10 January 2018, Volume 38 Issue 1
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jgg. 2018, 38(1): 1-4.
Based on the microgravity method for the repeated surveys, regional time-lapse gravity changes can be detected. Using this method, the monitoring capability for the crustal deep mass changes can be established. In this paper, we propose a novel gravity array observation system, which jointly uses the high-precision absolute gravity, relative gravity, leveling, GNSS instruments and hydrological meters in the optimal observation station, on the basis of earthquake monitoring system. The key advantage of this approach is it isolates the microgravity signal with respect to the different field source depths. Moreover, except for improving signal noise ratio related to the deep source, the parameters of arrayed observation can be adjusted for monitoring special sensitive regions. The results are beneficial to estimating the crustal deep mass variation and help us to understand the earthquake preparation and the cause of geophysical field changes as the direct scientific evidence.
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jgg. 2018, 38(1): 5-7.
We process the data from the static and dynamic performance testing of the two new CG-6 relative gravimeters. The results show that the observation accuracy and the standard deviation of the repeatability for the two CG-6 gravimeters are better than 10 μGal and 5 μGal, respectively. The amplitudes of the static, dynamic and mixed zero-drift rate are all less than 8 μGal·h-1. The linear characteristics are presented in the static and mixed zero drift.
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jgg. 2018, 38(1): 8-13.
The purpose of this study is to evaluate the influence factors, improvement conditions and overall adaptability of hydrological models in the Tibetan plateau area. Two important indicators include using GRACE-derived terrestrial water storage (TWS) to compare with outputs from GLDAS, and using rainfall and temperature from in-situ measurements to compare with inputs from GLDAS. This paper uses correlation and error analysis to evaluate the input parameters of GLDAS, and compares it with the actual observation data as model prediction data. Results show that the indicators of GLDAS/Noah are in good agreement with GRACE. The annual amplitude and phase of rainfall and temperature data present higher coefficient of NSE and high consistency between the GLDAS model and the ground observation data.
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jgg. 2018, 38(1): 14-17.
We calculate the focal depth of the Badong M4.3 earthquake sequence and analyze the depth error using the data from the Three Gorges telemetry network and the mobile station. The results show that the sequence of the focal depth is mainly distributed in the 3－5 km; mobile station observation can obviously improve the accuracy of the sequence determination of focal depth, and focal depth error is reduced from 1.8 km to 1.1 km. It is considered that the focal depth in the Three Gorges telemetry network (especially after setting up the mobile station) can be determined by direct wave method.
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jgg. 2018, 38(1): 18-23.
M4.3 and M4.1 double earthquakes occurred in Zigui and Badong counties of Hubei province in June 16 and June 18, 2017. The Wuhan city circle earthquake early warning and intensity expedited reporting system demonstration project network successively obtained 13 and 11 strong motion records of the two events. We analyze the response spectrum and Fourier spectrum of the two earthquakes, and obtain the peak acceleration and instrumental intensity map. Results show that the maximum intensity of the instrument is 7.1 degrees, which is basically consistent with the intensity of the disaster assessment on the site of the epicentre of 7 degrees and 5 degrees in most areas. These results fully reflect the efficiency of Wuhan city circle earthquake early warning and intensity expedited reporting system demonstration project.
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jgg. 2018, 38(1): 24-27.
This study extracts ocean tides in the China sea areas and western Pacific ocean by the ERS-2 and Envisat-1 series of sun synchronous satellite altimeter data over a tidal period of about 15 years. Orthotide response analysis is performed tocompute harmonic constants of 12 constituents along the tracks, and the accuracy of tidal parameters is assessed at the crossovers. The results show that the major constituents derived from the ERS series altimeter data are reasonable and reliable, excepting the S2 and K1 constituents. Considering the additional information from crossovers and adjacent tracks, it is possible to improve the accuracy of harmonics for coastal zones and high latitude areas.
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jgg. 2018, 38(1): 28-31.
According to the forward theory of electromagnetic method, this paper has compiled the forward program of high frequency magnetotelluric method (HMT). In the frequency range of 10 to 105 Hz, we use the adaptive finite element method to simulate the effect of HMT data with undulating terrain. We make three models including peaks, valleys and undulating terrain to simulate the response curves of HMT. The influence of apparent resistivity and impedance phase curves of two polarization modes of TE and TM are analyzed and summarized. The conclusion can provide reference for the interpretation of HMT data under complex terrain conditions.
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jgg. 2018, 38(1): 32-35.
As a collision orogenic belt, Dabie mountain is between the Yangtze and North China blocks. To calculate integrally the rate field of Dabie mountain, we use linear deformation models based on leveling observation data in 1980, 2005 and 2015. Our research shows that: Huaihe plain ground is subsiding due to drawing groundwater; Dabie mountain is lifting as caused by inheritance movement; Yangtze river valley is also dominated by inheritance movement; and the southern segment of the Tanlu fault is in the stage of strain accumulation. Preparation for a potential earthquake should be undertaken.
