scholarly journals 3-D Inversion of Gravity Data Using Iterative Calculation for Subsurface Modeling of Mt. Pandan, East Java, Indonesia

2018 ◽  
Vol 16 (3) ◽  
pp. 28
Author(s):  
Waskito Aji ◽  
E. J. Wahyudi ◽  
D. Santoso ◽  
W. G.A. Kadir
Keyword(s):  
Gravity Data ◽  
Gravity Inversion ◽  
Geological Condition ◽  
Linear Inversion ◽  
Data Inversion ◽  
The North ◽  
Iterative Calculation ◽  
Model Response ◽  
Active Tectonic ◽  
Surface Geology

Mount Pandan is one of the volcanoes located in East Java.There was an earthquake with magnitude 4.2 onThursday, June 25, 2015, at 10.35 pm located in the area of Mount Pandan. The earthquake indicates the active tectonic of Mount Pandan. In addition, Mount Pandan is one of eleven geothermal prospects in East Java. Thus, it is interesting to do a study related to the geological condition of Mount Pandan. So far, most studies have discussed the related surface geology of Mount Pandan. This study aims to provide information related to the subsurface condition of Mount Pandan based on gravity data. In this research, gravity data inversion modeling technique is used to image the subsurface condition of Mount Pandan. The inversion technique used is non linear inversion with iterative calculation method. In this modeling scheme, the model to be determinedis a layer boundary depth model of two layers of rock based on gravity anomaly data. In each layer the rock is assumed to be composed of a set of rectangular prisms with a certain dimension. A collection of prisms representing the rock layers is then computed by the model response and evaluated by comparing it to the observed data. From this evaluation, a modication of the length of the prism is made so thatthe boundary layer model will change. The process of evalu ation and modication of the model is done iteratively until it reaches the number of predened iterations. The result obtained from this gravity inversion modeling is a model of the subsurface boundary of Mount Pandan. The subsurface model obtained is the existence of a formation resembling a rock intrusion, in this case interpreted as an andesitic rockthat intrudes overlying rock layers. This intrusive formation lies at the peak of Mount Pandan and is continuously to the north, with the undisturbed intrusion located around the summit of Mount Pandan.

Inferences of the lunar interior from a probabilistic gravity inversion approach

2020 ◽  
Author(s):  
Kristel Izquierdo ◽  
Laurent Montesi ◽  
Vedran Lekic
Keyword(s):  
Gravity Data ◽  
Gravity Inversion ◽  
Positive Density ◽  
The Moon ◽  
Distribution Models ◽  
Linear Inversion ◽  
Spherical Harmonic Degree ◽  
Data Set ◽  
Voronoi Region ◽  
Gravity Acceleration

<p>The shape and location of density anomalies inside the Moon provide insights into processes that produced them and their subsequent evolution. Gravity measurements provide the most complete data set to infer these anomalies on the Moon [1]. However, gravity inversions suffer from inherent non-uniqueness. To circumvent this issue, it is often assumed that the Bouguer gravity anomalies are produced by the relief of the crust-mantle or other internal interface [2]. This approach limits the recovery of 3D density anomalies or any anomaly at different depths. In this work, we develop an algorithm that provides a set of likely three-dimensional models consistent with the observed gravity data with no need to constrain the depth of anomalies a priori.</p><p>The volume of a sphere is divided in 6480 tesseroids and n Voronoi regions. The algorithm first assigns a density value to each Voronoi region, which can encompass one or more tesseroids. At each iteration, it can add or delete a region, or change its location [2, 3]. The optimal density of each region is then obtained by linear inversion of the gravity field and the likelihood of the solution is calculated using Bayes’ theorem. After convergence, the algorithm then outputs an ensemble of models with good fit to the observed data and high posterior probability. The ensemble might contain essentially similar interior density distribution models or many different ones, providing a view of the non-uniqueness of the inversion results.</p><p>We use the lunar radial gravity acceleration obtained by the GRAIL mission [4] up to spherical harmonic degree 400 as input data in the algorithm. The gravity acceleration data of the resulting models match the input gravity very well, only missing the gravity signature of smaller craters. A group of models show a deep positive density anomaly in the general area of the Clavius basin. The anomaly is centered at approximately 50°S and 10°E, at about 800 km depth. Density anomalies in this group of models remain relatively small and could be explained by mineralogical differences in the mantle. Major variations in crustal structure, such as the near side / far side dichotomy and the South Pole Aitken basin are also apparent, giving geological credence to these models. A different group of models points towards two high density regions with a much higher mass than the one described by the other group of models. It may be regarded as an unrealistic model. Our method embraces the non-uniqueness of gravity inversions and does not impose a single view of the interior although geological knowledge and geodynamic analyses are of course important to evaluate the realism of each solution.</p><p>References: [1] Wieczorek, M. A. (2006), Treatise on Geophysics 153-193. doi: 10.1016/B978-0-444-53802-4.00169-X. [2] Izquierdo, K et al. (2019) Geophys. J. Int. 220, 1687-1699, doi: 10.1093/gji/ggz544, [3]  Izquierdo, K. et al., (2019) LPSC 50, abstr. 2157. [4] Lemoine, F. G., et al. ( 2013), J. Geophys. Res. 118, 1676–1698 doi: 10.1002/jgre.20118.</p><p> </p>

