The nucleation phase of the 2009 L'Aquila earthquake: insights from the Shannon entropy of array seismic records
Abstract
Investigating earthquake nucleation is a keystone to understand how earthquake s begin , and would greatly improve seismic hazard assessment . Traditional investigation s of earthquake nucleation are based on elaborated seismological observations (e.g. seismic catalog). These observations are often incomplete because of the presence of noise, or the lack of data. T his can bias the analyses of earthquake nucleation as we miss some signals from active fault processes. We propose to tackle this issue by analyzing the statistical properties of the continuous seismograms to study the earthquake nucleation process. We calculate the Shannon entropy of the seismic wavefield recorded at an array of stations from the covariance matrix spectrum. High values of seismic entropy (stochastic state) are related to whether background seismic noise, or large amount of seismic sources (large r than the number of stations in the array) equiparted in space occurring in the time scale of analysis. Low entropy values are related to statistically deterministic wavefields, such as seismic sources repeating over time at similar spatial locations, or only a few seismic sources (far less than the number of stations in the array) in the time window of analysis. Using different time scales, we observe both localization of seismic sources during earthquake nucleation or activation of sources over large volumes for aftershock sequences. The locations of the seismic sources are encoded in the covariance matrix eigenvectors, and are used to classify earthquake signals and reveal the spatial and temporal variation of seismic sources, or to reveal other signals related to earthquake nucleation. The method is here applied to study recent earthquakes in Italy as the L'Aquila 2009, Emilia 2012 and Norcia 2016.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S24A..07S
- Keywords:
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- 1242 Seismic cycle related deformations;
- GEODESY AND GRAVITY;
- 7215 Earthquake source observations;
- SEISMOLOGY;
- 7223 Earthquake interaction;
- forecasting;
- and prediction;
- SEISMOLOGY;
- 8109 Continental tectonics: extensional;
- TECTONOPHYSICS