From melting ice to earthquakes

Climate-driven changes in snow and glaciers can modify groundwater infiltration and pore-fluid pressure within fractured mountain rocks. At the Grandes Jorasses, in the Mont Blanc Massif, we found evidence that seasonal meltwater infiltration contributes to triggering earthquake activity.

The question: can melting ice trigger earthquakes?

The melting of snow and glaciers increases the amount of water entering the mountain hydrological system. But what happens when this water infiltrates deep into fractured rock?

At the Grandes Jorasses, we found evidence that meltwater reaches a major fault zone and modifies the hydraulic conditions that control earthquake activity. This provides observational evidence for a link between cryosphere change, groundwater circulation and seismicity.

The observation: something changed in 2015

We analysed 15 years of seismic activity at the Grandes Jorasses, from 2006 to 2022, using an enhanced earthquake catalogue based on template matching. The method identified 12,303 additional earthquakes, considerably improving the detection of the small events forming the sequence.

A strong annual periodicity suddenly appeared in autumn 2015. This change coincided with an increase in high-altitude glacier melt and intense heat-wave conditions affecting the Mont Blanc Massif.

The seasonal seismicity is consistent with the propagation of meltwater-induced pore-pressure changes through the fractured rock mass, eventually affecting faults at depth.

2006–2015 → relatively low activity

2015 onward → strong seasonal activity

A link between surface water and deep seismicity

The earthquakes are concentrated along a major fault zone that also outcrops in the Mont Blanc Tunnel.

Hydrological observations from the tunnel, together with runoff and isotope data, indicate that the groundwater inflows contain a significant contribution from young surface meltwater.

This provides an important connection between:

the high-altitude cryosphere

and

the deep fractured rock mass where the earthquakes occur.

The earthquakes follow the water

Meltwater can propagate pressure to depth

The key mechanism is not simply the presence of water underground.

What matters is the propagation of hydraulic pressure changes through the fractured massif.

We modelled meltwater infiltration using a one-dimensional hydraulic diffusion model, constrained by the S2M meteorological snowpack model.

The model reproduces much of the observed seasonal evolution of the earthquake sequence, supporting a meltwater-induced pore-pressure mechanism.

Seasonal meltwater infiltration can modify pore pressure at depth and influence the activity of faults within a fractured mountain massif.

Hydrological observations indicate that young surface meltwater reaches the groundwater system feeding the fault zone.

Why did the seasonal pattern appear in 2015?

Our results suggest that the onset of the new seasonal seismic behaviour is related to changes in the high-altitude cryosphere.

Increasing glacier melt, permafrost degradation and associated changes in the mountain surface can modify meltwater infiltration pathways.

These changes can allow larger amounts of water to reach previously less active parts of the fractured system, producing pore-pressure changes capable of triggering earthquakes.

The 2015 heat wave appears to have played an important role in initiating this change in the Grandes Jorasses earthquake sequence.

Two components of the earthquake sequence

The seismicity does not have a single mechanism.

The observations indicate that, after an initial hydrological triggering, its subsequent evolution is mainly controlled by a tectonic mechanism involving aseismic slip and earthquake interactions.

Implications for seismic hazard

The hydrological control of seismicity also has implications for short-term seismic hazard. During periods of strong meltwater-driven activity, the probability of earthquakes increases substantially compared with the pre-2015 level. The study therefore provides observational evidence that changes in the cryosphere can modify local seismic hazard in high mountain environments.

This mechanism may be relevant to other glaciated mountain regions where groundwater can circulate deeply through fractured rock.

My contribution

My contribution to this study focused on the investigation, formal analysis and validation of the hydrological and geological interpretation.This work builds on my long-term research on groundwater flow in fractured mountain massifs and the interaction between groundwater circulation and geological structures.

Publication

Simon, V., Kraft, T., Maréchal, J.-C., Helmstetter, A. & Diehl, T. (2025).

Climate-change-induced seismicity: The recent onset of seasonal microseismicity at the Grandes Jorasses, Mont Blanc Massif, France/Italy. Earth and Planetary Science Letters, 666, 119372.

DOI: 10.1016/j.epsl.2025.119372

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