scholarly journals A New Moho Depth Model for Fennoscandia with Special Correction for the Glacial Isostatic Effect

2021 ◽  
Author(s):  
M. Abrehdary ◽  
L. E. Sjöberg
Keyword(s):  
Mean Value ◽  
Crustal Thickening ◽  
Moho Depth ◽  
Data Sets ◽  
Gravity Disturbance ◽  
Value Differences ◽  
Isostatic Adjustment ◽  
Crustal Model ◽  
Vening Meinesz ◽  
Specific Correction

AbstractIn this study, we present a new Moho depth model in Fennoscandia and its surroundings. The model is tailored from data sets of XGM2019e gravitationl field, Earth2014 topography and seismic crustal model CRUST1.0 using the Vening Meinesz-Moritz model based on isostatic theory to a resolution of 1° × 1°. To that end, the refined Bouguer gravity disturbance is determined by reducing the observed field for gravity effect of topography, density heterogeneities related to bathymetry, ice, sediments, and other crustal components. Moreover, stripping of non-isostatic effects of gravity signals from mass anomalies below the crust due to crustal thickening/thinning, thermal expansion of the mantle, Delayed Glacial Isostatic Adjustment (DGIA), i.e., the effect of future GIA, and plate flexure has also been performed. As Fennoscandia is a key area for GIA research, we particularly investigate the DGIA effect on the gravity disturbance and gravimetric Moho depth determination in this area. One may ask whether the DGIA effect is sufficiently well removed in the application of the general non-isostatic effects in such an area, and to answer this question, the Moho depth is determined both with and without specific removal of the DGIA effect prior to non-isostatic effect and Moho depth determinations. The numerical results yield that the RMS difference of the Moho depth from our model HVMD19 vs. the seismic CRUST19 and GRAD09 models are 3.8/4.2 km and 3.7/4.0 km when the above strategy for removing the DGIA effect is/is not applied, respectively, and the mean value differences are 1.2/1.4 km and 0.98/1.4 km, respectively. Hence, our study shows that the specific correction for the DGIA effect on gravity disturbance is slightly significant, resulting in individual changes in the gravimetric Moho depth up to − 1.3 km towards the seismic results. On the other hand, our study shows large discrepancies between gravimetric and seismic Moho models along the Norwegian coastline, which might be due to uncompensated non-isostatic effects caused by tectonic motions.

A new Moho depth model for Fennoscandia and surroundings

2020 ◽  
Author(s):  
Majid Abrehdary ◽  
Lars Sjöberg
Keyword(s):  
Seismic Data ◽  
Earth Satellite ◽  
Mean Value ◽  
Crustal Thickening ◽  
Moho Depth ◽  
Gravity Disturbance ◽  
Satellite Gravity ◽  
Value Differences ◽  
Isostatic Adjustment ◽  
Vening Meinesz

<p>Seismic data are the preliminary information for investigating Earth’s interior structure. Since large parts of the world are not yet sufficiently covered by such data, products from Earth satellite gravity and altimetry missions can be used as complimentary for this purpose. This is particularly the case in most of the ocean areas, where seismic data are sparse. One important information of Earth’s interior is the crustal/Moho depth, which is widely mapped from seismic surveys. In this study, we aim at presenting a new Moho depth model from satellite altimetry derived gravity and seismic data in Fennoscandia and its surroundings using the Vening Meinesz-Moritz (VMM) model based on isostatic theory. To that end, the refined Bouguer gravity disturbance (reduced for gravity of topography, density heterogeneities related to bathymetry, ice, sediments, and other crustal components by applying so-called stripping gravity corrections) is corrected for so-called non-isostatic effects (NIEs) of nuisance gravity signals from mass anomalies below the crust due to crustal thickening/thinning, thermal expansion of the mantle, Delayed Glacial Isostatic Adjustment (DGIA) and plate flexure. As Fennoscandia is a key area for GIA research, we particularly investigate the DGIA effect on the gravity disturbance and Moho depth determination from gravity in this area. To do so, the DGIA effect is removed and restored from the NIEs prior to the application of the VMM formula. The numerical results show that the RMS difference of the Moho depth from the (mostly) seismic CRUST1.0 model is 3.6/4.3 km when the above strategy for removing the DGIA effect is/is not applied, respectively. Also, the mean value differences are 0.9 and 1.5 km, respectively. Hence, our study shows that our method of correcting for the DGIA effect on gravity disturbance is significant, resulting in individual changes in Moho depth up to several kilometres.</p>

