scholarly journals New insights on the dynamics of the Sumatra and Mariana complexes inferred from the comparative analysis of gravity data and model predictions

2020 ◽  
Author(s):  
Arcangela Bollino ◽  
Anna Maria Marotta ◽  
Federica Restelli ◽  
Alessandro Regorda ◽  
Roberto Sabadini
Keyword(s):  
Comparative Analysis ◽  
Gravity Field ◽  
Wide Spectrum ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Phase Changes ◽  
Wide Range ◽  
Model Predictions ◽  
Dip Angle ◽  
The Masses

<p>Subduction is responsible for surface displacements and deep mass redistribution. This rearrangement generates density anomalies in a wide spectrum of wavelengths which, in turn, causes important anomalies in the Earth's gravity field that are visible as lineaments parallel to the arc-trench systems. In these areas, when the traditional analysis of the deformation and stress fields is combined with the analysis of the perturbation of the gravity field and its slow time variation, new information on the background environment controlling the tectonic loading phase can be disclosed.</p><p>Here we present the results of a comparative analysis between the geodetically retrieved gravitational anomalies, based on the EIGEN-6C4 model, and those predicted by a 2D thermo-chemical mechanical modeling of the Sumatra and Mariana complexes.</p><p>The 2D model accounts for a wide range of parameters, such as the convergence velocity, the shallow dip angle, the different degrees of coupling between the facing plates. The marker in cell technique is used to compositionally differentiate the system. Phase changes in the crust and in the mantle and mantle hydration are also allowed. To be compliant with the geodetic EIGEN-6C4 gravity data, we define a model normal Earth considering the vertical density distribution at the margins of the model domain, where the masses are not perturbed by the subduction process.</p><p>Model predictions are in good agreement with data, both in terms of wavelengths and magnitude of the gravity anomalies measured in the surroundings of the Sumatra and Marina subductions. Furthermore, our modeling supports that the differences in the style of the gravity anomaly observed in the two areas are attributable to the different environments – ocean-ocean or ocean-continental subduction – that drives a significantly different dynamic in the wedge area.</p>

scholarly journals The static and time-dependent signature of ocean–continent and ocean–ocean subduction: the case studies of Sumatra and Mariana complexes

2020 ◽  
Vol 221 (2) ◽  
pp. 788-825 ◽  
Author(s):  
A M Marotta ◽  
F Restelli ◽  
A Bollino ◽  
A Regorda ◽  
R Sabadini
Keyword(s):  
Subduction Zones ◽  
Gravity Data ◽  
Phase Changes ◽  
Small Scale ◽  
Wide Range ◽  
Anomalous Density ◽  
Dip Angle ◽  
Disturbance Pattern ◽  
Different Characteristics ◽  
Gravitational Disturbance

SUMMARY The anomalous density structure at subduction zones, both in the wedge and in the upper mantle, is analysed to shed light on the processes that are responsible for the characteristic gravity fingerprints of two types of subduction: ocean–continent and ocean–ocean. Our modelling is then performed within the frame of the EIGEN-6C4 gravitational disturbance pattern of two subductions representative of the above two types, the Sumatra and Mariana complexes, finally enabling the different characteristics of the two patterns to be observed and understood on a physical basis, including some small-scale details. A 2-D viscous modelling perpendicular to the trench accounts for the effects on the gravity pattern caused by a wide range of parameters in terms of convergence velocity, subduction dip angle and lateral variability of the crustal thickness of the overriding plate, as well as compositional differentiation, phase changes and hydration of the mantle. Plate coupling, modelled within a new scheme where the relative velocity at the plate contact results self-consistently from the thermomechanical evolution of the system, is shown to have an important impact on the gravity signature. Beyond the already understood general bipolar fingerprint of subduction, perpendicular to the trench, we obtain the density and gravity signatures of the processes occurring within the wedge and mantle that are responsible for the two different gravity patterns. To be compliant with the geodetic EIGEN-6C4 gravitational disturbance and to compare our predictions with the gravity at Sumatra and Mariana, we define a model normal Earth. Although the peak-to-peak gravitational disturbance is comparable for the two types of subductions, approximately 250 mGal, from both observations and modelling, encompassing the highest positive maximum on the overriding plates and the negative minimum on the trench, the trough is wider for the ocean–ocean subduction: approximately 300 km compared to approximately 180 km for the ocean–continent subduction. Furthermore, the gravitational disturbance pattern is more symmetric for the ocean–ocean subduction compared to the ocean–continent subduction in terms of the amplitudes of the two positive maxima over the overriding and subducting plates. Their difference is, for the ocean–ocean type, approximately one half of the ocean–continent one. These different characteristics of the two types of subductions are exploited herein in terms of the different crustal thicknesses of the overriding plate and of the different dynamics in the wedge and in the mantle for the two types of subduction, in close agreement with the gravity data.

