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

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.  </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  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>

On the general solution of elastic wave equations in a homogeneous medium with applications to the study of earthquake source mechanisms

1965 ◽  
Vol 55 (2) ◽  
pp. 283-301 ◽  
Author(s):  
Arabinda Roy
Keyword(s):  
Elastic Wave ◽  
Wave Equations ◽  
Homogeneous Medium ◽  
Finite Size ◽  
Surface Displacement ◽  
Point Sources ◽  
Force System ◽  
Surface Displacements ◽  
Elastic Wave Equations ◽  
Source Mechanisms

Abstract The elastic wave equation in an isotropic homogeneous semi-infinite elastic medium has been transformed by a combination of Fourier and Laplace-transforms and the surface displacements due to general force-system in three mutually perpendicular directions have been directly obtained. By suitably specifying the force-system, the surface displacements for all possible types of point sources so far used, have been calculated, obtaining in particular, the results previously derived by Haskell for a dipolar point source of arbitrary direction. It has been shown that now the surface displacement for finite size of the source can be calculated for both body and surface waves. Expressions for the displacements at any point of the medium have been derived, giving in particular the displacements associated with incident wave in the medium, separately.

Surface Displacement Measurement of Soil Mass by White Light Digital Image Analysis in Frequency Domain

2014 ◽  
Vol 915-916 ◽  
pp. 1234-1237
Author(s):  
Jun Jun Li ◽  
Xin Wei Yang ◽  
Wen Guang Shi
Keyword(s):  
Image Analysis ◽  
Frequency Domain ◽  
Digital Image ◽  
White Light ◽  
Digital Image Analysis ◽  
Surface Displacement ◽  
Soil Mass ◽  
Measuring System ◽  
Surface Displacements ◽  
Simple Measuring

The surface displacement of soil mass is an important standard for safety in civil engineering. In this paper, white light digital image analysis in frequency domain is introduced tomeasure surface displacement of soil mass. This method has the characteristics of whole-field, non-contact measurement and the simple measuring system and can obtain displacements by frequency domination correlation arithmetic. Surface displacements of soil mass are obtained by white light digital image analysis in frequency domain. Comparing the experimental results and the theoretical values, the little error exists and the usefulness of this method is certified.

scholarly journals IBEM Simulation of Seismic Wave Scattering by a 3D Tunnel Mountain

2021 ◽  
Vol 2021 ◽  
pp. 1-23
Author(s):  
Ping-Lin Jiang ◽  
Hua Jiang ◽  
Yu-Sheng Jiang ◽  
Dai Wang ◽  
Nan Li ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Seismic Wave ◽  
Wave Scattering ◽  
Surface Displacement ◽  
Elastic Half Space ◽  
P Wave ◽  
Severe Damage ◽  
Surface Displacements ◽  
Seismic Wave Scattering ◽  
The One

The seismic wave scattering by a 3D tunnel mountain is investigated by the indirect boundary element method (IBEM). Without loss of generality, the 3D physical model of hemispherical tunnel mountain in an elastic half-space is established, and the influence of the incidence frequency and angle of P or SV wave on the mountain surface displacements is mainly examined. It is shown that there exists quite a difference between the spatial distribution of displacement amplitude under the incident P wave and the one under SV wave and that the incidence frequency and angle of wave, especially the existence of tunnel excavated in the mountain, have a great effect on the surface displacements of mountain; the presence of the tunnel in the mountain may cause the greater amplification of surface displacement, which is unfavorable to the mountain projects. In addition, it should be noted that the tunnel may suffer the more severe damage under the incident SV wave.

Do active faults’ clay mineral compositions affect whether earthquake ruptures they host will displace the surface?

