Surface displacements, deformations and gravity changes due to underground heat source

Abstract Thermo-elastic strains and stresses play a considerable role in the stress state of the lithosphere and its dynamics, especially at pronounced positive geothermal anomalies. Topography has a significant effect on ground deformation. Two methods for including the topographic effects in the thermo-viscoelastic model are described. First we use an approximate methodology which assumes that the main effect of topography is due to the distance from the source to the free surface and permits to have an analytical solution very attractive for solving the inverse problem. A numerical solution (for 2D plain strain case) is also computed using finite element method (FEM). The numerical method allows to include the local shape of the topography in the modeling. In the numerical model the buried magmatic body is represented by a finite volume thermal source. The temperature distribution is computed by the higher-degree FEM. For analytical as well as numerical model solution only the forces of thermal origin are considered. The results show that for the volcanic areas with prominent topography, its effect on the perturbation of the thermo-viscoelastic solution (deformation and total gravity anomaly) can be quite significant. In consequence, neglecting the topography could give erroneous results in the estimated source parameters.

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3D analytical and numerical modelling of the regional topography influence on the surface deformation due to underground heat source

Contributions to Geophysics and Geodesy ◽

10.2478/v10126-011-0010-3 ◽

2011 ◽

Vol 41 (3) ◽

pp. 251-265

Author(s):

Ladislav Brimich ◽

María Charco ◽

Igor Kohút ◽

José Fernández

Keyword(s):

Numerical Model ◽

Numerical Modelling ◽

Heat Source ◽

Surface Deformation ◽

Ground Deformation ◽

Source Parameters ◽

Viscoelastic Model ◽

Thermal Source ◽

Topographic Effects ◽

Regional Topography

3D analytical and numerical modelling of the regional topography influence on the surface deformation due to underground heat source Thermo-elastic strains and stresses play a considerable role in the stress state of the lithosphere and its dynamics, especially at pronounced positive geothermal anomalies. Topography has a significant effect on ground deformation. In this paper we describe two methods for including the topographic effects in the thermo-viscoelastic model. First we use an approximate methodology which assumes that the main effect of the topography is due to distance from the source to the free surface and permits to have an analytical solution very attractive for solving the inverse problem. A numerical solution using Finite Element Method (FEM) is also computed. The numerical method allows to include the local shape of the topography in the modelling. In the numerical model the buried magmatic body is represented by a finite volume thermal source. The temperature distribution is computed by the higher-degree FEM. For analytical as well as numerical model solution only the forces of thermal origin are considered. The comparison of the results obtained using both analytical and numerical techniques shows the qualitative agreement of the vertical displacements. In the numerical values small differences were obtained. The results show that for the volcanic areas with an important relief the perturbation of the thermo-viscoelastic solution (deformation and total gravity anomaly) due to the topography can be quite significant. In consequence, neglecting topography could give erroneous results in the estimated source parameters.

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Finite element modelling of topographic effects on elastic ground deformation at Mt. Etna

Journal of Volcanology and Geothermal Research ◽

10.1016/j.jvolgeores.2004.11.031 ◽

2005 ◽

Vol 144 (1-4) ◽

pp. 257-271 ◽

Cited By ~ 22

Author(s):

L. Lungarini ◽

C. Troise ◽

M. Meo ◽

G. De Natale

Keyword(s):

Finite Element ◽

Finite Element Modelling ◽

Ground Deformation ◽

Topographic Effects ◽

Element Modelling ◽

Mt Etna

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Source Model of the 2014 Mw 6.9 Yutian Earthquake at the Southwestern End of the Altyn Tagh Fault in Tibet Estimated from Satellite Images

Seismological Research Letters ◽

10.1785/0220190361 ◽

2020 ◽

Vol 91 (6) ◽

pp. 3161-3170

Author(s):

Xing Li ◽

Wenbin Xu ◽

Sigurjón Jónsson ◽

Yann Klinger ◽

Guohong Zhang

Keyword(s):

