Monitoring Saturation Changes with Ambient Seismic Noise and Gravimetry in a Karst Environment

Fores, Benjamin; Champollion, Cédric; Mainsant, G.; Albaric, Julie; Fort, Ada

doi:10.2136/vzj2017.09.0163

Cited by 29 publications

(28 citation statements)

References 70 publications

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“…Therefore, only the variations of velocity changes and their relative amplitudes can be compared. In the Chalk layer, the anti-correlation between the S-wave and the P-wave velocity change, with similar amplitudes, could suggest a saturation effect (Fores et al 2018). However, in the Netherlands it is most probable that the ground is fully saturated at these depths, ruling out this interpretation.…”

Section: Discussionmentioning

confidence: 97%

“…It has also been used to monitor the response of the crust to large earthquakes (e.g., Wegler & Sens-Schönfelder 2007;Brenguier et al 2008a;Minato et al 2012;Brenguier et al 2014) or slow-slip events (Rivet et al 2011). More recently, it has contributed to the fast emergence of environmental seismology applications (Mainsant et al 2012;Gassenmeier et al 2014;Larose et al 2015;Mordret et al 2016;Lecocq et al 2017;Clements & Denolle 2018;Mao et al 2019a; Corresponding author, mordret@mit.edu Ballistic Surface Wave Monitoring 3 Fores et al 2018) and passive seismic monitoring of civil engineering structures (Nakata & Snieder 2013;Salvermoser et al 2015;Planès et al 2015;Mordret et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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Noise-based ballistic wave passive seismic monitoring – Part 2: surface waves

Mordret

Courbis

Brenguier

et al. 2020

Geophysical Journal International

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SUMMARY We develop a new method to monitor and locate seismic velocity changes in the subsurface using seismic noise interferometry. Contrary to most ambient noise monitoring techniques, we use the ballistic Rayleigh waves computed from 30 d records on a dense nodal array located above the Groningen gas field (the Netherlands), instead of their coda waves. We infer the daily relative phase velocity dispersion changes as a function of frequency and propagation distance with a cross-wavelet transform processing. Assuming a 1-D velocity change within the medium, the induced ballistic Rayleigh wave phase shift exhibits a linear trend as a function of the propagation distance. Measuring this trend for the fundamental mode and the first overtone of the Rayleigh waves for frequencies between 0.5 and 1.1 Hz enables us to invert for shear wave daily velocity changes in the first 1.5 km of the subsurface. The observed deep velocity changes (±1.5 per cent) are difficult to interpret given the environmental factors information available. Most of the observed shallow changes seem associated with effective pressure variations. We observe a reduction of shear wave velocity (–0.2 per cent) at the time of a large rain event accompanied by a strong decrease in atmospheric pressure loading, followed by a migration at depth of the velocity decrease. Combined with P-wave velocity changes observations from a companion paper, we interpret the changes as caused by the diffusion of effective pressure variations at depth. As a new method, noise-based ballistic wave passive monitoring could be used on several dynamic (hydro-)geological targets and in particular, it could be used to estimate hydrological parameters such as the hydraulic conductivity and diffusivity.

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Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Noise-based ballistic wave passive seismic monitoring – Part 2: surface waves

Mordret

Courbis

Brenguier

et al. 2020

Geophysical Journal International

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“…The Bouguer plate equivalent was corrected for the estimated averaged daily deep percolation discharge of one mm per day (Fores et al (2018)). The investigated precipitation event took place during the winter months, evapotranspiration was thus not considered.…”

Section: Drift Accuracy and Sensitivitymentioning

confidence: 99%

Evaluation of the capacities of a field absolute quantum gravimeter (AQG#B01)

Cooke¹,

Champollion²,

Moigne³

2020

Preprint

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Abstract. Quantum gravimeters are a promising new development allowing for continuous, high-frequency absolute gravity monitoring while remaining user-friendly and transportable. In this study, we present experiments carried out to assess the capacity of the AQG#B01 in view of future deployment as a field gravimeter for hydro-geophysical applications. The AQG#B01 is the field version follow-up of the AQG#A01 portable absolute quantum gravimeter developed by MuQuans. We assess the instrument's performance in terms of stability (absence of instrumental drift), sensitivity in relation to other gravimeters, and hydrogeological mass changes. We discuss the observations concerning the accuracy of the AQG#B01 in comparison with a state-of-the-art absolute gravimeter (Micro-g-LaCoste, FG5#228). Repeatability is tested by instrument displacement between close-by measurement positions. We report the repeatability to be better than 50 nm s−2. No significant instrumental drift was observed over several weeks of measurement. This study furthermore investigates whether changes of instrument tilt and external temperature and combination of both, which are likely to occur during field campaigns, influence the measurement of gravitational attraction. We repeatedly tested external temperatures between 20 and 30 °C and did not find any significant effect. As an example of a geophysical signal, a 100 nm s−2 gravity change is detected with the AQG#B01 after a rainfall event at the Larzac geodetic observatory (Southern France). The data agreed with the gravity changes measured with a superconducting relative gravimeter (GWR, iGrav#002) and the expected gravity change simulated as an infinite Bouguer slab approximation. We close with operational recommendations for potential users and discuss specific possible future field applications. While not claiming completeness, we nevertheless present the first characterisation of a quantum gravimeter carried out by future users. Crucial criteria for the assessment of its suitability in field applications have been investigated and are complemented with a discussion of further necessary experiments.

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“…The limitation of SNMR in such lithological and hydrogeological contexts is the very low ambient electromagnetic noise level required to allow the monitoring of temporal variations in water content. SNMR evidence of seasonal variation in water content in karst UZ has, nevertheless, been reported in a few studies [3,14].…”

Section: Introductionmentioning

confidence: 97%

Surface Nuclear Magnetic Resonance Monitoring Reveals Karst Unsaturated Zone Recharge Dynamics during a Rain Event

Mazzilli

Chalikakis

Carrière

et al. 2020

Water

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Understanding karst unsaturated zone (UZ) recharge dynamics is crucial for achieving sustainable management of karst hydrosystems. In this paper, we provide the first report of the application of surface nuclear magnetic resonance (SNMR) monitoring of a karst UZ during a typical Mediterranean rain event. This 79 days’ SNMR monitoring is a part of a more than 2 years of SNMR monitoring at the Low Noise Underground Laboratory (LSBB) experimental site located within the Fontaine de Vaucluse karst hydrosystem (southeastern France). We present eight SNMR soundings conducted before and after the rain event that accumulated 168 mm in 5 days. The obtained results demonstrate the applicability and the efficiency of SNMR for investigating infiltration dynamics in karst UZs at the time scale of a few days. We present the SNMR amplitudes that highlight strong signal variations related to water dynamics in the karst UZ. Infiltrated water cause increased SNMR signal during 5 days after the rain event. A significant draining process of the medium starts 15 days after the main event. Finally, after 42 days, the SNMR signal returns close to the initial state.

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Monitoring Saturation Changes with Ambient Seismic Noise and Gravimetry in a Karst Environment

Cited by 29 publications

References 70 publications

Noise-based ballistic wave passive seismic monitoring – Part 2: surface waves

Noise-based ballistic wave passive seismic monitoring – Part 2: surface waves

Evaluation of the capacities of a field absolute quantum gravimeter (AQG#B01)

Surface Nuclear Magnetic Resonance Monitoring Reveals Karst Unsaturated Zone Recharge Dynamics during a Rain Event

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