Towards an updated, enhanced regional gravity field solution for Antarctica

2021 ◽  
Author(s):  
Mirko Scheinert ◽  
Philipp Zingerle ◽  
Theresa Schaller ◽  
Roland Pail ◽  
Martin Willberg
Keyword(s):  
Gravity Anomaly ◽  
Gravity Field ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Data Set ◽  
Gravity Field Model ◽  
Terrestrial Gravity ◽  
Field Solution ◽  
Gravity Disturbances ◽  
Regional Gravity

<p>In the frame of the IAG Subcommission 2.4f “Gravity and Geoid in Antarctica” (AntGG) a first Antarctic-wide grid of ground-based gravity anomalies was released in 2016 (Scheinert et al. 2016). That data set was provided with a grid space of 10 km and covered about 73% of the Antarctic continent. Since then a considerably amount of new data has been made available, mainly collected by means of airborne gravimetry. Regions which were formerly void of any terrestrial gravity observations and have now been surveyed include especially the polar data gap originating from GOCE satellite gravimetry. Thus, it is timely to come up with an updated and enhanced regional gravity field solution for Antarctica. For this, we aim to improve further aspects in comparison to the AntGG 2016 solution: The grid spacing will be enhanced to 5 km. Instead of providing gravity anomalies only for parts of Antarctica, now the entire continent should be covered. In addition to the gravity anomaly also a regional geoid solution should be provided along with further desirable functionals (e.g. gravity anomaly vs. disturbance, different height levels).</p><p>We will discuss the expanded AntGG data base which now includes terrestrial gravity data from Antarctic surveys conducted over the past 40 years. The methodology applied in the analysis is based on the remove-compute-restore technique. Here we utilize the newly developed combined spherical-harmonic gravity field model SATOP1 (Zingerle et al. 2019) which is based on the global satellite-only model GOCO05s and the high-resolution topographic model EARTH2014. We will demonstrate the feasibility to adequately reduce the original gravity data and, thus, to also cross-validate and evaluate the accuracy of the data especially where different data set overlap. For the compute step the recently developed partition-enhanced least-squares collocation (PE-LSC) has been used (Zingerle et al. 2021, in review; cf. the contribution of Zingerle et al. in the same session). This method allows to treat all data available in Antarctica in one single computation step in an efficient and fast way. Thus, it becomes feasible to iterate the computations within short time once any input data or parameters are changed, and to easily predict the desirable functionals also in regions void of terrestrial measurements as well as at any height level (e.g. gravity anomalies at the surface or gravity disturbances at constant height).</p><p>We will discuss the results and give an outlook on the data products which shall be finally provided to present the new regional gravity field solution for Antarctica. Furthermore, implications for further applications will be discussed e.g. with respect to geophysical modelling of the Earth’s interior (cf. the contribution of Schaller et al. in session G4.3).</p>

scholarly journals Evaluation of Gravity Data Derived from Global Gravity Field Models Using Terrestrial Gravity Data in Enugu State, Nigeria

2018 ◽  
Vol 8 (1) ◽  
pp. 145-153 ◽  
Author(s):  
O.I. Apeh ◽  
E.C. Moka ◽  
V.N. Uzodinma
Keyword(s):  
Gravity Field ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Mean Square ◽  
Bouguer Gravity ◽  
Bouguer Anomalies ◽  
The Earth ◽  
Global Gravity ◽  
Enugu State ◽  
Gravity Field Models

