{"id":20956,"date":"2026-09-28T09:00:04","date_gmt":"2026-09-28T07:00:04","guid":{"rendered":"https:\/\/navier-lab.fr\/?p=20956"},"modified":"2026-09-24T18:34:45","modified_gmt":"2026-09-24T16:34:45","slug":"thesis-defense-serafim-egorov","status":"publish","type":"post","link":"https:\/\/navier-lab.fr\/en\/thesis-defense-serafim-egorov\/","title":{"rendered":"Thesis defense \u2013 Serafim Egorov"},"content":{"rendered":"<p style=\"text-align:justify;\">Serafim Egorov, PhD student in the Geotechnics and Multi-scale teams of the Navier laboratory, will defend his thesis \u201c<em>Understanding intermittency and aseismic slip induced by fluid injection using perturbation theory<\/em>\u201d on 1 October 2026 at 2 pm in Amphitheatre Navier, \u00c9cole Nationale des Ponts et Chauss\u00e9es. The defense will be held in English.<\/p>\n<p style=\"text-align:justify;\">The thesis jury consists of the following members:<\/p>\n<ul style=\"list-style:none; margin:0; padding:0;\">\n<li style=\"margin:0 0 0.5em 0;\"><span style=\"color:#E2A034; margin-right:0.5em;\">\u25cf<\/span>Jean Sulem, \u00c9cole des Ponts (Laboratoire Navier) , Thesis supervisor<\/li>\n<li style=\"margin:0 0 0.5em 0;\"><span style=\"color:#E2A034; margin-right:0.5em;\">\u25cf<\/span>Mathias Lebihain, \u00c9cole des Ponts (Laboratoire Navier) , Thesis co-supervisor<\/li>\n<li style=\"margin:0 0 0.5em 0;\"><span style=\"color:#E2A034; margin-right:0.5em;\">\u25cf<\/span>Pathikrit Bhattacharya, National Institute of Science Education and Research (Earth &amp; Planetary Sciences), Reviewer<\/li>\n<li style=\"margin:0 0 0.5em 0;\"><span style=\"color:#E2A034; margin-right:0.5em;\">\u25cf<\/span>Renaud Toussaint, Universit\u00e9 de Strasbourg (ITES) , Reviewer<\/li>\n<li style=\"margin:0 0 0.5em 0;\"><span style=\"color:#E2A034; margin-right:0.5em;\">\u25cf<\/span>V\u00e9ronique Lazarus, ENSTA Paris (IMSIA) , Examiner<\/li>\n<li style=\"margin:0 0 0.5em 0;\"><span style=\"color:#E2A034; margin-right:0.5em;\">\u25cf<\/span>Anne Tanguy, \u00c9cole polytechnique (LMS), Examiner<\/li>\n<li style=\"margin:0 0 0.5em 0;\"><span style=\"color:#E2A034; margin-right:0.5em;\">\u25cf<\/span>Paul Antony Selvadurai, ETH Zurich (Swiss Seismological Service), Examiner<\/li>\n<li style=\"margin:0 0 0.5em 0;\"><span style=\"color:#E2A034; margin-right:0.5em;\">\u25cf<\/span>Pierre Dublanchet, Mines Paris-Universit\u00e9 PSL (Centre de G\u00e9osciences), Examiner<\/li>\n<li style=\"margin:0 0 0.5em 0;\"><span style=\"color:#E2A034; margin-right:0.5em;\">\u25cf<\/span>J\u00e9r\u00e9my Bleyer, \u00c9cole des Ponts (Laboratoire Navier), Invited member<\/li>\n<\/ul>\n<style>\n.resume-toggle summary::-webkit-details-marker{display:none;}\n.resume-toggle summary{list-style:none;}\n.resume-toggle .resume-arrow{display:inline-block;transition:transform .15s ease;}\n.resume-toggle[open] .resume-arrow{transform:rotate(90deg);}\n<\/style>\n<details class=\"resume-toggle\">\n<summary style=\"cursor:pointer; color:#1e73be; font-weight:600;\"><span class=\"resume-arrow\">\u25b8<\/span> Abstract<\/summary>\n<p style=\"text-align:justify;\">Fluid injection into low-permeability rock at great depth is commonly used to develop enhanced geothermal systems. Such injections can induce complex, intermittent slip on pre-existing faults, leading to seismicity that manifests as events of varying magnitude distributed in space and time. However, reproducing the rich statistical response of real faults, in particular the intermittency of slip, generally requires computationally demanding simulations, which motivates reduced-order approaches.<\/p>\n<p>Using the Bueckner\u2013Rice weight-function theory (Rice, 1985; Bueckner, 1987; Rice, 1989), we construct reduced-order frameworks for frictionless heterogeneous and frictional homogeneous cracks. Both problems are studied within the common context of understanding fluid-induced seismicity, with the aim of developing single-fault models that can simulate aseismic and microseismic slip during fluid injection.<\/p>\n<p style=\"text-align:justify;\">To address intermittency, we present a variational model of three-dimensional coplanar frictionless crack propagation in a disordered fracture-energy field under mixed-mode I+II+III loading. The approach bridges the variational formulation of Francfort and Marigo (1998) and the perturbation theory of Rice (1985). Equilibrium crack-front configurations are obtained by minimizing the total energy, defined as the sum of (i) the elastic potential energy, evaluated asymptotically from front deformations, and (ii) the dissipated energy, determined by the fracture-energy field. The numerical framework relies on a matrix-free trust-region Newton\u2013conjugate-gradient algorithm with physics-based preconditioning and reproduces the transition from smooth to intermittent crack growth in multiscale simulations.<\/p>\n<p style=\"text-align:justify;\">Fault slip is, however, governed by friction, which the previous model overlooked. We therefore consider three-dimensional coplanar propagation of a frictional crack along a homogeneous fault. To construct a reduced-order model, we extend the perturbation theory of Rice (1985) to Coulomb friction. The resulting first-order semi-analytical framework is used to explore the influence of Poisson&#8217;s ratio and of the injection scenario on the quasi-elliptic shape of the aseismic slip front. Finally, we outline the main components required to recover the first-order slip displacement and stress fields on the frictional interface, which are needed to account for the spatial heterogeneities in fault properties.<\/p>\n<\/details>\n","protected":false},"excerpt":{"rendered":"<p>Serafim Egorov, PhD student in the Geotechnics and Multi-scale teams of the Navier laboratory, will defend his thesis \u201cUnderstanding intermittency and aseismic slip induced by fluid injection using perturbation theory\u201d on 1 October 2026 at 2 pm in Amphitheatre Navier, \u00c9cole Nationale des Ponts et Chauss\u00e9es. The defense will be held in English. The thesis [&hellip;]<\/p>\n","protected":false},"author":188,"featured_media":20961,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[266,251,291,299],"tags":[],"class_list":["post-20956","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-actualites-en","category-annonces-en","category-annonces-geotech-en","category-soutenances-de-these-en"],"acf":[],"_links":{"self":[{"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/posts\/20956","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/users\/188"}],"replies":[{"embeddable":true,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/comments?post=20956"}],"version-history":[{"count":3,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/posts\/20956\/revisions"}],"predecessor-version":[{"id":20965,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/posts\/20956\/revisions\/20965"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/media\/20961"}],"wp:attachment":[{"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/media?parent=20956"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/categories?post=20956"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/tags?post=20956"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}