A recent study from Earth and Planetary Science Letters is the first to directly link earthquakes to climate change-induced glacial melt. Scientists analyzed 15 years of seismic activity in the Grandes Jorasses—a peak that is part of the Mont Blanc massif between Italy and France—to better understand this association. This massif is one of the more seismologically active areas in the region, and examining how climate change may affect earthquakes there could prove useful in preparing for them.

“Researchers had long observed seasonal fluctuations in earthquake activity and proposed several external drivers [as causes],” said Verena Simon, one of the lead authors of the study and a postdoctoral researcher at the Swiss Seismological Service. In an interview with GlacierHub, she explained that snow and ice load changes, intense rainfall and atmospheric-pressure changes have previously been proposed as triggers for seismic activity.

“Fluids of various types are very much involved in fault motions,” said John Mutter, a seismologist at Columbia University’s Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School. “Where two chunks of rock meet one another, is a fault plane. That fault plane usually contains something called gouge, which is soft material that has been caused by the milling of one crystal rock against the other. If there is fluid in those gouge sediments, that facilitates the motion.”

Additionally, water that percolates through porous rock can also increase pressures between tectonic plates, leading to slip. Picture a melting glacier on the surface of the Earth with meltwater running downstream. Some of this water will seep into the rock below it, trickling downward through the Earth’s crust. As it descends, it fills pores in the rock, changing the pressures between plates. Mutter explained it is possible that if “you change the stress regime, that could trigger a fault,” though he was uncertain whether meltwater could do so given the depth it would need to reach. The study posits that if enough meltwater penetrates, infiltration pathways can be formed and pore-pressure can shift underground, triggering earthquakes.  

Before the study, “direct observational links from climate-change-driven melt to increased seismic hazard did not, to our knowledge, exist,” said Simon. While there was a previously known relationship between water and earthquakes, Simon’s team was the first to connect specifically climate change-related meltwater to earthquakes. The scientists sought to determine whether glacial meltwater driven by global warming could play a hand in increasing seismic activity too. “Our study provides the first direct observational link between climate-change-driven snow and glacier melt and a measurable increase in short-term seismic hazard.”

In the Mont Blanc region the team focused on, seasonal earthquakes driven by yearly snowmelt have already been observed. The area experiences increased tremors in late summer when meltwater has peaked, and fewer tremors through the winter months. Using seismometers, the researchers compiled a catalog of 12,303 earthquakes between 2006 and 2022. “The earthquakes cluster along a known shear zone that intersects the Mont Blanc Tunnel, where water temperature, conductivity and isotope data indicate a dominant input of young surface meltwater,” explained Simon. This zone, with its prevalence of meltwater, exhibits more earthquakes than the rest of the region.

In 2015, a severe heatwave in the area resulted in a sharp increase of glacial meltwater and coincided with an increase in tremors. The earthquake catalog shows a clear jump in seismic activity in the following years, both in frequency and magnitude.

Next, Simon and her team turned to modelling for confirmation of the heatwave-induced meltwater’s responsibility in increased seismic activity.

“The model shows a clear increase in earthquakes from 2015 onward for higher altitudes in the Mont Blanc Massif and neighboring Swiss Alps. This indicates stronger melt at elevations that previously remained frozen, opening new infiltration pathways,” Simon explained. Additionally, the models demonstrated a time-delay. Earthquakes are triggered only once the meltwater has time to seep down through the rock. “Shallow earthquakes aligned with the previous year’s runoff and deeper events aligned with runoff from two years earlier.”

The results indicate the possibility of a new relationship between climate change and earthquakes that was previously unknown, and they suggest a need for further research. Mutter expressed skepticism over how likely it is that meltwater may actually be responsible for the earthquakes saying, “meltwater is on the surface. It’s not clear to me how you get the water down into the fault.”

However, should further investigation continue to strengthen this link, there may be concern for earthquake-affected communities around the world. Climate change’s warming temperatures and heatwaves will increase glacial melt and could result in more earthquakes globally.

Mutter suggested recording earthquake activity more closely so that humans can be prepared for impacts: “What you can do is monitor the induced seismicity very carefully. You can map the distribution of these little earthquakes and that could tell you which faults are being activated.”

As climate change continues to melt the world’s remaining glaciers, Simon warned that the resulting meltwater will likely affect tectonic plate pressures and increase seismic hazard. She said that “in the future, this may elevate risk for alpine communities, and other glaciated regions could face similar, climate-modulated seismic hazards.”

The research done by Simon and her team opens the door to the possibility of better earthquake preparedness for mountain communities near glaciers worldwide.