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

Showing 1 - 15 of 15 Journals sorted alphabetically
Advances in Climate Change Research     Open Access   (Followers: 14, SJR: 0.485, CiteScore: 1)
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Non-coding RNA Research     Open Access  
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Plant Diversity     Open Access  
Synthetic and Systems Biotechnology     Open Access   (SJR: 0.841, CiteScore: 0)
World J. of Otorhinolaryngology - Head and Neck Surgery     Open Access  
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Geodesy and Geodynamics
Journal Prestige (SJR): 0.469
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ISSN (Print) 1674-9847
Published by Ke Ai Homepage  [15 journals]
  • Detection of Earth's free oscillation excited by the Japan Mw9.0
           Earthquake using different tiltmeter and strainmeter

    • Abstract: Publication date: Available online 4 August 2018Source: Geodesy and GeodynamicsAuthor(s): Yan Zhang, Fangjie MengAbstractThe observatory network of the Crustal Deformation China Seismological Bureau was equipped with vertical pendulum tiltmeter, borehole tiltmeter, tunnel extension meters, multi-component borehole strainmeter, body strainmeter and other tilt and strain observation instruments. All of these instruments have recorded the Earth's free oscillation excited by the Japan Mw9.0 Earthquake. By analyzing those observations, all of the spheroidal oscillation modes (0S3—0S30) and toroidal oscillation modes (0T3—0T20) excited by the Japan Mw9.0 Earthquake were detected in this paper. In addition, comparing the different observation results which obtained by those instruments, we revealed their capacity to observe different kinds of oscillation and different frequency band modes, and analyzed report the reason. We found that the body strainmeter and the vertical pendulum tiltmeter have better observing results for spheroidal oscillation. Because of high noise in low frequency band, the borehole tiltmeter cannot observe the low-order spheroidal oscillation. In terms of observing the toroidal oscillation, the multi-component borehole strainmeter got a best result. The vertical pendulum tiltmeter observes a few toroidal oscillation modes, and the tunnel extension meters can only observe some low-order modes.
       
  • Isostatic anomaly characteristics and tectonism of the New Britain Trench
           and neighboring Papua New Guinea

    • Abstract: Publication date: Available online 4 August 2018Source: Geodesy and GeodynamicsAuthor(s): Guangliang Yang, Chongyang Shen, Jiapei Wang, Songbai Xuan, Guiju Wu, Hongbo TanAbstractIn this paper, we calculated Bouguer gravity anomalies and Airy-Heiskanen isostatic anomalies in the New Britain Trench and surrounding areas of Papua New Guinea. The calculations are based on a topographic model and a gravity anomaly model from the Scripps Institute of Oceanography. Characteristics of the isostatic anomaly and the earthquake dynamic environment of this region are analyzed, and the results show that there are obvious differences in the isostatic state between each block in the region. Tectonic movements are very intense in regions with high positive or negative isostatic gravity anomalies, and a number of sub-plates in this area are driven by external tectonic action, such as plate subduction and thrusting, of the Pacific, Indo-Australian and Eurasian plates. From the distribution of the isostatic gravity anomaly, the tectonic action of anti-isostatic movement obviously is the main source of power. Based on isostatic gravity and spatial distribution of earthquakes in the region, it is obvious that further contraction of the Indo-Australian Plate will result in the southwestern part of the Solomon Plate becoming part of the Owen Stanley thrust belt, and the northern part will enter the lower part of the Bismarck Plate. The eastern part of the Solomon Plate will enter the front of the Pacific Plate, resulting in northward and eastward migration of significant earthquakes along the Solomon Plate.
       
  • Anomalies of geomagnetic field related to natural and technogenic events
           in Charvak area

    • Abstract: Publication date: Available online 3 August 2018Source: Geodesy and GeodynamicsAuthor(s): V.R. YusupovAbstractBased on the long-term geomagnetic observations in the area of the Charvak reservoir, the analysis results of geomagnetic variations are presented in the article. It is revealed that local anomalies of geomagnetic field related to the change process of water volume in reservoir and local seismicity happen simultaneously. It is also considered that these results will be used for earthquake forecasting.
       
