15 May 2018, Volume 38 Issue 5
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jgg. 2018, 38(5): 441-446.
In this study, the hierarchical clustering method is adopted to classify GPS horizontal velocity field of the Sichuan-Yunnan region, then the F statistic test is employed to correct the misclassification of the GPS site in the geographical space. On this basis, taking account of the DB index and the irreversibility of the hierarchical clustering, the former classification is re-clustered. Finally, the Sichuan-Yunnan region is ultimately divided into six blocks: Tibet block (BYw), Aba block (BYe), Sichuan-Yunnan rhombic block (CD), south China block (SC), Tengchong-Baoshan block (DSw) and Indosinian block (DSe). Among them, the west and north boundaries of the CD block are the three-river fault area of “three-river parallel flow” and a velocity step line in the Batang region, respectively. Moreover, main Bayan Har fault divides the Bayan Har block (BY) into two blocks: BYw and BYe. The block division model of the Sichuan-Yunnan region is a reasonable scheme in mathematical sense, which is basically consistent with the results from geological data, can provide an explanation in another dimension for the division of the Sichuan-Yunnan region.
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jgg. 2018, 38(5): 447-453.
In this study, the hierarchical clustering method is adopted to classify GPS horizontal velocity field of the Sichuan-Yunnan region, then the F statistic test is employed to correct the misclassification of the GPS site in the geographical space. On this basis, taking account of the DB index and the irreversibility of the hierarchical clustering, the former classification is re-clustered. Finally, the Sichuan-Yunnan region is ultimately divided into six blocks: Tibet block (BYw), Aba block (BYe), Sichuan-Yunnan rhombic block (CD), south China block (SC), Tengchong-Baoshan block (DSw) and Indosinian block (DSe). Among them, the west and north boundaries of the CD block are the three-river fault area of “three-river parallel flow” and a velocity step line in the Batang region, respectively. Moreover, main Bayan Har fault divides the Bayan Har block (BY) into two blocks: BYw and BYe. The block division model of the Sichuan-Yunnan region is a reasonable scheme in mathematical sense, which is basically consistent with the results from geological data, can provide an explanation in another dimension for the division of the Sichuan-Yunnan region.
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jgg. 2018, 38(5): 454-458.
The RANSAC-PSO algorithm is used to study the problem of gross errors ingeodetic data as a resultof fault slip parameters inversion. In the simulation experiment, 1%, 5% and 10% of the gross errors are added to the theoretical observations. Particle swarm optimization, selecting weight iteration and RANSAC-PSO algorithm are used to inverse the fault slip parameters. The results show that the difference from the theoretical value is 23.2 cm by the PSO, it is 26.2 cm by the selecting weight iteration, however, it is less than 1cm by RANSAC-PSO, when the gross error rate is 10%.The characteristics of Lushan earthquake are thrust-dominated with a small amount of left-lateral strike-slip.In this paper, the PSO algorithm and RANSAC-PSO algorithm are used to calculate the fault slip parameters,respectively, with the coseismal GPS displacement data. The strike-slip is 00518 m and dip-slip is 0.8289 m by RANSAC-PSO algorithm, which are greater than the results of PSO. In addition, the energy released is 1.000 9×1019 N·m(MW6.63), which is consistent with GCMT 1.060 0×1019 N·m. The horizontal displacements of the ground surface are recalculated with the sliding parameters that invert by the RANSAC-PSO algorithm and the PSO algorithm, respectively. The results show that the calculated horizontal displacements and GPS observations are basically the same as when the points are far away from the fault, the RANSAC-PSO algorithm performs better than PSO when the calculating points are near the fault. The calculated value of LS07 completely coincides with GPS observations.
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jgg. 2018, 38(5): 459-463.
Based on the theory of rectangular dislocation and the seismic wave inversion in the elastic-viscoelastic stratified half-space, combined with the average velocity of the crust-upper mantle in the study area, PSGRN/PSCMP software is used to simulate the 2012 Sumatra MW8.6 earthquake co-seismic effect, taking into account the surface deformation and seismic effects of gravity changes from the 2004 MW9.1 earthquake. At the same time, the annual variation rates of post-earthquake deformation and gravity are given. The coseismic deformation and gravity change show the left-lateral strike-slip characteristics of the seismogenic fault; the changes mainly focus on the fault; the redistribution of seawater quality has a significant effect on the vertical displacement and coseismic gravity change. The mean annual rate of change after 50 years reveals the changes of surface deformation and gravity change. The average deformation in the near field after 50 years is 10 mm/year. The average annual deformation of the far-field is less than 1 mm/a, and the average annual variation of gravity is generally less than 0.1 μGal/a. The horizontal deformation changes obviously within 400 years after the earthquake. The rate gradually decreases and stabilizes after 800 years. The vertical displacement and gravity change are particularly notable within 100 years after the earthquake, and the rate of change rapidly decayed, and basically remained unchanged after 400 years.
