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Publisher: Ke Ai   (Total: 15 journals)   [Sort by number of followers]

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Advances in Climate Change Research     Open Access   (Followers: 12, SJR: 0.321, h-index: 5)
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Non-coding RNA Research     Open Access  
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Plant Diversity     Open Access  
Synthetic and Systems Biotechnology     Open Access  
World J. of Otorhinolaryngology - Head and Neck Surgery     Open Access  
Journal Cover Geodesy and Geodynamics
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   ISSN (Print) 1674-9847
   Published by Ke Ai Homepage  [15 journals]
  • Earth crust vertical movements according to ITRF2000, ITRF2005, ITRF2008
           and ITRF2014 coordinate systems and their comparing analysis

    • Abstract: Publication date: Available online 8 January 2018
      Source:Geodesy and Geodynamics
      Author(s): N.A. Chujkova, T.G. Maximova, T.S. Chesnokova, A.N. Grushinsky


      PubDate: 2018-01-09T20:37:58Z
       
  • An efficiency algorithm on Gaussian mixture UKF for BDS/INS navigation
           system

    • Abstract: Publication date: Available online 29 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Qing Dai, Lifen Sui, Lingxuan Wang, Tian Zeng, Yuan Tian
      To further improve the performance of UKF (Unscented Kalman Filter) algorithm used in BDS/SINS (BeiDou Navigation Satellite System/Strap down Inertial Navigation System), an improved GM-UKF (Gaussian Mixture Unscented Kalman Filter) considering non-Gaussian distribution is discussed in this paper. This new algorithm using SVD (Singular Value Decomposition) is proposed to alternative covariance square root calculation in UKF sigma point production. And to end the rapidly increasing number of Gaussian distributions, PDF (Probability Density Function) re-approximation is conducted. In principle this efficiency algorithm proposed here can achieve higher computational speed compared with traditional GM-UKF. And simulation experiment result show that, compared with UKF and GM-UKF algorithm, new algorithm implemented in BDS/SINS tightly integrated navigation system is suitable for handling nonlinear/non-Gaussian integrated navigation position calculation, for its lower computational complexity with high accuracy.

      PubDate: 2018-01-09T20:37:58Z
       
  • Seismic-gravimetric analysis of the subducted Nazca plate between 32° S
           and 36° S

    • Abstract: Publication date: Available online 19 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Lujan Eckerman, Alejo Agüero, Silvana Spagnotto, Patricia Martinez, Silvina Nacif
      The study region is seismically and tectonically characterized by the angle variations in the subduction of the Nazca plate. The results obtained from earthquakes location between 32° and 36°S latitude and between 67° and 71°W longitude are presented in this work. The presence of a wedge of asthenospheric materials and the partial or total eclogitization of the subducted Nazca plate and its relation with isostatic cortex models published was analyzed. In addition, a gravimetric profile obtained from gravity forward modelling is presented at 33.5°S, proposing a new configuration at depths for the main tectonic components: Nazca plate, asthenospheric wedge and South American plate. Also, a new density scheme using recently published velocity models was obtained.

      PubDate: 2018-01-09T20:37:58Z
       
  • Within plate seismicity analysis in the segment between the high
           Cordillera and the Precordillera of northern Mendoza (Southern Central
           Andes)

    • Abstract: Publication date: Available online 18 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Julián Olivar, Silvina Nacif, Lucas Fennell, Andrés Folguera
      Crustal seismicity in northwestern Mendoza Province in Argentina, corresponding to the transition zone between the Chilean-Pampean flat subduction zone (26.5–33.5°S) and the Southern Central Andes normal subduction zone to the south, is studied in order to i) identify its relationship with the mapped structure, ii) determine deformational mechanisms and iii) constrain the geometry of the fold and thrust belt in the lower crust. Through this, we aim to determine which are the structures that contribute to Andean construction, east of the Frontal Cordillera in Argentina and at the western Principal Cordillera in Chile. Data from a temporary local seismic network are reprocessed in order to achieve a precise location of hypocenters and, whenever possible, to build focal mechanisms. Results are interpreted and compared with previous seismic studies and structural models. Analyzed seismicity is grouped around the eastern front of Frontal Cordillera, with hypocenters mainly at depths of 25–40 km. Contrastingly, earthquakes in the Principal Cordillera to the west are located at the axial Andean sector and Chilean slope, with depths shallower than 15 km. Obtained focal mechanisms indicate mainly strike-slip displacements, left lateral at Frontal Cordillera and right lateral at Principal Cordillera. Based on these observations, new possible structural models are proposed, where seismogenic sources could be either associated with inherited basement structures from the Cuyania-Chilenia suture; or correspond to deep-blind thrusts linked with a deeper-than-previously-assumed decollement that could be shared between Frontal Cordillera and western Precordillera. This deeper decollement would coincide in turn with the one determined from receiver function analysis for the eastern Sierras Pampeanas in previous works, potentially implying a common decollement all through the fold and thrust belt configuration. Apart from this, a new interpretation of seismogenic structures in Principal Cordillera near the Argentina–Chile boundary is provided.

      PubDate: 2018-01-09T20:37:58Z
       
  • Preliminary study of gravimetric anomalies in the Magallanes-Fagnano fault
           system, South America

    • Abstract: Publication date: Available online 15 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Juan Manuel Alcacer, María Romina Onorato, Laura P. Perucca, Silvia Miranda
      The main objective of this research is to recognize several geological structures associated with the shear zones of the MFFS (Magallanes – Fagnano fault system) by the analysis and interpretation of gravimetric anomalies. Besides, to compare the gravimetrical response of the cortical blocks that integrate the region under study, which is related to the different morphotectonic domains recognized in the region. This research was developed employing data obtained from World Gravity 1.0, which includes earth and satellite gravity data derived from the EGM2008 model. The study and interpretation of the MFFS from the analysis and processing of the gravimetric data, allowed appreciation of a noticeable correlation with the most superficial cortical structure.