  • Intensities of ancient earthquakes, earthquake magnitude and soil dynamics
           effects. Evidence from the 1750 Croatia earthquake

    • Abstract: Publication date: Available online 24 July 2018Source: Geodesy and GeodynamicsAuthor(s): Stathis C. StirosAbstractA problem in the study of pre-instrumental earthquakes is how to reconstruct their parameters based on usually fragmentary evidence of seismic intensities, which reflect the combined effect of fault dynamics, of radiation of seismic waves, and of local amplification or attenuation of strong seismic motions. This problem is highlighted in the 1750 earthquake in Croatia, in the active compressional margin of NW Adriatic, an area with rarely known seismic history. Recent high-quality historical and archaeological data revealed that the 1750 earthquake was associated with high (up to VIII) seismic intensities, which were assigned to local amplification of strong motion generated by a magnitude 5 earthquake. This scenario points to a nearly aseismic plate boundary and to an unusually long meizoseismal zone for a small earthquake. On the contrary, in this study, the 1750 earthquake is associated with a segment of a major thrust and with a M > 6.0 earthquake which produced moderate accelerations. These results were based on a triple correlation between (1) a Finite Fault Model derived from elastic dislocation analysis of differential subsidence of submerged coastal notches, (2) a major composite thrust and (3) the distribution of areas of high seismic intensities. This result provides some input for the estimation of the seismic hazard/risk in the study area, indicates that the Adria-Eurasia collision front in NW Croatia is not essentially aseismic, and highlights the need to include soil dynamics effects in the study of palaeoseismic events.
       
  • Tectonic evolution of structures in Southern Sindh Monocline, Indus Basin,
           Pakistan formed in multi-extensional tectonic episodes of Indian Plate

    • Abstract: Publication date: Available online 20 July 2018Source: Geodesy and GeodynamicsAuthor(s): Shabeer Ahmed, Sarfraz Hussain Solangi, M. Saeed Khan Jadoon, Adeel NazeerAbstractThere are a number of structures and structural styles found in extensional tectonic settings of the world, and it is a big challenge to study the evolution of these structures. Evolution of structures formed in extensional tectonic settings have been studied by researchers on different extensional basins of the world. Southern Sindh Monocline lies on the western corner of Indian Plate and the tectonic history of Indian plate has also experienced different extensional episodes, and its journey rifted from Gondwanaland to its final welding to Asia. The aim of this study is to figure out the evolution of structures in the subsurface of Southern Sindh Monocline, Pakistan using the seismic data interpretation and flattening of horizons approach. Structures within the subsurface of Southern Sindh Monocline have been characterized by different tectonic episodes of Indian plate while rifting from Gondwanaland, rifting from other plates at different geological times and to its collision with the Asia. Basic structures within study area are classified into nine types while the structural styles have been classified into six types as horst and grabens, dominos, crotch, synthetic and antithetic, negative and flashlight structural style. The structures within the study area revealed evidence for three major structural episodes which can be characterized as Episode 1: Structures associated with rifting of Indian plate from Gondwanaland during Late Jurassic to Early Cretaceous, Episode 2: Modification and reactivation of previous structures while Madagascar rifted from Indian Plate during the Middle Cretaceous and during Episode 3: Inversion and reactivation of structures occurred when Indian Plate collided with Asia during Early Eocene.
       
  • Online computation of International Reference Ionosphere Extended to
           Plasmasphere (IRI-Plas) model for space weather

    • Abstract: Publication date: Available online 12 July 2018Source: Geodesy and GeodynamicsAuthor(s): Umut Sezen, T.L. Gulyaeva, Feza ArikanAbstractIonosphere is the most challenging part of Space Weather with its spatio-temporal variability and dispersive nature. Ionospheric models are very important in reducing positioning error in GNSS system. International Reference Ionosphere (IRI) is an empirical, deterministic and climatic model of ionosphere up to 2000 km in height. Recently, IRI Extended to Plasmasphere (IRI-Plas) model has been developed to extend the interest region of IRI to the GPS orbital height of 20,000 km. Both IRI and IRI-Plas provide ionospheric parameters such as electron density, electron and ion temperatures according to their height profiles. In order to update the model to current ionospheric conditions, IRI-Plas can input F2 layer critical frequency (foF2), maximum ionization height (hmF2), and also Total Electron Content (TEC). Online IRI-Plas is developed for the ionospheric community to run multiple tasks at various locations, dates and times with optional foF2, hmF2 and TEC inputs in a user-friendly manner. In this paper, we are going to present the capabilities of the Online IRI-Plas service and provide some comparisons between IRI-Plas outputs and ionosonde measurements. The comparison between online IRI-Plas foF2 outputs and ionosonde foF2 measurements indicates that the model with TEC input can significantly improve the representation of the current ionospheric state, which is very successful especially in the geomagnetically disturbed days.
       