Utilisation of stochastic MT inversion results to constrain potential field inversion

2020 ◽  
Author(s):  
Jérémie Giraud ◽  
Hoël Seillé ◽  
Gerhard Visser ◽  
Mark Lindsay ◽  
Mark Jessell
Keyword(s):  
Prior Information ◽  
Clustering Algorithm ◽  
Gravity Data ◽  
Synthetic Data ◽  
Least Square ◽  
Gravity Inversion ◽  
Physical Parameters ◽  
Real World Data ◽  
Magnetotelluric Data ◽  
Data Inversion

<p>We introduce a methodology for the integration of results from 1D stochastic magnetotelluric (MT) data inversion into deterministic least-square inversions of gravity measurements. The goal of this study is to provide a technique capable of exploiting complementary information between 1D magnetotelluric data and gravity data to reduce the effect of non-uniqueness existing in both methodologies. Complementarity exists in terms of resolution, the 1D MT being mostly sensitive to vertical changes and gravity data sensitive to lateral property variations, but also in terms of the related petrophysics, where the sensitivity to different physical parameters (electrical conductivity and density) allows to distinguish between different contrasts in lithologies.  To this end, we perform a three-step workflow. Stochastic 1D MT inversions are performed first. The results are then fused to create 2D model ensembles. Thirdly, these ensembles are utilised as a source of prior information for gravity inversion. This is achieved by extracting geological information from the ensemble of resistivity model realisations honouring MT data (typically, ensemble comprising several thousands of models) to constrain gravity data inversion. <br><br>In our investigations, we generate synthetic data using the 3D geological structural framework of the Mansfield area  (Victoria, Australia) and subsequently perform stochastic MT inversions using a 1D trans-dimensional Markov chain Monte Carlo sampler. These inversions are designed to account for the uncertainty introduced by the presence of non-1D structures.  Following this, the 1D probabilistic ensembles for each site are fused into an ensemble of 2D models which can then be used for further modelling. The fusion method incorporates prior knowledge in terms of spatial lateral continuity and lithological sequencing, to create an image that reflects different scenarios from the ensemble of models from 1D MT inversion. It identifies several domains across the considered area where it is plausible for the different lithologies to occur. This information is then used to constrain gravity inversion using a clustering algorithm by varying the weights assigned to the different lithologies spatially accordingly with the domains defined from MT inversions. <br><br>Our results reveal that gravity inversion constrained by MT modelling results in this fashion provide models that present a lower model misfit and are geologically closer to the causative model than without MT-derived prior information. This is particularly true in areas poorly constrained by gravity data such as the basement. Importantly, in this example, the basement is better imaged by the combination of both gravity and MT data than by the separate techniques. The same applies, to a lesser extent, to dipping geological structures closer to surface. In the case of the Mansfield area, the synthetic modelling investigation we performed shows the potential of the workflow introduced here and that it can be confidently applied to real world data.</p>

scholarly journals 3D Mafic Topography of the Transition Zone between the North-Western Boundary of the Congo Craton and the Kribi-Campo Sedimentary Basin from Gravity Inversion

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Sévérin Nguiya ◽  
Willy Lemotio ◽  
Philippe Njandjock Nouck ◽  
Marcelin M. Pemi ◽  
Alain-Pierre K. Tokam ◽  
...  
Keyword(s):  
Transition Zone ◽  
Sedimentary Basin ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Gravity Inversion ◽  
Western Boundary ◽  
Northern Margin ◽  
Velocity Models ◽  
The North ◽  
North Western