scholarly journals On Moho Determination by the Vening Meinesz-Moritz Technique

2021 ◽  
Author(s):  
Lars Erik Sjöberg ◽  
Majid Abrehdary
Keyword(s):  
Least Squares ◽  
Moho Depth ◽  
Glacial Isostatic Adjustment ◽  
Altimetry Data ◽  
Satellite Gravity ◽  
Isostatic Adjustment ◽  
Uncertainty Estimates ◽  
Least Squares Adjustment ◽  
Moho Depths ◽  
Vening Meinesz

This chapter describes a theory and application of satellite gravity and altimetry data for determining Moho constituents (i.e. Moho depth and density contrast) with support from a seismic Moho model in a least-squares adjustment. It presents and applies the Vening Meinesz-Moritz gravimetric-isostatic model in recovering the global Moho features. Internal and external uncertainty estimates are also determined. Special emphasis is devoted to presenting methods for eliminating the so-called non-isostatic effects, i.e. the gravimetric signals from the Earth both below the crust and from partly unknown density variations in the crust and effects due to delayed Glacial Isostatic Adjustment as well as for capturing Moho features not related with isostatic balance. The global means of the computed Moho depths and density contrasts are 23.8±0.05 km and 340.5 ± 0.37 kg/m3, respectively. The two Moho features vary between 7.6 and 70.3 km as well as between 21.0 and 650.0 kg/m3. Validation checks were performed for our modeled crustal depths using a recently published seismic model, yielding an RMS difference of 4 km.

Geodetic observations for constraining mantle processes in Antarctica

2021 ◽  
pp. M56-2021-22
Author(s):  
Mirko Scheinert ◽  
Olga Engels ◽  
Ernst J. O. Schrama ◽  
Wouter van der Wal ◽  
Martin Horwath
Keyword(s):  
Data Sets ◽  
Satellite Mission ◽  
Amundsen Sea ◽  
Isostatic Adjustment ◽  
Geodynamic Processes ◽  
Grace Satellite ◽  
Mantle Processes ◽  
Gnss Measurements ◽  
The Individual ◽  
Seismic Deformation

AbstractGeodynamic processes in Antarctica such as glacial isostatic adjustment (GIA) and post-seismic deformation are measured by geodetic observations such as GNSS and satellite gravimetry. GNSS measurements have been comprising continuous measurements as well as episodic measurements since the mid-1990s. The estimated velocities typically reach an accuracy of 1 mm/a for horizontal and 2 mm/a for vertical velocities. However, the elastic deformation due to present-day ice-load change needs to be considered accordingly.Space gravimetry derives mass changes from small variations in the inter-satellite distance of a pair of satellites, starting with the GRACE satellite mission in 2002 and continuing with the GRACE-FO mission launched in 2018. The spatial resolution of the measurements is low (about 300 km) but the measurement error is homogeneous across Antarctica. The estimated trends contain signals from ice mass change, local and global GIA signal. To combine the strengths of the individual data sets statistical combinations of GNSS, GRACE and satellite altimetry data have been developed. These combinations rely on realistic error estimates and assumptions of snow density. Nevertheless, they capture signal that is missing from geodynamic forward models such as the large uplift in the Amundsen Sea sector due to low-viscous response to century-scale ice-mass changes.

Contribution of satellite altimetry in modelling Moho density contrast in oceanic areas

2019 ◽  
Vol 13 (1) ◽  
pp. 33-40 ◽  
Author(s):  
M. Abrehdary ◽  
L. E. Sjöberg ◽  
D. Sampietro
Keyword(s):  
Satellite Altimetry ◽  
Density Contrast ◽  
Contrast Model ◽  
Bathymetric Data ◽  
Crustal Model ◽  
Marine Gravity ◽  
Study Results ◽  
Vening Meinesz ◽  
Satellite Altimetry Data