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jgg. 2018, 38(1): 36-42.
In order to determine the future seismic risk of Yinchuan area, we undertake a comprehensive study of the main faults and tectonic evolution, GPS velocity field, modern seismic activity and hypocenter depth profile of the Yinchuan basin. The results show that the power of the Yinchuan basin is mainly due to the influence of the NW subduction of the Pacific plate and the NE compression of the Qinghai-Tibet plateau, and that the basin is in the environment ofshearing and pulling. The GPS velocity field shows that the velocity in the south of the Yinchuan basin is larger than that in the north. Horizontal tensile deformation and shear deformation during the period of 2009-2015 are reduced compared with that in 1999-2007, but the rate is increasing. According to modern seismic data and hypocenter depth profile, the distribution of the earthquake is mainly near the fault and the focal depth of the earthquake is controlled by the faults, indicating that the fault has a good control of the earthquake. Furthermore, the GPS parallel velocity and small seismicity in the basin have good correlation with the fault activity. The GPS parallel velocity is high, the activity of the small earthquake is intensive and the activity of the fault is strong.
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jgg. 2018, 38(1): 43-47.
In this paper, we use InSAR data from the Sentinel-1A satellite to invert the focal mechanism solutions of the MS7.4 earthquake，which occurred in Tajikistan on 7 December 2015. First,two-pass interferometry technique is utilized to obtain the coseismic deformation of the region, covering the whole epicenter of the Tajikistan earthquake. Second, we utilize the distributed slip model inversion method to obtain a more precise distribution of fault slip by means of down-sampling the original observation data. The results indicates that inversion results are consistent with the observation data. In addition, the inversion results show that the seismogenic fault is dominated by sinistral strike-slip movement. The maximum slip of the earthquake fault is 4.42 m, and the coseismic seismic moment is about 73.71×1018 Nm (MW7.19), which is consistent with the seismic research results available from USGS, GCMT, IPGP after this event. It also shows that this earthquake is a normal and inevitable rupture event in the significant tectonic setting with left-lateral strike-slip motion.
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jgg. 2018, 38(1): 48-52.
In this study, 3 consecutive years of radiosonde observation data since 2012 from three sites of Changsha, Huaihua and Chenzhou in Hunan province has been used to establish multi-factor Tm local models based on the numerical integration and least squares principle. The results showed that Tm has a positive correlation with ground temperature (Ts) and water vapor pressure (es) , while it has a negative correlation with atmospheric pressure (Ps). Compared with the bias of single-factor local Tm model (-2~3 K), the bias of Bevis model is mainly in 0~4 K, which means that Bevis model exists a system deviation in Hunan region. The research also reveals that the two-factor model and three-factor model have an approximate accuracy, but they are all better than single-factor model. Summarily, the two-factor local Tm model is better than single-factor model which is better the Bevis model at the same time. Therefore, it can be applied to researches and applications of GPS meteorology in Hunan region.
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jgg. 2018, 38(1): 53-58.
To determine the characteristics of total electric contents data and the deficiencies of the original models, a model combining modified ensemble empirical model decomposition and ARMA residual correction model is proposed. We use the total electric contents data provided by IGS in 2015, and use the three models to predict the data within 5 days. The results indicate that the mean relative precision of TEC predicted is 96% by the improved model , while the EMD-ARMA model and ARMA model are 94.5%, 93% accurate, respectively.
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jgg. 2018, 38(1): 59-63.
Adopting precise satellite orbits and clocks provided by GFZ, data from MGEX are processed to analyze the performance of BDS carrier phase time and frequency transfer. The results show that the accuracy of BDS time transfer is 0.2 ns when the average number of visible satellites is 10.1 at KARR, which is equivalent to GLONASS and GPS. When the average number of visible satellites is 6.9 at PTVL, the average TDOP is obviously bigger than GLONASS and GPS, and the accuracy of time transfer is only 068 ns, which is significantly worse than GLONASS and GPS. At present, BDS convergence time is significantly longer than GLONASS and GPS, due to the lack of global tracking stations and fewer MEO satellites. The frequency transfer result and frequency stability of the three systems are basically equivalent and have the same change trend. As the station KARR, PTVL is not equipped with atomic clocks, the frequency transfer results and frequency stability are relatively poor.
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jgg. 2018, 38(1): 64-67.
Aiming at the serious ill-posed problem of double-difference equations in BDS short baseline single epoch differential positioning, we use the TIKHONOV regularization criterion to improve the ill-posed problem, and then obtain the reliable floating point solution and its corresponding variance covariance matrix. The partial ambiguity fixed strategy, using the LAMBDA method to obtain an accurate fixed solution, is then applied to achieve centimeter results in BDS real-time positioning.
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jgg. 2018, 38(1): 68-72.