      PubDate: 2018-01-09T20:37:58Z
       
  • Depth to the bottom of magnetic layer in South America and its
           relationship to Curie isotherm, Moho depth and seismicity behavior

    • Abstract: Publication date: Available online 15 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Javier Idárraga-García, Carlos A. Vargas
      We have estimated the DBML (depth to the bottom of the magnetic layer) in South America from the inversion of magnetic anomaly data extracted from the EMAG2 grid. The results show that the DBML values, interpreted as the Curie isotherm, vary between ∼10 and ∼60 km. The deepest values (>∼45) are mainly observed forming two anomalous zones in the central part of the Andes Cordillera. To the east of the Andes, in most of the stable cratonic area of South America, intermediate values (between ∼25 and ∼45 km) are predominant. The shallowest values (<∼25 km) are present in northwestern corner of South America, southern Patagonia, and in a few sectors to the east of the Andes Cordillera. Based on these results, we estimated the heat flow variations along the study area and found a very good correlation with the DBML. Also striking is the observation that the thermal anomalies of low heat flow are closely related to segments of flat subduction, where the presence of a cold and thick subducting oceanic slab beneath the continent, with a virtual absence of hot mantle wedge, leads to a decrease in the heat transfer from the deeper parts of the system. After comparing our results with the Moho depths reported by other authors, we have found that the Curie isotherm is deeper than Moho in most of the South American Platform (northward to ∼20°S), which is located in the stable cratonic area at the east of the Andes. This is evidence that the lithospheric mantle here is magnetic and contributes to the long wavelength magnetic signal. Also, our results support the hypothesis that the Curie isotherm may be acting as a boundary above which most of the crustal seismicity is concentrated. Below this boundary the occurrence of seismic events decreases dramatically.

      PubDate: 2018-01-09T20:37:58Z
       
  • Goce derived geoid changes before the Pisagua 2014 earthquake

    • Abstract: Publication date: Available online 13 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Orlando Álvarez, Mario Gimenez, Andrés Folguera, Sofia Guillen, Claudia Tocho
      The analysis of space – time surface deformation during earthquakes reveals the variable state of stress that occurs at deep crustal levels, and this information can be used to better understand the seismic cycle. Understanding the possible mechanisms that produce earthquake precursors is a key issue for earthquake prediction. In the last years, modern geodesy can map the degree of seismic coupling during the interseismic period, as well as the coseismic and postseismic slip for great earthquakes along subduction zones. Earthquakes usually occur due to mass transfer and consequent gravity variations, where these changes have been monitored for intraplate earthquakes by means of terrestrial gravity measurements. When stresses and correspondent rupture areas are large, affecting hundreds of thousands of square kilometres (as occurs in some segments along plate interface zones), satellite gravimetry data become relevant. This is due to the higher spatial resolution of this type of data when compared to terrestrial data, and also due to their homogeneous precision and availability across the whole Earth. Satellite gravity missions as GOCE can map the Earth gravity field with unprecedented precision and resolution. We mapped geoid changes from two GOCE satellite models obtained by the direct approach, which combines data from other gravity missions as GRACE and LAGEOS regarding their best characteristics. The results show that the geoid height diminished from a year to five months before the main seismic event in the region where maximum slip occurred after the Pisagua Mw = 8.2 great megathrust earthquake. This diminution is interpreted as accelerated inland-directed interseismic mass transfer before the earthquake, coinciding with the intermediate degree of seismic coupling reported in the region. We highlight the advantage of satellite data for modelling surficial deformation related to pre-seismic displacements. This deformation, combined to geodetical and seismological data, could be useful for delimiting and monitoring areas of higher seismic hazard potential.

      PubDate: 2018-01-09T20:37:58Z
       
  • Identification of expected seismic activity areas by forecasting complex
           seismic-mode parameters in Uzbekistan

    • Abstract: Publication date: Available online 8 December 2017
      Source:Geodesy and Geodynamics
      Author(s): T.U. Artikov, R.S. Ibragimov, T.L. Ibragimova, M.A. Mirzaev


      PubDate: 2018-01-09T20:37:58Z
       
  • Rayleigh waves from correlation of seismic noise in Great Island of Tierra
           del Fuego, Argentina: Constraints on upper crustal structure

    • Abstract: Publication date: Available online 7 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Carolina Buffoni, Martin Schimmel, Nora Cristina Sabbione, María Laura Rosa, Gerardo Connon
      In this study, the ambient seismic noise cross-correlation technique is applied to estimate the upper structure of the crust beneath Great Island of Tierra del Fuego (TdF), Argentina, by the analysis of short-period Rayleigh wave group velocities. The island, situated in the southernmost South America, is a key area of investigation among the interaction between the South American and Scotia plates and is considered as a very seismically active one. Through cross-correlating the vertical components of ambient seismic noise registered at four broadband stations in TdF, we were able to extract Rayleigh waves which were used to estimate group velocities in the period band of 2.5–16 s using a time-frequency analysis. Although ambient noise sources are distributed inhomogeneously, robust empirical Green's functions could be recovered from the cross-correlation of 12 months of ambient noise. The observed group velocities were inverted considering a non-linear iterative damped least-squares inversion procedure and several 1-D shear wave velocity models of the upper crust were obtained. According to the inversion results, the S-wave velocity ranges between 1.75 and 3.7 km/s in the first 10 km of crust, depending on the pair of stations considered. These results are in agreement to the major known surface and sub-surface geological and tectonic features known in the area. This study represents the first ambient seismic noise analysis in TdF in order to constraint the upper crust beneath this region. It can also be considered as a successful feasibility study for future analyses with a denser station deployment for a more detailed imaging of structure.

