scholarly journals Modeling of co- and post-seismic surface deformation and gravity changes of MW6.9 Yushu, Qinghai, earthquake

2011 ◽  
Vol 24 (2) ◽  
pp. 177-183 ◽  
Author(s):  
Chengli Liu ◽  
Bin Shan ◽  
Yong Zheng ◽  
Ying Jiang ◽  
Xiong Xiong
Keyword(s):  
Surface Deformation ◽  
Gravity Changes

scholarly journals Co- and post-seismic surface deformation and gravity changes of MS7.0 Lushan, earthquake

2013 ◽  
Vol 26 (3-4) ◽  
pp. 207-212 ◽  
Author(s):  
Kai Wang ◽  
Chengli Liu ◽  
Xiong Xiong ◽  
Yong Zheng
Keyword(s):  
Surface Deformation ◽  
Lushan Earthquake ◽  
Gravity Changes

scholarly journals Minimum Detectable Mass and Volume Fluxes During Magmatic Recharge at High Prominence Volcanoes: An Application to Erciyes Dağ Volcano (Turkey)

2021 ◽  
Vol 9 ◽  
Author(s):  
Katie Males ◽  
Jo Gottsmann
Keyword(s):  
Surface Deformation ◽  
Ground Deformation ◽  
Element Analysis ◽  
Mechanical Heterogeneity ◽  
Reservoir Volume ◽  
Gravity Changes ◽  
Mt Etna ◽  
Vertical Displacements ◽  
Magma Recharge ◽  
Ground Displacements

Magma reservoir recharge is widely recognised as a precursor of eruptive activity. However, the causative relationships between reservoir rejuvenation and surface observables such as gravitational potential field changes and ground deformation are still poorly understood. At intermediate and silicic intra-plate volcanoes where crustal mechanical heterogeneity combined with high-prominence are expected to fundamentally affect the crustal stress and strain relationship, protracted period of repose and absence of monitoring data raise questions about the detectability of magma recharge. Here we report results from integrated geodetic forward modelling of ground displacements and gravity changes from reservoir recharge at Erciyes Dağ, a large prominence (∼2,800 m), yet poorly studied, stratovolcano of the Central Anatolian Volcanic Province in Turkey. The most recent eruption at ∼7000 BC, close proximity to the Kayseri Metropolitan Area and absence of dedicated volcano monitoring set a precedent to explore stealth magmatic processes at the volcano. Using finite element analysis we systematically explore the influence of subsurface mechanical heterogeneities and topography on surface deformation and gravity changes from magmatic recharge of Erciyes Dağ’s reservoir. We show that whilst crustal heterogeneity amplifies ground displacements and gravity variations, the volcano’s substantial prominence has the opposite effect. For generic reservoir pressure and density changes of 10 MPa and 10 kg m−3 predicted vertical displacements vary by a factor of 5 while residual gravity changes vary by a factor of 12 between models ignoring topography or mechanical heterogeneity and those that do not. We deduce reservoir volume and mass changes of order 10–3 km3 and 1010 kg, respectively, at the detectability limit of conventional surveying techniques at the volcano. Though dependent on model assumptions, all results indicate that magma recharge at Erciyes Dağ may go undetected at fluxes 1) sufficient to maintain an active reservoir containing eruptable magma and 2) similar to those reported for intermediate/silicic volcanoes with repose times of 100–1,000s of years (e.g., Parinacota) and persistently active mafic volcanoes such as Mt. Etna and Stromboli. Our findings may be utilised to inform integrated geodetic and gravimetric monitoring at Erciyes Dağ and other large prominence silicic volcanoes and could provide early insights into reservoir rejuvenation with implications for the development of disaster risk reduction initiatives.

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

2021 ◽  
Vol 51 (4) ◽  
pp. 345-371
Author(s):  
Giovanna BERRINO ◽  
Peter VAJDA ◽  
Pavol ZAHOREC ◽  
Antonio G. CAMACHO ◽  
Vincenzo DE NOVELLIS ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Gravitational Effect ◽  
Vertical Displacement ◽  
Time Lapse ◽  
Residual Gravity ◽  
Gravity Changes ◽  
Elevation Changes ◽  
Weak Points ◽  
Lidar Dem ◽  
Island Of Ischia

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.

