The hidden mechanics of earthquake ignition

(Press-News.org) A new study has unravelled the hidden mechanics of how earthquakes ignite, shedding light on the mysterious transition from quiet, creeping motion to the violent ruptures that shake the Earth. Using cutting-edge experiments and innovative models, the research reveals that slow, silent stress release is a prelude and a necessary trigger for seismic activity. By incorporating the overlooked role of fault geometry, the study challenges long-held beliefs and offers a fresh perspective on how and when earthquakes begin. These findings not only deepen our understanding of nature’s most powerful forces but also pave the way for improved predictions of seismic events.

Researchers from the Racah Institute of Physics at the Hebrew University of Jerusalem, led by Prof. Jay Fineberg and PhD. Student Shahar Gvirtzman in collaboration with Prof. David S. Kammer from ETH Zurich and Prof. Mokhtar Adda-Bedia from École Normale Supérieure de Lyon, have unveiled groundbreaking insights into the mechanisms driving frictional rupture and earthquake nucleation. Their study bridges critical gaps in our understanding of the transition from slow, aseismic motion to rapid seismic rupture.

The team conducted experiments and developed theoretical models to demonstrate how slow, steady creep at stress thresholds transitions into the dynamic rupture associated with earthquakes. By extending the principles of fracture mechanics, the researchers incorporated the finite width of fault interfaces, a factor often overlooked in traditional models.

"Our findings challenge and refine conventional models of rupture dynamics," explained Prof. Fineberg. "We show that slow, aseismic processes are a prerequisite for seismic rupture, driven by localized stress and geometric constraints. This has profound implications for understanding when and how earthquakes begin."

Key highlights of the study include groundbreaking experimental validation, where the researchers employed high-speed imaging and innovative methodologies to observe how rupture nucleation begins. Their findings reveal that the process initiates as small, slow-moving two-dimensional patches of frictional motion. These patches gradually expand and eventually transition into the rapid dynamics traditionally described by classical fracture mechanics, marking a significant leap in our understanding of this phenomenon.

The study also emphasizes the critical role of geometric transitions in controlling nucleation dynamics. By incorporating the finite width of fault interfaces into their models, the researchers challenged and refined existing theories of earthquake initiation. This focus on the geometric properties of faults provides fresh insights into the structural and mechanical factors that influence the onset of seismic activity.

Furthermore, the research has far-reaching real-world applications. The newly developed framework also offers a deeper understanding of important everyday processes of both friction and  material fracture. In addition, the new framework underscores the importance of slow, aseismic processes that often precede earthquakes. Even seemingly 'quiet' seismic precursors, which might previously have been overlooked, could hold critical information about impending seismic events. This discovery has the potential to inform predictive models and improve our ability to anticipate and mitigate earthquake risks.

The study's implications extend beyond earthquake science, offering insights into material strength, fracture dynamics, and the development of predictive models for seismic activity.

 

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