Interpretation of spatiotemporal gravity changes accompanying the earthquake of 21 August 2017 on Ischia (Italy)

We analyse spatiotemporal gravity changes observed on the Ischia island (Italy) accompanying the destructive earthquake of 21 August 2017. The 29 May 2016 to 22 September 2017 time-lapse gravity changes observed at 18 benchmarks of the Ischia gravimetric network are first corrected for the gravitational effect of the surface deformation using the deformation-induced topographic effect (DITE) correction. The co-seismic DITE is computed by Newtonian volumetric integration using the Toposk software, a high-resolution LiDAR DEM and the co-seismic vertical displacement field derived from Sentinel-1 InSAR data. We compare numerically the DITE field with its commonly used Bouguer approximation over the island of Ischia with the outcome that the Bouguer approximation of DITE is adequate and accurate in this case. The residual gravity changes are then computed at gravity benchmarks by correcting the observed gravity changes for the planar Bouguer effect of the elevation changes at benchmarks over the same period. The residual gravity changes are then inverted using an inversion approach based on model exploration and growing source bodies, making use of the Growth-dg inversion tool. The found inversion model, given as subsurface time-lapse density changes, is then interpreted as mainly due to a co-seismic or post-seismic disturbance of the hydrothermal system of the island. Pros and weak points of such interpretation are discussed.

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Application of deformation–induced topographic effect in interpretation of 2013–2016 spatiotemporal gravity changes at Laguna del Maule (Chile)

10.5194/egusphere-egu21-467 ◽

2021 ◽

Author(s):

Peter Vajda ◽

Pavol Zahorec ◽

Craig A. Miller ◽

Hélène Le Mével ◽

Juraj Papčo ◽

...

Keyword(s):

Surface Deformation ◽

Source Parameters ◽

Gravitational Effect ◽

Time Lapse ◽

Volcanic Field ◽

Topographic Effect ◽

Gravity Changes ◽

Elevation Changes ◽

Gravity Network ◽

The Impact

<p>The accurate deformation-induced topographic effect (DITE) should be used to account for the gravitational effect of surface deformation when analyzing residual spatiotemporal (time-lapse) gravity changes in volcano gravimetric or 4D micro-gravimetric studies, in general. Numerical realization of DITE requires the deformation field available in grid form. We compute the accurate DITE correction for gravity changes observed at the Laguna del Maule volcanic field in Chile over three nearly annual periods spanning 2013&#8211;2016 and compare it numerically with the previously used free-air effect (FAE) correction. We assess the impact of replacing the FAE by DITE on the model source parameters of analytic inversion solutions and apply a new inversion approach based on model exploration and growing source bodies. The new inversion results based on the DITE correction shift the position of the mass intrusion upwards by a few hundred meters and lower the total mass of the migrated fluids to roughly a half, compared to the inversion results based on the local-FAE correction. Our new Growth inversion results indicate that vertical dip-slip faults beneath the lake, as well as the Troncoso fault play active roles in hosting migrating liquid. We also show that for the study period, the DITE at Laguna del Maule can be accurately evaluated by the planar Bouguer approximation, which only requires the availability of elevation changes at gravity network benchmarks. We hypothesize that this finding may be generalized to all volcanic areas with flatter or less rugged terrain and may alter interpretations based on the commonly used FAE corrections.</p>

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Deformation-induced topographic effect due to shallow dyke: Etna December 2018 fissure eruption case study

Contributions to Geophysics and Geodesy ◽

10.31577/congeo.2021.51.2.4 ◽

2021 ◽

Vol 51 (2) ◽

pp. 165-188

Author(s):

Peter VAJDA ◽

Pavol ZAHOREC ◽

Juraj PAPČO ◽

Richard CZIKHARDT

Keyword(s):