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

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 2013–2016 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>

scholarly journals Deformation induced topographic effects in inversion of temporal gravity changes: First look at Free Air and Bouguer terms

2015 ◽  
Vol 45 (2) ◽  
pp. 149-171 ◽  
Author(s):  
Peter Vajda ◽  
Pavol Zahorec Pavol ◽  
Juraj Papčo ◽  
Anna Kubová
Keyword(s):  
Surface Deformation ◽  
Vertical Gradient ◽  
Spatial Behavior ◽  
The Other ◽  
Volcanic Complex ◽  
Topographic Effects ◽  
Deformation Effect ◽  
Gravity Station ◽  
Gravity Changes ◽  
Free Air

Abstract We review here the gravitational effects on the temporal (time-lapse) gravity changes induced by the surface deformation (vertical displacements). We focus on two terms, one induced by the displacement of the benchmark (gravity station) in the ambient gravity field, and the other imposed by the attraction of the masses within the topographic deformation rind. The first term, coined often the Free Air Effect (FAE), is the product of the vertical gradient of gravity (VGG) and the vertical displacement of the benchmark. We examine the use of the vertical gradient of normal gravity, typically called the theoretical or normal Free Air Gradient (normal FAG), as a replacement for the true VGG in the FAE, as well as the contribution of the topography to the VGG. We compute a topographic correction to the normal FAG, to offer a better approximation of the VGG, and evaluate its size and shape (spatial behavior) for a volcanic study area selected as the Central Volcanic Complex (CVC) on Tenerife, where this correction reaches 77% of the normal FAG and varies rapidly with terrain. The second term, imposed by the attraction of the vertically displaced topo-masses, referred to here as the Topographic Deformation Effect (TDE) must be computed by numerical evaluation of the Newton volumetric integral. As the effect wanes off quickly with distance, a high resolution DEM is required for its evaluation. In practice this effect is often approximated by the planar or spherical Bouguer deformation effect (BDE). By a synthetic simulation at the CVC of Tenerife we show the difference between the rigorously evaluated TDE and its approximation by the planar BDE. The complete effect, coined here the Deformation Induced Topographic Effect (DITE) is the sum of FAE and TDE. Next we compare by means of synthetic simulations the DITE with two approximations of DITE typically used in practice: one amounting only to the first term in which the VGG is approximated by normal FAG, the other adopting a Bouguer corrected normal FAG (BCFAG).

scholarly journals Modeling 3D Free-geometry Volumetric Sources Associated to Geological and Anthropogenic Hazards from Space and Terrestrial Geodetic Data

2019 ◽  
Vol 11 (17) ◽  
pp. 2042 ◽  
Author(s):  
Camacho ◽  
Fernández
Keyword(s):  
Numerical Solutions ◽  
Surface Deformation ◽  
A Priori ◽  
Three Dimensional ◽  
Remote Sensing Data ◽  
Point Sources ◽  
Geodetic Data ◽  
Nonlinear Inversion ◽  
Gravity Changes ◽  
Oblate Spheroids

Recent decades have shown an explosion in the quantity and quality of geodetic data, mainly space-based geodetic data, that are being applied to geological and anthropogenic hazards. This has produced the need for new approaches for analyzing, modeling and interpreting these geodetic data. Typically, modeling of deformation and gravity changes follows an inverse approach using analytical or numerical solutions, where normally regular geometries (point sources, disks, prolate or oblate spheroids, etc.) are assumed at the initial stages and the inversion is carried out in a linear context. Here we review an original methodology for the simultaneous, nonlinear inversion of gravity changes and/or surface deformation (measured with different techniques) to determine 3D (three-dimensional) bodies, without any a priori assumption about their geometries, embedded into an elastic or poroelastic medium. Such a fully nonlinear inversion has led to interesting results in volcanic environments and in the study of water tables variation due to its exploitation. This methodology can be used to invert geodetic remote sensing data or terrestrial data alone, or in combination.

An Optoelectronic System for Real-Time Surface Deformation Measurements

Vestnik MEI ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 101-108
Author(s):  
Anton Yu. Poroykov ◽  
◽  
Konstantin M. Lapitskiy ◽  
Keyword(s):  
Real Time ◽  
Surface Deformation ◽  
Optoelectronic System ◽  
Deformation Measurements
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