The structure of the transition zone between the north-western boundary of the Congo Craton and the Kribi-Campo sedimentary basin is still a matter of scientific debate. In this study, the existing gravity data are interpreted in order to better understand the geodynamics of the area. Qualitatively, results show that the major gravity highs are associated with long-wavelength shallow sources of the coastal sedimentary basin, while large negative anomalies trending E-W correlate to low dense intrusive bodies found along the northern limit of the Congo Craton. For the delineation of the causative sources, the gravity anomalies have been inverted based on the Parker-Oldenburg iterative process. As inputs, we used a reference depth of 20 km obtained by spectral analysis and successively, the density contrasts 0.19 g/cm3 and 0.24 g/cm3, deduced from available 1D shear wave velocity models. The results reveal an irregular topography of the mafic interface characterized by a sequence of horst and graben structures with mafic depths varying between 15.6 km and 23.4 km. The shallower depths (15.6-17 km) are associated with the uprising of the mafic interface towards the upper crust. This intrusion may have been initiated during the extension of the Archean Ntem crust resulting in a thinning of the continental crust beneath the coastal sedimentary basin. The subsidence of the mafic interface beneath the craton is materialized by 2 similar graben structures located beneath both Matomb and Ebolowa at a maximum depth of 23.4 km. The intermediate depths (18-22 km) are correlated to the suture zone along the Pouma-Bipindi area. The location of some landslides across the area matches within the northern margin of the Congo Craton and suggests that this margin may also impact on their occurrence. This work provides new insights into the geodynamics, regional tectonics, and basin geometry.

THE PALEOPROTEROZOIC MYLONITE OF KINGS CANYON, COLORADO: A CA. 1.6 GA GREENSCHIST FACIES MYLONITE FAR TO THE NORTH OF THE CONCURRENT ACTIVE TECTONIC MARGIN

2018 ◽  
Author(s):  
Bart T. Cubrich ◽  
◽  
Kevin R. Chamberlain ◽  
Ernest M. Duebendorfer ◽  
Michael L. Williams ◽  
...  
Keyword(s):  
Greenschist Facies ◽  
The North ◽  
Active Tectonic

Assessing Model Uncertainty for the Scaling Function Inversion of Potential Fields

Geophysics ◽  
2021 ◽  
pp. 1-39
Author(s):  
Mahak Singh Chauhan ◽  
Ivano Pierri ◽  
Mrinal K. Sen ◽  
Maurizio FEDI
Keyword(s):  
Simulated Annealing Algorithm ◽  
Scaling Function ◽  
Vertical Section ◽  
Gravity Data ◽  
Geometric Model ◽  
Salt Dome ◽  
The Body ◽  
Gravity Inversion ◽  
Geometrical Parameters ◽  
The Scaling Function

We use the very fast simulated annealing algorithm to invert the scaling function along selected ridges, lying in a vertical section formed by upward continuing gravity data to a set of altitudes. The scaling function is formed by the ratio of the field derivative by the field itself and it is evaluated along the lines formed by the zeroes of the horizontal field derivative at a set of altitudes. We also use the same algorithm to invert gravity anomalies only at the measurement altitude. Our goal is analyzing the different models obtained through the two different inversions and evaluating the relative uncertainties. One main difference is that the scaling function inversion is independent on density and the unknowns are the geometrical parameters of the source. The gravity data are instead inverted for the source geometry and the density simultaneously. A priori information used for both the inversions is that the source has a known depth to the top. We examine the results over the synthetic examples of a salt dome structure generated by Talwani’s approach and real gravity datasets over the Mors salt dome and the Decorah (USA) basin. For all these cases, the scaling function inversion yielded models with a better sensitivity to specific features of the sources, such as the tilt of the body, and reduced uncertainty. We finally analyzed the density, which is one of the unknowns for the gravity inversion and it is estimated from the geometric model for the scaling function inversion. The histograms over the density estimated at many iterations show a very concentrated distribution for the scaling function, while the density contrast retrieved by the gravity inversion, according to the fundamental ambiguity density/volume, is widely dispersed, this making difficult to assess its best estimate.

scholarly journals Increased Water Storage in the Qaidam Basin, the North Tibet Plateau from GRACE Gravity Data

PLoS ONE ◽  
2015 ◽  
Vol 10 (10) ◽  
pp. e0141442 ◽  
Author(s):  
Jiu Jimmy Jiao ◽  
Xiaotao Zhang ◽  
Yi Liu ◽  
Xingxing Kuang
Keyword(s):  
Qaidam Basin ◽  
Gravity Data ◽  
Water Storage ◽  
Tibet Plateau ◽  
The North

scholarly journals Monitoring mass changes in the Volta River basin using GRACE satellite gravity and TRMM precipitation

