11 September 2017, Volume 37 Issue 9
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jgg. 2017, 37(9): 881-883.
Based on GPS measurements from crustal movement observation network of China, we derive the crustal movement velocity field and strain rate for the Tibetan plateau and its surrounding areas. Preliminary analysis indicates that the distribution of current strain rate across the Tibetan plateau is consistent with long-term tectonic settings and its earthquake activities. The principal compressive strain rate, maximum shear rate and the dilation rate are in good agreement with the crustal shortening across the margin of the Tibetan plateau and the Tianshan, the approximately west-east extension in southern Tibet, and the strike slip faults in the Tibetan plateau, indicating that the strain field derived from decade-long GPS observations is compatible with long-term active settings and earthquake activities in the Tibetan plateau.
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jgg. 2017, 37(9): 884-887.
Using the observation data from 10 North-South seismic belt hole strain stations, based on wavelet decomposition and norm calculation, we acquire anomaly information from the Minxian-Zhangxian earthquake M6.6 (Jul.22,2013). The results show, in addition to Sunan station, the rest of the 9 stations present anomaly information before the earthquake. The earliest anomalies occur in early Jun 2013 (about 50 days before the earthquake); at Dangchang station, which is nearest to the epicenter, anomalies occur in early July 2013. Combined with other research results, the characteristics of abnormal information are discussed. We believe that there is a close relationship between it and the movement of eastern side from south to north in South- North seismic belt. The deformation transfer process after the earthquake is a reverse direction process. In addition, it is proved that the method is simple, effective and reliable to extract the deformation anomaly before the earthquake.
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jgg. 2017, 37(9): 888-892.
The paper considers the Wenchuan and Lushan earthquakes, which occurred in the Longmenshan fault zone. Based on the cross fault leveling data of Longmenshan, Xianshuihe and Anninghe-Zemuhe fault zones, the annual deformation rate of different sites and the accumulation rate of fault vertical deformation are calculated. The analyses of the annual deformation rate and the spatial distribution of Dc contour map changes reveal the fault activity law. We ascertain the regional strain and the stress field before and after the Wenchuan earthquake, then discuss the correlation of the two earthquakes. The results show: (1) The occurrence of the Wenchuan earthquake obviously increases the fault activity in the southern tip of the Longmenshan fault zone. The average annual rate of change before the earthquake is increased by <1 mm/a, increasing to a maximum of 10.01 mm/a after the earthquake. The occurrence of Wenchuan earthquake has great impact on Tangjiaping and Xichang sites on Anninghe-Zemuhe fault zone, where the annual rate of change increases, and the activity of the fault is strengthened. (2) Before the occurrence of the Wenchuan earthquake, the northeast section of Longmenshan fault shows a high Dc value area; afterward, it gradually reduces. The occurrence of Wenchuan earthquake presents a background of stress accumulation. The spatial distribution of Dc in the Longmeshan fault zone obviously changes after the Wenchuan earthquake, accelerating the formation of a high Dc value around the site of Shuanghe site. The Lushan earthquake epicenter is located in the high value and the low value region, with a significant spatial difference.
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jgg. 2017, 37(9): 893-897.
On February 6, 2016, a MW6.4 earthquake occurred in Meinung district of Kaohsiung city, Taiwan,China. The epicenter area, determined by seismic data, lies in a region bounded by Chaochou and Chishan faults. The co-seismic surface deformation of the region is extracted using Sentinel-1A radar data based on differential interferometry. We get reliable co-seismic displacement fields compared with GPS data. InSAR-derived displacement field shows that there is an uplift zone along line-of-sight of about 30 km diameter, located at about 15 km west of the epicenter with a maximum displacement of about 12 cm. There is no apparent rupture around the macro-epicenter from the spatial distribution of displacement. The InSAR application of determining the macro-epicenter quickly shows the scientific significance of relief supplies and rapid assessment after earthquake.
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jgg. 2017, 37(9): 898-902.
In this paper, we propose the improved Kriging interpolation model which considers the influence of additional stress and soil compression properties, based on ground subsidence mechanism induced by building load. It is illustrated that this method can be effectively used in spatial trend surface imitation and calculation. The results accurately and clearly show subsidence deformation values and trends. So, this research provides a scientific basis for land subsidence spatial modeling, visual analysis and summary of subsidence discipline induced by building load in urban areas.
