenario that has been modeled to produce much greater shaking to populated areas. Second, it establishes that large earthquakes can start on both ends of the fault, which was not previously known.
Applying the Method to California’s Faults
“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.
A New Era in Earthquake Preparedness
Ultimately, Barth and his team hope that earthquake scientists around the world will start applying this new technique to unravel the past history of their faults. Barth is particularly enthusiastic about applying this technique across California’s fault network, including the notorious San Andreas Fault, to improve predictions and preparedness for one of the most earthquake-prone regions in the United States.
“There is no doubt that this new knowledge will enhance our understanding and modeling of earthquake behavior in California and globally,” he said.
Reference: “Rupture direction of paleoearthquakes on the Alpine Fault, New Zealand, as recorded by curved slickenlines” by Nicolas C. Barth, Jesse R. Kearse, Timothy A. Little and Russ J. Van Dissen, 7 October 2024, Geology.
DOI: 10.1130/G52543.1
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