  • Analysis and combination of four technique-individual EOP time series

    • Abstract: Publication date: Available online 7 July 2018Source: Geodesy and GeodynamicsAuthor(s): Lizhen Lian, Jiexian Wang, Chengli HuangAbstractBased on four intra-technique combined solutions in SINEX format, we tried at first to assess the accuracy of each single-technique Earth Orientation Parameters (EOPs) series over a past time interval of at least15 years by comparison with IERS EOP 08C04 combined solution as the reference in this paper. The EOPs studied here mainly consist of four elements, i.e. polar motion (XPO, YPO), Universal Time (UT1-UTC) and length-of-day (LOD). We combined these intra-technique EOP series, each of them associated with a given space geodetic technique by taking advantage of the relationship of the first three EOP components and three rotational parameters which carry the orientation of technique-related reference frame with respect to the estimated weekly inter-technique combined reference frame. Results indicated that the discrepancy between the pole coordinates (XPO, YPO) series, extracted from the intra-SLR combined loose-constraint solutions and the IERS EOP 08C04, seemed to be clearly characterized by systematic errors. Although both the XPO and YPO series determined by intra-VLBI combination had no significant characteristic of system error, they had relatively large difference values at some point with respect to the IERS EOP 08C04, which may be limited by the quantity of observation stations. Since the number of GPS stations is on the increase aimed at better global coverage, the accuracy of pole coordinates provided by IGS was superior to that derived from other space-geodetic techniques. As for DORIS XPO and YPO series from intra-DORIS combined minimal-constraint solutions, the discrepancy range of the former with respect to IERS EOP 08C04 was a little smaller than that of the latter. The objective of this study is twofold: on the one hand to analysis individual EOP series derived from the various space-geodetic techniques, on the other hand to present the new inter-technique combined EOP solution consistent with weekly inter-technique combined reference frame.
       
  • Establishing geothermometric constraints on the local geothermal
           gradients: Case study of the Eastern Cordillera Basin, Colombia

    • Abstract: Publication date: July 2018Source: Geodesy and Geodynamics, Volume 9, Issue 4Author(s): Carlos A. Barrera, Carlos A. Vargas, Jorge E. CortesAbstractGeochemical analyses were performed on 170 coal bed-trapped groundwater samples from 97 underground mines located in the Eastern Cordillera Basin, Colombia. The waters analyzed in this paper are from exploited coal beds, located up to 0.73 km deep, which emerge along with the local fault systems. The hydrochemical facies were classified based on the concentration of major ions by inferring the equilibrium state and rock water source. The main hydrochemical facies presented in the groundwater study are SO4CaMg, HCO3Ca, HCO3CaMg, and SO4HCO3 mixed waters. We used geothermometric equations to estimate the most probable temperature under in-situ conditions and the propagation of errors theory to test the results. The geothermal gradient in the study area is close to 30 °C/km, which is consistent with measurements from oil wells within the study area. Principal Component Analysis was used to explain factors affecting formation water composition and hydrogeochemical evolution of aquifers.
       
  • Crustal structure along the Zhenkang–Luxi deep seismic sounding profile
           in Yunnan derived from receiver functions

    • Abstract: Publication date: July 2018Source: Geodesy and Geodynamics, Volume 9, Issue 4Author(s): Zhanyong Gao, Yanna Zhao, Xiaoguo Deng, Yudong YangAbstractThe crustal thicknesses and the Poisson's ratios under the seismic stations can be calculated by receiver function method with H-ҡ stacking effectively. But the stacking results are affected to some extent by the average crustal P-wave velocity. To eliminate this effect and get more accurate crustal structure along the Zhenkang–Luxi deep seismic sounding profile which lies in Yunnan Province, we calculate the receiver functions from the teleseismic events recorded by 11 temporary stations as well as 5 permanent ones along the profile and carry out the stacking with Vp obtained from the profile in this study. Our study shows that the crustal thicknesses along the Zhenkang–Luxi profile range from 34.8 km to 41.8 km with an average of 39 km. The crust is thicker in the middle part of the profile and thinner in both sides in general. Dramatic changes of crustal thickness about 3 km are detected across both the Lancangjiang fault and the Xiaojiang fault, which implies that these faults cut through the Moho. The lowest Poisson's ratio under the stations is 0.22 and the highest is 0.27 with the mean of 0.25, which is lower than the global average value 0.27 in the continental crust. It suggests that most of the crust along the profile lacks mafic component, but contains more felsic substance. The low Poisson's ratio also indicates that there is no satisfying condition for partial melting. We deduce that the material flow in the middle-lower crust in the southeastern margin of the Tibetan plateau may occur only in the north region of 24°N.
       