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jgg. 2017, 37(9): 903-907.
Based on gravity observations from 2013 to 2015 of west Tianshan area, and considering regional earthquake catalogue,we analyze the relationship between variation of gravity field and earthquakes in the west Tianshan mountains. The results show that: (1) The west Tianshan area is one of the most active areas in the gravity field. Gravity field change “enhance-weakened-enhance” correspond with seismic trend activity “active-quiet-active”. The change of regional gravity field is related to the north drift rotation of Tarim plate.(2)The epicenter is located in the high gradient zone of gravity variation and is close to the “0” equivalent line. (3) Before the earthquake in the west Tianshan area, the cross-fault section shows a turning image.
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jgg. 2017, 37(9): 908-912.
We calculate vertical integrated horizontal deviatoric stresses by solving force balance equations in a thin sheet approximation involving gravitational potential energy terms through a finite element method. GPE values, eliminated the effects of dynamic topography, are derived from the Crust 1.0 model, the V24.1 gravitational model and the V18.1 topography model data sets. The results show that GPE in north China area presents aspatially heterogeneous distribution. Areas in high values of GPE are tensile, whereas compression exists in regions of low values of GPE. The GPE shows high values occurring at the north central area of Yinshan mountain-Yanshan mountain fault block, where the direction of maximal horizontal tensile stress is N-S. The orientation of maximal horizontal principal compressional stress in low values of GPE, such as the northeast and southwest of the north China plain block and the north areas of central Hehuai plain, is dominated by NWW-EES.
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jgg. 2017, 37(9): 913-916.
First of all, this paper uses the particle swarm algorithm, genetic algorithm, and the Monte Carlo method, respectively combined with the dislocation model, to invert three-dimensional sliding rate of the single fault by gravity data simulated by the pure strike-slip fault. By the result, the paper selects the optimal nonlinear algorithm. Then, the three-dimensional sliding rate of Xianshuihe fault is inverted by two phase ground gravity data, recorded from September 2013 to September 2014 and from September 2014 to April 2015. The results show: (1) The particle swarm algorithm, as compared with the genetic algorithm and the Monte Carlo method, has good convergence, strong stability and high precision; but on the whole, they all have certain application value. (2) There are some characteristics of sliding in the Xianshuihe fault zone, which presents a left-lateral strike-slip movement, with thrust fault on the whole and extrusion on the local scale. (3) The strike-slip and dip-slip parameter of Xianshuihe fault inverted by gravity data from September 2014 to April 2015 is greater than the inversion result by gravity data from September 2013 to September 2014.
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jgg. 2017, 37(9): 917-922.
Aiming at analyzing the coordinate time series of crustal movement observation network of China (CMONOC), this paper explores the effect of three reference frames of different size and two kinds of similarity transformations with different transformation parameters on velocity field, annual term and residual position time series of the stations. On the basis of these solutions, for a long-term continuously observed GPS network covering a large area such as the Chinese mainland, a global reference frame makes the analysis results of the coordinate time series more stable and less sensitive to transformation parameters. By contrast, selecting a regional reference frame, especially one covering an area closer to the studied region, can present more information of regional deformation which aids in the study of the dynamic mechanism of this deformation.
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jgg. 2017, 37(9): 923-927.
In this paper, GNSS observational data from the Qingdao continuously operating reference station system(QDCORS) from 2014 and 2015 are processed by GAMIT / GLOBK software combined with 16 IGS stations. The regional network calculation of ITRF2008 is acquired by time series analysis of coordinates.The variation trend between QDCORS and the surrounding stations of the crustal movement observation network of China is nearly consistent, with horizontal velocity of 34.41 mm/a in the direction of E19.62°S under ITRF2008. Using one fiducial station as a fixed reference, the velocity of other fiducial stations is around 1 mm/a horizontally and less than 5 mm/a vertically, which reflects the overall stability of QDCORS. Considering the environment of fiducial stations, the conclusion can be made that the main factors causing anabnormal fiducial station is the multipath effect of GNSS and urban construction procedures.
