Unraveling the Ridgecrest Earthquakes: Unprecedented Insights into Seismic “Segment-Jumping” by Scientists

During the Ridgecrest earthquakes in California, seismic waves propagated and faults unzipped in an unusual pattern. Scientists utilized a supercomputer to visualize 15 TB of simulation data for a clearer understanding of this event. The credit goes to Greg Abram and Francesca Samsel from the Texas Advanced Computing Center, and Alice Gabriel from UC San Diego/Ludwig Maximilian University of Munich.

Scientists employed a supercomputer to expose the complex dynamics of earthquakes occurring along multiple faults.

Early morning of July 4, 2019, a 6.4 magnitude earthquake hit Searles Valley in California’s Mojave Desert, shaking Southern California. Notably, just 34 hours later, Ridgecrest, a nearby town, faced a 7.1 magnitude earthquake. This tremor was so forceful that millions across California and even in neighboring locations like Arizona, Nevada, and Baja California, Mexico felt it.

These collective seismic events, known as the Ridgecrest earthquakes, were the strongest to hit California in over 20 years. They caused significant structural damage, power outages, and injuries. The initial 6.4 magnitude Searles Valley event was later recognized as a foreshock to the Ridgecrest 7.1 event, with each earthquake followed by numerous aftershocks.

The sequence of these seismic events puzzled researchers, prompting questions regarding the delay between the foreshock and main shock, the ability of earthquakes to “jump” from one fault system segment to another, and whether earthquakes could interact dynamically.

To answer these queries, seismologists from Scripps Institution of Oceanography at UC San Diego and Ludwig Maximilian University of Munich (LMU) conducted a new study focusing on the relationship between the two major earthquakes occurring along a multi-fault system. They utilized a high-capacity supercomputer incorporating data-rich and physics-based models to establish a link between the earthquakes.

Alice Gabriel, a seismologist at Scripps Oceanography, led the study with her former Ph.D. student from LMU, Taufiq Taufiqurrahman, and several other co-authors. Their results were recently published in the Nature journal.

Gabriel stated, “We deployed the most advanced algorithms on the largest available computers to understand this perplexing sequence of earthquakes in California in 2019.” She further noted that high-performance computing has helped unravel the underlying factors of these significant events, thus contributing to seismic hazard assessment and preparedness.

Gabriel emphasized the importance of understanding multi-fault ruptures, as they are generally more potent than single fault earthquakes. For instance, the twin earthquakes in Turkey–Syria on Feb. 6, 2023, resulted in substantial loss and damage, with both breaking across multiple faults only nine hours apart.

The Ridgecrest earthquakes of 2019, originating in the Eastern California Shear Zone along a strike-slip fault system, featured mainly horizontal fault movement, with no vertical motion. These earthquakes cascaded across intertwined and previously unknown “antithetic” faults, leading to discussions within the seismological community about which fault segments actively slipped and what conditions encourage cascading earthquakes.

The researchers’ new study presents the first multi-fault model combining seismograms, tectonic data, field mapping, satellite data, and other space-based geodetic datasets with earthquake physics. Unlike earlier models, this one is not purely data-driven.

Taufiqurrahman said, “Through the lens of data-infused modeling, enhanced by supercomputing, we decipher the complexities of multi-fault conjugate earthquakes and shed light on the physics governing cascading rupture dynamics.”

The researchers, using the SuperMUC-NG supercomputer at the Leibniz Supercomputing Centre (LRZ) in Germany, showed the interconnectedness of the Searles Valley and Ridgecrest events. The earthquakes interacted across a statically robust but dynamically weak fault system, driven by intricate fault geometries and low dynamic friction.

The team’s 3-D rupture simulation elucidates how strong faults can become very weak during fast earthquake movement, thus explaining the dynamics of how multiple faults can rupture concurrently.

According to Gabriel, these unexpected interactions during fault system ruptures are challenging to incorporate into seismic hazard assessments. However, the team believes their models could significantly impact the field of seismology by improving the assessment of seismic hazards in active multi-fault systems, which are often underestimated.

Gabriel added, “With the help of supercomputers and physics, we have unraveled arguably the most detailed data set of a complex earthquake rupture pattern. Our findings suggest that similar models could incorporate more physics into seismic hazard assessment and preparedness.”

The study, titled “Dynamics, interactions and delays of the 2019 Ridgecrest rupture sequence”, was supported by the European Union’s Horizon 2020 Research and Innovation Programme, Horizon Europe, the National Science Foundation, the German Research Foundation, and the Southern California Earthquake Center.

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More about Ridgecrest Earthquakes Analysis

• Scripps Institution of Oceanography
• Ludwig Maximilian University of Munich (LMU)
• Ridgecrest Earthquakes
• Leibniz Supercomputing Centre (LRZ)
• Study in Nature Journal
• European Union’s Horizon 2020 Research and Innovation Programme
• National Science Foundation
• German Research Foundation
• Southern California Earthquake Center