2012 ◽  
Vol 18 (4) ◽  
pp. 549-563 ◽  
Author(s):  
Vagner G. Ferreira ◽  
Zheng Gong ◽  
Samuel A. Andam-Akorful
Keyword(s):  
River Basin ◽  
Gravity Data ◽  
West African ◽  
Rainfall Time Series ◽  
Tropical Rainfall Measurement Mission ◽  
Satellite Gravity ◽  
Rainfall Events ◽  
The North ◽  
Trmm Precipitation ◽  
Grace Satellite

GRACE satellite gravity data was used to estimate mass changes within the Volta River basin in West African for the period of January, 2005 to December, 2010. We also used the precipitation data from the Tropical Rainfall Measurement Mission (TRMM) to determine relative contributions source to the seasonal hydrological balance within the Volta River basin. We found out that the seasonal mass change tends to be detected by GRACE for periods from 1 month in the south to 4 months in the north of the basin after the rainfall events. The results suggested a significant gain in water storage in the basin at reference epoch 2007.5 and a dominant annual cycle for the period under consideration for both in the mass changes and rainfall time series. However, there was a low correlation between mass changes and rainfall implying that there must be other processes which cause mass changes without rainfall in the upstream of the Volta River basin.

3D stochastic gravity inversion using nonstationary covariances

Geophysics ◽  
2013 ◽  
Vol 78 (2) ◽  
pp. G15-G24 ◽  
Author(s):  
Pejman Shamsipour ◽  
Denis Marcotte ◽  
Michel Chouteau ◽  
Martine Rivest ◽  
Abderrezak Bouchedda
Keyword(s):  
Real Data ◽  
Gravity Inversion ◽  
Data Set ◽  
The Real ◽  
Statistical Homogeneity ◽  
Nonstationary Covariance ◽  
Surface Geology ◽  
Synthetic Models ◽  
Stochastic Gravity

The flexibility of geostatistical inversions in geophysics is limited by the use of stationary covariances, which, implicitly and mostly for mathematical convenience, assumes statistical homogeneity of the studied field. For fields showing sharp contrasts due, for example, to faults or folds, an approach based on the use of nonstationary covariances for cokriging inversion was developed. The approach was tested on two synthetic cases and one real data set. Inversion results based on the nonstationary covariance were compared to the results from the stationary covariance for two synthetic models. The nonstationary covariance better recovered the known synthetic models. With the real data set, the nonstationary assumption resulted in a better match with the known surface geology.

scholarly journals Current knowledge on the crustal properties of Italy

1994 ◽  
Vol 37 (5 Sup.) ◽  
Author(s):  
C. Morelli
Keyword(s):  
Adriatic Sea ◽  
Current Knowledge ◽  
Gravity Data ◽  
Maximum Depth ◽  
Gravity Models ◽  
Tyrrhenian Sea ◽  
Po Plain ◽  
Reflection Seismic ◽  
Adriatic Plate ◽  
The North

The recent advances in experimental petrography together with the information derived from the super-deep drilling projects have provided additional constraints for the interpretation of refraction and reflection seismic data. These constraints can also be used in the interpretation of magnetic and gravity data to resolve nonuniqueness. In this study, we re-interpret the magnetic and gravity data of the Italian peninsula and neighbouring areas. In view of the constraints mentioned above, it is now possible to find an agreement between the seismic and gravity models of the Central Alps. By taking into account the overall crustal thickness, we have recognized the existence of three types of Moho: 1) European which extends to the north and west of the peninsula and in the Corsican-Sardinian block. Its margin was the foreland in the Alpine Orogeny and it was the ramp on which European and Adriatic mantle and crustal slices were overthrusted. This additional load caused bending and deepening and the Moho which now lies beneath the Adriatic plate reaching a maximum depth of approximately 75 km. 2) Adriatic (or African) which lies beneath the Po plain, the Apennines and the Adriatic Sea. The average depth of the Moho is about 30-35 km below the Po plain and the Adriatic Sea and it increases toward the Alps and the Tyrrhenian Sea (acting as foreland along this margin). The maximum depth (50 km) is reached in Calabria. 3) Pery-Tyrrhenian. This is an oceanic or thinned continental crust type of Moho. It borders the oceanic Moho of the Tyrrhenian Sea and it acquires a transitional character in the Ligurian and Provençal basins (<15 km thickness) while further thickening occurs toward the East where the Adriatic plate is overthrusted. In addition, the interpretation of the heat flow data appears to confirm the origin of this Moho and its geodynamic allocation.

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