Abstract Spherical harmonic expansion is a commonly applied mathematical representation of the earth’s gravity field. This representation is implied by the potential coeffcients determined by using elements/parameters of the field observed on the surface of the earth and/or in space outside the earth in the spherical harmonic expansion of the field. International Centre for Gravity Earth Models (ICGEM) publishes, from time to time, Global Gravity Field Models (GGMs) that have been developed. These GGMs need evaluation with terrestrial data of different locations to ascertain their accuracy for application in those locations. In this study, Bouguer gravity anomalies derived from a total of eleven (11) recent GGMs, using sixty sample points, were evaluated by means of Root-Mean-Square difference and correlation coeficient. The Root-Mean-Square differences of the computed Bouguer anomalies from ICGEMwebsite compared to their positionally corresponding terrestrial Bouguer anomalies range from 9.530mgal to 37.113mgal. Additionally, the correlation coe_cients of the structure of the signal of the terrestrial and GGM-derived Bouguer anomalies range from 0.480 to 0.879. It was observed that GECO derived Bouguer gravity anomalies have the best signal structure relationship with the terrestrial data than the other ten GGMs. We also discovered that EIGEN-6C4 and GECO derived Bouguer anomalies have enormous potential to be used as supplements to the terrestrial Bouguer anomalies for Enugu State, Nigeria.

scholarly journals GRAVITY ANOMALY ASSESSMENT USING GGMS AND AIRBORNE GRAVITY DATA TOWARDS BATHYMETRY ESTIMATION

2016 ◽  
Vol XLII-4/W1 ◽  
pp. 287-297
Author(s):  
A. Tugi ◽  
A. H. M. Din ◽  
K. M. Omar ◽  
A. S. Mardi ◽  
Z. A. M. Som ◽  
...  
Keyword(s):  
Gravity Anomaly ◽  
Gravity Field ◽  
Ocean Circulation ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Airborne Gravity ◽  
Satellite Gravity ◽  
Earth’S Gravity Field ◽  
Explorer Mission ◽  
Satellite Gravity Missions

The Earth’s potential information is important for exploration of the Earth’s gravity field. The techniques of measuring the Earth’s gravity using the terrestrial and ship borne technique are time consuming and have limitation on the vast area. With the space-based measuring technique, these limitations can be overcome. The satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), and Gravity-Field and Steady-State Ocean Circulation Explorer Mission (GOCE) has introduced a better way in providing the information on the Earth’s gravity field. From these satellite gravity missions, the Global Geopotential Models (GGMs) has been produced from the spherical harmonics coefficient data type. The information of the gravity anomaly can be used to predict the bathymetry because the gravity anomaly and bathymetry have relationships between each other. There are many GGMs that have been published and each of the models gives a different value of the Earth’s gravity field information. Therefore, this study is conducted to assess the most reliable GGM for the Malaysian Seas. This study covered the area of the marine area on the South China Sea at Sabah extent. Seven GGMs have been selected from the three satellite gravity missions. The gravity anomalies derived from the GGMs are compared with the airborne gravity anomaly, in order to figure out the correlation (R<sup>2</sup>) and the root mean square error (RMSE) of the data. From these assessments, the most suitable GGMs for the study area is GOCE model, GO_CONS_GCF_2_TIMR4 with the R<sup>2</sup> and RMSE value of 0.7899 and 9.886 mGal, respectively. This selected model will be used in the estimating the bathymetry for Malaysian Seas in future.

scholarly journals Comparative Analysis of Dynamic Plasticity Models

2018 ◽  
Vol 57 (2) ◽  
pp. 199-211 ◽  
Author(s):  
N.S. Selyutina ◽  
Yu.V. Petrov
Keyword(s):  
Plastic Deformation ◽  
Comparative Analysis ◽  
Wide Spectrum ◽  
High Rate ◽  
Relaxation Model ◽  
Time Model ◽  
Slow Dynamic ◽  
Stress Strain Relation ◽  
Wide Range ◽  
Deformation Models

Abstract In the paper, a new phenomenological interpretation of some of the principal temporal effects of high-rate plastic deformation of metals from a united viewpoint is represented. A comparative analysis of some of the well-known dynamic plastic deformation models is given. Influence of strain rate on the stress-strain relation in a wide range of strain rates for different types of aluminum alloys and steels is described by the relaxation model of plasticity, by original and improved empirical Johnson-Cook models, and by the phenomenological Rusinek-Klepaczko model. It is shown that the structural-time model (“the relaxation model of plasticity”) is capable to effectively predict a wide spectrum of materials responses to fast and slow dynamic loading.

scholarly journals Application of Radial Basis Functions for Height Datum Unification

Geosciences ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 369 ◽  
Author(s):  
Ismael Foroughi ◽  
Abdolreza Safari ◽  
Pavel Novák ◽  
Marcelo Santos
Keyword(s):  
Gravity Field ◽  
Satellite Altimetry ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Basis Functions ◽  
Gravity Potential ◽  
Field Modelling ◽  
Marine Gravity ◽  
Local Gravity ◽  
Local Gravity Field Modelling