Displacement Field ◽

Surface Deformation ◽

Gravitational Effect ◽

Vertical Gradient ◽

Vertical Displacement ◽

Fissure Eruption ◽

Topographic Effect ◽

Elevation Changes ◽

Elevation Model

Gravitational effect of surface deformation is in 4D microgravimetry treated as the deformation-induced topographic effect (DITE). The DITE field is computed using Newtonian volumetric integration which requires high resolution digital elevation model (DEM) and vertical displacement field in areal form. If only elevation changes on benchmarks of the gravimetric network are available, instead of the vertical displacement field, the DITE on benchmarks can be evaluated only approximately, using a planar Bouguer or a normal free-air-effect (nFAE) approximation. Here we analyze the adequacy and accuracy of these two approximations in a case study for the December 2018 fissure eruption on Etna accompanied by significant surface deformation caused primarily by a relatively shallow dyke. The outcome is that in volcanic areas of similar morphology as that over the Etna summit area, and for surface deformation fields due to relatively shallow dykes, neither the Bouguer nor the nFAE approximation of the DITE is accurate enough. In such situations the residual gravity changes should be computed with both the Bouguer and nFAE corrections and interpreted as two marginal cases. In addition we analyze also a correction for the effect of benchmark elevation change based on the topographically modelled (predicted) vertical gradient of gravity (VGG) meant to approximate the in-situ VGG values at benchmarks. This correction does not appear suitable to approximate the DITE in conditions of our case study or in broader sense.

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Reservoir-Induced Land Deformation: Case Study from the Grand Ethiopian Renaissance Dam

Remote Sensing ◽

10.3390/rs13050874 ◽

2021 ◽

Vol 13 (5) ◽

pp. 874

Author(s):

Yu Chen ◽

Mohamed Ahmed ◽

Natthachet Tangdamrongsub ◽

Dorina Murgulet

Keyword(s):

Land Surface ◽

Large Scale ◽

Surface Deformation ◽

Vertical Displacement ◽

Nile River ◽

Reservoir Volume ◽

Novel Approach ◽

Land Deformation ◽

Large Scale Land ◽

The Impact

The Nile River stretches from south to north throughout the Nile River Basin (NRB) in Northeast Africa. Ethiopia, where the Blue Nile originates, has begun the construction of the Grand Ethiopian Renaissance Dam (GERD), which will be used to generate electricity. However, the impact of the GERD on land deformation caused by significant water relocation has not been rigorously considered in the scientific research. In this study, we develop a novel approach for predicting large-scale land deformation induced by the construction of the GERD reservoir. We also investigate the limitations of using the Gravity Recovery and Climate Experiment Follow On (GRACE-FO) mission to detect GERD-induced land deformation. We simulated three land deformation scenarios related to filling the expected reservoir volume, 70 km3, using 5-, 10-, and 15-year filling scenarios. The results indicated: (i) trends in downward vertical displacement estimated at −17.79 ± 0.02, −8.90 ± 0.09, and −5.94 ± 0.05 mm/year, for the 5-, 10-, and 15-year filling scenarios, respectively; (ii) the western (eastern) parts of the GERD reservoir are estimated to move toward the reservoir’s center by +0.98 ± 0.01 (−0.98 ± 0.01), +0.48 ± 0.00 (−0.48 ± 0.00), and +0.33 ± 0.00 (−0.33 ± 0.00) mm/year, under the 5-, 10- and 15-year filling strategies, respectively; (iii) the northern part of the GERD reservoir is moving southward by +1.28 ± 0.02, +0.64 ± 0.01, and +0.43 ± 0.00 mm/year, while the southern part is moving northward by −3.75 ± 0.04, −1.87 ± 0.02, and −1.25 ± 0.01 mm/year, during the three examined scenarios, respectively; and (iv) the GRACE-FO mission can only detect 15% of the large-scale land deformation produced by the GERD reservoir. Methods and results demonstrated in this study provide insights into possible impacts of reservoir impoundment on land surface deformation, which can be adopted into the GERD project or similar future dam construction plans.