      PubDate: 2018-01-09T20:37:58Z
       
  • Anomalously deep earthquakes related to the Ojo de Agua Lineament and its
           tectonic significance, Sierras Pampeanas of Córdoba, Central Argentina

    • Abstract: Publication date: Available online 6 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Ana Caro Montero, Roberto D. Martino, Alina B. Guereschi
      The Sierras de Córdoba are the easternmost uplifted ranges of the Sierras Pampeanas geological province of Argentina. They are composed of a Neoproterozoic–Paleozoic basement arranged in north–south aligned mountain ranges, limited by west-vergent reverse faults, reactivated or formed by compressive tectonics during the Andean orogeny. The ranges are also affected by oblique subvertical lineaments, probably related to pan-Gondwanan structures. The recorded seismicity shows anomalously deep earthquakes (up to 80 km depth) concentrated in the northwestern area. We attribute this seismicity to the current tectonic activity of the Ojo de Agua Lineament. This lineament is a N130º–135° strike, 70º–80° NE dip, macrostructure with more than 80 km depth and 160 km length. A sinistral transcompressional kinematics (convergent oblique shear) is deduced by the focal mechanism of a deep earthquake, together with hydrological and geomorphological features strongly modified. The continental lithosphere under the Sierras de Córdoba would be colder and more rigid than in a normal subduction area, due to the retraction of the asthenospheric wedge to the foreland, causing seismicity to depths greater than 40 km, below the Mohorovičić discontinuity. Neogene volcanism would be closely related to this lineament, allowing the rapid ascent of melts from the mantle.

      PubDate: 2018-01-09T20:37:58Z
       
  • Seismic hazard analysis for central-western Argentina

    • Abstract: Publication date: Available online 6 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Salvador Daniel Gregori, Rodolfo Christiansen
      In this study, we present a PSHA (Probabilistic Seismic Hazard Analysis) for the city of San Juan, which is located in the central-western region of Argentina (30°S–35.5°S; 66.5°W–71°W). In addition to crustal earthquakes provided by catalogues, recent paleoseismological and neotectonic investigations have permitted to consider events which occurred during the last 400 years. Four seismogenic sources that could cause damages to the studied site corresponding to Precordillera, Western Sierras Pampeanas, Basement of the Cuyana Basin and Cordillera Principal were identified. Based on the evaluation of the contribution of these sources, maximum moment magnitudes above 7.5 (Mw) are expected. High values of SA (spectral acceleration) (0.2 and 1 s periods) and PGA (peak ground acceleration) were found in the city of San Juan, which suggests that it is located in a zone of high seismic hazard. Finally, the obtained SA spectra were compared with the seismic-resistant construction standards of Argentina INPRES-CIRSOC 103 [1]. Results suggest that for the city of San Juan and for a return period of 475 years, it covers the seismic requirements of the structures.

      PubDate: 2018-01-09T20:37:58Z
       
  • Letter from guest editor to all the readers

    • Abstract: Publication date: Available online 6 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Silvana Liz Spagnotto


      PubDate: 2018-01-09T20:37:58Z
       
  • GRACE time-varying gravity field solutions based on PANDA software

    • Abstract: Publication date: Available online 1 December 2017
      Source:Geodesy and Geodynamics
      Author(s): Xiang Guo, Qile Zhao
      The conventional dynamic approach for gravity filed modelling has been implemented in the PANDA (Position and Navigation Data Analyst) software. A variant of the so-called ‘two-step’ method for gravity field modelling is adopted for this purpose, where the GRACE (Gravity Recovery and Climate Experiment) orbits are derived from the GPS (Global Positioning System) data in a first step followed by a simultaneous determination of dynamic orbit and gravity filed from the GPS-derived orbits and K-band range-rate measurements in a second step. In this way, the monthly gravity field solutions complete to degree and order 96 are produced for the period Jan. 2005 to Dec. 2010. Their performance is assessed by comparing them with the official solutions, i.e., CSR RL05, GFZ RL05a and JPL RL05. A comparison in the spectral domain in terms of geoid heights reveals that the obtained solutions present the smallest degree amplitudes at degree 30–75. A further analysis of mass changes in the spatial domain demonstrates that the main signals observed from the obtained solutions are in great agreement with those from the official solutions. Remarkably, the correlation coefficients of mass changes in large river basins from the official solutions with respect to those from the obtained solutions are all above 0.97. These results demonstrate that the obtained solutions are comparable to the official solutions.

      PubDate: 2018-01-09T20:37:58Z
       
  • Probabilistic seismic hazard assessment of Kazakhstan and Almaty city in
           peak ground accelerations

    • Abstract: Publication date: Available online 28 November 2017
      Source:Geodesy and Geodynamics
      Author(s): N.V. Silacheva, U.K. Kulbayeva, N.A. Kravchenko
      As for many post-soviet countries, Kazakhstan's building code for seismic design was based on a deterministic approach. Recently, Kazakhstan seismologists are engaged to adapt the PSHA (probabilistic hazard assessment) procedure to the large amount of available geological, geophysical and tectonic Kazakh data and to meet standard requirements for the Eurocode 8. The new procedure has been used within National projects to develop the Probabilistic GSZ (General Seismic Zoning) maps of the Kazakhstan territory and the SMZ (Probabilistic Seismic Microzoning) maps of Almaty city. They agree with the seismic design principles of Eurocode 8 and are expressed in terms of not only seismic intensity, but also engineering parameters (peak ground acceleration PGA). The whole packet of maps has been developed by the Institute of Seismology, together with other Kazakhstan Institutions. Our group was responsible for making analysis in PGA. The GSZ maps and hazard assessment maps for SMZ in terms of PGA for return periods 475 and 2475 years are considered in the article.

      PubDate: 2018-01-09T20:37:58Z
       
  • Interpretation of the west segment of the coastal fault zone in the
           coastal region of South China based on the gravity data

    • Abstract: Publication date: Available online 24 November 2017
      Source:Geodesy and Geodynamics
      Author(s): Lisi Bi, Zhenhuan Ren, Xiuwei Ye, Tianyou Liu, Jihua Qiao
      By systemic processing, comprehensive analysis, and interpretation of gravity data, we confirmed the existence of the west segment of the coastal fault zone (west of Yangjiang to Beibu Bay) in the coastal region of South China. This showed an apparent high gravity gradient in the NEE direction, and worse linearity and less compactness than that in the Pearl River month. This also revealed a relatively large curvature and a complicated gravity structure. In the finding images processed by the gravity data system, each fault was well reflected and primarily characterized by isolines or thick black stripes with a cutting depth greater than 30 km. Though mutually cut by NW-trending and NE-trending faults, the apparent NEE stripe-shaped structure of the west segment of the coastal fault zone remained unchanged, with good continuity and an activity strength higher than that of NW and NE-trending faults. Moreover, we determined that the west segment of the coastal fault zone is the major seismogenic structure responsible for strong earthquakes in the coastal region in the border area of Guangdong, Guangxi, and Hainan.

