Study finds solar heat affects seismic activity

On summer days, the same sun heat that heats the skin on summer days can also subtly affect earthquakes, according to new research published in the journal Chaos.

Japanese and international researchers have found evidence that heat from the sun contributes to seismic activity on Earth, which may open up new avenues for improving seismic prediction models.

The study is based on previous work to establish a causal relationship between solar activity and earthquakes, but scientists have now identified a specific mechanism: heat transfer from the sun to the Earth’s surface.

“Solar heat drives changes in atmospheric temperature, which in turn affects rock performance and groundwater movement,” said Matheus Henrique Junqueira Saldanha, one of the authors of the study. “For example, this fluctuation makes the rock more brittle and prone to rupture – changes in rainfall and melting snow can change the pressure on the boundaries of the tectonic plates.”

Although traditional seismology focuses primarily on the movement and accumulation of strain energy in tectonic plates, this study suggests that environmental factors affected by the sun may play a supporting role in determining when energy is released.

The researchers examined a variety of evidence, including seasonal changes in Earth’s seismic patterns and the relationship between surface temperature and earthquake occurrence. By analyzing a wide range of data sets of seismic records and measurements of solar activity and surface temperature, they identified meaningful correlations.

This approach, unlike earlier theories that suggest electromagnetic action or tidal forces, may 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 striking is that when the earthquake prediction model incorporates the Earth’s surface temperature data, the earthquake prediction model becomes more accurate. This improvement is particularly evident for shallow earthquakes.

“This makes sense because heat and water mainly affect the upper layers of the Earth’s upper layers,” Junqueira Saldanha noted.

The timing element proves to be particularly revealed. The researchers observed that seismic predictability differs when considering delayed sunspot activity, consistent with the expected time range to allow heat to transfer through the Earth’s system.

This study is at a time when seismic prediction remains one of the biggest challenges in seismology. Despite significant progress in understanding the occurrence of earthquakes, earthquakes were predicted with sufficient accuracy and the early time to save lives remains elusive.

Japan’s 2011 northern earthquake triggered a devastating tsunami and contributed to the Fukushima nuclear disaster, killing more than 18,000 people. It is a striking reminder of the importance of improving earthquake prediction capabilities.

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

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

The researchers used complex mathematical and computational methods to analyze the relationship between these variables. Their analysis reveals what they call the “shared dynamic information” between solar activity and earthquakes, prompting interconnected systems rather than isolated phenomena.

The study also documented a “large degree of non-determinism” in the relationship between solar activity and earthquakes. This suggests that while solar heat contributes to seismic activity, it is a factor that is a number rather than a major cause.

Another author of the study, Dr. Yoshito Hirata, worked with Junqueira Saldanha for a 2022 study, which first established the causal relationship between solar activity and earthquakes. Their ongoing investigation now points to the practical application of this knowledge.

The research team includes scientists from Duscuba University 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 can still play a role that helps predict seismic activity,” Junqueira Saldanha explained.

Going forward, researchers suggest that incorporating solar activity predictions into detailed Earth temperature models can enhance seismic prediction systems. This integration will explain the multiple ways in which solar heat ultimately affects seismic activity.

Even modest improvements in predictive capacity can be invaluable for emergency preparedness and response in areas prone to destruction.

“This is an exciting direction and we hope our research will shed light on the bigger situations that trigger the earthquake,” Junqueira Saldanha concluded.

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