The federation
Intranet
ISTerre seminar
Seasonal modulation of seismicity in intraplate regions
Friday 13 November 2026 - 14h00
Farzaneh Mohammadi - ENS Paris---
While most earthquakes occur along plate boundaries, significant seismicity also occurs within stable continental regions (SCRs), despite their low tectonic strain rates. These earthquakes raise fundamental questions about how elastic strain accumulates, is stored, and is released in slowly deforming continental crust. Here, we develop high-resolution seismicity catalogs for southeastern Australia (2005–2024) and northwestern France (2017–2025) using a back-projection and matched-filtering workflow, substantially increasing the number of detected earthquakes and lowering the magnitude of completeness in both regions. Using these enhanced catalogs, we identify statistically significant seasonal modulation of seismicity, with earthquake rates peaking during the local spring and summer months. These seasonal variations broadly correspond to changes in terrestrial water storage derived from GRACE satellite observations. By jointly analyzing seismicity, GNSS displacements, and GRACE-derived hydrological loading using multichannel singular spectrum analysis, we identify coherent temporal modes shared across the three datasets. These observations are consistent with seasonal hydrological loading producing elastic stress perturbations that modulate earthquake occurrence. Such naturally occurring, non-tectonic stress perturbations provide an opportunity to probe the mechanical response of intraplate faults and investigate the frictional and rheological processes governing earthquake occurrence in slowly deforming crust. Together, our results suggest that even modest environmental stress perturbations can influence earthquake activity in stable continental regions, offering new insights into fault sensitivity and the physical mechanisms controlling intraplate seismicity.
Organizing team : Cycle sismique et déformations transitoires
Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères