Venezuela’s 39-second doublet warns California models: faults act like a network

Two major earthquakes struck Venezuela just 39 seconds apart on June 24, 2024, with the first a M7.2 near San Felipe and the second a M7.5 near Yumare, leaving thousands dead and thousands more injured, according to government officials. But the scientific “why now” is what keeps showing up in the research conversation: the sequence is a rare earthquake doublet that could sharpen how large fault systems interact when stress transfers between structures.

In seismology, the usual storyline is tidy. A big quake happens, then smaller aftershocks follow as the system settles. The Venezuela case also fits a second, less common pattern: particularly intense events can alter stress on nearby faults or along the same fault, triggering another major earthquake. Researchers point to this as an opportunity to test rupture-interaction concepts that paleoseismic models can only infer indirectly, because the doublet provides a real-world example of how different fault segments can fire in close succession.

That matters for California because many hazard models assume faults can be treated like isolated structures. In the Live Science reporting, seismologists argue this may underestimate destructive power in places where multiple tectonic faults meet, including the region around California’s San Andreas Fault system. The reason is straightforward: if stress is shared and transferred across adjacent structures, the “worst shaking” may not be the shaking from one fault acting alone. Instead, multi-fault interactions can change timing, rupture pathways, and the duration of strong ground motion.

The case for comparison is not casual. The fault system involved in Venezuela includes the Boconó, Morón, San Sebastián, and El Pilar faults, and it shares several key characteristics with the San Andreas Fault. Both are right-lateral strike-slip fault systems, where crustal blocks slide horizontally past each other. Both sit along plate boundaries, with Venezuela’s South American and Caribbean plates and California’s Pacific and North American plates. The similarities are useful, because they let researchers ask: if these systems look alike in a few big ways, why might they still behave differently in the details that matter for hazard models?

Researchers caution that the Venezuelan plate boundary has much more complex fault architecture, largely because the Maracaibo block interacts with surrounding faults to create a more intricate boundary than California’s. There is also a speed difference. In Venezuela, tectonic plates move at about 0.8 inches (20 millimeters) per year, compared with roughly 1.2 inches (30 millimeters) along the San Andreas Fault. Faster plate motion can allow stress to accumulate more quickly over long timescales, but it does not determine when the next quake will strike.

Frequency is where planners get tempted to rely on averages, even though earthquakes do not honor calendars. Along the San Andreas Fault, magnitude 7 or larger earthquakes occur on average every 100 to 200 years, with recurrence varying along the fault. The last major rupture in Southern California was the magnitude 7.9 Fort Tejon earthquake in 1857. In Venezuela, estimated slip rates suggest recurrence intervals of one to two centuries, and the region experienced two devastating earthquakes in 1812 as part of a multiple-rupture sequence that included events of magnitude 7.5, 7.2, and 6.5. A 2018 study concluded that the Boconó Fault had already accumulated enough strain to generate another major earthquake. Still, the reporting emphasizes that these are statistical averages and recurrence is highly irregular, so a major event could occur in 100 years or even tomorrow.

For executives and boards, this is where the risk framing starts to look like a governance problem, not just a science problem. Hazard models feed into building codes, infrastructure planning, and underwriting assumptions. If the models miss multi-fault interactions, they can produce a narrower set of “acceptable” scenarios than reality demands. Live Science quotes Liliane Burkhard, a geologist and geophysicist at the University of Bern and first author of a recent study on Cajon Pass stress, arguing that the Venezuela doublet can test rupture-interaction concepts. Burkhard also describes a specific lesson for California: interactions between neighboring faults can play an important role in the evolution of large earthquakes, and single-fault hazard models break down at junctions where stress sharing and transfer matter, such as Cajon Pass where the San Andreas and San Jacinto systems meet, and the Boconó-San Sebastián area in Venezuela.

The “how” also matters. Burkhard distinguishes the Venezuelan sequence from the “earthquake gate” concept used at Cajon Pass, which explores whether a single rupture can jump from one fault system to another during the same earthquake over tens of seconds of rupture propagation along a continuous fault trace. The Venezuelan doublet, she says, looks like two distinct ruptures on what may be two separate fault structures triggered in close succession. The upshot is a shift in modeling style: represent ruptures as interconnected networks, not as lone actors. The reporting adds that California has roughly 300 active faults that may interact in ways traditional hazard models do not capture.

This is not purely theoretical. The article notes that New Zealand already incorporated the multi-fault rupture lesson after the 2016 Kaikōura earthquake, which ruptured at least 12 faults in a single event, prompting revisions to its National Seismic Hazard Model to include complex multifault ruptures. It also frames why the operational consequences can be nasty even when magnitude alone is not the villain. Earthquakes involving multiple faults can produce longer-lasting shaking that increases structural fatigue and ultimately the risk of collapse. In other words, multi-fault scenarios can turn “a short, intense jolt” into “a sustained beating,” which changes how systems age under stress.

The strategic stake is simple: if you plan for the wrong rupture pattern, you might design for the wrong kind of shaking. Julián García Mayordomo, a senior scientist at the Geological and Mining Institute of Spain, argues that both Venezuela and the United States should incorporate complex rupture scenarios into seismic hazard assessments and building codes. He uses a boxing-math analogy: like a boxing match, sometimes the winner is not the boxer who lands the hardest punch, but the one who keeps punching for longer. Researchers also urge caution against overgeneralizing from a single earthquake, with Judith Hubbard of Cornell University saying each earthquake gives one possible scenario and that the range of behaviors is wide. That is exactly why decision-makers should care. The Venezuela doublet is not a prediction engine. It is a stress test for assumptions.

Even with wide variability, the direction of travel in the research is clear: multi-fault interactions may pose greater destructive power than some seismic models predict, especially in regions where faults meet. For California, where hazard models and building codes sit downstream of scientific assumptions, the doublet’s warning is less about panic and more about precision. If you want infrastructure that survives the real world, you have to model the real world, including the parts where systems do not act alone.