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jgg. 2017, 37(9): 928-932.
We put forward a new tomography model based on the classical tropospheric tomography model. To begin with, the water vapor densities at the vertexes of voxel are estimated using a non-iterative reconstruction algorithm (NIRA). Then, the humidity information at the center of the voxel is derived from NIRA-results through interpolation method, and as initial value was amended again by an iterative reconstruction algorithm. The combined reconstruction algorithm has the advantage of providing initial values which are high quality and reliable in the iterative reconstruction algorithm. Test results show that its accuracy is better than a single reconstruction algorithm.
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jgg. 2017, 37(9): 933-936.
In order to verify the feasibility of precipitable water vapor(PWV) retrieval with ground-based GPS in the way of spectrum analysis, PWV value calculated from ground-based GPS and microwave radiometer(MWR) data are studied in a long period and two short periods, based on singular spectrum analysis(SSA). The major trends and cycles can be extracted from those two kinds of data in different periods. The results show that RMSE of PWV value calculated from ground-based GPS and MWR value is about 2 mm. Between the two kinds of data, there is a strong correlation in major trends and similarity in cycles. This shows that PWV retrieval with ground-based GPS is feasible.
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jgg. 2017, 37(9): 937-941.
In this paper, the method of precise orbit determination and time synchronization(ODTS) is proposed to calculate the precise clock bias of two external high-precision atomic clocks, and then the performance of the system noise is analyzed. The products of IGS, Sta(published by IAC Russian space bureau analysis center) and GBMare employed for computations and comparisons respectively. The results show that the IGS and Sta clock products can be used to assess the performance of the satellite on-board clock. Furthermore, the GBM product can effectively achieve the performance evaluation of the BDS rubidium clock and the day stability of the hydrogen clock.
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jgg. 2017, 37(9): 942-945.
We consider the shortcomings of single satellite clock error prediction model.In this paper, based on three kinds of single model, i.e., the quadratic polynomial, the gray GM (1, 1) and the ARIMA models, the optimal non-negative variable weight combination forecasting model is proposed. Comparison with the single model and the classic weight combination model, shows that the RMS value of the optimal non-negative variable weight combination model prediction residual is smallest and its accuracy is higher. Moreover, it can give different weights according to the advantages and disadvantages of each model and sum up the advantages of a variety of single models in a certain degree and reduce the forecast risk. Furthermore，it can also improve the reliability of the model forecast.
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jgg. 2017, 37(9): 946-950.
Currently, the Kalman filter is widely used to calculate satellite clock offset in real-time based on the un-differenced method. Square root filter can enhance the stability of numerical calculation, and avoiding filtering divergence, but the inversion computation time of matrix will take longer. The sequential algorithm can improve computational efficiency for avoiding direct matrix inversion. Taking the advantages of these two algorithms, a new square root filter method is proposed based on the sequential algorithm; it is then applied to satellite clock offset calculating in real-time. The result shows that the accuracy of satellite clock offset is better than 0.2 ns, and the calculation time is reduced by 40%.
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jgg. 2017, 37(9): 951-955.
Quality assessment of Tianhui-1C for space-borne dual-frequency GPS is put forward in this paper. The reduced-dynamics satellite orbit determination is based on pseudo-stochastic pulse estimation. The orbit quality tests are performed through orbit overlap comparisons. Then, the influence of the satellite receiver change from single frequency GPS to dual frequency GPS for the satellite photogrammerty is analyzed in theory. The results show that data availability of five types of observations collected by the Tianhui-1C onboard GPS receiver is better than 80%. The ratio of cycle slip is better than 47. The averaged RMSs of MPCs for P1-code and P2-code measurements are 0.22m, 0.23 m, respectively. Two sessions, which have a total of 48 h of space-borne GPS measurements, are compared through orbit overlap comparisons. The orbit quality tests are performed through orbit overlap comparisons with two sessions, in which the orbit accuracy of precise orbit determination with space-borne GPS measurements can achieve 3.65 centimeters. Increasing orbit accuracy will help improve the accuracy of the satellite photogrammerty without ground control points (CI) precision to 3.866 m, and ellipsoidal height error increase to 1.171 m.
