Data-intensive analysis of seismic tremors and long period events: a new paradigm for understanding transient deformation processes in active geological systems

Project Information

SEISMAZE

Grant agreement ID: 787399

DOI

10.3030/787399

Project closed

EC signature date 20 June 2018

Start date 1 January 2019

End date 31 December 2024

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 490 000,00

EU contribution

€ 2 490 000,00

Coordinated by

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
France

Periodic Reporting for period 4 - SEISMAZE (Data-intensive analysis of seismic tremors and long period events: a new paradigm for understanding transient deformation processes in active geological systems)

Reporting period: 2023-07-01 to 2024-12-31

Summary of the context and overall objectives of the project

What is the problem/issue being addressed?
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The SEISMAZE project is aimed at studying low frequency seismic tremors and earthquakes that form a broad class of signals generated by internal sources that are different from classical earthquakes. While the physical origin of this type of signals remains to be fully understood, they are related to slow transient energy release processes that occur in active geological systems during the accumulation of mechanical energy that is then released during catastrophic events, such as strong earthquakes or volcanic eruptions. Therefore, low-frequency seismic tremors and earthquakes represent a unique source of information that can be used to understand the physics of these ‘preparation’ processes and to design new monitoring and forecasting approaches.

Why is it important for society?
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Low-frequency seismic tremors and earthquakes are manifestation of the slow processes that accommodate the mechanical evolution of geologically active systems under slow large-scale forcing prior to and after cataclysmic energy release during volcanic eruptions or strong earthquakes. They provide, therefore, a new paradigm for studying active geological processes in a variety of tectonic settings and for improving monitoring methods of seismic and volcanic hazards.

What are the overall objectives?
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Modern digital seismological networks record huge numbers of tremors in different active regions, and breakthroughs can be achieved with systematic exploration of these observations that includes data analysis and physical modeling. The main objective of the SEISMAZE project is to undertake such an effort via the development of a new unified framework for the study of low-frequency seismic tremors and earthquakes. The plan to combine advanced methods for data mining, signal processing, and numerical simulations of the generating processes, to apply these to different large datasets of volcanic and tectonic low-frequency tremors and earthquakes.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Analysis of observations in targeted regions
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- We built a new LFE catalogue in Shikoku, Japan and studied their source scaling properties based on analysis of more than 130 thousand events.
- More than two years of the data from Guerrero, Mexico have been analysed to study the source scaling properties of the tectonic LFE. Their size-duration scaling has been found very different from the “regular” earthquakes.
- The data of the KISS seismic experiment in Kamchatka have been used to build a new catalog of volcanic tremors that revealed an active transcrustal magmatic system.
- The data from the seismic experiment on the Gorely volcano have been used to create a new catalogue of co-eruptive volcanic LFEs and to study their temporal clustering.
- 10 years of the data of the seismic network of the Piton de la Fournaise volcano have been used to build a new catalogue of seismo-volcanic tremors.
- Earthquakes generated during “laboratory” experiments.
- Data of 15 broadband seismometers during the Fagradalsfjall eruption in Iceland.
- Data of two broadband seismometers recorded the 2018 eruption and caldera collapse of Kīlauea volcano.
- Three years of seismic records by the network of the Alaska Volcano Observatory rueing the reactivation of the Trident (Katmai volcanic cluster) in Alaska.
- We analyzed signals earthquakes occurred beneath the French Massif Central between 2012 and 2024.

New methods for analysis of STER seismic signals
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- Method based on the network covariances (cross-correlations) to detect seismic tremors and to characterize their sources (openly source python package “covseisnet”).
- Machine-learning approaches to classify seismo-volcanic low frequency earthquakes and tremors.
- Statistical methods for analyzing source properties of the LFE sources and their time-space patterns.
- Differential phases analysis to detect seismic tremors and to characterize the stability of the source position.
- Method to measure earthquake source properties from scattered seismic waves (coda).
- Unsupervised machine learning approach that provides a low-dimension representation of continuous seism-volcanic data and allows to link their different features to specific volcanic processes.
- Inversion method based on amplitude ratios between S- and P-waves to study source mechanisms of Deep Long Period volcanic earthquakes.

Physical modeling of tremor and LFE generating processes.
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- Physical model of the source of volcanic LFE generated due to rapid degassing at depth and investigated its relationship with the H2O/CO2 content in the magmas.
- Model of generation of seismic waves by the pressure variations caused by bubble growth in a sill filled with basaltic magma. This model describes a possibile “interaction” between closely located intrusions with the bubble growth triggered by elastic stresses.
- Model of the source region of the tectonic LFEs is subduction zone. This model considers as main driving mechanism the pore-pressure diffusion via a subduction channel with a spatially heterogeneous and pressure-dependent permeability. We demonstrated that the model can reproduce some of the key features of the observed LFE catalogues such as strong intermittency and rapid migrations.
- Numerical experiments to model the generation of seismic radiation from a fault zone in a visco-elastic media with damaging rheology.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

- We studied datasets of tremors in tectonic and volcanic regions. As a result, we deduced a significant difference in the distribution of their sources. While volcanic tremors are produced by sources well localized in space, tectonic tremor are be explained by a spatially extended distribution of sources.
- Systematic analysis of the source scaling properties in different regions is a very important task. To date, the comparison of the results from Japan and Mexico seems to indicate that the scaling might vary for different regions. We performed a similar source scaling analysis with the data from volcanic regions and with laboratory earthqukes.
- We demonstrated that degassing of magma in the deep route of volcanoes can generate volcanic low-frequency earthquakes.
- We show that rapid pore-pressure migration can be the driving mechanism of the time-space patterns of the low-frequency earthquakes in subduction zones.
- We imaged a very large trans-crustal active plumbing system and observed how it is activated by fast pressure transients prior to eruptions.
- We applied the unsupervised ML approach to the KISS continuous seismic data and connected signal variations to different volcanic processes.
- We demonstrated that the Deep Long Period volcanic earthquakes in Kamchatka are better explained by a source mechanisms containing strong volumetric or single force components which is compatible with the magma stored in nearly horizontal sills near the crust-mantle boundary and penetrating into the crust through neatly vertical conduits.
- We discovered Deep Long Period volcanic earthquakes beneath the French Massif Central which is the important manifestation of the deep magmatic activity beneath this large European volcanic province.

Results of unsupervised ML analysis of continuous seismograms in Klyuchevskoy volcano (Kamchatka)

Model of hydraulically generated seismic tremors (Farge et al.:https://doi.org/10.1029/2021JB02189)

Trans-crustal magmatic system in Kamchatka (Journeau et al.: Sci. Adv.; doi:10.1126/sciadv.abj1571)

Volcanic earthquakes generated by magmatic degassing (Nature Comm.; doi: 10.1038/s41467-020-17759-4)