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jgg. 2018, 38(5): 464-468.
In this paper, GAMIT/GLOBK is used to solve the data of 50 CORS stations covering Sichuan province from 2006 to 2015, and the time series is extracted and the velocity field model is obtained. The results show that the average velocity of CORS stations in Sichuan is 38.72 mm/a, and the advantage direction of velocity field is S73.9°E. The average velocity in the horizontal direction of Eurasia is 14.40 mm/a, the dominant direction is S77.78°E, which is 24.32 mm/a lower than the ITRF2008 frame. The average speed in the vertical direction is 3.43 mm/a, the whole is uplifted, and a small part located in the east plains of the station are in a downward trend, probably due to groundwater or excessive logging of natural resources such as coal mines and oil. The maximum principal strain rate is 7.31×10-11 /a and the minimum principal strain rate is -5.4×10-11/a. The regional crustal surface expansion and maximum shear strain rate are distributed in the southwest near the three fault zones.
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jgg. 2018, 38(5): 469-472.
In order to determine the relative fixed positioning method of Shanxi station’s speed model based on the “Shanxi 2015 velocity model”, 103 earthquake events with the maximum clearance angle of less than 45° from 2010 to 2016 and more than 40 positioning stations are selected as targets. The results show that the residuals of the simplex method and Hyposat combined with PTD determination and the epicenter distance of the net margin earthquake are superior to that of Hypo2000 and of Hyposat binding PTD in terms of focal depth.According to the comprehensive analysis, when the Shanxi 2015 velocity model is used to locate the earthquake, the Shanxi network should be fixed with Hyposat and PTD method.
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jgg. 2018, 38(5): 473-476.
According to the nonlinear characteristics of the deformation monitoring data of high speed railways, a combined forecasting model based on wavelet and gray support vector machine is proposed.Using wavelet analysis to obtain the random sequence and approximate sequence of different time-frequency scales,through the determination of embedding dimension and the correlation analysis of high and low frequency data,the reconstructed random sequence is used as the genetic algorithm to optimize the input of the SVR model.The grey support vector machine is then used to describe the evolution of the approximate sequence. Finally, the two prediction results are coupled and superimposed,and the result of the combined model of wavelet-gray-support vector machine (SVM) is obtained.Taking the measured data of Guizhou-Guangzhou high-speed railway as an example, the mean square error, the mean absolute error and the mean absolute relative error are used to evaluate the prediction results.The example shows that the model fits the approximate component well, and avoids the over fitting of the detail components.
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jgg. 2018, 38(5): 477-481.
In this paper, the three-dimensional finite element model of the underground reservoir of Hutubi wall is established using the geological and geophysical data of Hutubi underground gas storage. The boundary of the gas storage model is constrained by the pressure change of the gas storage chamber. We simulate the data of the period to evaluate the reliability of the geometric model. The results show that the gas injection is similar to the respiration of the earth during the whole gas injection process and the gas production process. During the gas injection process, the ground point exponentially expands due to the pressure. During the process of gas production, the ground point of the ground surface is concentrated toward the vertical upward cover of the gas storage layer, showing a tendency to collapse inward.
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jgg. 2018, 38(5): 482-486.
The microtremor array method is used to detect underground Karst in Jiangxia district, Wuhan metro line 27. Based on the spatial autocorrelation theory(SPAC), the Rayleigh wave velocity dispersion curves are extracted, and through the inversion of dispersion curves,acquires the S-wave velocity structure and 2D profile. The results show that the research area top-down can be divided into four layers. The low-speed areas are developed in the third layer, suggesting that low-speed areas would be karst structures and are not small scale. Compared with the engineering drilling chart data, the stratigraphic stratification and Karst scale results of the SPAC method are basically consistent with the actual result.
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jgg. 2018, 38(5): 487-492.