2021 ◽  
Author(s):  
Selina S. Fenske ◽  
Virginia G. Toy ◽  
Bernhard Schuck ◽  
Anja M. Schleicher ◽  
Klaus Reicherter
Keyword(s):  
Fault Zone ◽  
Clay Mineral ◽  
Active Faults ◽  
Surface Displacement ◽  
Surface Rupture ◽  
Near Surface ◽  
Ground Shaking ◽  
Physical Measurements ◽  
Surface Displacements ◽  
Earthquake Ruptures

<p>The tectonophysical paradigm that earthquake ruptures should not start, or easily propagate into, the shallowest few kilometers of Earth’s crust makes it difficult to understand why damaging surface displacements have occurred during historic events. The paradigm is supported by decades of analyses demonstrating that near the surface, most major fault zones are composed of clay minerals – particularly extraordinarily weak smectites – which most laboratory physical measurements suggest should prevent surface rupture if present. Recent studies of New Zealand’s Alpine Fault Zone (AFZ) demonstrate smectites are absent from some near surface fault outcrops, which may explain why this fault was able to offset the surface locally in past events. The absence of smectites in places within the AFZ can be attributed to locally exceptionally high geothermal gradients related to circulation of meteoric (surface-derived) water into the fault zone, driven by significant topographic gradients. The record of surface rupture of the AFZ is heterogeneous, and no one has yet systematically examined the distribution of segments devoid of evidence for recent displacement. There are significant implications for seismic hazard, which comprises both surface displacements and ground shaking with intensity related to the area of fault plane that ruptures (which will be reduced if ruptures do not reach the surface).  We will present results of new rigorous XRD clay mineral analyses of AFZ principal slip zone gouges that indicate where smectites are present, and consider if these display systematic relationships to surface displacement records. We also plan to apply the same methodology to the Carboneras Fault Zone in Spain, and the infrequent Holocene-active faults in Western Germany.</p>

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

2019 ◽  
Vol 220 (1) ◽  
pp. 345-351 ◽  
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.

scholarly journals A Spatial Analysis to Define Data Requirements for Hydrological and Water Quality Models in Data-Limited Regions

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 267 ◽  
Author(s):  
Ersilia D’Ambrosio ◽  
Anna De Girolamo ◽  
Marinella Spanò ◽  
Vera Corbelli ◽  
Gennaro Capasso ◽  
...  
Keyword(s):  
Water Quality ◽  
Spatial Analysis ◽  
Surface Water ◽  
Source Parameters ◽  
Quality Parameters ◽  
Point Sources ◽  
Water Quality Parameters ◽  
Limited Area ◽  
Climatic Data ◽  
Basin Scale

The objective of the present work is a spatial analysis aimed at supporting hydrological and water quality model applications in the Canale d’Aiedda basin (Puglia, Italy), a data-limited area. The basin is part of the sensitive environmental area of Taranto that requires remediation of the soil, subsoil, surface water, and groundwater. A monitoring plan was defined to record the streamflow and water quality parameters needed for calibrating and validating models, and a database archived in a GIS environment was built, which includes climatic data, soil hydraulic parameters, groundwater data, surface water quality parameters, point-source parameters, and information on agricultural practices. Based on a one-year monitoring of activities, the average annual loads of N-NO3 and P-PO4 delivered to the Mar Piccolo amounted to about 42 t year−1, and 2 t year−1, respectively. Knowledge uncertainty in monthly load estimation was found to be up to 25% for N-NO3 and 40% for P-PO4. The contributions of point sources in terms of N-NO3 and P-PO4 were estimated at 45% and 77%, respectively. This study defines a procedure for supporting modelling activities at the basin scale for data-limited regions.