Ground Deformation ◽

Source Parameters ◽

Source Model ◽

Coseismic Slip ◽

Remote Sensing Technology ◽

Sensing Technology ◽

Altyn Tagh ◽

Coulomb Failure Stress Change ◽

Coulomb Failure ◽

Source Geometry

Abstract Multiple fault segments ruptured during the 2014 Yutian earthquake, but the detailed source parameters and the mechanism of rupture complexity remain poorly understood. Here, we use high-resolution TanDEM-X satellite data and Satellite Pour l’Observation de la Terre-6/7 images to map the coseismic ground deformation field of the event. We find that the majority of coseismic slip occurred in the upper 10 km with the maximum left-lateral fault slip of ∼2.5 m at ∼6 km depth. The fault ruptured across a large 4.5 km extensional stepover from one left-lateral fault segment to another, with some right-lateral relay faulting in between. We find that the earthquake was followed by shallow afterslip concentrating at the southwestern end of coseismic rupture, in an area of many aftershocks and positive Coulomb failure stress change. Our findings demonstrate the power of satellite remote sensing technology in constraining source geometry and slip model of complex earthquakes when ground measurements are limited.

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Constraints on the location, depth and yield of the 2017 September 3 North Korean nuclear test from InSAR measurements and modelling

Geophysical Journal International ◽

10.1093/gji/ggz451 ◽

2019 ◽

Vol 220 (1) ◽

pp. 345-351 ◽

Cited By ~ 3

Author(s):

K M Sreejith ◽

Ritesh Agrawal ◽

A S Rajawat

Keyword(s):

Large Scale ◽

Surface Deformation ◽

Nuclear Explosion ◽

Source Parameters ◽

Test Site ◽

Nuclear Test ◽

Interferometric Synthetic Aperture Radar ◽

Surface Displacements ◽

Detailed Surface ◽

Scale Surface

SUMMARY The Democratic People's Republic of Korea (North Korea) conducted its sixth and largest affirmed underground nuclear test on 2017 September 3. Analysis of Interferometric Synthetic Aperture Radar (InSAR) data revealed detailed surface displacements associated with the nuclear explosion. The nuclear explosion produced large-scale surface deformation causing decorrelation of the InSAR data directly above the test site, Mt. Mantap, while the flanks of the Mountain experienced displacements up to 0.5 m along the Line-of-Sight of the Satellite. We determined source parameters of the explosion using the Bayesian inversion of the InSAR data. The explosive yield was estimated as 245–271 kiloton (kt) of TNT, while the previous yield estimations range from 70–400 kt. We determined the nuclear source at a depth of 542 ± 30 m below Mt. Mantap (129.0769°E, 41.0324°N). We demonstrated that the Bayesian modelling of the InSAR data reduces the uncertainties in the source parameters of the nuclear test, particularly the yield and source depth that are otherwise poorly resolved in seismic methods.

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Analytical modelling and joint inversion of surface displacements and gravity changes at volcanoes

10.5194/egusphere-egu21-4887 ◽

2021 ◽

Author(s):

Mehdi Nikkhoo ◽

Eleonora Rivalta

Keyword(s):