In this paper, remote sensing interpretation and comparative analysis of active faults are made based on remote sensing data, earthquake data and focal mechanism solutions. Our research shows that the geomorphic features of the northern segment of the Yadong-Gulu fault are results of combined action of normal fault and dextral strike-slip fault. Extensional movement, sinistral strike slip movement and graben structures are found in the middle segment of the Yadong-Gulu fault, and gully dislocations show a horizontal displacement of 6 m to 66 m along this fault.The 1411 southern Damxung earthquake of M=8.0 caused a horizontal displacement of 6 m to 16 m along the fault. Secondary faults are fully developed in the southern segment of the Yadong-Gulu fault. The north end of the southern segment shows characteristics of dextral movement, while it turns to sinistral movement on the south side. Graben structures are also fully developed in this segment. The strike-slip faults control the occurrence of earthquakes in the shallow crust (above 8 km), which are mainly strike-slip type. Graben structures are caused by normal fracture tress mechanism in the deep crust (below 8 km) and control the earthquakes in the deep crust. The Lhari fault is generally buried. The dextral motion is found in its west part, while the southeast part of the Lhari fault shows characteristics of sinistral movement. The stress mechanism and earthquake events in the Lhari fault area are strike-slip type.
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jgg. 2018, 38(5): 493-496.
In this paper, based on the satellite elevation angle threshold, an improved algorithm of selecting six satellites is proposed to solve the shortcomings of satellite selection. By comparing the BDS/GPS observations with different lengths of baseline, the difference between the positioning accuracy and the efficiency of the different selection strategies is analyzed and compared. The results show that the improvement of the positioning accuracy of the improved six-satellite selection algorithm in the elevation direction is 40% and the average of the solution time is 70%, and the plane positioning is quite accurate.
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jgg. 2018, 38(5): 497-503.
This paper focusses on the five factors that affect the accuracy and timeliness of orbits, including the ambiguity fixed of different types of satellites, the number of regional ground monitoring stations, the length of the observation data arc, the selection of solar pressure perturbation model and multi-system combination orbit determination, and analyzes the optimal strategy of orbit determination under regional station distribution. The experimental results show that selecting 27 uniformly distributed ground area monitoring stations in China, using 72 h arc length of the BDS/GPS multi-system observation data, and adopting the ECOM 5 parameters model of the solar pressure perturbation, can achieve better orbit accuracy. The accuracy of the GEO satellite orbit is about 291 cm, and the accuracy of the IGSO/MEO satellite is better than 11 cm. If the above strategy is used for BDS single system orbit determination, GEO satellite 299 cm and IGSO/MEO satellite 14.4cm orbit accuracy can be achieved.
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jgg. 2018, 38(5): 504-509.
Tropospheric delay is one of the important factors that affect GPS short baseline resolution. When the height difference between stations is large, the spatial correlation of tropospheric delay is weak, and consequently cannot be eliminated by double difference treatment completely. This not only affects the precision of single session solution, but also leads to the error in the long-term span of time series observation and it affects the long-term linear speed estimation of measuring stations. To analyze the influence of estimation of tropospheric delay on time series of GPS short baseline with big height differences based on the wavelet analysis method, 5 pairs of short baselines from IGS stations are selected as the research objects and two different baseline solutions for data processing are used.The result shows that for the short baseline,if the height difference is more than 100 m, it will bring about spurious signals in height direction time series without the estimation of tropospheric delay,and the annual amplitude is up to 17.7 mm.The spurious signals aresignificantly reduced with tropospheric delay; in addition, it is found that there is some correlation between the zenith delay difference and the error in the elevation direction.
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jgg. 2018, 38(5): 510-515.
In this paper, GAMIT/GLOBK software is used to deal with the data of 23 consecutive GPS reference stations in Sichuan province during 2010-2015.The coordinate time series of each station is obtained.The stacking method is used for spatial filtering to eliminate the common mode error, and the noise of the filtered GPS station coordinate time series is analyzed by means of spectral index calculation and maximum likelihood estimation.The results show that the optimal noise model of N and U in the coordinate time series of Sichuan GPS fiducial station is WN+FN, and the optimal noise model in E direction is WN+FN+RWN; spatial filtering can reduce flicker noise, and at the same time, some stations show random walk noise; the effect of colored noise should be taken into account when the reference station speed is estimated according to the GPS coordinate time series.
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jgg. 2018, 38(5): 516-519.