      PubDate: 2018-01-09T20:37:58Z
       
  • On rotational normal modes of the Earth: Resonance, excitation,
           convolution, deconvolution and all that

    • Abstract: Publication date: November 2017
      Source:Geodesy and Geodynamics, Volume 8, Issue 6
      Author(s): Benjamin Fong Chao
      Earth's Coriolis force profoundly alters the eigen frequencies, eigen functions, and excitation of rotational normal modes. Some rotational modes of the solid mantle-fluid outer core-solid inner core Earth system are confirmed observationally and some remain elusive. Here we bring together from literature assertions about an excited resonance system in terms of the Green's function and temporal convolution. We raise caveats against taking the face values of the oscillational motion which have been “masqueraded” by the convolution, necessitating deconvolution for retrieving the excitation function which reflects the true variability. Lastly we exemplify successful applications of the deconvolution in estimating resonance complex frequencies.

      PubDate: 2018-01-09T20:37:58Z
       
  • IGS polar motion measurement accuracy

    • Abstract: Publication date: November 2017
      Source:Geodesy and Geodynamics, Volume 8, Issue 6
      Author(s): Jim Ray, Paul Rebischung, Jake Griffiths
      We elaborate an error budget for the long-term accuracy of IGS (International Global Navigation Satellite System Service) polar motion estimates, concluding that it is probably about 25–30 μas (1-sigma) overall, although it is not possible to quantify possible contributions (mainly annual) that might transfer directly from aliases of subdaily rotational tide errors. The leading sources are biases arising from the need to align daily, observed terrestrial frames, within which the pole coordinates are expressed and which are continuously deforming, to the secular, linear international reference frame. Such biases are largest over spans longer than about a year. Thanks to the very large number of IGS tracking stations, the formal covariance errors are much smaller, around 5 to 10 μas. Large networks also permit the systematic frame-related errors to be more effectively minimized but not eliminated. A number of periodic errors probably also influence polar motion results, mainly at annual, GPS (Global Positioning System) draconitic, and fortnightly periods, but their impact on the overall error budget is unlikely to be significant except possibly for annual tidal aliases. Nevertheless, caution should be exercised in interpreting geophysical excitations near any of the suspect periods.

      PubDate: 2018-01-09T20:37:58Z
       
  • Atmospheric acceleration and Earth-expansion deceleration of the Earth
           rotation

    • Abstract: Publication date: November 2017
      Source:Geodesy and Geodynamics, Volume 8, Issue 6
      Author(s): Wenbin Shen, Sung-Ho Na
      Previous studies suggest that tidal friction gives rise to the secular deceleration of the Earth rotation by a quantity of about 2.25 ms/cy. Here we just consider additional contributions to the secular Earth rotation deceleration. Atmospheric solar semi-diurnal tide has a small amplitude and certain amount of phase lead. This periodic global air-mass excess distribution exerts a quasi-constant torque to accelerate the Earth's spin rotation. Using an updated atmospheric tide model, we re-estimate the amounts of this atmospheric acceleration torque and corresponding energy input, of which the associated change rate in LOD (length of day) is −0.1 ms/cy. In another aspect, evidences from space-geodesy and sea level rise observations suggest that Earth expands at a rate of 0.35 mm/yr in recent decades, which gives rise to the increase of LOD at rate of 1.0 ms/cy. Hence, if the previous estimate due to the tidal friction is correct, the secular Earth rotation deceleration due to tidal friction and Earth expansion should be 3.15 ms/cy.

      PubDate: 2018-01-09T20:37:58Z
       
  • Investigation of the different weight models in Kalman filter: A case
           study of GNSS monitoring results

    • Abstract: Publication date: Available online 1 November 2017
      Source:Geodesy and Geodynamics
      Author(s): Roman Shults, Andriy Annenkov
      During geodetic monitoring with GNSS technology one of important steps is the correct processing and analysis of the measured displacements. We used the processing method of Kalman filter smoothing algorithm, which allows to evaluate not only displacements, but also the speed, acceleration, and other characteristics of the deformation model. One of the important issues is the calculation of the observations weight matrix in the Kalman filter. Recurrence algorithm of Kalman filtering can calculate and specify the weights during processing. However, the weights obtained in such way do not always exactly correspond to the actual observation accuracy. We established the observations weights based on the accuracy of baseline measurements. In the presented study, we offered and investigated different models of establishing the accuracy of the baselines. The offered models and the processing of the measured displacements were tested on an experimentally geodetic GNSS network. The research results show that despite of different weight models, changing weights up to 2 times do not change Kalman filtering accuracy extremely. The significant improvements for Kalman filtering accuracy for baselines shorter than 10 km were not got. Therefore, for typical GNSS monitoring networks with baseline range 10–15 km, we recommend to use any kind of models. The compulsory condition for getting correct and reliable results is checking results on blunders. For baselines, which are longer than 15 km we propose to use weight model which include baseline standard deviation from network adjustment and corrections for baseline length and its accuracy.

      PubDate: 2017-11-06T07:37:07Z
       
  • Application of S-transform threshold filtering in Anhui experiment airgun
           sounding data de-noising

    • Abstract: Publication date: Available online 16 October 2017
      Source:Geodesy and Geodynamics
      Author(s): Chenglong Zheng, Xiaofeng Tian, Zhuoxin Yang, Shuaijun Wang, Zhenyu Fan
      As a relatively new method of processing non-stationary signal with high time-frequency resolution, S transform can be used to analyze the time-frequency characteristics of seismic signals. It has the following characteristics: its time-frequency resolution corresponding to the signal frequency, reversible inverse transform, basic wavelet that does not have to meet the permit conditions. We combined the threshold method, proposed the S-transform threshold filtering on the basis of S transform time-frequency filtering, and processed airgun seismic records from temporary stations in “Yangtze Program” (the Anhui experiment). Compared with the results of the bandpass filtering, the S transform threshold filtering can improve the signal to noise ratio (SNR) of seismic waves and provide effective help for first arrival pickup and accurate travel time. The first arrival wave seismic phase can be traced farther continuously, and the Pm seismic phase in the subsequent zone is also highlighted.

