Osaka, Japan — In a groundbreaking study, researchers at The University of Osaka have unlocked secrets of slow earthquakes using an innovative laboratory experiment involving gel beads on a liquid surface. Published in the journal Nature Communications, the study provides new insights into the anomalously slow, long-lasting, and small slips characteristic of slow earthquakes, phenomena that occur adjacent to more destructive regular earthquakes.
More than two decades after the initial discovery of slow earthquakes, scientists have struggled to explain their unique characteristics. These events are marked by weak or imperceptible vibrations and can involve slow slip over a year or more. Traditional experimental approaches have primarily focused on the slowness of fault slip, but the new study emphasizes the statistical features of slow earthquakes, which had rarely been replicated in laboratory settings.
Innovative Laboratory Approach
Yuto Sasaki, a study author, explained the significance of their experiment, which utilized a simple setup of “gel jelly beads raft” to simulate the fault regions of slow earthquakes. “Slow earthquakes have traditionally attracted attention mainly for their slow slip rate, but the statistical properties of their duration and recurrence relative to earthquake magnitude have so far been addressed only in a few limited experiments,” Sasaki stated.
The experiment’s simplicity belies its potential. By using gel jelly beads in a liquid solution, the researchers could directly observe internal structures during deformation, a task that is notoriously difficult in traditional rock-deformation experiments. This innovative approach revealed that the mixture of gel jelly beads and liquid solution exhibits significantly different features compared to dry, rigid beads, showing longer and smaller events akin to slow earthquakes.
Understanding Slow Earthquake Dynamics
The findings suggest that the inefficiency of soft wet beads in transmitting force and deformation could explain the longer and isolated small slips observed in slow earthquakes. Sasaki noted, “In retrospect, this experimental system seems to have been well suited for studying fault systems of slow earthquakes, while our prior target was deeper part of tectonic plate.”
Slow earthquakes often occur near the source regions of regular, destructive earthquakes. According to Sasaki, the observed slow earthquake statistics could be interpreted as fault conditions, contributing to probabilistic assessments of seismic activity. This understanding could advance the study of slow earthquakes and their potential influence on more destructive seismic events.
Broader Implications and Future Research
The simplicity of the experimental setup means that the results could represent general characteristics of soft bead and liquid mixtures, offering insights into both fundamental soft-matter physics and geological phenomena. Hiroaki Katsuragi, another author of the study, expressed excitement about the potential applications of their findings. “Nothing excites me more than realizing that tabletop experiments in soft matter can unlock the mysteries of both fundamental soft-matter physics and geological-scale phenomena,” Katsuragi said.
This research opens the door for further contributions from a wide range of fields, including laboratory experiments, observational studies, and geological analyses. The hope is that these efforts will deepen our understanding of slow earthquakes and improve assessments of their impact on conventional, destructive earthquakes.
As the scientific community continues to explore the complexities of slow earthquakes, this study marks a significant step forward. By bridging the gap between experimental physics and geological phenomena, researchers are poised to unravel the longstanding mysteries of these elusive seismic events.