  • An analysis of the characteristics of crustal magnetic anomaly in China
           based on CHAMP satellite data

    • Abstract: Publication date: July 2018Source: Geodesy and Geodynamics, Volume 9, Issue 4Author(s): Jianguo Zhang, Xiaodong Yang, Jungang Yan, Xiaoping WuAbstractBased on the observation data of CHAMP satellite from 2006 to 2009, a 2D crustal magnetic anomaly model in China is established to study the distribution characteristics of crustal magnetic anomaly. In this paper, the 2D anomaly model is derived from the Legendre polynomial expansion of harmonic term N=6−50. The result shows that many elaborate structures reflected in magnetic anomaly map well correspond to the geologic structures in China and its adjacent area. The magnetic anomaly at low satellite height behaves complexly, which is mainly caused by the magnetic disturbance of shallow rocks. In contrast, the magnetic field isolines at high satellite height are relatively sparse and only magnetic anomalies of deep crust are reflected. This fact implies that the 2D model of crustal magnetic anomaly provides an important method of the space prolongation of geomagnetic field, and is of theoretical and practice importance in geologic structure analysis and geophysical prospecting.
       
  • Initial orbit determination of BDS-3 satellites based on new code signals

    • Abstract: Publication date: July 2018Source: Geodesy and Geodynamics, Volume 9, Issue 4Author(s): Fei Ye, Yunbin Yuan, Jikun OuAbstractFor the two newly launched satellites (PRN number 27 and 28) of the future global BeiDou navigation satellite system (BDS-3), there is no available broadcast ephemeris data and other initial orbit information, but the initial orbit is the fundamental of the comprehensive analysis of the satellites and their signals. Precise orbit determination (POD) also requires determination of a priori initial value with a certain precision in order to avoid problems such as filter divergence during POD. Compared with the Newton iteration method, which relies on the initial value, this study utilizes the Bancroft algorithm to directly solve the nonlinear equations with the advantage of numerical stability. The initial orbits of these two satellites are calculated based on new code signals, and their results are analyzed and discussed. The experimental results show that, with the exception of very few epochs, when the new code signal is utilized, the median and robust variance factor of the observed residuals computed using pseudo-range observations and the solved initial orbits are less than 4 and 2 m, respectively. It also shows that this solution can be used for rapid initial orbit recovery after maneuvers of the new BeiDou satellites.
       
  • Application of S-transform threshold filtering in Anhui experiment airgun
           sounding data de-noising

    • Abstract: Publication date: July 2018Source: Geodesy and Geodynamics, Volume 9, Issue 4Author(s): Chenglong Zheng, Xiaofeng Tian, Zhuoxin Yang, Shuaijun Wang, Zhenyu FanAbstractAs 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.
       
  • Study on the basement structure in the southeastern North China by
           blasting seismic

    • Abstract: Publication date: July 2018Source: Geodesy and Geodynamics, Volume 9, Issue 4Author(s): Zhenyu Fan, Jinren Zhao, Suzhen Pan, Cejun Ma, Mingxin Qu, Yan Hai, Xiaoguo DengAbstractSince the Mesozoic, southeastern North China Craton has experienced intense crustal thinning and lithosphere destruction. Some of the responses of the deep activity in the upper crust crystalline basement have been retained in a series of tectonic evolution. The study of the upper crust velocity structure, especially the properties of the basement interface, is of great significance for studying the tectonic evolution and seismic hazard in the southeastern part of North China. In this study, we selected Pg waves of the blasting seismic data in the southeastern part of North China in recent years, which reflect the west Shandong uplift, offshore sedimentary basins and the Tanlu Fault zone and the Sulu orogenic transition zone, to study the structural and seismological characteristics of basement in North China Craton. The results of this study showed as follows: First, the obvious lag of Pg wave arrival time in Dongying depression and North Jiangsu basin reveals the thick sedimentary, low velocity and unstable basement structure. Second, the advance Pg wave arrival time with high apparent velocity, which reflects the basement structure of the west Shandong uplift, indicates the thin sediments and the shallow basement. Third, combined with many geophysical phenomena, such as electrical structure, density structure and terrestrial heat flow, we hold that the Tanlu tectonic belt and the Sulu orogenic belt have experienced great lithosphere destruction and there is shallow crust and the thinnest lithosphere in the vicinity of the Tanlu fault zone.
       
