Séminaire ISTerre

SEISMIC GROUND-MOTION PREDICTION IN EUROPE: PHYSICS, STATISTICS, AND ENGINEERING PRACTICE

jeudi 21 octobre 2021 - 11h00
Sreeram Reddy Kotha - ISTerre
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Seismic hazard analysts perform seismic hazard assessment of a built environment to ascertain ground-motion levels that can probably be exceeded at least once in the buildings’ design lifetime. Earthquake engineers rely on these predictions to optimize building design for seismic resilience. Seismic risk analysts integrate this knowledge and convey, to policy-makers, insurance-reinsurance firms, disaster response networks, and society at large, a motive to mitigate the risk of a seismic catastrophe. A critical prior to this chain of decisions is the one of probabilistic ground-motion prediction; which is an engineering seismologist’s domain of assimilating expertise from civil engineers, seismologists, geophysicists, and statisticians. Here, I present the needs and deeds of an engineering seismologist in developing the Ground-Motion Models (GMM). GMM is an empirical relation that seeks to explain the observed ground-motions at seismic stations from past earthquakes, and to predict ground-motions at new sites from future earthquakes. It is necessary that these predictive models are statistically well-constrained and physically well-behaved for a variety of prospective seismic sources, seismic wave propagation paths, and seismically shakable sites and structures. For a good predictive model, we prefer an enormous sample of high quality, uniformly processed, ground-motion data collected at several thousands of sites over a long history of seismic activity. To circumvent such impractical expectations, a traditional practice has been to liken the long-term sampling of ground-motion at every single site to the short-term sampling at several sites scattered across the globe. A decade ago, this so-called ‘ergodic assumption in ground-motion prediction’ addressed the GMMs’ ‘well-constrained’ requirement quite reasonably. In this decade however, the ‘well-behaved’ problem has aggravated with the exponential increase of data and the apparent increase in its natural randomness. The GMMs’ ergodic assumption governs its prediction accuracy and precision, which in turn has a profound impact on seismic hazard and risk assessments, and subsequent decisions. It has thus become essential to review the ergodic assumption and to resolve the apparent inflation of aleatory variability in ground-motion data. I will present to you the progress we have aided so far: the engineering needs, ground-motion datasets, statistical analyses, patent and latent physical phenomenon, development and deployment of GMMs in hazard and risk assessments, and the open challenges in the entire process – with an intent to enhance cross-disciplinary interactions.
Zoom link : https://univ-grenoble-alpes-fr.zoom.us/j/98469369573?pwd=ekV1Smg4T1U2TDdWcmRiTXFVd3cxZz09

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

“Minimalist seismology”: studying earthquakes with sparse instrumentation

jeudi 17 septembre 2026 - 11h00

Mathieu Causse - ISTerre

Equipe organisatrice : Organisation labo

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

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Stable‑to‑dynamic expansion of fault slipping area through fluid injection observed in laboratory experiments using a sub‑meter scale specimen

vendredi 18 septembre 2026 - 14h00

Takatoshi Ito  - Université de Tohoku, Japan

Equipe organisatrice : Mécanique des failles

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

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Tectonics, Mantle Dynamics and Coupled Lithosphere-Mantle-Core Evolution of Earth and Other Rocky Worlds

jeudi 24 septembre 2026 - 11h00

Paul Tackley - ETH Zurich

Equipe organisatrice : Grands Séminaires ISTerre

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

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Tectonics, Mantle Dynamics and Coupled Lithosphere-Mantle-Core Evolution of Earth and Other Rocky Worlds

jeudi 24 septembre 2026 - 11h00

Paul Tackley - ETH Zurich

Equipe organisatrice : Grands Séminaires ISTerre

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

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Apport des expériences analogiques pour la modélisation et le suivi en temps réel de la propagation du magma en profondeur : Exemple du Rift Est Africain

jeudi 1er octobre 2026 - 11h00

Virginie Pinel - ISTerre

Equipe organisatrice : Organisation labo

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

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A t-on encore besoin de plaques pour expliquer la tectonique de la vallée du Rhône et des Alpes Occidentales ?

vendredi 2 octobre 2026 - 11h00

philippe VERNANT - Geosciences Montpellier

Equipe organisatrice : Tectonique active et sismicité

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 2 octobre 2026 - 14h00

Hugo Boulze - 

Equipe organisatrice : Cycle sismique et déformations transitoires

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

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TBA

vendredi 9 octobre 2026 - 11h00

Eric Beaucé - ISTerre

Equipe organisatrice : Cycle sismique et déformations transitoires

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 20 novembre 2026 - 11h00

Farzaneh Mohammadi - ENS Paris

Equipe organisatrice : Cycle sismique et déformations transitoires

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

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