Based on fundamentals of cycle slip detection and correction through triple-frequency code-phase and geometry-free phase combination, we analyze the rate of electron content (TECR) in ionospheric activity phase. We then present a new triple-frequency method of cycle slip detection and correction for weakening the ionospheric error. The algorithm is validated by triple-frequency observed data in ionospheric activity phase, and the experimental results show that the method can detect and validlyrepair all the cycle slip in observed data in ionospheric activity phases. Moreover, the threshold of cycle slip detection on method is small and the method has no sensitive cycle slip.
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jgg. 2018, 38(5): 520-523.
A modified solution for ill-posed EIV model based on regularization matrix, which is established by eigenvector of normal matrix, is proposed in this paper. The modified solution can overcome the weaknesses of algorithms for EIV model. At last, an instance of height anomaly fitting is utilized to verify the feasibility of the presented solution.By comparison with current solutions, the de-regularization and regularization characters of current solutions are also verified.
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jgg. 2018, 38(5): 524-528.
This paper uses fuzzy sets to describe the fuzzy priori information of the unknown parameter vector based on the fuzzy theory, which is included in the mathematical model in the form of constraint conditions.The adjustment model with fuzzy prior information is given.The new adjustment criterion is established by using the normal fuzzy number, and proposes a new adjustment algorithm with fuzzy priori information. The new method can effectively solve the ill-posed problem of normal equations in surveying adjustment.The error analysis shows that the new method is better than the least squares estimation, the truncated singular value method and ridge estimation.
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jgg. 2018, 38(5): 529-532.
Using finite difference methods, we deduce the solving algorithms for the one-dimensional groundwater diffusion equation. Then, we compare the influence of different differential schemes on groundwater simulation and the corresponding hydrological effects on gravity. The issues of determining the inter-block parameters and linearizing the nonlinear equations are discussed. The results show that, for the superconducting gravimeter (SG) station at Isawa Fan, the influence of different weighting methods of determining inter-block parameters on modeling of groundwater hydrological effects on gravity can reach up to 0.15 μGal, within 1.9% of the total groundwater hydrological effect on gravity, while the influence of different differential schemes and linearizing methods can reach up to 0.12 μGal, within 1.9% of the total groundwater hydrological effect on gravity.
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jgg. 2018, 38(5): 533-538.
By the cuboid model, we use correlation analysis to study the selection of wavelet base and order, and conduct an experiment testing the power spectrum depth estimation technique. The results show that using appropriate wavelet base and order to decompose gravity field, we can obtain the depth information of the stratum. We calculate the Moho depth of north epicontinental areas of the south China sea and Zhujiangkou, Taixinan basin. We acquire results of 28.3, 23.9, and 20.8 km, which are consistent with references.
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jgg. 2018, 38(5): 539-541.
Gravity measurements are performed by adopting the technical requirementsof first-class level measurement. For leveling data analysis and calculation during the course of processing, we deal with the same level staff correction, not parallel of the normal level correct, the feet long correct of leveling staff, and so on. In the process of the gravity anomaly correction, this paper uses the observed gravity anomaly correction and Bouguer anomaly correction for gravity anomaly correction in two different ways. Finally, we compare the results of the leveling point elevation correction and analyze the precision of the two methods.
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jgg. 2018, 38(5): 542-545.
Based on previous research on the current gravity gradiometer,this paper shows a new type of gravity gradient measurement system combining three-axis accelerometer and rotating system.We establishits mathematical proof of feasibility and superiority. This research will provide reference for the independent research and development of domestic gravity gradient gradiometer.
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jgg. 2018, 38(5): 546-550.
Current research on digital zenith camera is mainly focused on the positioning application, so a method of calculating the angle between the x axis and the north direction of the CCD coordinate system is studied.Based on the calculation of the astronomical coordinates of the rotating axis of the zenith telescope obtained from the two stars in the symmetric position, and calculating the true value of the position of the measuring station, the corresponding tangent of the tangent plane coordinate system is obtained.With the angle of 2-axis inclinometer measurement, we calculate the inclinometer X-sensitive axis azimuth angle, and using the least squares algorithm, calculate the directional inclinometer angle.Finally,we calculate the CCD x axis azimuth, directionally.The experimental results show that the digital zenith camera in a work cycle of data calculation, gets the azimuth angle of the standard deviation of σ=3.06′.Thus CCD x axis azimuth meet the requirements of 3σ, can achieve the purpose of orientation.
