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Long-term Erosion as a Catalyst of Shallow Seismicity in Stable Continental Regions – Examples of Metropolitan France

Description: 

In this study, we test the impact of long-term erosion rates on potential fault activity and seismicity in a specific regions of metropolitan France and neighboring intraplate Western Europe. We first develop models of long-term (Holocene to Quaternary) erosion rates based on statistical analyses of measured denudation rates from cosmogenic nuclide concentrations, complemented by weathering rates from river load data and sedimentation rates from offshore surveys. These erosion rate models are used as a driving force on 2D planar models of lithospheric deformation based on an elastic plate approximation, with a variety of lithosphere rigidity models to account for spatial variations in geotherms and lithologies. The predicted stress perturbations are then combined with models of the background stress field to derive 2D planar models of local stress tensors that include the effects of erosion rates. These can then be projected on any given fault geometry to compute the full Coulomb stress and the fault tendency to slip in response to the effect of erosion. We apply this approach to subsets of faults and tectonic structures in different regions of metropolitan France with various seismicity and tectonic characteristics: the Western Alps - Rhone Valley (including the fault associated with the 2019 Le Teil earthquake), northern France and the Paris Basin, and the Armorican Massif. In most cases, stress perturbations due to long-term erosion promote fault instability in agreement with the observed tectonic style from earthquake focal mechanisms, with the most significant effects limited to the uppermost crust (0 – 5 km depth). Thus, long-term erosion rates may act as a catalyst – and potentially as a primary driver – of shallow seismicity in these regions. Further modeling analyses, including more detailed considerations of the various sources of uncertainties, are required to strengthen these preliminary conclusions.

Session: Earthquakes, Lithospheric Structure, and Dynamics in Stable Continental Region [Poster]

Type: Poster

Date: 4/17/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Stephane

Student Presenter: No

Invited Presentation: 

Poster Number: 66

Authors