  • Upper crustal anisotropy from local shear-wave splitting and crust-mantle
           coupling of Yunnan, SE margin of Tibetan Plateau

    • Abstract: Publication date: July 2018Source: Geodesy and Geodynamics, Volume 9, Issue 4Author(s): Bo Zhang, Shuangxi Zhang, Tengfei Wu, Yujin HuaAbstractThe upper crustal anisotropy of Yunnan area, SE margin of Tibetan Plateau, is investigated by measuring the shear wave splitting of local earthquakes. The mean value of the measured delay times is 0.054 s and far less than that from Pms splitting analysis, indicating that the crustal anisotropy is contributed mostly from mid-lower crust. The fast polarization directions are mostly sub-parallel to the maximum horizontal compression directions while the stations near fault zones show fault-parallel fast polarization directions, suggesting both stress and geological structure contribute to the upper crust anisotropy. Comparing fast polarization directions from shear wave splitting of local earthquakes and Pms, large angle differences are shown at most stations, implying different anisotropy properties between upper and mid-lower crust. However, in southwestern Yunnan, the fast polarization directions of Pms and S-wave splitting are nearly parallel, and the stress and surface strain rate directions show strong correlation, which may indicate that the surface and deep crust deformations can be explained by the same mechanism and the surface deformation can represent the deformation of the whole crust. Therefore, the high correlation between surface strain and mantle deformation in this area suggests the mechanical coupling between crust and mantle in southwestern Yunnan. In the rest region of Yunnan, the crust-mantle coupling mechanisms are supported by the lack of significant crustal anisotropy with NS fast polarization directions from Pms splitting. Therefore, we conclude that the crust and upper mantle are coupled in Yunnan, SE margin of Tibetan Plateau.
       
  • Analysis of the merged quasi-geoid of neighbouring areas

    • Abstract: Publication date: July 2018Source: Geodesy and Geodynamics, Volume 9, Issue 4Author(s): Chunxi Guo, Jianliang Nie, Bin Wang, Jie Tian, Guangwei Jiang, Junying Chen, Shijuan ZhangAbstractEmploying the merged quasi-geoid, we analyses the causes of systematic errors in modelling of quasi-geoid of neighbouring areas in the paper, and the efficient method is introduced to improve the accuracy of quasi-geoid. First, the systematic error is weakened with the moving window method applied to established quasi-geoids in two adjacent regions, and the accuracy of the merged quasi-geoid in the stitching region is checked using the measured GPS benchmark data; Second, the whole quasi-geoid is recomputed with data obtained from two adjacent regions if the accuracy of the quasi-geoid obtained from the first step in the stitching region is low; Finally, the quasi-geoids in two adjacent regions are recomputed respectively using GPS benchmark data of own region and adjacent region with the same solution if the accuracy of whole quasi-geoid obtained from the second step also is low. Actual data sets from Sichuan Province and Chongqing City are employed to test the moving window method. It is shown that the quasi-geoid models with high resolution and accuracy were obtained.
       
  • Application of time series modeling to a national reference frame
           realization

    • Abstract: Publication date: July 2018Source: Geodesy and Geodynamics, Volume 9, Issue 4Author(s): D. Fazilova, Sh. Ehgamberdiev, S. KuzinAbstractThis paper presents an option for modern dynamic terrestrial reference system realization in Uzbekistan for user needs. An additive model is explored to predict patterns of time series and investigate means of constructing forecast time series models in the future. The main components (trend, periodical, and irregular) of the KIUB (DORIS) and KIT3, TASH, MADK, and MTAL (GNSS) international stations coordinate time series were investigated. It was shown that seasonal nonlinear trends occurred both in the height (U) component of all stations and the east (E) component of high mountainous stations such as MTAL and MADK. The seasonal periodical portion of the time series determined from the additive model has a complicated pattern for all sites and can be explained as both hydrological signals in the region and improvement of observational quality. Amplitudes of the best-fitting sinusoids in the North component ranged between 1.73 and 8.76 mm; the East component ranged between 0.82 and 11.92 mm; and the Up component ranged between 3.11 and 40.81 mm. Regression analysis of the irregular portion of the height component of the two techniques at the Kitab station using tropospheric parameters (pressure and temperature) was confirmed as only 57% of the stochastic portion of the time series.
       
