For over thirty years, scientists have been puzzled about why some underwater faults trigger earthquakes more reliably than others. These earthquakes often occur at regular intervals and typically have similar magnitudes.
A recent study offers some intriguing insights. Researchers from the U.S. and Canada focused on oceanic transform faults. They discovered that surrounding barrier zones function like natural brakes, slowing down earthquake activity. This phenomenon is linked to a process called dilatancy strengthening, where seawater seeps into the rock, acting as a buffer during larger earthquakes.
Jianhua Gong, a seismologist at Indiana University Bloomington, explains, “We’ve known these barriers existed for a long time. However, we never fully understood what they’re made of or why they consistently prevent earthquakes.”
The team studied two sections of the Gofar transform fault, located along the boundary between the Pacific and Nazca tectonic plates, off the coast of Ecuador. These plates are moving past each other at about 140 millimeters (5.5 inches) annually. Since record-keeping began in 1995, the fault has produced magnitude six earthquakes every five to six years.
In experiments conducted from 2008 to 2022, researchers used ocean bottom seismometers placed on the seafloor to capture thousands of tiny earthquakes around two significant ones. Their analysis revealed that the barrier zones are complex networks of smaller faults that absorb minor shocks before larger quakes.
When a major earthquake happens, the fluid-filled rock around the barriers expands, allowing more water to move in. This change in pressure locks the rock into place, preventing further sliding and stopping the earthquake from increasing in size.
Gong emphasizes that these barriers are dynamic components of the fault system. “Understanding how they work changes our view of earthquake limits,” he adds. Surprisingly, seismologists have observed similar patterns in other oceanic transform faults worldwide, suggesting these barriers may play a role in various locations.
The potential for understanding these features is vast. Future research could involve techniques like seafloor drilling to explore whether similar buffer zones exist in other faults. While the Gofar fault poses little risk to populated areas, its study could have implications for understanding more hazardous earthquake zones.
Recent data show that most faults, whether in the ocean or on land, produce unpredictable earthquakes. Each discovery edges us closer to accurately predicting when and where quakes might strike.
One study noted, “Long-term monitoring of seismicity at these faults is crucial for uncovering the mechanisms behind oceanic transform earthquakes.”
Such insights could significantly enhance our earthquake models, improving safety and preparedness in at-risk areas.
For more detailed information, see the published study in Science here.
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