Source Parameters ◽

Surface Displacement ◽

Point Sources ◽

Gravity Change ◽

Density Estimate ◽

Mass Change ◽

Long Valley Caldera ◽

Gravity Changes ◽

Surface Displacements ◽

Volcanic Reservoirs

<p>Gravity change observations at volcanoes provide information on the location and mass change of intruded magma bodies. Gravity change and surface displacement observations are often combined in order to infer the density of the intruded materials. Previous studies have highlighted that it is crucial to account for magma compressibility and the shape of the gravity change and deformation source to avoid large biases in the density estimate. Currently, an analytical model for the deformation field and gravity change due to a source of arbitrary shape is lacking, affecting our ability to perform rapid inversions and assess the nature of volcanic unrest. &#160;</p><p>Here, we propose an efficient approach for rapid joint-inversions of surface displacement and gravity change observations associated with underground pressurized reservoirs. We derive analytical solutions for deformations and gravity changes due to the volume changes of triaxial point-sources in an isotropic elastic half-space. The method can be applied to &#160;volcanic reservoirs that are deep compared to their size (far field approximation). We show that the gravity changes not only allow inferring mass changes within the reservoirs, but also help better constrain location, shape and the volume change of the source. We discuss how the inherent uncertainties in the realistic shape of volcanic reservoirs are reflected in large uncertainties on the density estimates. We apply our approach to the surface displacements and gravity changes at Long Valley caldera over the 1985-1999 time period. We show that gravity changes together with only vertical displacements are sufficient to constrain the mass change and all the other source parameters. We also show that while mass change is well constrained by gravity change observations the density estimate is more uncertain even if the magma compressibility is accounted for in the model.</p>

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Analysis of Topographic Effects in Dynamic Response of a Typical Rocky Populated Slope in Lima, Peru

Journal of Disaster Research ◽

10.20965/jdr.2014.p0946 ◽

2014 ◽

Vol 9 (6) ◽

pp. 946-953 ◽

Cited By ~ 1

Author(s):

Carlos Gonzales ◽

◽

Shoichi Nakai ◽

Toru Sekiguchi ◽

Diana Calderon ◽

...

Keyword(s):

Seismic Response ◽

Element Model ◽

Target Area ◽

Topographic Effects ◽

Rocky Slope ◽

Megathrust Earthquakes ◽

Short Period ◽

Plain Strain ◽

The Time Domain ◽

Input Motion

A currently populated slope in the northeast part of the city of Lima was selected as the target area of this study, with the aim of analyzing the influence of topography on its seismic response. A finite element model was constructed using soil information obtained by microtremor arraymeasurements conducted in flat and sloping areas, and solved for plain strain conditions in the time domain using an input motion developed for the most critical slip model of a simulation for megathrust earthquakes. Results showed that for this typical rocky slope, topographic effects do not have a significant influence on its seismic response, except for areas close to the foot of the slope where, even if soil vibration is restricted, an amplification of the seismic motion is still expected for short period structures.

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Hydroelastic response of floating elastic discs to regular waves. Part 2. Modal analysis

Journal of Fluid Mechanics ◽

10.1017/jfm.2013.124 ◽

2013 ◽

Vol 723 ◽

pp. 629-652 ◽

Cited By ~ 30

Author(s):

F. Montiel ◽

L. G. Bennetts ◽

V. A. Squire ◽

F. Bonnefoy ◽

P. Ferrant

Keyword(s):

Numerical Model ◽

Rigid Body ◽

Viscoelastic Model ◽

Wave Interactions ◽

Wave Basin ◽

Modes Of Vibration ◽

Rigid Body Motions ◽

Using Data ◽

Improved Model ◽

Hydroelastic Response

AbstractValidation of a linear numerical model of wave interactions with floating compliant discs is sought using data obtained from the wave basin experiments reported in Part 1 (Montiel et al. J. Fluid Mech., vol. 723, 2013, pp. 604–628). Comparisons are made for both single-disc tests and the two-disc tests in which wave interactions between discs are observed. The deflection of the disc or discs is separated into the natural modes of vibration in vacuo. The decomposition allows the rigid-body motions and flexural motions to be analysed separately. Rigid-body motions are accurately replicated by the numerical model but, although passable agreement is found, the amplitudes of flexural modes are consistently overestimated. Extensions of the numerical model are used to discount the experimental configuration as a source of the discrepancies. An enhanced viscoelastic model for the discs is also proposed, which results in improved model/data agreement for the flexural motions but cannot account for all of the disagreement.