Abstract The determination of the oceanic Moho (or crust-mantle) density contrast derived from seismic acquisitions suffers from severe lack of data in large parts of the oceans, where have not yet been sufficiently covered by such data. In order to overcome this limitation, gravitational field models obtained by means of satellite altimetry missions can be proficiently exploited, as they provide global uniform information with a sufficient accuracy and resolution for such a task. In this article, we estimate a new Moho density contrast model named MDC2018, using the marine gravity field from satellite altimetry in combination with a seismic-based crustal model and Earth’s topographic/bathymetric data. The solution is based on the theory leading to Vening Meinesz-Moritz’s isostatic model. The study results in a high-accuracy Moho density contrast model with a resolution of 1° × 1° in oceanic areas. The numerical investigations show that the estimated density contrast ranges from 14.2 to 599.7 kg/m3 with a global average of 293 kg/m3. In order to evaluate the accuracy of the MDC2018 model, the result was compared with some published global models, revealing that our altimetric model is able to image rather reliable information in most of the oceanic areas. However, the differences between this model and the published results are most notable along the coastal and polar zones, which are most likely due to that the quality and coverage of the satellite altimetry data are worsened in these regions.

scholarly journals Empirical estimation of present-day Antarctic glacial isostatic adjustment and ice mass change

2013 ◽  
Vol 7 (4) ◽  
pp. 3497-3541 ◽  
Author(s):  
B. C. Gunter ◽  
O. Didova ◽  
R. E. M. Riva ◽  
S. R. M. Ligtenberg ◽  
J. T. M. Lenaerts ◽  
...  
Keyword(s):  
Time Frame ◽  
Gravity Models ◽  
Mass Change ◽  
Data Sets ◽  
Glacial Isostatic Adjustment ◽  
Empirical Estimation ◽  
Satellite Gravity ◽  
Amundsen Sea ◽  
Average Value ◽  
Isostatic Adjustment

Abstract. This study explores an approach that simultaneously estimates Antarctic mass balance and glacial isostatic adjustment (GIA) through the combination of satellite gravity and altimetry data sets. The results improve upon previous efforts by incorporating reprocessed data sets over a longer period of time, and now include a firn densification model to account for firn compaction and surface processes. A range of different GRACE gravity models were evaluated, as well as a new ICESat surface height trend map computed using an overlapping footprint approach. When the GIA models created from the combination approach were compared to in-situ GPS ground station displacements, the vertical rates estimated showed consistently better agreement than existing GIA models. In addition, the new empirically derived GIA rates suggest the presence of strong uplift in the Amundsen Sea and Philippi/Denman sectors, as well as subsidence in large parts of East Antarctica. The total GIA mass change estimates for the entire Antarctic ice sheet ranged from 53 to 100 Gt yr−1, depending on the GRACE solution used, and with an estimated uncertainty of ±40 Gt yr−1. Over the time frame February 2003–October 2009, the corresponding ice mass change showed an average value of −100 ± 44 Gt yr−1 (EA: 5 ± 38, WA: −105 ± 22), consistent with other recent estimates in the literature, with the mass loss mostly concentrated in West Antarctica. The refined approach presented in this study shows the contribution that such data combinations can make towards improving estimates of present day GIA and ice mass change, particularly with respect to determining more reliable uncertainties.

Forward  Modelling of Bouguer Anomalies along a transect of the Southern Apennines and the Tyrrhenian back-arc basin.

2021 ◽  
Author(s):  
Assel Akimbekova ◽  
Paolo Mancinelli ◽  
Massimiliano Rinaldo Barchi ◽  
Cristina Pauselli ◽  
Giorgio Minelli
Keyword(s):  
Gravity Anomalies ◽  
Moho Depth ◽  
Positive Trend ◽  
Tyrrhenian Sea ◽  
Southern Apennines ◽  
Bouguer Anomalies ◽  
Crustal Model ◽  
Density Values ◽  
Best Fitting ◽  
Fitting Model