Geometry of surface deformations caused by induced shocks in the area of underground copper exploitation

2020 ◽  
Author(s):  
Karolina Owczarz ◽  
Anna Kopeć ◽  
Dariusz Głąbicki
Keyword(s):  
Surface Deformation ◽  
Underground Mining ◽  
Surface Displacement ◽  
3D Models ◽  
Radar Interferometry ◽  
Time Interval ◽  
Mining Operations ◽  
Copper Ore ◽  
Surface Displacements ◽  
Satellite Radar

<p>The level of intensity of induced seismic phenomena occurring in areas of mining activity is very diverse. Induced shocks may be directly related to the exploitation carried out or to mining and tectonic factors. In the case of impact on the surface, two types of mining tremors are distinguished: energetically weak shocks, not causing surface deformation, and shocks exceeding a certain energy level, which cause terrain deformations. Surface displacements are the most common form of the effects of underground mining operations, including induced seismicity. Geological research uses Sentinel-1 imagery to determine the geometry of surface displacements that were caused by induced shocks by satellite radar interferometry. In this research four induced shocks with magnitude M>4.0 was used, which occurred in the Legnica-Glogow Copper District in the Rudna mine. This area is one of the most seismically active places in Poland due to the underground exploitation of copper ore. For calculations, the differential satellite radar interferometry (DInSAR) method was used. The DInSAR technique allowed the determination of surface displacement towards the Line of Sight (LOS) between two images acquired at different times (before and after induced shock) with millimeter accuracy. In the presented research calculations were carried out separately for observations acquired in descending and ascending orbits. The Sentinel-1 satellites are a constellation of two radar satellites that observe the surface of lands and oceans at a time interval of 6 days. Therefore, 6 days, 12 days, 18 days and 24 days were assumed as the time intervals between the images. Vertical displacements were calculated based on the generated LOS displacement maps. In addition, charts of subsidence in the N-S and W-E directions were prepared, 3D models of subsidence were made, and deformation geometry was analyzed for individual shocks. As a result of the research, the spatial extent of deformation in the horizontal surface was determined: N-S and W-E, which in both directions was over 2 km. However, surface displacements caused by induced shocks reached values up to 10 cm.</p>

Detection and measurement of landslide deformation prior to their failure by satellite radar interferometry.

2020 ◽  
Author(s):  
Alessandro Simoni ◽  
Benedikt Bayer ◽  
Pierpaolo Ciuffi ◽  
Silvia Franceschini ◽  
Matteo Berti
Keyword(s):  
Surface Displacement ◽  
Radar Interferometry ◽  
Rock Outcrops ◽  
Bare Rock ◽  
Rainfall Events ◽  
Surface Displacements ◽  
Catastrophic Failures ◽  
Before And After ◽  
Slow Moving ◽  
Satellite Radar

<p>Landslides are widespread landscape features in the Northern Apennine mountain chain and their activity frequently cause damages to settlements and infrastructures. In such context, slow-moving landslides are very common and typically affect fine-grained weathered rocks. Long periods of sustained slow-movements (cms/year) can be interrupted by rapid acceleration and catastrophic failures (ms/day) that are caused by intense rainfall events. Space-borne synthetic aperture radar interferometry (InSAR) proved effective to detect actively deforming phenomena and monitor their evolution in the periods before and after failures. We present InSAR results derived from the Sentinel 1 satellite constellation for landslide cases that underwent reactivation during 2019. In all cases, the catastrophic failures were unexpected and no ground-based monitoring data are available. We processed pre- and post-failure interferograms of SAR images acquired by Sentinel 1 A/B with time spans ranging from 6 to 24 days, removing those having low coherence by manual inspection. The conventional 2-pass technique allowed us to obtain measurements of surface displacement despite the fact that sparse to none infrastructures nor bare rock outcrops are present on the landslide bodies. Our interferograms show that surface displacements are visible well in advance of the actual failure. They display nearly continuous downslope motion with seasonal velocity changes. Time series between 2015 and 2019 shows that surface displacements can be appreciated throughout most part of the year with snow cover and summer peak of vegetation being the most notable exceptions. Distinct accelerations can be detected in space and time during the weeks and months preceding the reactivation.</p><p>We compare time-dependent deformations to precipitation patterns to explore their relationship and to document the transition from stable to unstable deformation. Our work suggests that InSAR interferometry can be successfully used to measure pre-failure displacements and detect slow-moving landslides that are more prone to reactivation in case of rainfall events.</p>

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