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Progressive Degradation of an Ice Rumple in the Thwaites Ice Shelf, Antarctica, as Observed from High-Resolution Digital Elevation Models

Remote Sensing ◽

10.3390/rs10081236 ◽

2018 ◽

Vol 10 (8) ◽

pp. 1236 ◽

Cited By ~ 1

Author(s):

Seung Hee Kim ◽

Duk-jin Kim ◽

Hyun-Cheol Kim

Keyword(s):

High Resolution ◽

Surface Deformation ◽

Surface Expression ◽

Deformation Model ◽

Ice Shelf ◽

Pressure Source ◽

Viscoelastic Deformation ◽

Shelf Stability ◽

Transient Nature ◽

Elevation Changes

Ice rumples are locally-grounded features of flowing ice shelves, elevated tens of meters above the surrounding surface. These features may significantly impact the dynamics of ice-shelf grounding lines, which are strongly related to shelf stability. In this study, we used TanDEM-X data to construct high-resolution DEMs of the Thwaites ice shelf in West Antarctica from 2011 to 2013. We also generated surface deformation maps which allowed us to detect and monitor the elevation changes of an ice rumple that appeared sometime between the observations of a grounding line of the Thwaites glacier using Double-Differential Interferometric SAR (DDInSAR) in 1996 and 2011. The observed degradation of the ice rumple during 2011–2013 may be related to a loss of contact with the underlying bathymetry caused by the thinning of the ice shelf. We subsequently used a viscoelastic deformation model with a finite spherical pressure source to reproduce the surface expression of the ice rumple. Global optimization allowed us to fit the model to the observed deformation map, producing reasonable estimates of the ice thickness at the center of the pressure source. Our conclusion is that combining the use of multiple high-resolution DEMs and the simple viscoelastic deformation model is feasible for observing and understanding the transient nature of small ice rumples, with implications for monitoring ice shelf stability.

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Kalirin-RAC controls nucleokinetic migration in ADRN-type neuroblastoma

Life Science Alliance ◽

10.26508/lsa.201900332 ◽

2021 ◽

Vol 4 (5) ◽

pp. e201900332

Author(s):

Elena A Afanasyeva ◽

Moritz Gartlgruber ◽

Tatsiana Ryl ◽

Bieke Decaesteker ◽

Geertrui Denecker ◽

...

Keyword(s):

Enrichment Analysis ◽

Time Lapse ◽

Dna Methyltransferases ◽

Gene Set Enrichment Analysis ◽

Gene Set Enrichment ◽

Gene Set ◽

Risk Characteristics ◽

Weak Points ◽

Treatment Research ◽

Time Lapse Imaging

The migrational propensity of neuroblastoma is affected by cell identity, but the mechanisms behind the divergence remain unknown. Using RNAi and time-lapse imaging, we show that ADRN-type NB cells exhibit RAC1- and kalirin-dependent nucleokinetic (NUC) migration that relies on several integral components of neuronal migration. Inhibition of NUC migration by RAC1 and kalirin-GEF1 inhibitors occurs without hampering cell proliferation and ADRN identity. Using three clinically relevant expression dichotomies, we reveal that most of up-regulated mRNAs in RAC1- and kalirin–GEF1–suppressed ADRN-type NB cells are associated with low-risk characteristics. The computational analysis shows that, in a context of overall gene set poverty, the upregulomes in RAC1- and kalirin–GEF1–suppressed ADRN-type cells are a batch of AU-rich element–containing mRNAs, which suggests a link between NUC migration and mRNA stability. Gene set enrichment analysis–based search for vulnerabilities reveals prospective weak points in RAC1- and kalirin–GEF1–suppressed ADRN-type NB cells, including activities of H3K27- and DNA methyltransferases. Altogether, these data support the introduction of NUC inhibitors into cancer treatment research.

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Quantifying sediment mass redistribution from joint time-lapse gravimetry and photogrammetry surveys

10.5194/esurf-2019-35 ◽

2019 ◽

Author(s):

Maxime Mouyen ◽

Philippe Steer ◽

Kuo-Jen Chang ◽

Nicolas Le Moigne ◽

Cheinway Hwang ◽

...

