A comprehensive study of seismic sequences : foreshocks, aftershocks and swarm

• Main Author: Cabrera Castro, Leoncio Ezequiel
• Other Authors: Institut des Sciences de la Terre (ISTerre), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), Université Grenoble Alpes 2020-., Michel Campillo
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2023
• Subjects: Earthquake; Aftershock; Foreshock; Italy; Séisme; Réplique; Précurseur; Italie; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Antarc*; Antarctica; Orca
• Online Access: https://theses.hal.science/tel-04319581; https://theses.hal.science/tel-04319581/document; https://theses.hal.science/tel-04319581/file/CABRERA_2023_diffusion.pdf

Seismic sequences are usually classified into three types: Mainshock-Aftershocks, Swarm and Foreshocks-Mainshock-Aftershocks. However, which are the physical processes that control them is still not well understood (e.g., static/dynamic stress transfer, fluids, aseismic slip, or a combination of processes). By studying three types of sequences in different seismotectonic settings using high-resolution seismic catalogues in combination with statistical seismology, modelling, and geodetic observations among others, we aim to better understand the physical process driving the seismicity and their role during fault slip. In the first part, we analyze the variations of the source properties and aftershock activity of six ~Mw 6.3 intermediate depth earthquakes in the subduction zone of northern Chile to characterize the mainshock-aftershock process. We show that while the mainshocks exhibit similar rupture geometry and stress drop, the aftershock productivity systematically decreases for the deeper events within the slab, especially below the 400–450°C isotherm depth. We propose that this isotherm separates high- and low-hydrated zones, thus controlling the aftershock productivity. Subsequently, we study a seismic swarm that occurred in the Antarctica. We create a seismic catalog of ~36,000 events (Aug/2020-Jun/2021). In addition, we observe a prominent geodetic deformation signal at a nearby GNSS station. Based on the dynamics of the seismicity and the geodetic deformation, we infer a volcanic origin for this swarm, which occurred close to a ridge axis and the Orca Volcano. In the third part we start the study of crustal seismic sequences in Central Italy by analyzing the precursory phase of the Mw 6.1 2009 L’Aquila earthquake. To do this, we create a seismic catalogue of ~5,000 events starting ~3.5 months before the mainshock. We observe that the precursory phase experiences multiple accelerations of the seismicity rate that we divide into two main sequences with different features. While the first part is ...