ISTerre seminar

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Scaling laws of spectra of laboratory and volcano-tectonic earthquakes from coda of seismogram

Friday 4 April 2025 - 11h00

Tatiana Kartseva - ISTerre
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The physics of small earthquake generation across geological settings remains debated. Given the unobservable in situ conditions and long seismic cycle, laboratory experiments help investigate these earthquake generation processes. Source spectral scaling (corner frequencies, seismic moments, stress drops) in both natural and laboratory experiments can provide insights into common mechanisms. However, observational limitations may pose a serious obstacle to such analyses. In this study, we compare results of analysis of two datasets. The first is composed of thousands of acoustic emission events (M ~ –8) in two rock fracturing experiments (carried out in the RESC of IPE RAS). The second includes ~3500 summital events (M < 3) occurring before recurrent eruptions of Piton de la Fournaise volcano, La Réunion, France. We propose a method to estimate spectral source parameters from coda amplitude spectral ratios. Due to its averaging nature, coda waves simplify several requirements of the spectral ratio method, which are difficult to satisfy in these settings. Source spectrum analyses revealed a high degree of similarity between the fracturing of pre-existing inhomogeneities in rock samples under evenly distributed external pressure and well-studied tectonic earthquakes, exhibiting an inverse cubic scaling between corner frequencies and seismic moments. In contrast, under the loading regime with active formation of new fractures in the laboratory, the observed scaling strongly deviates from cubic scaling. The volcano-tectonic earthquakes caused by pre-eruptive pressurization and occurring along a persisting ring-fault structure also show a cubic scaling between corner frequencies and seismic moments which suggests that they are generated by triggering pre-existing weak fractures.

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Organizing team : Cycle sismique et déformations transitoires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

Informations de visio :

https://univ-grenoble-alpes-fr.zoom.us/j/92956342169?pwd=atRbmXkR3hcDaXyMw5rsnD8AbkUqdG.1