The barriers are composed of fault structures filled with seawater. The pressure inside the rock filled with fluid drops suddenly, which prevents earthquakes from taking on large proportions.
Scientists discovered the mechanism behind one of the earthquake patterns most unusual in the world, solving a decades-old mystery in the depths of the Pacific Ocean.
A new published in the journal Science reveals why a geological fault located approximately 1600 kilometers off the coast of Ecuador has produce remarkably consistent earthquakes for more than three decades.
The fault, known as the Gofar transform fault, generates earthquakes of magnitude 6 every five or six years with impressive regularity. Even more unusual, earthquakes occur repeatedly in almost identical locations and with similar intensity.
Investigators claim to have identified the reason: “barrier zones” hidden within the fault act as natural braking systems, preventing earthquakes from intensifying.
“We have known about the existence of these barriers for a long time, but the issue has always been What are they made of and why do they prevent earthquakes? so reliably,” said Jianhua Gong, lead author of the study and assistant professor at Indiana University in Bloomington.
The international research team included scientists from institutions including Woods Hole Oceanographic Institution, Scripps Oceanographic Institution, United States Geological Survey (USGS), Boston College and McGill University. His work focused on understanding why Gofar fault behaves so differently most seismic zones.
The fault is located along the Eastern Pacific Ridge, where the Pacific and Nazca tectonic plates slide horizontally past each other at a speed of about 140 millimeters per year. Although transform faults are common beneath the oceans, Gofar stands out because its largest magnitude earthquakes consistently start and end in the same areas, explains the .
To investigate the phenomenon, scientists analyzed data collected during two large seafloor studiescarried out in 2008 and between 2019 and 2022. Seismographs installed on the ocean floor recorded tens of thousands of small earthquakes around two distinct magnitude 6 events, providing researchers with an unprecedented view of the internal behavior of the fault.
The data revealed that quieter “barrier” regions become highly active, with small earthquakes in the days before a large earthquakebefore going almost completely silent afterwards. The researchers observed the same pattern in two distinct fault sections, more than a decade apart.
Additional analyzes showed that the barriers are composed of complex, fractured fault structures filled with seawater. When a large rupture hits these zones, the pressure inside the fluid-filled rock suddenly drops, temporarily blocking the rupture and delaying failure. Scientists call this process “strengthening by dilatancy”.
The researchers claim that the discovery could have global implications. Similar underwater transform faults exist around the world, and the findings suggest that many may contain comparable natural braking systems that limit the magnitude of earthquakes.