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jgg. 2017, 37(9): 956-960.
In this paper, SLR observations are used to validate the CODE final orbit of GLONASS satellites. The CODE final orbits of GLONASS are evaluated using the SLR data from January 1, 2015 to December 31, 2015 of EDC. The validation is statistically analyzed according to different satellite PRN and SLR sites. The results show that validations are uneven, which is related to the service life of the satellite. The new satellites have better validation results than satellites of the first track orbit by GLONASS. The site-satellite distance measured with SLR is shorter than that from final orbit and site coordinates. There remain small systematic errors, and the cause of these biases is not yet fully clear. The validations show that SLR observation accuracy is about 1.2 cm for GLONASS satellites. The accuracy of GLONASS satellite orbit validated by SLR date is mostly better than 3.3 cm.
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jgg. 2017, 37(9): 961-967.
Environmental loading effects have spatial differences, in order to provide the basis for subsequent loading data selection to correct reference station coordinate time series. In this paper, we calculate 4 different kinds of environmental loadings (atmosphere pressure, non-tidal ocean, snow pressure and soil moisture displacement time series) that are related to 417 global IGS stations. Referring to the analysis of these data, this article discusses the relationship between the same kind of load displacement of global IGS stations and geographical position. The result shows that the effect of atmospheric pressure on the GPS time series displacement is maximum; the displacement of U direction can reach 20 mm. The effect of snow loading on the GPS time series displacement is minimal. Effects of four environmental loadings on GPS time series in elevation direction can reach the centimeter level. Furthermore, non-tidal ocean and atmospheric loading shows significant regional characteristics.
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jgg. 2017, 37(9): 968-972.
In order to improve the calculation efficiency of the adjustment model with part uncertainty, a directly iterative algorithm is developed. Another algorithm is also discussed when the iterative algorithm is divergent. The results of a straight line fitting and a plane coordinate transformation illustrate that the proposed algorithm for adjustment model with part uncertainty can be practiced, has higher calculation efficiency, and has improved stability.
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jgg. 2017, 37(9): 973-976.
High speed ADC is employed in the free fall absolute gravimeter to record the integral fringe waveform, acquiring more information about local gravity. We discuss variations in gravity acceleration due to some parameters such as amplitude of the fringe voltage signal, ADC bits, reference voltage, and sampling frequency. The analysis shows that the gravity error caused by ADC quantization could be limited to 0.01 μGal by parameters optimization.
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jgg. 2017, 37(9): 977-982.
RAYINVR is an inversion algorithm for calculating two-dimensional velocity structure based on seismic wave traveltime. It consists of 3 parts, including model parameterization, ray tracing and damped least squares inversion. In order to analyze the influence factors of the algorithm on the imaging results, numerical experiments are analyzed from the four aspects of the initial model, observation data, damping factor and identification errors. The results show that the program can be performed quickly with efficient inversion. Meanwhile, the initial model, observation data, damping factor, identification errors, and so on, have an impact on the results of inversion and resolution.
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jgg. 2017, 37(9): 983-986.
A MS6.4 earthquake occurred at Menyuan county, Qinghai province, on 21 January, 2016. The system issued an earthquake alarm and recorded the destructive earthquake data. This paper computes peak ground acceleration (PGA), peak ground velocity (PGV) and instrumental seismic intensity of stations along the railway. The results show that the instrumental seismic intensity is a more robust alarm parameter than PGA, because it is less affected by site conditions. Then, the response spectra ratios of the near and far away high-speed railway observation points are calculated to interpret PGA changes on the local complex ground conditions. Finally, by comparing station computing response spectrum and high-speed railway bridge design response spectrum, it is possible to estimate earthquake damage of the high-speed railway bridge near the station.
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jgg. 2017, 37(9): 987-990.
Design TDC based on the conventional counting TDC method, through use the FPGA chip’s internal PLL phase delay and inner resource build delay chain technology improved TDC by counting method, can get a time interval measurement precision of 200 ps. The method has practical significance in the study of precision time measuring system for laser ranging, 3D laser scanner, and absolute gravimeter instruments.