<p>Abstract</p><p> </p><p>In the present study, starting from original measurement stations, we created the Bouguer anomaly map of Southern Italy with a reduction density of 2670 kg m<sup>-3</sup>. We perform a regional gravity modelling at crustal scale along the trace of the CROP-04 (on-shore) and MB6 (off-shore) deep seismic reflection profiles crossing the Southern Apennines and the Southern Tyrrhenian Sea. Along the 320 km-long modelled profile, we investigate crustal-scale sources for the observed gravity anomalies. </p><p>After a compelling review of the published Moho geometries in the area, that were retrieved from either active or passive seismic methods, we test them in the observed gravity field through forward modeling of the Bouguer gravity anomalies. The comparison between the different Moho interpretations shows that the steepness of the subducting slab, the position of the step between the western (Tyrrhenian) and the eastern (Adriatic) Moho and Moho depth represent the main features influencing the observed Bouguer anomalies at crustal scale.</p><p>Finally, we provide a best-fitting model across both onshore and offshore areas. In the proposed best-fitting model, the wide wavelength and strong regional Bouguer anomalies correlate with the geometry of the Moho discontinuity and deep tectonic structures. On the other hand, the small-amplitude oscillations of the gravity anomalies were attributed to the low-density values of the Pliocene-Quaternary deposits both on- (e.g. the Bradanic trough) and off-shore (e.g. recent deposits in the Tyrrhenian sea bottom). Gravity minima correspond to the crustal doubling underneath the Southern Apennines where the Tyrrhenian Moho (~27 km depth) overlies the deeper Adriatic Moho (~50 km depth). The positive trend of the observed anomaly toward NE is related to the shallowing of the Adriatic Moho to depths of ~28 km in the Adriatic. Similarly, towards SW, the observed anomaly follows a positive trend towards the maxima located in the Central Tyrrhenian Sea. We model this trend as representative of crustal thinning and shallowing to values of ~12 km depth of the Tyrrhenian Moho. We also model a crustal transition from geometries and density values typical of a continental crust in the Adriatic domain towards a more oceanic structure and composition in the Tyrrhenian domain. This crustal model locates the westward flexure of the Adriatic Moho, mimicking the subduction of the Adriatic lithosphere beneath the Peri-Tyrrhenian block and locates step between the western (Tyrrhenian) and the eastern (Adriatic) Moho beneath the Apennines range.</p><p>The resulted gravity forward model provide contributions to the tectonic settings understanding of the area by providing a robust crustal model ranging from the Tyrrhenian Sea to the Apulian foreland.</p><p> Finally, we believe that the proposed model can serve as a starting point for future studies investigating the upper crustal geometries in the area and addressing open questions about its relations with seismicity distribution.</p><p> </p>

Characterization of HRV by Poincare Plot Analysis among the Female Tea Garden Workers of Northern Hilly Regions of West Bengal

2010 ◽  
Vol 5 (2) ◽  
pp. 49-59 ◽  
Author(s):  
Somsirsa Chatterjee ◽  
Ankur Ganguly ◽  
Saugat Bhattacharya
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Standard Deviation ◽  
West Bengal ◽  
Mean Value ◽  
Data Sets ◽  
Short Term ◽  
Poincaré Plot ◽  
Tea Garden

Recent research on Heart Rate Variability (HRV) has proven that Poincare Plot is a powerful tool to mark Short Term and Long Term Heart Rate Variability. This study focuses a comprehensive characterization of HRV among the Tea Garden Workers of the Northern Hilly Regions of West Bengal. The characterization, as available from the data sets, projects the average values of SD1 characteristics, that is, Short Term HRV in females as 58.265ms and SD2 as 149.474. The SDRR shows a mean value of 87.298 with a standard deviation of 119.669 and the S Characterization as 16505.99 ms and Standard deviation of 45882.31 ms. The SDRR shows a mean value of 87.298 with a standard deviation of 119.669 and the S Characterization as 16505.99 ms and Standard deviation of 45882.31 ms. ApEn Characterization showed mean value of 0.961 and standard deviation of 0.274.

scholarly journals Vertical Deflections and Gravity Disturbances Derived from HY-2A Data

2020 ◽  
Vol 12 (14) ◽  
pp. 2287
Author(s):  
Xiaoyun Wan ◽  
Richard Fiifi Annan ◽  
Shuanggen Jin ◽  
Xiaoqi Gong
Keyword(s):  
Gravity Field ◽  
Systematic Errors ◽  
Mean Value ◽  
Gravity Disturbance ◽  
Long Wavelength ◽  
The North ◽  
Marine Gravity ◽  
Gravity Disturbances ◽  
Sea Surface Heights ◽  
East Component