Keyword(s):

Gravity Data ◽

River Sediments ◽

Time Lapse ◽

New Combination ◽

Gravity Changes ◽

Sediment Mass ◽

Mass Redistribution ◽

Sediment Redistribution ◽

Average Loss ◽

Slow Landslide

Abstract. The accurate quantification of sediment mass redistribution is central to the study of surface processes, yet it remains a challenging task. Here we test a new combination of terrestrial gravity and drone photogrammetry methods to quantify sediment redistribution over a 1-km2 area. Gravity and photogrammetry are complementary methods. Indeed, gravity changes are sensitive to mass changes and to their location. Thus, by using photogrammetry data to constrain this location, the sediment mass can be properly estimated from the gravity data. We carried out 3 joint gravity-photogrammetry surveys, once a year in 2015, 2016 and 2017 over a 1-km2 area in southern Taiwan featuring both a wide meander of the Laonong River and a slow landslide. We first removed the gravity changes from non-sediment effects, such as tides, groundwater, surface displacements and air pressure variations. Then, we inverted the density of the sediment, with an attempt to distinguish the density of the landslide from the density of the river sediments. We eventually estimate an average loss of 4.7 ± 0.4 × 109 kg of sediment from 2015 to 2017, mostly due to the slow landslide. Although the gravity devices used in this study are expensive and need week-long surveys, new instrumentation progresses shall enable dense and continuous measurements at lower cost, making this method relevant to improve the estimation of erosion, sediment transfer and deposition in landscapes.

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Growth of a young pingo in the Canadian Arctic observed by RADARSAT-2 interferometric satellite radar

The Cryosphere ◽

10.5194/tc-10-799-2016 ◽

2016 ◽

Vol 10 (2) ◽

pp. 799-810 ◽

Cited By ~ 10

Author(s):

Sergey V. Samsonov ◽

Trevor C. Lantz ◽

Steven V. Kokelj ◽

Yu Zhang

Keyword(s):

Surface Deformation ◽

Seasonal Pattern ◽

Field Studies ◽

Aerial Photographs ◽

Lake Basin ◽

Maximum Height ◽

Observation Methods ◽

Elevation Changes ◽

Satellite Radar ◽

Small Baseline

Abstract. Advancements in radar technology are increasing our ability to detect Earth surface deformation in permafrost environments. In this paper we use satellite Differential Interferometric Synthetic Aperture Radar (DInSAR) to describe the growth of a large, relatively young pingo in the Tuktoyaktuk Coastlands. High-resolution RADARSAT-2 imagery (2011–2014) analyzed with the Multidimensional Small Baseline Subset (MSBAS) DInSAR revealed a maximum 2.7 cm yr−1 of domed uplift located in a drained lake basin. Satellite measurements suggest that this feature is one of the largest diameter pingos in the region that is presently growing. Observed changes in elevation were modeled as a 348  ×  290 m uniformly loaded elliptical plate with clamped edge. Analysis of historical aerial photographs suggested that ground uplift at this location initiated sometime between 1935 and 1951 following drainage of the residual pond. Uplift is largely due to the growth of intrusive ice, because the 9 % expansion of pore water associated with permafrost aggradation into saturated sands is not sufficient to explain the observed short- and long-term deformation rates. The modeled thickness of ice-rich permafrost using the Northern Ecosystem Soil Temperature (NEST) was consistent with the maximum height of this feature. Modeled permafrost aggradation from 1972 to 2014 approximated elevation changes estimated from aerial photographs for that time period. Taken together, these lines of evidence indicate that uplift is at least in part a result of freezing of the sub-pingo water lens. Seasonal variations in the uplift rate seen in the DInSAR data closely match the modeled seasonal pattern in the deepening rate of freezing front. This study demonstrates that interferometric satellite radar can detect and contribute to understanding the dynamics of terrain uplift in response to permafrost aggradation and ground ice development in remote polar environments. The present-day growth rate is smaller than predicted by the modeling and no clear growth is observed at other smaller pingos in contrast with field studies performed mainly before the 1990s. Investigation of this apparent discrepancy provides an opportunity to further develop observation methods and models.

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