Novel treatment of the deformation–induced topographic effect for interpretation of spatiotemporal gravity changes: Laguna del Maule (Chile)

Vajda, P.; Zahorec, Pavol; Miller, Craig A.; Mével, H. Le; Papčo, Juraj; Camacho, Antonio

doi:10.1016/j.jvolgeores.2021.107230

Cited by 5 publications

(5 citation statements)

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“…Deviations from the theoretical free‐air gradient impose additional uncertainties that are not easily quantified. The local free‐air gradient depends significantly on the source of deformation and may be different for, for example, post‐glacial rebound (Olsson et al., 2015) compared to volcano deformation involving subsurface fluid redistribution, where the free‐air gradient or Bouguer corrected free‐air gradient (Vajda et al., 2020, 2021) may be more suitable. Free‐body geometry inversions (Camacho et al., 2021) or coupled inversions of surface deformation and gravity (Nikkhoo & Rivalta, 2021) may provide an alternative to recover source parameters; however, mass accumulation without commensurate surface deformation that involves non‐elastic behavior, for example, density changes through degassing or the compressibility of gas‐rich magma (Rivalta & Segall, 2008), makes joint inversions of gravity and deformation nontrivial.…”

Section: Discussionmentioning

confidence: 99%

Microgravity Change During the 2008–2018 Kı̄lauea Summit Eruption: Nearly a Decade of Subsurface Mass Accumulation

et al. 2022

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Results from nine microgravity campaigns from Kı̄lauea, Hawaiʻi, spanning most of the volcano's 2008–2018 summit eruption, indicate persistent mass accumulation at shallow levels. A weighted least squares approach is used to recover microgravity results from a network of benchmarks around Kı̄lauea's summit, eliminate instrumental drift, and restore suspected data tares. A total mass of 1.9 × 1011 kg was determined from these microgravity campaigns to have accumulated below Kı̄lauea Caldera during 2009–2015 at an estimated depth of 1.3 km below sea level. Only a fraction of this mass is reflected in surface deformation, and this is consistent with previously reported discrepancies between subsurface mass accumulation and observed surface deformation. The discrepancy, amongst other independent evidence from gas emissions, seismicity, and continuous gravimetry, indicate densification of magma in the reservoirs below the volcano summit. This densification may have been driven by degassing through the summit vent. It is hypothesized that during the final years of the summit eruption, magma densification resulted in a buildup of pressure in the reservoirs that may have contributed to the lower East Rift Zone outbreak of 2018. The observed mass accumulation beneath Kı̄lauea could not have been detected through other techniques and illustrates the importance of microgravity measurements in volcano monitoring.

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Section: Discussionmentioning

confidence: 99%

Microgravity Change During the 2008–2018 Kı̄lauea Summit Eruption: Nearly a Decade of Subsurface Mass Accumulation

et al. 2022

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“…They can identify the subsurface locations of the most significant density changes, indicate the nature of the sources and shed light on the subsurface geodynamic process. We compared the two approaches in a case study at the Laguna del Maule volcanic field, Chile (Vajda et al 2021), and found that the Growth approach may offer additional insights compared to the simple source analytical optimization inversion methods.…”

Section: Methods Applied To Interpret the Tenerife 2004-2005 Gravity ...mentioning

confidence: 99%

“…In other cases, the source of the surface deformation produces no significant gravity changes while the source of the gravity changes produces no significant deformation. The two sources thus differ in their location and must be sought as separate sources (e.g., Miller et al 2017a;Vajda et al 2021). In this situation, the spatiotemporal gravity changes properly corrected for the gravitational effect of the surface deformation (decoupled from the surface deformation) can be inverse-modelled as a stand-alone quantity (e.g., Vajda et al 2021).…”

Section: Introductionmentioning

confidence: 99%

“…The two sources thus differ in their location and must be sought as separate sources (e.g., Miller et al 2017a;Vajda et al 2021). In this situation, the spatiotemporal gravity changes properly corrected for the gravitational effect of the surface deformation (decoupled from the surface deformation) can be inverse-modelled as a stand-alone quantity (e.g., Vajda et al 2021). When the two sources differ, the "density of the source", which points to the nature of the process, cannot be determined by combining the volume change obtained from deformation modelling and the mass change obtained from gravity change modelling; in this case, the nature of the process can be inferred from the location and spatial character of the mass change source in the context of the geological structure determined by independent studies (e.g., Miller et al 2017b).…”

