Study Finds Solar Heat Influences Earthquake Activity

The same solar heat that warms your skin on a summer day might also be subtly influencing when and where earthquakes occur, according to new research published Tuesday in the journal Chaos.

Japanese and international researchers have discovered evidence that heat from the sun contributes to seismic activity on Earth, potentially opening new avenues for improving earthquake forecasting models.

The study builds upon previous work that established a causal connection between solar activity and earthquakes, but scientists have now identified a specific mechanism: heat transfer from the sun to Earth’s surface.

“Solar heat drives atmospheric temperature changes, which in turn can affect things like rock properties and underground water movement,” said Matheus Henrique Junqueira Saldanha, one of the study’s authors. “Such fluctuations can make rocks more brittle and prone to fracturing, for example — and changes in rainfall and snowmelt can alter the pressure on tectonic plate boundaries.”

While traditional seismology focuses primarily on tectonic plate movements and the buildup of strain energy, this research suggests environmental factors influenced by the sun may play a supporting role in determining when that energy releases.

The researchers examined multiple lines of evidence, including seasonal variations in Earth’s seismicity patterns and the relationship between surface temperatures and earthquake occurrences. By analyzing extensive datasets of earthquake records alongside solar activity and surface temperature measurements, they identified meaningful correlations.

This approach differs from earlier theories that suggested electromagnetic effects or tidal forces might link solar activity to earthquakes. Instead, the heat-transfer hypothesis provides a more direct and measurable connection between the sun and seismic events.

Perhaps most compelling was the discovery that earthquake prediction models become more accurate when they incorporate Earth’s surface temperature data. This improvement was especially noticeable for shallow earthquakes.

“That makes sense, since heat and water mostly affect the upper layers of the Earth’s crust,” noted Junqueira Saldanha.

The timing element proved particularly revealing. The researchers observed that earthquake predictability varies when accounting for delayed sunspot activity, aligning with the expected timeframes for heat to transfer through Earth’s systems.

This research comes at a time when earthquake forecasting remains one of seismology’s greatest challenges. Despite significant advances in understanding how earthquakes occur, predicting them with sufficient accuracy and lead time to save lives has remained elusive.

The 2011 Tōhoku earthquake in Japan, which triggered a devastating tsunami and contributed to the Fukushima nuclear disaster, killed more than 18,000 people. It serves as a stark reminder of the importance of improving earthquake forecasting capabilities.

Current prediction models rely heavily on historical seismic patterns, fault line characteristics, and strain measurements. However, these approaches have significant limitations in providing actionable warnings.

By examining seasonal variations in earthquake patterns, the researchers found that seismic activity does not remain constant throughout the year. This seasonal fluctuation supports the hypothesis that environmental factors influenced by solar heat—such as groundwater movement, rainfall patterns, and thermal expansion of rocks—play a role in earthquake triggering.

The researchers employed sophisticated mathematical and computational methods to analyze the relationship between these variables. Their analysis revealed what they describe as “shared dynamical information” between solar activity and earthquakes, suggesting an interconnected system rather than isolated phenomena.

The study also documented a “large degree of non-determinism” in the relationship between solar activity and earthquakes. This indicates that while solar heat contributes to earthquake activity, it operates as one factor among many rather than a primary cause.

Dr. Yoshito Hirata, another author of the study, collaborated with Junqueira Saldanha on the 2022 research that first established the causal connection between solar activity and earthquakes. Their continued investigation now points toward practical applications for this knowledge.

The research team included scientists from the University of Tsukuba and the National Institute of Advanced Industrial Science and Technology in Japan, bringing together expertise in complex systems, geophysics, and statistical analysis.

“While these factors may not be the main drivers of earthquakes, they could still be playing a role that can help to predict seismic activity,” Junqueira Saldanha explained.

Looking ahead, the researchers suggest that incorporating solar activity predictions into detailed Earth temperature models could enhance earthquake forecasting systems. This integration would account for the multiple pathways through which solar heat ultimately influences seismic activity.

For regions prone to devastating earthquakes, even modest improvements in prediction capabilities could prove invaluable for emergency preparedness and response.

“It’s an exciting direction, and we hope our study sheds some light on the bigger picture of what triggers earthquakes,” concluded Junqueira Saldanha.

The findings appear in the March 4 issue of Chaos, published by the American Institute of Physics.