The data quality of space-borne GPS for Swarm satellites is analyzed from the aspects of satellite visibility, DOP value, multipath error, SNR, and so on. The analysis results are compared with data quality of the GRACE satellite GPS. The results show that the multipath effect and the measurement noise of the pseudo-range for Swarm satellites are larger than those of the GRACE satellite, but DOP values are roughly equivalent for both satellites. Although the channel number of the Swarm satellite receiver is small, its tracking ability is stronger than that of the GRACE satellite. Finally, the reduced dynamics orbits for Swarm satellites and GRACE satellites are determined using GPS data, and the results show that the pseudo-range and carrier phase residuals of Swarm satellites are larger than that of GRACE satellites.
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jgg. 2018, 38(1): 73-77.
ZY3-02’s precise orbit is determined from its satellite-borne GPS data and rapid emphasis of CODE with the zero-difference reduced-dynamic method.Overlap arcs are used to valuate satellite’s orbit,the radial orbit of the accuracy is 3.90 cm and the position accuracy is around 5.52 cm. Compared with SLR data,the study shows that the accuracy approaches to 4 cm.Using an extrapolation method and osculating Kepler element to predict satellite orbit,the result shows that the radial accuracy can reach to 30 m in 12 hours.
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jgg. 2018, 38(1): 78-82.
The data of 12 continuous GPS reference stations from Jan 1st, 2006 to Dec 31st, 2014 are computed and compared using stacking filtering, PCA, and KLE methods. The mean baseline of these GPS sites is 2 000 km. After common mode error is removed, the mean RMS of coordinate time series declined 69%, 60% and 41% in N, E, U directions respectively, and position precision is highly improved. For large-scale GPS Networks, PCA and KLE methods can reveal spatial patterns of different sites, more effectively than the stacking filtering method.
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jgg. 2018, 38(1): 83-86.
In this paper,which is concerned with the weighting problem of individual forecasting models in the traditional combination forecasting model, we propose an optimal deformation combination forecasting model based on the Theil inequality coefficient and the IOWA operator. We use the IOWA operator to endow different weight coefficients based on the different accuracy of each time with respect to the predicted value of each individual forecasting model, and then establish the optimal combination forecasting model. The model is applied in deformation data analysis and prediction. The experimental results show that the forecast results of the proposed approach are more accurate than those of individual models and the traditional combination model.
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jgg. 2018, 38(1): 87-91.
In the field of 3D modeling, the precision of the traditional ICP algorithm is not high when the point cloud overlap is low, so we propose a registration algorithm based on consistent sphere. For the registration algorithm, on finding the corresponding points, the proposed algorithm innovatively combines the rotation invariance of the sphere with the SVD orthogonal consistency algorithm based on neighborhood. This helps the registration algorithm obtain the corresponding points with higher accuracy, and on this basis, spread and get more corresponding points. It then uses the rigid constraints to eliminate the error points. Finally, we use the quaternion method to solve transformation matrix. The results show that the proposed algorithm has not only overcome the shortcomings of the traditional ICP algorithm, but has better accuracy.
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jgg. 2018, 38(1): 92-96.
In sphere surface fitting, the errors in the coefficient matrix and observation vector are from the same place, which is the coordinate of the spherical point.The same elements exist in different places.These same elements ought to have the same corrections.The linear form appears in the observation vector.Therefore, an improved total least squares algorithm is deduced which can overcome the above problems.Through analysis of examples,we discover that the parameters obtained from the method in the paper are more reliable.This demonstrates that the method is feasible and effective.
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jgg. 2018, 38(1): 97-101.
The observation error is derived from the pressure measurement, water density, and gravity acceleration error. The errors caused by the density and acceleration of gravity is related to the height of the water column. Error analysis results of the water density and gravity acceleration of the water level observation network in China show that the observation error caused by the error of water density and gravity acceleration can be ignored for most of the observation well. In order to reduce the measurement error of the instrument, the water level sensor should not be too deep, and water temperature in the observation well should not be too high. The influence of density cannot be ignored for observation wells with a high degree of mineralization and rich bubbles, and non-artesian wells with high water temperature. Finally, the testing situation of the water level instrument for many years is summarized. In the last few years the test method combining pressure input and simulation wells to test the observation error of net pressure type water level instrument is more scientific and precise.
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jgg. 2018, 38(1): 102-105.
A cam driver design method is proposed. First, the free-fall cam driver based on absolute gravimeter is introduced in this paper. The path planning is realized by theoretical requirements of the free-falling object. The results are validated by SolidWorks simulation. The results show that the method may solve the design problems for cam-driven absolute gravimeter.
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jgg. 2018, 38(1): 106-110.
This paper introduces the structure and decoding principle of data stream in BINEX format that are received by the Trimble BD970 OEM board. The corresponding observation and navigation files are acquired, implying that the mission of decoding to the measured data is accomplished successfully. In addition, indicators and methods of GNSS observation data quality evaluation are described in this paper. The research conducts data analysis based on decoded data of the BD970 OEM board and eventually acquires relevant indicators on the quality of observational data, providing reliable data for the subsequent product applications.
