Osaka, Japan — In a groundbreaking study published in Nature Communications, researchers at The University of Osaka have successfully recreated the enigmatic features of slow earthquakes in a laboratory setting. These slow earthquakes, characterized by their anomalously slow, long-lasting, and small slips, occur adjacent to regular earthquakes, which are known for their catastrophic vibrations.
Despite being discovered over two decades ago, slow earthquakes remain a mystery, lacking a unified explanation for their peculiar characteristics. Unlike regular earthquakes, which are defined by their intense seismic activity, slow earthquakes involve weak or imperceptible vibrations and can persist for up to a year. Previous experimental studies have primarily focused on the slowness of fault slip, but the statistical features of slow earthquakes have rarely been replicated or explained in laboratory settings.
Revolutionary Laboratory Experiment
The University of Osaka’s research team, led by Yuto Sasaki, has devised an innovative experimental system using “gel jelly beads raft” to simulate the conditions of slow earthquakes. This simple yet effective setup involves soft gel jelly beads in a liquid solution, mimicking the fluid-rich and soft-grain environment of fault regions where slow earthquakes occur.
“Slow earthquakes have traditionally attracted attention mainly for their slow slip rate,” Sasaki explains. “However, the statistical properties of their duration and recurrence relative to earthquake magnitude have so far been addressed only in a few limited experiments.”
“This table-top experimental system is available even in your home, but it shows a surprising variety of behaviors and offers us a wealth of fascinating clues about slow earthquakes underground,” says Sasaki.
Understanding the Mechanics
The experiment demonstrated that the mixture of gel jelly beads and a liquid solution exhibits significantly different features compared to dry, rigid beads. While rigid beads in a dry cup create intermittent and fast scratches similar to regular earthquakes, the gel beads produce longer and smaller events akin to slow earthquakes.
According to Sasaki, “In contrast to dry rigid beads, soft wet beads are inefficient in transmitting force and deformation. This property potentially induces longer and isolated small slips.”
This insight is crucial as slow earthquakes often occur near the source regions of regular, destructive earthquakes. The researchers suggest that the observed slow earthquake statistics could be interpreted as fault conditions, contributing to probabilistic assessments of earthquakes.
Implications for Earthquake Research
The findings from this study are expected to advance the understanding of slow earthquakes and their influence on conventional, destructive earthquakes. Sasaki notes, “This experimental result will serve as a starting point for further contributions from a wider range of fields.”
Moreover, the simplicity of the experimental setup allows for broader applications beyond geological phenomena. Hiroaki Katsuragi, another author of the study, highlights the potential for these experiments to reveal fundamental aspects of sheared soft-matter systems.
“By analyzing the detailed relationship between microscopic bead rearrangements and macroscopic slips, fundamental aspects of sheared soft-matter systems can be revealed, as well as the origin of characteristic features of slow earthquakes,” says Katsuragi.
Future Directions
The research team anticipates that their findings will inspire further experimental reports from high-temperature and pressure experiments using rock and fault material. Additionally, observational studies and geological analyses are expected to build on these results, ultimately enhancing earthquake prediction and risk assessment capabilities.
As the scientific community continues to explore the mysteries of slow earthquakes, this study marks a significant step forward in understanding the complex dynamics of our planet’s seismic activity.
