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

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.

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Estimating the atmospheric phase delay for quantifying co-seismic deformation using repeat pass Differential SAR Interferometry: Observations from 20th April 2013 Lushan (China) Earthquake

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsarchives-xl-8-57-2014 ◽

2014 ◽

Vol XL-8 ◽

pp. 57-64 ◽

Cited By ~ 1

Author(s):

J. Mathew ◽

R. Majumdar ◽

K. Vinod Kumar

Keyword(s):

Surface Deformation ◽

Lushan Earthquake ◽

Phase Delay ◽

Sar Interferometry ◽

Electron Content ◽

Phase Component ◽

Total Electron ◽

China Earthquake ◽

Delay Component ◽

Seismic Deformation

Atmospheric phase contribution significantly influences co-seismic surface deformation estimates from repeat pass Differential Synthetic Aperture Radar Interferometry (DInSAR). Present study investigates the contribution of the atmosphere in co-seismic deformation estimation associated with the 20 April 2013 Lushan (China) earthquake. The Lushan Earthquake occurred in the south-western segment of the Longmenshan fault zone, on the eastern margin of the Qinghai-Tibetan Plateau. Using pre- and postearthquake Radarsat-2 interferometric pair, the co-seismic deformation of the Lushan earthquake has been estimated. The tropospheric phase delay component has been estimated using tropospheric models in conjunction with surface temperature and pressure data from MODIS atmospheric products. The ionospheric phase component has been computed using the Total Electron Content (TEC) data. The net atmospheric path addition in the study area varies from 3.022 m to 4.621 m for the pre-earthquake SAR acquisition and from 2.687 m to 4.199 m for the post-event data acquisition. Comparison of the Line of Sight (LOS) displacement values computed using un-corrected and corrected interferometric data shows that the atmospheric phase component has introduced considerable contribution in the LOS displacement values. The uncorrected LOS displacement values vary from 0.902 m to −0.157 m where as those from the phase-corrected interferometric data are in the range of 0.052 m and −0.062 m. The corrected LOS displacement values show close agreement to a few GPS based co-seismic surface deformation components from published literature. Thus removal of atmospheric phase contribution is a necessary step in using repeat pass DInSAR for co-seismic surface deformation estimation.

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

Contributions to Geophysics and Geodesy ◽

10.31577/congeo.2021.51.4.3 ◽

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.

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

Earthquake Science ◽

10.1007/s11589-010-0782-y ◽

2011 ◽

Vol 24 (2) ◽

pp. 177-183 ◽

Cited By ~ 2

Author(s):

Chengli Liu ◽

Bin Shan ◽

Yong Zheng ◽

Ying Jiang ◽

Xiong Xiong

Keyword(s):

Surface Deformation ◽

Gravity Changes

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Near-field surface deformation during the April 20, 2013, Ms7. 0 Lushan earthquake measured by 1-Hz GNSS

Geodesy and Geodynamics ◽

10.3724/sp.j.1246.2013.02001 ◽

2013 ◽

Vol 4 (2) ◽

pp. 1-5 ◽

Cited By ~ 2

Author(s):

Liu Gang ◽

Zhao Bin ◽

Zhang Rui ◽

Huang Yong ◽

Wang Jun ◽

...

Keyword(s):

Surface Deformation ◽

Near Field ◽

Lushan Earthquake

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

Contributions to Geophysics and Geodesy ◽

10.1515/congeo-2015-0018 ◽

2015 ◽

Vol 45 (2) ◽

pp. 149-171 ◽

Cited By ~ 2

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).

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Seismotectonic Mechanisms of Lushan (Ms7.0) Earthquake in the Frontal Propagation Belt of the Longmen Shan, Sichuan, China

Journal of Earthquake and Tsunami ◽

10.1142/s1793431115500050 ◽

2015 ◽

Vol 09 (02) ◽

pp. 1550005 ◽

Cited By ~ 1

Author(s):

Li Yong ◽

Yan Liang ◽

Zhou Rongjun ◽

Shao Chongjian ◽

Zhao Guohua ◽

...

Keyword(s):

Surface Deformation ◽

Active Faults ◽

Seismic Source ◽

Seismic Intensity ◽

Lushan Earthquake ◽

Focal Mechanism Solution ◽

Tectonic Deformation ◽

Seismogenic Fault ◽

Detachment Surface ◽

Lushan Ms7.0 Earthquake

In recent years, the apparent seismic activity around Longmen Shan and its front has included the Wenchuan (Ms8.0) Earthquake and the Lushan (Ms7.0) Earthquake, occurring in 2008 and 2013, respectively. Based on the focal mechanism solution, rupture processes, seismic intensity, surface deformation, and aftershocks of the Lushan Earthquake and the active fault on Longmen Shan, we divided the Longmen Shan and its front into two tectonic deformation belts, the Longmen Shan thrust belt and the frontal propagation belt. By comparing the differences in the tectonic deformation styles, active faults, and earthquake histories of the two belts, we propose two kinds of seismotectonic models: one is a thrusting belt characterized by napping and detachment, and the other is a frontal propagation belt characterized by thrusting and detachment folding. By analyzing the seismogenic mechanisms of thrusting and detachment folding in the frontal propagation belt during the Lushan Earthquake, we have inferred that the Lushan Earthquake was formed by thrusting and detachment folding in the frontal propagation belt. The seismogenic fault of the Lushan Earthquake was the Dayi Fault, which dips NW with a listric surface, and converges on the detachment surface. The detachment surface is the seismic source layer of the Lushan Earthquake.

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