The first Chinese altimetry satellite, Haiyang-2A (HY-2A), which was launched in 2011, has provided a large amount of sea surface heights which can be used to derive marine gravity field. This paper derived the vertical deflections and gravity disturbances using HY-2A observations for the major area of the whole Earth’s ocean from 60°S and 60°N. The results showed that the standard deviations (STD) of vertical deflections differences were 1.1 s and 3.5 s for the north component and the east component between HY-2A’s observations and those from EGM2008 and EIGEN-6C4, respectively. This indicates the accuracy of the east component was poorer than that of the north component. In order to clearly demonstrate contribution of HY-2A’s observations to gravity disturbances, reference models and the commonly used remove-restore method were not adopted in this study. Therefore, the results can be seen as ‘pure’ signals from HY-2A. Assuming the values from EGM2008 were the true values, the accuracy of the gravity disturbances was about −1.1 mGal in terms of mean value of the errors and 8.0 mGal in terms of the STD. This shows systematic errors if only HY-2A observations were used. An index of STD showed that the accuracy of HY-2A was close to the theoretical accuracy according to the vertical deflection products. To verify whether the systematic errors of gravity field were from the long wavelengths, the long-wavelength parts of HY-2A’s gravity disturbance with wavelengths larger than 500 km were replaced by those from EGM2008. By comparing with ‘pure’ HY-2A version of gravity disturbance, the accuracy of the new version products was improved largely. The systematic errors no longer existed and the error STD was reduced to 6.1 mGal.

How Accurate is Qcbed ? -- the Case of Rutile (TiO2)

2001 ◽  
Vol 7 (S2) ◽  
pp. 368-369
Author(s):  
B. Jiang ◽  
J. Friis ◽  
J.C.H. Spence
Keyword(s):  
Systematic Errors ◽  
Mean Value ◽  
Order Structure ◽  
Data Sets ◽  
X Ray ◽  
Silicon Crystals ◽  
Structure Factors ◽  
The Mean ◽  
Mott Formula ◽  
Better Than

An accuracy of better than 1% is needed to measure the changes in charge density due to bonding. Here we report an accuracy up to 0.025% (random error) obtained in rutile crystal structure factors measurement by QCBED. This error is the standard deviation in the mean value obtained from ten data sets. Systematic errors may be present. Figure 1 gives an example of the (200) refinement results. Table 1 lists several low order structure factor refinement results. The accuracy of the measured electron structure factors was 0.1-0.2% but after conversion to x-ray structure factors, the accuracy for low orders improved due to the Mott formula [1] For (110) and (101) reflections, the accuracy in x-ray structure factors became 0.025% and 0.048% respectively. This accuracy is equivalent to that of the X-ray single crystal Pendellosung method on silicon crystals [2].The experiments were done on a Leo 912 Omega TEM.

Development of waste occurrence level indicator in Vietnam construction industry

2015 ◽  
Vol 22 (6) ◽  
pp. 715-731 ◽  
Author(s):  
Ha Duy Khanh ◽  
Soo Yong Kim
Keyword(s):  
Factor Analysis ◽  
Construction Industry ◽  
Construction Projects ◽  
Quantitative Information ◽  
Mean Value ◽  
Data Sets ◽  
Level Indicator ◽  
Content Type ◽  
Analysis Technique ◽  
Significant Difference

Purpose – The purpose of this paper is to evaluate the waste occurrence level in the construction industry. It includes: first, identifying the mean value of frequency of waste occurrence according to respondents’ characteristics; second, identifying the main predictive factors for waste occurrence based on latent relationships between initial waste factors; and third, identifying the waste occurrence-level indicator (WOLI) for the construction industry based on the main waste measurement factors. Design/methodology/approach – A total of 19 waste factors were sorted from the literature review. A structured questionnaire was adopted to carry out the survey. The respondents are professionals who have much experience in construction and management of project. Shapiro-Wilk test of normality, Levene’s test, ANOVA test, and factor analysis technique were used to analyze the collected data. Findings – Frequency of waste occurrence in construction projects is quite high. There was no statistically and practically significant difference in means for waste occurrence between selected population categories. Based on factor analysis technique, there were five principal components extracted with 56.7 percent of total variance. The WOLI in the construction industry was found as 61.55 per the scale of 100. Research limitations/implications – The non-probability sampling was applied to collect data because of several certain limitations and difficulties. The number of data sets is relatively small. This study has only examined the frequency of waste occurrence without quantitative information. Practical implications – This is another study of waste factors in the construction industry, which is different from traditional waste studies. Originality/value – The contribution of this study to the practical project management is that a proposed evaluation sheet for WOLI could be applied for any construction firm.

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