      PubDate: 2017-10-21T20:57:03Z
       
  • Comparative study on vertical deformation based on GPS and leveling data

    • Abstract: Publication date: Available online 16 October 2017
      Source:Geodesy and Geodynamics
      Author(s): Shanlan Qin, Wenping Wang, Shangwu Song
      The development of GPS (Global Positioning System) technology has led to increasingly widely and successful applications of GPS surveys for monitoring crustal movements. However, multi-period GPS survey solutions have not been applied in monitoring vertical crustal movements with normal backgrounds. In this paper, we carried out a comparative study on the vertical deformation of the comprehensive profile of the cross-fault zone in Shanyin, Shanxi province, China, based on GPS and precise leveling observation data for multiple time periods. The vertical deformation rates observed with repeating GPS survey are obviously different (over 20 mm/y at some sites) from those with repeating leveling survey within a relatively short period. However, the deviations in the vertical displacement between GPS and leveling in a long-term survey (over three years) showed good consistency at 3–4 mm/y at most sites, on GPS forced offset surveying and fixed survey instruments in a long-term survey (over three years). Therefore, GPS vertical displacement results can be applied to the study of vertical crustal movements.

      PubDate: 2017-10-21T20:57:03Z
       
  • Bathymetry predicting using the altimetry gravity anomalies in South China
           Sea

    • Abstract: Publication date: Available online 6 October 2017
      Source:Geodesy and Geodynamics
      Author(s): Zhongmiao Sun, Mingda Ouyang, Bin Guan
      In South China Sea (112°E–119°E, 12°N–20°N), 81159 ship soundings published by NGDC (National Geophysics Data Center) and the altimetry gravity anomalies published by SIO (Scripps Institute of Oceanography) were used to predict bathymetry by GGM (gravity-geologic method) and SAS (Smith and Sandwell) method respectively. The residual 40576 ship soundings were used to estimate precisions of the predicted bathymetry models. Results showed that: the standard deviation of difference between the GGM model and ship soundings was 59.75 m and the relative accuracy was 1.86%. The SAS model is 60.07 m and 1.87%. The power spectral densities of the ETOPO1, SIO, GGM and SAS models were also compared and analyzed. At last, we presented an integrated bathymetry model by weighted averaging method, the weighted factors were determined by precisions of the ETOPO1, SIO, GGM, and SAS model respectively.

      PubDate: 2017-10-06T21:55:27Z
       
  • Geological inferences about the upper crustal configuration of the
           

    • Abstract: Publication date: Available online 15 August 2017
      Source:Geodesy and Geodynamics
      Author(s): Jose David Henao Casas, Gaspar Monsalve
      In regions of complex geology and tectonic assembly, strong motion seismic arrival time records can be used to test the plausibility of existing hypothesis about the origin of lithological and tectonic features and how they are related in space and time. In this study we use differential travel time residuals at some strong motion accelerographic stations in the Medellin – Aburrá Valley, in the northern Central Cordillera of the Colombian Andes, to discuss some aspects of the geological configuration. We based our work on the hypothesis that the differences between seismic travel time residuals among pairs of stations are a function of the differences in the surface geology and the near-surface upper crustal configuration. Our results are consistent with the volcanic rocks of the Quebradagrande Complex being less mafic, more weathered or more tectonically affected than previously thought, with the presence of a relatively thin dunite body on top of the metamorphic basement, and with a large lateral heterogeneity in the mainly mafic San Diego Stock.

      PubDate: 2017-08-31T17:21:39Z
       
  • Geological inferences about the upper crustal configuration of the
           

    • Abstract: Publication date: Available online 12 August 2017
      Source:Geodesy and Geodynamics
      Author(s): Jose David Henao Casas, Gaspar Monsalve
      In regions of complex geology and tectonic assembly, strong motion seismic arrival time records can be used to test the plausibility of existing hypothesis about the origin of lithological and tectonic features and how they are related in space and time. In this study we use differential travel time residuals at some strong motion accelerographic stations in the Medellin – Aburrá Valley, in the northern Central Cordillera of the Colombian Andes, to discuss some aspects of the geological configuration. We based our work on the hypothesis that the differences between seismic travel time residuals among pairs of stations are a function of the differences in the surface geology and the near-surface upper crustal configuration. Our results are consistent with the volcanic rocks of the Quebradagrande Complex being less mafic, more weathered or more tectonically affected than previously thought, with the presence of a relatively thin dunite body on top of the metamorphic basement, and with a large lateral heterogeneity in the mainly mafic San Diego Stock.

      PubDate: 2017-08-31T17:21:39Z
       
  • Seasonal features of topside scale height based on COSMIC measurements

    • Abstract: Publication date: Available online 9 August 2017
      Source:Geodesy and Geodynamics
      Author(s): Fanfan Su, Jian Lin, Fuying Zhu, Yiyan Zhou, Jian Yang, Liangchen Hu
      Plasma scale height is an important parameter of topside ionosphere and contains information about ionospheric physics and dynamic. We investigated the seasonal features of vertical scale height with the electron density profiles from COSMIC. We found that vertical scale height around 660 km at middle latitudes generally has larger values in winter than in summer and had similar structures at March Equinox and September Equinox no matter daytime or nighttime. Bands of large vertical scale height appear at night around ±36° magnetic latitude in all seasons except summer for low solar activity, and mostly appear in winter for moderate solar activity. Vertical scale height in the middle latitudes generally has smaller values for moderate solar activity than that for low solar activity around 660 km, and has smaller values in the daytime than at night.

