Spherical and ellipsoidal volcanic sources at Long Valley caldera, California, using a genetic algorithm inversion technique

Tiampo, K. F.; Rundle, John B.; Fernández, José; Langbein, John

doi:10.1016/s0377-0273(00)00185-2

Cited by 117 publications

(98 citation statements)

References 31 publications

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“…The medium was assumed to be homogeneous and isotropic with a Young modulus of 75 GPa and a Poisson ratio of 0.25 (e.g., Aloisi et al, 2011). The volume change V was estimated by means of the formulation described in Tiampo et al (2000), using a shear modulus of 30 GPa. It is noteworthy that this value is an overestimation for a hot volcanic region and that a more correct evaluation of the shear modulus needs more attention, for example using a non-elastic rheology that is beyond the scope of this work.…”

Section: Medium-term Recharging /Discharging Phases Inferred By Gps Datamentioning

confidence: 99%

Coupled Short- and Medium-Term Geophysical Signals at Etna Volcano: Using Deformation and Strain to Infer Magmatic Processes From 2009 to 2017

et al. 2018

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In active volcanoes a main challenge is to identify and characterize the dynamics of magmatic sources from deformation and strain data. This task is of primary importance in frequently eruptive volcanoes, such as Etna. After the main flank eruption of [2008][2009] and until 2017, Etna volcano was characterized by a lively eruptive activity of different phases. These comprised 44 lava fountain episodes from the New South East Crater (NSEC), two sequences of close episodes of lava fountains from the Voragine crater (VOR), as well as some periods of summit effusive activity with a more prolonged supply of lava flows. Several studies have described and modeled single lava fountains episodes of the NSEC and VOR, in particular through high precision data from borehole strain-meters. In this study, we broaden the analysis also considering the medium-term volcano recharging/discharging periods preceding/accompanying the different eruptive phases during 2009-2017 by constraining the source positions through deformation recorded by the permanent GPS network. Together with the modeling deduced from the strain-meter data we produce a more complete representation of the different sources that characterized the different periods both in the medium-term (i.e., the preparatory phases showing inflation and the eruptive phases showing deflation) and in the short-term (i.e., the fast discharge associated with eruptive events). Our modeling explains the pathway of magma from the intermediate-shallow plumbing system to the surface and highlights a clear separation between the inflation and the deflation source depths, coherently with petrological constraints on the spatio-temporal evolution of magma transfer and storage.

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Section: Medium-term Recharging /Discharging Phases Inferred By Gps Datamentioning

confidence: 99%

Coupled Short- and Medium-Term Geophysical Signals at Etna Volcano: Using Deformation and Strain to Infer Magmatic Processes From 2009 to 2017

et al. 2018

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“…We incorporate the relations for magma compressibility b m = 1/ρ m * ∂ρ m /∂ρ, spherical chamber compressibility is b c = 3/4µ (e.g., Tiampo et al, 2000), and reservoir volume change due to inflation dV = pa 3 dp/µ (Mogi, 1958). As a result, for connected source and sink reservoirs the volume ratio becomes:…”

Section: Mass Balance Between Dipole Reservoirsmentioning

confidence: 99%

Time-dependent deformation of Uturuncu volcano, Bolivia, constrained by GPS and InSAR measurements and implications for source models