Local gravity field modelling demands high-quality gravity data as well as an appropriate mathematical model. Particularly in coastal areas, there may be different types of gravity observations available, for instance, terrestrial, aerial, marine gravity, and satellite altimetry data. Thus, it is important to develop a proper tool to merge the different data types for local gravity field modelling and determination of the geoid. In this study, radial basis functions, as a commonly useful tool for gravity data integration, are employed to model the gravity potential field of the southern part of Iran using terrestrial gravity anomalies, gravity anomalies derived from re-tracked satellite altimetry, marine gravity anomalies, and gravity anomalies synthesized from an Earth gravity model. Reference GNSS/levelling (geometric) geoidal heights are used to evaluate the accuracy of the estimated local gravity field model. The gravimetric geoidal heights are in acceptable agreement with the geometric ones in terms of the standard deviation and the mean value which are 4.1 and 12 cm, respectively. Besides, the reference benchmark of the national first-order levelling network of Iran is located in the study area. The derived gravity model was used to compute the gravity potential difference at this point and then transformed into a height difference which results in the value of the shift of this benchmark with respect to the geoid. The estimated shift shows a good agreement with previously published studies.

scholarly journals Validation of GOCE global gravity field models using terrestrial gravity data in Norway

2012 ◽  
Vol 2 (2) ◽  
pp. 134-143 ◽  
Author(s):  
M. Šprlák ◽  
C. Gerlach ◽  
B. Pettersen
Keyword(s):  
Harmonic Analysis ◽  
Gravity Field ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Gravity Field Model ◽  
Terrestrial Gravity ◽  
Free Air ◽  
Global Gravity ◽  
Free Air Gravity ◽  
Gravity Field Models

Validation of GOCE global gravity field models using terrestrial gravity data in NorwayThe GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite gravity gradiometry mission maps the Earth's gravity field. Harmonic analysis of GOCE observations provides a global gravity field model (GGFM). Three theoretical strategies, namely the direct, the space-wise and the time-wise approach, have been proposed for GOCE harmonic analysis. Based on these three methods, several GGFMs have been provided to the user community by ESA. Thereby different releases are derived from different periods of GOCE observations and some of the models are based on combinations with other sources of gravity field information. Due to the multitude of GOCE GGFMs, validation against independent data is a crucial task for the quality description of the different models.In this study, GOCE GGFMs from three releases are validated with respect to terrestrial free-air gravity anomalies in Norway. The spectral enhancement method is applied to avoid spectral inconsistency between the terrestrial and the GOCE free-air gravity anomalies.The results indicate that the time-wise approach is a reliable harmonic analysis procedure in all three releases of GOCE models. The space-wise approach, available in two releases, provides similar results as the time-wise approach. The direct approach seems to be highly affected by a-priori information.

scholarly journals A Precise Geoid Model for Africa: AFRgeo2019

2020 ◽  
Author(s):  
Hussein A. Abd-Elmotaal ◽  
Norbert Kühtreiber ◽  
Kurt Seitz ◽  
Bernhard Heck
Keyword(s):  
Gravity Field ◽  
Reference Model ◽  
International Association ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Large Data ◽  
Geoid Undulation ◽  
Geopotential Model ◽  
Geoid Model ◽  
Data Gaps

Abstract In the framework of the IAG African Geoid Project, an attempt towards a precise geoid model for Africa is presented in this investigation. The available gravity data set suffers from significantly large data gaps. These data gaps are filled using the EIGEN-6C4 model on a 15′× 15′ grid prior to the gravity reduction scheme. The window remove-restore technique (Abd-Elmotaal and Kühtreiber, Phys Chem Earth Pt A 24(1):53–59, 1999; J Geod 77(1–2):77–85, 2003) has been used to generate reduced anomalies having a minimum variance to minimize the interpolation errors, especially at the large data gaps. The EIGEN-6C4 global model, complete to degree and order 2190, has served as the reference model. The reduced anomalies are gridded on a 5′× 5′ grid employing an un-equal weight least-squares prediction technique. The reduced gravity anomalies are then used to compute their contribution to the geoid undulation employing Stokes’ integral with Meissl (Preparation for the numerical evaluation of second order Molodensky-type formulas. Ohio State University, Department of Geodetic Science and Surveying, Rep 163, 1971) modified kernel for better combination of the different wavelengths of the earth’s gravity field. Finally the restore step within the window remove-restore technique took place generating the full gravimetric geoid. In the last step, the computed geoid is fitted to the DIR_R5 GOCE satellite-only model by applying an offset and two tilt parameters. The DIR_R5 model is used because it turned out that it represents the best available global geopotential model approximating the African gravity field. A comparison between the geoid computed within the current investigation and the existing former geoid model AGP2003 (Merry et al., A window on the future of geodesy. International Association of Geodesy Symposia, vol 128, pp 374–379, 2005) for Africa has been carried out.