  • Cassini's motions of the Moon and Mercury and possible excitations of free
           librations

    • Abstract: Publication date: Available online 27 June 2018Source: Geodesy and GeodynamicsAuthor(s): Yu.V. Barkin, Jose Ferrandiz, Shuanggen Jin, M. Yu. BarkinAbstractOn the basis of conditionally-periodic solutions of Hamiltonian systems at resonance of main frequencies Cassini's motions, their stability, Cassini's angle and periods of free librations of the Moon and Mercury have been recently studied and determined. The generalized formulations of Cassini's laws for the motion of the Moon and Mercury, that are considered as absolutely rigid non-spherical bodies, have been determined. The study of the second approximation equations of the desired quasi-periodic solutions in the case of the Moon allows us to determine the constant components of the first order for six Andoyer variables and the constant component of the second order for the angular velocity of the Moon. These effects are caused by the influence of the third harmonic of selenopotential. In this paper, these effects are described by analytical formulas, the dynamic and geometric interpretations are given, and a new interpretation of Mercury's motion under the generalized Cassini's laws has been proposed. Predictions of the existence of free librations of significant amplitude in the Mercury longitude, that are confirmed by the radar measurements data of the Mercury angular velocity, and in its pole motion in the body and in space have been made. The mechanism describing free librations of celestial bodies and their pole oscillations has been proposed due to the forced relative oscillations and wobble of the core-mantle system of celestial bodies (Moon, Mercury, Earth and other bodies in the solar system) under gravitational action of the external celestial bodies. The paper shows that the ascending node of equator of Mercury (and the intermediate plane orthogonal to the angular momentum) of epoch 2000.0 on the ecliptic does not coincide with the ascending node of orbital plane of Mercury on the same plane, and is ahead of it at an angle 23º4’. Angular momentum vector of the rotational motion of Mercury forms a constant angle ρG=4'1±1'1 with normal to the moveable plane of its orbit. The observed inclination of the angular velocityρω=2'1±0'1, can be considered as a possible evidence of a significant amplitude of the poles free motion of the Mercury rotation axis (c amplitude of about 2′- 4′).
       
  • Is the global sea surface temperature rise accelerating'

    • Abstract: Publication date: Available online 4 May 2018Source: Geodesy and GeodynamicsAuthor(s): H. Bâki IzAbstractThis is an exploratory investigation to search for the presence of an acceleration in global sea surface temperature rise, which is essential to identify anthropogenic contributions to the climate change during the 20th century. A weighted statistical model with an acceleration parameter was built progressively to reconstruct the variations in the global sea surface temperature data considering statistically significant confounders and autoregressive disturbances in the process. From the preliminary residual analysis of a weighted regression model, emerged a parsimonious model with first order autoregressive disturbances with a deterministic trend, acceleration and periodicity of 69 yr and its 138 yr subharmonic. The final model solution, selected from 29 alternative combinations of the model parameters using Mallows's Cp metric, revealed a statistically significant deterministic trend, 0.40 ± 0.03 °C/c (p 
       
  • An image segmentation based algorithm for imaging of slow slip earthquakes

    • Abstract: Publication date: May 2018Source: Geodesy and Geodynamics, Volume 9, Issue 3Author(s): Mohammad Hazrati Kashi, Noorbakhsh Mirzaei, Behzad MoshiriAbstractLaboratory experiments next to a variety of observations, especially in subduction zones, have explored the existence of a premonitory stable slow slip growth phase preceding large earthquakes. These phenomena play an important role in the earthquake cycle and thus precise imaging and monitoring of these events are of great significance. In the literature, ENIF (extended network inversion filter) has been proposed as a rigorous algorithm capable of isolating signal from different types of noise and thereby provides us with deep insight into spatio-temporal evolution of slow slip events. Despite its considerable advantages, ENIF still suffers from some limitations. ENIF applies Tikhonov method of regularization with a quadratic form of cost function. While anomalous slip regions have clear contrast with the background slip in reality, Tikhonov regularization tends to over smooth (globally smooth) the slipping portion on the estimated images. In order to avoid over smoothing phenomenon, we have incorporated into ENIF an image segmentation step which tries to preserve edges of slow-slip event. As a second limitation, due to the nonlinearity imposed by such constraint as non-negativity of slip rate, uncertainty propagation through model is not simple. As the core of ENIF, EKF (extended Kalman filter), performs uncertainty propagation by linearization of nonlinear model using Jacobian and Hessian matrices. As an alternative for EKF, we have also investigated the application of UKF (unscented Kalman filter) which uses UT (unscented transform) for uncertainty propagation. Finally, we tested our proposed algorithm using a low signal to noise ratio synthetic data set. The results show a significant improvement in the performance of ENIF when the segmentation step is incorporated into the algorithm.
       