Henderson

Pritchard

2017

Geosphere

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New continuous GPS observations near the summit of Uturuncu volcano, Bolivia, indicate an average uplift rate of 2.4 ± 1.9 mm/yr between April 2010 and November 2015, while previous interferometric synthetic aperture radar (InSAR) observations between May 1992 and January 2011 predict an average vertical uplift rate of 7 ± 2 mm/yr. However, the GPS time series is better fit with a timedependent function, such that the uplift rate in 2010 is less than 2 mm/yr and in 2015 may be as high as 9 mm/yr. Motivated by indications of a non-constant rate in the continuous GPS time series, we examine to what extent past InSAR measurements may have been temporally aliased. We present evidence that decreased uplift since 2004 is permitted by available InSAR and is consistent with a lower average GPS rate since 2010. We discuss how these variable rates may affect previously proposed magmatic models at Uturuncu including diapir ascent and reservoir pressurization. In particular, we explore a "dipole" reservoir model consisting of a magma source in the lower crust and sink in the middle crust for which variation in magma supply could explain sub-decadal fluctuations in deformation rate. Inversion of multiple InSAR data sets using homogeneous models constrains the deeper reservoir to 55-80 km depth (lower crust and upper mantle) and the shallower reservoir to 20-35 km. Consistent with previous work, the inferred ratio of volume change between the source:sink (i.e., deep:shallow) reservoirs is up to 10:1. We also incorporate new seismic tomography results in a 3D finite-element model to explore the combined effects of multiple sources and material heterogeneity on surface deformation. An important conclusion from our modeling efforts is that the commonly used diagnostic ratio of maximum radial to vertical surface displacements for shape of the deformation source is affected by both the presence of multiple reservoirs and subsurface heterogeneity. Ultimately, the dipole and diapir models have unresolved shortcomings given the entire suite of available geophysical data, but both provide valuable insight into the conditions for magmatic ascent in the Central Andes.

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“…Fifty samples of a GA approach, explained in detail in Tiampo et al (2000), have been computed with the implemented reweighted Q ll(r) matrix and are compared to the original samples which were carried out without any reweighting. The population size is given by 100.…”

Section: Implementation Of Tsis Into Gamentioning

confidence: 99%

“…The application of SAs can be found in the modeling of various branches of volcanology, e.g. volcanic conduit flow modeling, Proussevitch and Sahagian (2004), magma and pressure source modeling, Tiampo et al (2000), modeling of CO 2 , Schmid et al (2003), landslide modeling, Tinti and Zaniboni (2004), and ash cloud modeling, Peterson and Dean (2003).…”

Section: Introductionmentioning

confidence: 99%

Deeper understanding of non-linear geodetic data inversion using a quantitative sensitivity analysis

Tiede

Tiampo

Fernández³

et al. 2005

Nonlin. Processes Geophys.

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Abstract.A quantitative global sensitivity analysis (SA) is applied to the non-linear inversion of gravity changes and displacement data which measured in an active volcanic area. The common inversion of this data is based on the solution of the generalized Navier equations which couples both types of observation, gravity and displacement, in a homogeneous half space. The sensitivity analysis has been carried out using Sobol's variance-based approach which produces the total sensitivity indices (TSI), so that all interactions between the unknown input parameters are taken into account. Results of the SA show quite different sensitivities for the measured changes as they relate to the unknown parameters for the east, north and height component, as well as the pressure, radial and mass component of an elastic-gravitational source. The TSIs are implemented into the inversion in order to stabilize the computation of the unknown parameters, which showed wide dispersion ranges in earlier optimization approaches. Samples which were computed using a genetic algorithm (GA) optimization are compared to samples in which the results of the global sensitivity analysis are integrated by a reweighting of the cofactor matrix in the objective function. The comparison shows that the implementation of the TSI's can decrease the dispersion rate of unknown input parameters, producing a great improvement the reliable determination of the unknown parameters.

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Spherical and ellipsoidal volcanic sources at Long Valley caldera, California, using a genetic algorithm inversion technique

Cited by 117 publications

References 31 publications

Coupled Short- and Medium-Term Geophysical Signals at Etna Volcano: Using Deformation and Strain to Infer Magmatic Processes From 2009 to 2017

Coupled Short- and Medium-Term Geophysical Signals at Etna Volcano: Using Deformation and Strain to Infer Magmatic Processes From 2009 to 2017

Time-dependent deformation of Uturuncu volcano, Bolivia, constrained by GPS and InSAR measurements and implications for source models

Deeper understanding of non-linear geodetic data inversion using a quantitative sensitivity analysis

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