      PubDate: 2017-08-31T17:21:39Z
       
  • A combined method for high-speed rail seismic monitoring and early warning

    • Abstract: Publication date: Available online 1 August 2017
      Source:Geodesy and Geodynamics
      Author(s): Zhigao Chen, Jun Huang
      The ground motion characteristics include the strength, frequency spectrum and duration time. In China, the PGA (peak ground acceleration) is commonly used in determination of whether an earthquake warning is necessary when the high-speed train is on the rail. This method has not given an earthquake early warning time, and it only considers the strength factor of an earthquake, so the system may release an alarm for the near and small earthquakes which are no destructive. The new alarm method reconciles the timeliness and stability. It issues a P wave warning when the system receives seismic wave first, which will make the train to decelerate. Then, the system will confirm whether the P wave alarm is correct using the joint alarm result of CAV (cumulative absolute velocity) and PGA, and then take measures according to the result. The new method eliminates the interference from the near and small earthquakes, as well as the large and far earthquakes, and ensures the safety of the train when it is subjected to earthquakes. In this paper, we use seismic data to simulate the combined alarm of CAV and PGA, and then obtain the cumulative time of CAV and the time interval between CAV and PGA. Finally, we compare the new method with the double-station, earthquake monitoring alarm method which is currently used on China's high-speed rail, and find the new alarm method is better in the aspect of alarm timeliness.

      PubDate: 2017-08-31T17:21:39Z
       
  • Spectral investigation of traveling ionospheric disturbances: IONOLAB-FFT

    • Abstract: Publication date: Available online 25 July 2017
      Source:Geodesy and Geodynamics
      Author(s): Feza Arikan, Aysenur Yarici
      Ionosphere is an important layer of atmosphere which is under constant forcing from both below due to gravitational, geomagnetic and seismic activities, and above due to solar wind and galactic radiation. Spatio-temporal variability of ionosphere is made up of two major components that can be listed as spatio-temporal trends and secondary variabilities that are due to disturbances in the geomagnetic field, gravitational waves and coupling of seismic activities into the upper atmosphere and ionosphere. Some of these second order variabilities generate wave-like oscillations in the ionosphere which propagate at a certain frequency, duration and velocity. These oscillations cause major problems for navigation and guidance systems that utilize GNSS (Global Navigation Satellite Systems). In this study, the frequency and duration of wave-like oscillations are determined using a DFT (Discrete Fourier Transform) based algorithm over the STEC (slant total electron content) values estimated from single GPS (Global Positioning System) station. The performance of the developed method, namely IONOLABFFT, is first determined using synthetic oscillations with known frequencies and durations. Then, IONOLAB-FFT is applied to STEC data from various midlatitude GPS stations for detection of frequency and duration of both medium and large scale TIDs (traveling ionospheric disturbances). It is observed that IONOLAB-FFT can estimate TIDs with more than 80% accuracy for the following cases: frequencies from 0.6 mHz to 2.4 mHz and durations longer than 10 min; frequencies from 0.15 mHz to 0.6 mHz and durations longer than 50 min; frequencies higher than 0.29 mHz and durations longer than 50 min.

      PubDate: 2017-07-27T14:16:54Z
       
  • Damping modification factors for acceleration response spectra

    • Abstract: Publication date: Available online 23 June 2017
      Source:Geodesy and Geodynamics
      Author(s): Heng Li, Feng Chen
      DMF (Damping modification factors) are used to modify elastic response spectral values corresponding to damping ratio 5% to other damping levels. The influence of seismological parameters (magnitude, epicentral distances and site conditions) on DMF for acceleration spectra was analysed. The results show that for a given period as the magnitude or distance increase, the effect of damping on the seismic response will also increase, which indicates the response reduction from the structural damping will become more efficient. In the near-field of small earthquakes, the influence of site conditions on DMF is obvious, but it does not show a consistent rule. Furthermore, the DMF corresponding to different site conditions gradually close to unity with increasing magnitude and distance. The influence of the above mentioned parameters is related to the relative attenuation of the frequency components of the ground motion. The attenuation index alone is sufficient to take into account the influence. Based on these features, this paper proposes a formula of DMF for acceleration response spectra.

      PubDate: 2017-07-03T17:07:44Z
       
  • Evaluation of ASTER GDEM in the northeastern margin of Tibetan Plateau in
           gravity reduction

    • Abstract: Publication date: Available online 20 June 2017
      Source:Geodesy and Geodynamics
      Author(s): Guoqing Zhang, Wenbin Shen, Yiqing Zhu, Ying Wang, Yawen She
      In this paper, we first transferred the normal height of ASTER GDEM v2 to GPS ellipsoidal height based on the EGM96, and analyzed the precision of this digital elevation model in the northeastern margin of Tibetan Plateau (NETP) combining with 89 ground GPS measurements. The results demonstrate that the standard deviation of the difference between ASTER GDEM and GPS results is 9.3 m, and the precision of ASTER GDEM in this region is approximately 10 m. We also calculated the free-air gravity anomalies using the relative gravity data and DEM model in NETP. The results show that the gravity anomalies are generally negative with local positive values, ranging from −156 to 43 mGal (10−5 m/s2). At last, we compared the EGM2008 free-air gravity anomalies (FGAs) with the ground gravity measurements, and their spatial patterns are similar. While the point-to-point difference between the modeling and measuring results shows great discrepancy. The free-air gravity anomalies of EGM2008 in this region range from −154 to 96 mGal, and the difference between EGM2008 and the ground measurements ranges from −102 to 50 mGal. The mean difference is −17.34 mGal, and the standard deviation is 46.69 mGal, which demonstrates that the EGM2008 has poor precision in the northeastern margin of Tibet Plateau.

      PubDate: 2017-06-21T15:27:49Z
       
  • Multichannel singular spectrum analysis of the axial atmospheric angular
           momentum

    • Abstract: Publication date: Available online 16 June 2017
      Source:Geodesy and Geodynamics
      Author(s): Leonid Zotov, N.S. Sidorenkov, Ch. Bizouard, C.K. Shum, Wenbin Shen
      Earth's variable rotation is mainly produced by the variability of the atmospheric angular momentum (AAM). In particular, the axial AAM component χ 3, which undergoes especially strong variations, induces changes in the Earth's rotation rate. In this study we analysed maps of regional input into the effective axial AAM from 1948 through 2011 from NCEP/NCAR reanalysis. Global zonal circulation patterns related to the length of day (LOD) were described. We applied Multichannel Singular Spectrum Analysis (MSSA) jointly to the mass and motion components of AAM, which allowed us to extract annual, semiannual, 4-month, quasi-biennial, 5-year, and low-frequency oscillations. Principal components (PCs) strongly related to El nino southern oscillation (ENSO) were released. They can be used to study ENSO-induced changes in pressure and wind fields and their coupling to LOD. The PCs describing the trends have captured slow atmospheric circulation changes possibly related to climate variability.