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A 2-D FEM thermal model to simulate water flow in a porous media: Campi Flegrei caldera case study

Nonlinear Processes in Geophysics ◽

10.5194/npg-19-323-2012 ◽

2012 ◽

Vol 19 (3) ◽

pp. 323-333 ◽

Cited By ~ 2

Author(s):

V. Romano ◽

U. Tammaro ◽

P. Capuano

Keyword(s):

Porous Medium ◽

Water Flow ◽

Thermal Model ◽

Ground Deformation ◽

Campi Flegrei ◽

Magmatic Fluid ◽

Geothermal System ◽

Thermal Source ◽

Campi Flegrei Caldera ◽

Vertical Displacements

Abstract. Volcanic and geothermal aspects both exist in many geologically young areas. In these areas the heat transfer process is of fundamental importance, so that the thermal and fluid-dynamic processes characterizing a viscous fluid in a porous medium are very important to understand the complex dynamics of the these areas. The Campi Flegrei caldera, located west of the city of Naples, within the central-southern sector of the large graben of Campanian plain, is a region where both volcanic and geothermal phenomena are present. The upper part of the geothermal system can be considered roughly as a succession of volcanic porous material (tuff) saturated by a mixture formed mainly by water and carbon dioxide. We have implemented a finite elements approach in transient conditions to simulate water flow in a 2-D porous medium to model the changes of temperature in the geothermal system due to magmatic fluid inflow, accounting for a transient phase, not considered in the analytical solutions and fluid compressibility. The thermal model is described by means of conductive/convective equations, in which we propose a thermal source represented by a parabolic shape function to better simulate an increase of temperature in the central part (magma chamber) of a box, simulating the Campi Flegrei caldera and using more recent evaluations, from literature, for the medium's parameters (specific heat capacity, density, thermal conductivity, permeability). A best-fit velocity for the permeant is evaluated by comparing the simulated temperatures with those measured in wells drilled by Agip (Italian Oil Agency) in the 1980s in the framework of geothermal exploration. A few tens of days are enough to reach the thermal steady state, showing the quick response of the system to heat injection. The increase in the pressure due to the heat transport is then used to compute ground deformation, in particular the vertical displacements characteristics of the Campi Flegrei caldera behaviour. The vertical displacements range from 1 cm to 10 cm in accordance with the mini uplift, characterizing the recent behaviour of the caldera. The time needed to move fluid particles from the bottom to the upper layer (years) is compatible with the timing of the mini uplift.

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Micro-relief development in polygonal patterned ground in the Dry Valleys of Antarctica

Quaternary Research ◽

10.1016/j.yqres.2010.12.009 ◽

2011 ◽

Vol 75 (2) ◽

pp. 347-355 ◽

Cited By ~ 19

Author(s):

Bernard Hallet ◽

Ron Sletten ◽

Kevin Whilden

Keyword(s):

Remote Sensing ◽

Numerical Model ◽

Ground Surface ◽

Field Measurements ◽

Polar Regions ◽

Dry Valleys ◽

Patterned Ground ◽

Viscous Material ◽

Surface Displacements ◽

Subsurface Material

AbstractPolygonal patterned ground in polar regions of both Earth and Mars has received considerable attention. In comparison with the size, shape, and arrangement of the polygons, the diverse micro-relief and topography (termed here simply “relief”) of polygonal patterned ground have been understudied. And yet, the relief reflects important conditions and processes occurring directly below the ground surface, and it can be observed readily in the field and through remote sensing. Herein, we describe the relief characteristic of the simplest and relatively young form of patterned ground in the Dry Valleys of Antarctic. We also develop a numerical model to examine the generation of relief due to subsurface material being shouldered aside contraction cracks by incremental sand wedges growth, and to down-slope creep of loose granular material on the surface. We model the longterm subsurface deformation of ice-cemented permafrost as a non-linear viscous material. Our modeling is guided and validated using decades of field measurements of surface displacements of the permafrost and relief. This work has implications for assessing the activity of surfaces on Earth and Mars, and much larger scale potential manifestations of incremental wedging in icy material, namely the distinct paired ridges on Europa.

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