  • Finite element modelling of the geodynamic processes of the Central Andes
           subduction zone: A Reference Model

    • Abstract: Publication date: May 2018Source: Geodesy and Geodynamics, Volume 9, Issue 3Author(s): Chris SalomonAbstractThis paper presents preliminary results of three-dimensional thermomechanical finite-element models of a parameter study to compute the current temperature and stress distribution in the subduction zone of the central Andes (16°S–26°S) up to a depth of 400 km, the bottom of the asthenosphere. For this purpose a simulation running over c. 50,000 years will be realized based on the geometry of a generic subduction zone and an elasto-viscoplastic Drucker–Prager rheology. The kinematic and thermal boundary conditions as well as the rheological parameters represent the current state of the study area. In future works the model will be refined using a systematic study of physical parameters in order to estimate the influence of the main parameters (e.g. viscosity, fault friction, velocity, shear heating) on the results of the reference model presented here. The reference model is kept as simple as possible to be able to estimate the influence of the parameters in future studies in the best possible way, whilst minimizing computational time.
       
  • Feasibility study applied to mapping tidal effects in the Pannonian basin
           – An effort to check location dependencies at μGal level

    • Abstract: Publication date: May 2018Source: Geodesy and Geodynamics, Volume 9, Issue 3Author(s): G. Papp, J. Benedek, P. Varga, M. Kis, A. Koppán, B. Meurers, R. Leonhardt, M.K. BaraczaAbstractThis paper summarizes the main instrumental and methodological points of the tidal research which was performed in the framework of the National Scientific Research Fund Project K101603. Since the project is still running the tidal analysis results published here are only preliminary.Unmodelled tidal effects have been highlighted in some recent absolute gravity measurements carried out in the Pannonian basin resulting in a periodic modulation exceeding the typical standard deviations (±1microGal) of the drop sets. Since the most dominant source of the daily gravity variation is the bulk tidal effect, the goal of the project is to check its location dependency at μGal level. Unfortunately Hungary has had no dedicated instrumentation, so an effort was made to make the available LaCoste-Romberg spring G meters capable for continuous recording. As a reference instrument the GWR SG025 operated in the Conrad Observatory, Austria was also used and in the mean time of the project, a Scintrex CG-5 became also available. Eventually 6 instruments at 5 different locations were operated for 3–9 months mainly in co-located configuration. Although many experiments (moving mass calibrations) were done to determine the scale factors and scale functions of the instruments, the direct comparison of the tidal parameters obtained from the observations is still questionable. Therefore the ratio of the delta factors of O1 and M2 tidal constituents was investigated supposing that M2 is much more influenced by the ocean loading effect than O1. The slight detected increase of δ(O1)/δ(M2) (≈0.2%) toward east does not contradict to theory. This result has to be validated in the near future by analyzing available ocean loading models.
       
  • Non-tidal tilt and strain signals recorded at the Geodynamic Observatory
           Moxa, Thuringia / Germany

    • Abstract: Publication date: May 2018Source: Geodesy and Geodynamics, Volume 9, Issue 3Author(s): Th. JahrAbstractSince end of the 90s of the last century the seismological station Moxa was extended and developed into the modern Geodynamic Observatory. It comprises also the new installation of borehole-tilt meters in front of the observatory building and laser-strain meters in the gallery. The question arises how non-tidal signals are displayed in the measured time series. The investigation of such signals which can be caused naturally or man-made, can result in different sensitivities for the various tilt- and strainmeter systems, e.g. regarding barometric pressure impacts and hydrological induced pore pressure effects.
       
  • Investigation of the different weight models in Kalman filter: A case
           study of GNSS monitoring results

    • Abstract: Publication date: May 2018Source: Geodesy and Geodynamics, Volume 9, Issue 3Author(s): Roman Shults, Andriy AnnenkovAbstractDuring 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.
       
  • Automated Burris gravity meter for single and continuous observation

    • Abstract: Publication date: May 2018Source: Geodesy and Geodynamics, Volume 9, Issue 3Author(s): Gerhard Jentzsch, Richard Schulz, Adelheid WeiseAbstractThe Burris Gravity Meter™ manufactured by ZLS Corporation, Austin/Texas, USA, is based on the invention of L&R (L. LaCoste and A. Romberg): The ZLS (zero-length spring). A digital feedback system (range of about 50 mGal) is used to null the beam. Now, more than 120 gravity meters of this make exist worldwide and are used successfully in exploration, volcanology, geodetic work and surveying.The sensor is made of the well-known (L&R) metal-alloy zero-length spring providing a low drift characteristic. The drifts observed are comparable to L&R gravimeters and are less than 0.3 mGal per month, which is much lower than the drifts known for the fused quartz sensors.The dial is calibrated every 50 mGal over the entire 7000 mGal meter range. Since the gravity value is determined at these points, there are no periodic errors. By a fourth heater circuit temperature effects are totally avoided. The gravity meter is controlled via Bluetooth® either to a handheld computer (tablet) or a notebook computer.The feedback responds with high stability and accuracy. The nulling of the beam is controlled by the UltraGrav™ control system which incorporates an inherently linear PWM (pulse-width modulated) electrostatic feedback system. In order to improve the handling of the gravimeter we have developed two Windows based programs: AGESfield for single measurements and AGEScont for continuous readings.
       