      PubDate: 2017-06-21T15:27:49Z
       
  • Basic Earth's Parameters as estimated from VLBI observations

    • Abstract: Publication date: Available online 13 June 2017
      Source:Geodesy and Geodynamics
      Author(s): Ping Zhu, Attilio Rivoldini, Laurence Koot, Veronique Dehant
      The global Very Long Baseline Interferometry observation for measuring the Earth rotation's parameters was launched around 70 t h . Since then the precision of the measurements is continuously improving by taking into account various instrumental and environmental effects. The MHB2000 nutation model was introduced in 2002, which is constructed based on a revised nutation series derived from 20 years VLBI observations (1980–1999). In this work, we firstly estimated the amplitudes of all nutation terms from the IERS-EOP-C04 VLBI global solutions w.r.t. IAU1980, then we further inferred the Basic Earth's Parameters (BEPs) by fitting the major nutation terms. Meanwhile, the BEPs were obtained from the same nutation time series using a Bayesian Inversion (BI). The corrections to the precession rate and the estimated BEPs are in an agreement, independent of which methods have been applied.

      PubDate: 2017-06-16T15:07:08Z
       
  • Improved geophysical excitations constrained by polar motion observations
           and GRACE/SLR time-dependent gravity

    • Abstract: Publication date: Available online 5 June 2017
      Source:Geodesy and Geodynamics
      Author(s): Wei Chen, Jiancheng Li, Jim Ray, Minkang Cheng
      At seasonal and intraseasonal time scales, polar motions are mainly excited by angular momentum fluctuations due to mass redistributions and relative motions in the atmosphere, oceans, and continental water, snow, and ice, which are usually provided by various global atmospheric, oceanic, and hydrological models (some with meteorological observations assimilated; e.g., NCEP, ECCO, ECMWF, OMCT and LSDM etc.). Unfortunately, these model outputs are far from perfect and have notable discrepancies with respect to polar motion observations, due to non-uniform distributions of meteorological observatories, as well as theoretical approximations and non-global mass conservation in these models. In this study, the Least Difference Combination (LDC) method is adopted to obtain some improved atmospheric, oceanic, and hydrological/crospheric angular momentum (AAM, OAM and HAM/CAM, respectively) functions and excitation functions (termed as the LDCgsm solutions). Various Gravity Recovery and Climate Experiment (GRACE) and Satellite Laser Ranging (SLR) geopotential data are adopted to correct the non-global mass conservation problem, while polar motion data are used as general constraints. The LDCgsm solutions can reveal not only periodic fluctuations but also secular trends in AAM, OAM and HAM/CAM, and are in better agreement with polar motion observations, reducing the unexplained excitation to the level of about 5.5 mas (standard derivation value; about 1/5–1/4 of those corresponding to the original model outputs).

      PubDate: 2017-06-10T13:43:13Z
       
  • Evaluation of the geopotential value W0LVD of China

    • Abstract: Publication date: Available online 1 June 2017
      Source:Geodesy and Geodynamics
      Author(s): Lin He, Yonghai Chu, Nan Yu
      Estimation of the zero-height geopotential value W 0 LVD for the China Vertical Datum (CVD) plays a fundamental role in the connection of traditional height reference systems into a global height system. Estimation the W 0 LVD of China is based on the computation of the mean geopotential offset between the value W 0 = 62636856.0 m2s−2, selected as reference in this study, and the unknown geopotential value W 0 LVD. This estimation is based on the combination of ellipsoidal heights, levelled heights (referring to the CVD), and some physical parameters, such as geopotential values, gravity values, and geoid undulations. The geoid undulations derived from the Global Geopotential Models (GGM). This combination is performed through three approaches: The first one is based on the theory of Molodensky, and the second one compares levelled heights and geopotential values derived from the GGMs, while the third one analyses the differences between GPS/Levelling and GGMs geoid undulations. The approaches are evaluated at 65 benchmarks (BMs) covered around Qingdao where the tide gauge is used to observe the local mean sea level of China. The results from three approaches are very similar. Furthermore, the W 0 LVD determined for the China local vertical datum was 62636852.9462 m2s−2, indicates a bias of about 3.0538 m2/s−2 compared to the conventional value of 62636856.0 m2s−2.

      PubDate: 2017-06-05T12:36:41Z
       
  • Ionospheric forecasting model using fuzzy logic-based gradient descent
           method

    • Abstract: Publication date: Available online 26 May 2017
      Source:Geodesy and Geodynamics
      Author(s): D. Venkata Ratnam, G. Vindhya, J.R.K. Kumar Dabbakuti
      Space weather phenomena cause satellite to ground or satellite to aircraft transmission outages over the VHF to L-band frequency range, particularly in the low latitude region. Global Positioning System (GPS) is primarily susceptible to this form of space weather. Faulty GPS signals are attributed to ionospheric error, which is a function of Total Electron Content (TEC). Importantly, precise forecasts of space weather conditions and appropriate hazard observant cautions required for ionospheric space weather observations are limited. In this paper, a fuzzy logic-based gradient descent method has been proposed to forecast the ionospheric TEC values. In this technique, membership functions have been tuned based on the gradient descent estimated values. The proposed algorithm has been tested with the TEC data of two geomagnetic storms in the low latitude station of KL University, Guntur, India (16.44°N, 80.62°E). It has been found that the gradient descent method performs well and the predicted TEC values are close to the original TEC measurements.

