EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

A detailed study of the initiation process of a small (Mw4.4) normal fault earthquake in the middle lower crust

Hugo Sanchez-Reyes1, David Essing1, Eric Beauce2, and Piero Poli1
Hugo Sanchez-Reyes et al.
  • 1University Grenoble Alpes, ISTerre, Grenoble, France (
  • 2Massachusetts Institute of Technology, Massachusetts, USA (

Our knowledge about the physics behind the initiation process of large or small earthquakes remains limited. The current understanding of this process suggests that an earthquake occurs when increasing stress causes a pre-existing fault to fail suddenly (e.g. Dieterich 1992). Models such as the pre-slip instability growth or the triggered cascade of events have been proposed in order to theoretically explain this preparation stage (Dodge and Beroza, 1996; Ellsworth and Bullut, 2018; Bouchon et al., 2011). However, the mechanisms behind this process are still unknown. This debate is mainly due to the lack of direct observations of the subsurface shear stress evolution at the area of interest before and after an earthquake.

Considering that the shear stress evolves through time until the moment of failure, indirect observations of this change might be available but hidden inside the continuous seismic data. In this work, we analyze in detail the evolution of the seismic activity of a small (Mw 4.4) normal fault earthquake which occurred in Central Italy on 7th November 2019 at the middle lower crust (16 km depth). We first analyze the available continuous data using the Fast Matched Filter (Beauc\'e et al., 2017). Then, every new detected event is spatially localized with respect to the other events through the Double Difference algorithm (DD). As a result, we obtain the spatio-temporal evolution of the foreshock and aftershock sequences of that event.

The results from this analysis shed light on the patterns that the shear-stress spatio-temporal evolution follows before and after a given event. Therefore, we expect that this study will contribute to improve our understanding of the physics behind the earthquake initiation process.

How to cite: Sanchez-Reyes, H., Essing, D., Beauce, E., and Poli, P.: A detailed study of the initiation process of a small (Mw4.4) normal fault earthquake in the middle lower crust, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11661,, 2020

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Presentation version 1 – uploaded on 03 May 2020
  • AC1: Interactive poster, Hugo Sanchez-Reyes, 04 May 2020

    Hello everyone!

    For a much better experience with this poster you can download the interactive poster presentation at  The EGU team did not allow me to upload the SVG file. Read you out there soon!