  • Scintrex CG5 used for superconducting gravimeter calibration

    • Abstract: Publication date: May 2018Source: Geodesy and Geodynamics, Volume 9, Issue 3Author(s): Bruno MeurersAbstractThe scale factor accuracy of superconducting gravimeters (SG) can be largely improved by a high repetition rate of calibration experiments. At stations where the availability of absolute gravimeters is limited, carefully calibrated spring gravimeters can be used for providing the reference signal assuming the irregular drift is properly adjusted. The temporal stability of the SG scale factor is assessable by comparing the temporal variations of M2 tidal parameters observed at neighboring SG sites or from synthetic tide models. Combining these methods reduces the SG scale factor error to a few 0.1‰. The paper addresses the particular procedure required for evaluating the calibration experiments based on spring gravimeters and presents results obtained at Conrad observatory (Austria). Comparing the M2 amplitude factor modulation helped to reveal a SG scale factor offset of about 0.2‰ due to re-installation.
       
  • Editorial note for the Geodesy and Geodynamics journal special issue:
           Contemporary Research in Geodynamics and Earth Tides: An account of the
           18th Geodynamics and Earth Tides Symposium 2016, Trieste, Italy

    • Abstract: Publication date: May 2018Source: Geodesy and Geodynamics, Volume 9, Issue 3Author(s): C. Braitenberg, G. Rossi, J. Bogusz, L. Crescentini, D. Crossley, R.S. Gross, K. Heki, J. Hinderer, T. Jahr, B. Meurers, H. Schuh
       
  • Pre-seismic ionospheric anomalies of the 2013 Mw = 7.7 Pakistan
           earthquake from GPS and COSMIC observations

    • Abstract: Publication date: Available online 19 February 2018Source: Geodesy and GeodynamicsAuthor(s): Munawar Shah, Shuanggen JinAbstractThe seismo-ionospheric anomalies may provide some insights about the earthquake. However, pre-seismic ionospheric anomalies are still challenging. In this paper, seismo-ionospheric anomalies are investigated before the September 24, 2013 (Mw = 7.7) Awaran (Pakistan) earthquake from GPS TEC (Total Electron Content) and COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) data. The TEC data are showing anomalies on September 21, 2013. The abnormality detected in the temporal data is about 10 TECU beyond the 30-day running median. The percentage deviation of the TEC anomaly on September 21, is 30% above the upper confidence interval. The anomalies prevail 5° in Latitude and 10° in Longitude over the epicenter. The spatial and temporal data of TEC showed anomalies in TEC from UT = 08 to UT = 12. In addition, the enhancement on September 21, 2013 is also very significant in COSMIC data. The results of COSMIC completely agreed with GPS TEC anomalies on September 21, 2013. The percentage deviation of the peak plasma frequency on September 21 is 5% of the normal distribution. The storm indices are quiet before and after the earthquake. The pre-sesimic ionospheric anomalies are most probably associated with the 2013 Mw = 7.7 Awaran (Pakistan) earthquake.
       
  • Location correction technique based on mobile communication base station
           for earthquake population heat map

    • Abstract: Publication date: Available online 13 February 2018Source: Geodesy and GeodynamicsAuthor(s): Xiaoli Liu, Xue Li, Xiaolin Chen, Zhumei Liu, Shengle LiAbstractChina has mobile phone penetration rate of over 96.2%. Mobile phone has become the largest Internet terminal for Chinese Internet users. Population geographic distribution in earthquake zones can be got based on mobile phone positioning and map matching. For reducing earthquake black-box stage, we propose a real-time collection, correction and schedule algorithm of population position data by four stream processing environments (Redis, Hbase, Kafka, and Spark Streaming) in this paper. For labeling precisely population geographic distribution on the network map, matching of population geographic coordinates and map coordinates are optimized by sample comparison based on location data of mobile communication base stations and prefecture level cities. The test result shows the proposed system is high efficient and can rapidly respond to any emerging parallel tasks during the earthquake. A high-precision heat map of affected population can be produced and published on-line within 2 min after the devastating earthquake happened.
       
 
 
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