      PubDate: 2017-05-29T12:09:59Z
       
  • Earth gravity field solution with combining CHAMP and GRACE data

    • Abstract: Publication date: Available online 19 May 2017
      Source:Geodesy and Geodynamics
      Author(s): Tianhe Xu, Lei Ren, Ruru Gao
      Satellite gravity data fusion with multi-type and huge-amount is one of the hot topics in physical geodesy. After a brief review of dynamic approach, the CHAMP-only and GRACE-only gravity fields by using HL-SST and LL-SST data from 2003 to 2009 are recovered respectively. An combination strategy of CHAMP and GRACE data by using Helmert variance component estimation (VCE) is proposed based on normal equation level fusion. Three gravity field models with 150° and order by CHAMP-only data, GRACE-only data and combining CHAMP and GRACE data from 2003 to 2009 are recovered. The comparisons between our recovered models and those latest released models were performed. The external accuracy validations using marine gravity anomalies from DTU13 products and height anomalies from GPS/leveling data are also conducted in this paper. The results show that long-term CHAMP data do contribute to the accuracy improvement of gravity field solution. The accuracy of the combined model using CHAMP and GRACE data is better than those of the individuals and comparative to the models published by international groups.

      PubDate: 2017-05-23T11:59:44Z
       
  • Depositional setting analysis using seismic sedimentology: Example from
           the Paleogene Lishagang sequence in the Fushan depression, South China Sea
           

    • Abstract: Publication date: Available online 17 May 2017
      Source:Geodesy and Geodynamics
      Author(s): Yuan Li, Song Lin, Hua Wang, Denggui Luo
      The Fushan depression is a classic lacustrine rifted sub-basin in the Beibuwan Basin, South China Sea. The Paleogene Liushagang sequence is the main hydrocarbon-bearing stratigraphic unit in the depression. Using three-dimensional (3-D) seismic data and logging data, we analyzed depositional setting of the Liushagang sequence. We use wave impedance inversion to describe progradational directions of provenance and the general distribution of sand body. The seismic facies was analyzed by using the seismic sedimentology approach based on 3-D seismic data, and summed into eight types of seismic facies which could be well related to sedimentary facies. Seismic attributes with six objective sequence boundaries were extracted. Consequently, four provenance system of Liushagang sequence in the study area were confirmed by the corresponding relationship between the geologic information and the warm color and higher value area of seismic attributes: (i) the Hainan uplift provenance area in the south, (ii) the Linggao uplift provenance area in the west, (iii) the Yunlong uplift provenance area in the east and (iv) the northern provenance area. The seismic sedimentology used in this study may provide new insights into a better understanding of depositional setting in continental lacustrine rifted basins.

      PubDate: 2017-05-23T11:59:44Z
       
  • Understanding the effects of the core on the nutation of the Earth

    • Abstract: Publication date: Available online 16 May 2017
      Source:Geodesy and Geodynamics
      Author(s): Véronique Dehant, Raphael Laguerre, Jérémy Rekier, Attilio Rivoldini, Santiago Andres Triana, Antony Trinh, Tim Van Hoolst, Ping Zhu
      In this review paper, we examine the changes in the Earth orientation in space and focus on the nutation (shorter-term periodic variations), which is superimposed on precession (long-term trend on a timescale of years). We review the nutation modelling involving several coupling mechanisms at the core-mantle boundary using the Liouville angular momentum equations for a two-layered Earth with a liquid flattened core. The classical approach considers a Poincaré fluid for the core with an inertial pressure coupling mechanism at the core-mantle boundary. We examine possible additional coupling mechanisms to explain the observations. In particular, we examine how we can determine the flattening of the core as well as information on the magnetic field and the core flow from the nutation observations. The precision of the observations is shown to be high enough to increase our understanding on the coupling mechanisms at the core-mantle boundary.

      PubDate: 2017-05-17T11:28:14Z
       
  • Characteristics of isostatic gravity anomaly in Sichuan-Yunnan region,
           China

    • Abstract: Publication date: Available online 3 May 2017
      Source:Geodesy and Geodynamics
      Author(s): Bingcheng Liu, Yiyan Zhou, Guangliang Yang
      Sichuan-Yunnan region, a tectonic transition belt where earthquakes occurred frequently and intensely, has a distinct variation characteristic of gradient zone of Bouguer gravity anomaly (BGA). Many deep faults and epicenters of severe earthquake scatter along the BGA gradient zones. Here we apply two forward models (Airy model and Vening Meinesz model) of isostatic gravity mechanisms (local versus regional) in this region to calculated the isostatic gravity anomalies (IGA). Afterwards, the relationship between IGA and distribution of faults as well as seismicity is also illustrated. The IGA results show that the two models are similar and most parts of the study area are in an isostatic state. Most featured faults are distributed along the steep anomaly gradient zones; earthquakes tend to occur in the non-isostatic area and steep gradient belt of IGA. The distribution of root thickness based on regional mechanism can be associated with the main trend of BGA variation. The regional mechanism is more plausible and closer to the reality because of its relatively further consideration of the horizontal forces derived from adjacent particles in the crust. Then we analyze the effect of isostasy on the tectonic movements and find that the isostatic adjustment is not the main cause of the continuous uplift process of Longmenshan Mountain fault zone, which is due to the Indian-Eurasian continental collision.

      PubDate: 2017-05-06T10:44:46Z
       
  • Study on ionosphere change over Shandong based from SDCORS in 2012

    • Abstract: Publication date: Available online 29 April 2017
      Source:Geodesy and Geodynamics
      Author(s): Jinyun Guo, Zhenghua Dong, Zhimin Liu, Jijun Mao, Haiping Zhang
      Temporal and spatial variation of ionosphere can influence our daily communication activities. By solving the one-year global positioning system (GPS) data of Shandong Continuous Operational Reference System (SDCORS) in 2012, we modeled the single-layer spherical harmonic model of vertical total electron content (TEC) over Shandong Province, China, and analyzed the time series of TEC in 2012. The ionosphere over Shandong in 2012 was in the peak year of solar activity. The ionospheric model over Shandong was calibrated and verified using data of the Center for Orbit Determination in Europe (CODE) and the Crustal Movement Observation Network of China (CMONOC), respectively. The ionosphere is greatly influenced by latitude and solar activity and has the phenomenon of Winter anomaly and semi-annual anomaly as well as the session change, diurnal variation, monthly change and seasonal variations. So we can grasp the regularity of temporal and spatial distribution of ionosphere over Shandong, China.

      PubDate: 2017-05-06T10:44:46Z
       
 
 
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