Researchers discover mechanism increasing certain earthquake magnitudes
A team of scientists has uncovered a mechanism that can amplify the magnitude of specific earthquakes by altering fault dynamics. Published in Nature Geoscience, the findings reveal how fluid interactions in fault zones contribute to larger seismic events. This discovery could improve models for predicting earthquake severity in fluid-rich areas.
In a study published on October 23, 2023, in Nature Geoscience, researchers from the University of California, Santa Cruz, and international collaborators detailed a newly identified mechanism that ramps up the magnitude of certain earthquakes. The mechanism centers on poroelastic rebound, where changes in fluid pressure within fault zones reduce friction, allowing ruptures to propagate farther and release more energy.
Lead author Agron Bajraktari, a geophysicist at UC Santa Cruz, explained the process: "We found that when fluids are squeezed out of the fault during an earthquake, it creates a temporary increase in fault strength, but paradoxically, this can lead to larger slips in subsequent events." The team used laboratory experiments simulating fault conditions, applying high-pressure fluids to rock samples to observe how poroelastic effects influence rupture dynamics.
The research builds on observations from real-world earthquakes, such as those in subduction zones where fluids are abundant. For instance, the study references the 2011 Tohoku earthquake in Japan, noting similarities in fluid involvement, though it does not claim direct causation. Bajraktari added, "This mechanism explains why some earthquakes exceed expectations based on fault size alone, particularly in regions with high pore pressure."
Previous models often underestimated earthquake magnitudes by focusing solely on static friction, but this work incorporates dynamic fluid responses. Co-author Emily Brodsky, a professor at UC Santa Cruz, emphasized the implications: "Understanding poroelasticity could refine seismic hazard assessments, helping communities in earthquake-prone areas prepare for worst-case scenarios."
The discovery applies specifically to fluid-saturated faults, common in tectonic settings like the San Andreas Fault. While not all earthquakes are affected, the findings highlight a gap in current prediction tools. The researchers call for further field studies to validate the mechanism in natural settings.
This advancement underscores the complexity of earthquake physics, where seemingly minor fluid dynamics can have outsized impacts on disaster potential.