Section: Introductionmentioning

confidence: 99%

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Benefits and Limitations of the Growth Inversion Approach in Volcano Gravimetry Demonstrated on the Revisited 2004–2005 Tenerife Unrest

2022

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We review the current geoscientific knowledge of the volcanic unrest of 2004–2005 on Tenerife (Canary Islands) and revisit its gravimetric imprint. We revise the interpretation of the observed spatiotemporal (time-lapse) gravity changes accompanying the unrest by applying the Growth inversion approach based on model exploration and free geometry growing source bodies. We interpret the Growth solution, our new gravimetric model of the unrest, in the context of structural controls and the existing volcanological and geological knowledge of the central volcanic complex (CVC) of the island. Structural controls are inferred from the updated structural subsurface CVC density model obtained by our new Growth inversion of the available complete Bouguer anomalies (CBA data). Our gravimetric picture sees the unrest as a failed eruption, due to a stalled magma intrusion in the central position below the Teide–Pico Viejo stratocones, followed by upward and lateral migration of volcanic fluids reaching the aquifer and the SW end of the caldera wall. We thus classify the volcanic unrest of 2004–2005 as hybrid, in agreement with previous studies. The Growth inversion indicates that magma propagated along the boundary between the basaltic core of the island, the Boca Tauce volcanic body and the more permeable (less compacted) volcanic rocks with lower density. This gravimetric picture of the unrest provides new insights into the potential future reactivation of the volcanic system. Article Highlights Current geoscientific knowledge of the Tenerife volcanic unrest of 2004–2005 is reviewed New insights into the unrest are yielded by Growth inversion of observed time-lapse gravity changes Role of the freely adjustable inversion parameters in the Growth methodology is demonstrated Pros and cons of the Growth inversion approach in volcano gravimetric applications are illustrated

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“…Those, however, are not directly observable, unlike the surface vertical displacements, and their effect cannot be therefore computed and applied as a correction to observed gravity changes. It can be only estimated or modelled 50 , 52 . The application of all the above corrections to observed gravity changes results in the residual gravity changes that are used as input data in our inversion process.…”

Section: Methodsmentioning

confidence: 99%

A free-geometry geodynamic modelling of surface gravity changes using Growth-dg software

Camacho

Vajda

Miller

et al. 2021

Sci Rep

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Globally there is abundant terrestrial surface gravity data used to study the time variation of gravity related to subsurface mass and density changes in different geological, geodynamical and geotechnical environments. We present here a tool for analysing existing and newly acquired, 4D gravity data, which creates new findings from its reuse. Our method calculates in an almost automatic way the possible sources of density change responsible for the observed gravity variations. The specifics of the new methodology are: use of a low number of observation points, relatively small source structures, low signal/noise ratio in the data, and a free 3D source geometry without initial hypothesis. The process is based on the non-linear adjustment of structures defined by aggregation of small cells corresponding to a 3D section of the sub-floor volume. This methodology is implemented in a software tool, named GROWTH-dg, which can be freely downloaded for immediate use, together with a user manual and application examples.

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Novel treatment of the deformation–induced topographic effect for interpretation of spatiotemporal gravity changes: Laguna del Maule (Chile)

Cited by 5 publications

References 50 publications

Microgravity Change During the 2008–2018 Kı̄lauea Summit Eruption: Nearly a Decade of Subsurface Mass Accumulation

Microgravity Change During the 2008–2018 Kı̄lauea Summit Eruption: Nearly a Decade of Subsurface Mass Accumulation

Benefits and Limitations of the Growth Inversion Approach in Volcano Gravimetry Demonstrated on the Revisited 2004–2005 Tenerife Unrest

A free-geometry geodynamic modelling of surface gravity changes using Growth-dg software

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