scholarly journals COMPUTATION OF GRAVITY FIELD FUNCTIONALS WITH A LOCALIZED LEVEL ELLIPSOID

2021 ◽  
Vol 6 (24) ◽  
pp. 226-242
Author(s):  
Chivatsi Jonathan Nyoka ◽  
Ami Hassan Md Din ◽  
Muhammad Faiz Pa’suya
Keyword(s):  
Gravity Field ◽  
Spherical Harmonic ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Earth’S Gravity Field ◽  
Geopotential Models ◽  
Gravity Disturbances ◽  
Zero Degree ◽  
Equipotential Surfaces ◽  
Best Fit

The description of the earth’s gravity field is usually expressed in terms of spherical harmonic coefficients, derived from global geopotential models. These coefficients may be used to evaluate such quantities as geoid undulations, gravity anomalies, gravity disturbances, deflection of the vertical, etc. To accomplish this, a global reference normal ellipsoid, such as WGS84 and GRS80, is required to provide the computing reference surface. These global ellipsoids, however, may not always provide the best fit of the local geoid and may provide results that are aliased. In this study, a regional or localized geocentric level ellipsoid is used alongside the EGM2008 to compute gravity field functionals in the state of Johor. Residual gravity field quantities are then computed using GNSS-levelled and raw gravity data, and the results are compared with both the WGS84 and the GRS80 equipotential surfaces. It is demonstrated that regional level ellipsoids may be used to compute gravity field functionals with a better fit, provided the zero-degree spherical harmonic is considered. The resulting residual quantities are smaller when compared with those obtained with global ellipsoids. It is expected that when the remove-compute-restore method is employed with such residuals, the numerical quadrature of the Stoke’s integral may be evaluated on reduced gravity anomalies that are smoother compared to when global equipotential surfaces are used

Cucurbitacins as Anticancer Agents: A Patent Review

2019 ◽  
Vol 14 (2) ◽  
pp. 133-143 ◽  
Author(s):  
Hidayat Hussain ◽  
Ivan R. Green ◽  
Muhammad Saleem ◽  
Khanzadi F. Khattak ◽  
Muhammad Irshad ◽  
...  
Keyword(s):  
Anticancer Agents ◽  
Wide Spectrum ◽  
Biological Effects ◽  
Therapeutic Effects ◽  
Cytotoxic Effects ◽  
Natural Sources ◽  
Oh Groups ◽  
Drug Candidates ◽  
The Past ◽  
Wide Range

Background: Cucurbitacins belong to a group of tetracyclic triterpenoids that display a wide range of biological effects. In the past, numerous cucurbitacins have been isolated from natural sources and many active compounds have been synthesized using the privileged scaffold in order to enhance its cytotoxic effects. Objective: his review covers patents on the therapeutic effects of natural cucurbitacins and their synthetic analogs published during the past decade. By far, the majority of patents published are related to cancer and Structure-Activity Relationships (SAR) of these compounds are included to lend gravitas to this important class of natural products. Methods: The date about the published patents was downloaded via online open access patent databases. Results: Cucurbitacins display significant cytotoxic properties, in particular cucurbitacins B and D which possess very potent effects towards a number of cancer cells. Numerous cucurbitacins isolated from natural sources have been derivatized through chemical modification at the C(2)-OH and C(25)- OH groups. Most importantly, an acyl ester of the C(25)-OH and, iso-propyl, n-propyl and ethyl ether groups of the C(2)-OH demonstrated the most increased cytotoxic activity. Conclusion: The significant cytotoxic effects of natural and semi-synthetic cucurbitacins make them attractive as new drug candidates. Moreover, cucurbitacins have the capability to form conjugates with other anticancer drugs which will synergistically enhance their anticancer effects. The authors believe that in order to get lead compounds, there should be a greater focus on the synthesis of homodimers, heterodimers, and halo derivatives of cucurbitacins. In the opinion of the authors the analysis of the published patents on the cucurbitacins indicates that these compounds can be developed into a regimen to treat a wide spectrum of cancers.

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