15 November 2019, Volume 39 Issue 11
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jgg. 2019, 39(11): 1101-1105.
Based on GPS ground-to-earth observation velocity field data of the continental tectonic environment monitoring network of China mainland in the Bohai rim region from 2009 to 2014, we use the global rotation and linear strain models for calculation. The area is divided into five sub-blocks, and we obtain the strain field of 0.5°×0.5° of the research area relative to the Eurasian plate. The spatial variation of the deformation velocity field and the strain field are analyzed. It is found that the Bohai rim region presents a two-way trend expansion movement of 0.25×10-9/a NW-SE 111.3°. The strain details of each sub-block are provided: the Taihang block is NW-SE 116.3°, and the Shanxi block is the weak expansion movement of NW-SE 130°. The weak compression movement is NW-SE 144.3°, NE-SW 39.5° and NW-SE 155.6° in the Jiaoliao, Jilu, and Yinshan-Yanshan blocks respectively. The magnitude of the expansion motion of the Taihang block is larger than that of the other secondary blocks. Although the deformation of each sub-block in the Bohai rim region is spatially different, the direction of the main compressive strain axis of the Bohai rim region is basically NEE-SWW, the strain axis is basically NNW-SSE, and the main compressive strain axis direction is NE 47.70°～8974°, which is generally consistent with the dominant direction of the principal compressive strain axis of the region obtained by geophysical methods, indicating that the current crustal movement in the Bohai sea region is relatively stable.
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jgg. 2019, 39(11): 1106-1111.
In this study, InSAR data from Sentinel-1 satellite are used to image the coseismic deformation and constrain the focal mechanism of the MW6.3 earthquake that struck Jinghe county, in the central segment of the Tien Shan Orogenic system, northwestern China, on 9th August 2017. After the orbit and atmospheric error are corrected in the coseismic interferogram, we find a maximum surface displacement in line of sight (LOS) up to 7 cm, and no surface rupture in this event. Assuming an elastic homogeneous half-space, a two-step inversion strategy is adopted to inverse the fault geometry and slip distribution, respectively. Our results demonstrate this event is dominated by thrust-slip with no strike-slip, and the main slip zone is in depths of 8 to 17 km with a maximum slip of 0.6 m, suggesting this event is a blind reverse thrust rupture with one asperity. The seismic moment determined in this study is 2.91×1018 Nm, corresponding to MW6.25, which is consistent with the focal mechanism from USGS and CENC.
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jgg. 2019, 39(11): 1112-1117.
Aiming at the problem of insufficient monitoring information when InSAR technology is used to study the surface three-dimensional deformation, a three-dimensional deformation model with stochastic model constraints is established with GPS monitoring information as a priori. Considering that the LOS observation is insensitive to the North-South deformation due to the polar orbit of SAR satellite, the function constraint condition of 3D deformation solution is constructed with the strong constraint of GPS north-south deformation observation. The results of the simulation data and the measured data in Xi’an area show that the least squares solution based on the combination of stochastic model and functional model is more accurate than the parametric solution, with only functional model constraint or stochastic model constraint, and the parametric solution without any constraint.
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jgg. 2019, 39(11): 1118-1121.
The repeated gravity data of the Three Gorges gravity network are processed and analyzed. 11 differential and cumulative gravity change maps from March 2016 to September 2018 are obtained. The characteristics of gravity changes before the Zigui M4.5 and M4.1 earthquakes on October 11, 2018 are analyzed. The results show that: 1) since 2017, the gravity field of the epicenter region decreases, then increases, then decreases slightly before the earthquake occurs; 2) the two-year cumulative gravity changes show that gravity changes increase along the Xinhua-Longwangchong and Gaoqiao fault areas, which may be related to the preparation of these earthquakes; 3) as long as the observation network grid distance is reasonable and the data are properly processed, the regional mobile gravity survey network can give us potential detection capability for the change of gravity field before small earthquakes of magnitude 4.0.
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jgg. 2019, 39(11): 1122-1126.
We select Japan and its adjacent region as study areas,and divide it into some subareas.With the Schuster test we calculate the p-value of each subarea using tidal stresses caused by the sun and the moon.On this basis,the Schuster spectra are built for the subareas with p<5% in order to estimate the periodicity of seismicity in the subareas.Then,the correlation between seismicity and tidal stress in Japanis studied further.The results show that among the 75 subareas,the p-value of 22 subareas is less than 5%,and 2 of 22 subareas’ Schuster spectra show a distinct period of semidiurnal tides,which indicates the seismicity in these areas has a degree of triggering by tides.
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jgg. 2019, 39(11): 1127-1131.
In this paper, we use GRACE CSR Mascom data to analyze the effect on the leakage error correctionof boundary expansion and ocean signal within the boundary by means of fitting method in the Antarctic. Simulated results show that the minimum extending range is 300 km, when only considering the leakage-out error from the Antarctic.The ocean signal in the expansion boundary has a significant influence on the Antarctic mass change, particularly for spatial distribution of the mass change along the coastline region. When considering the leakage-out error and the influence of the adjacent ocean signal, the experiment suggests that the optimized extending range is 100 km. Then, the optimized extending range is applied to the fitting method, and the trend of the Antarctic mass change derived from the GRACE CSR RL05 data is -178.61 Gt/a, which is in good agreement with the Mascom results.
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jgg. 2019, 39(11): 1132-1136.
Based on strapdown marine gravity real data, we check the effectiveness of using wavelet threshold in filtering marine gravity anomaly. We test different wavelet, threshold techniques and decomposition levels. Results show that the db6, db7, db8, db9, db10, sym6, sym7, sym8, sym9, sym10, coif3, coif4 and coif5 are the thirteen wavelets suited for marine gravimetry, and wavelet decomposition level can be taken to 8 or 9 layers. The unbiased risk threshold filtering effect is better. When the wavelet is decomposed into the 8th and 9th layers, the result of the wavelet threshold filtering agrees well with the filtering results using the Butterworth low-pass filter with 0.005 Hz and 0.0033 Hz cut-off frequency, but the result of the wavelet threshold filtering is more smoothing than the Butterworth low-pass filter. Further, the RMSE of the difference between the two filtering results is within 0.25 mGal. Wavelet threshold filtering is easier to decompose the noise component than the Butterworth low-pass filter, which can eliminate gravity distortion more effectively.
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jgg. 2019, 39(11): 1137-1141.
This paper uses the Ts and Tm data of 13 stations in China’s coastal areas from 2010 to 2014 to improve the Tm model of China’s coastal areas through Fourier series analysis. The Tm data of the 2015 radiosonde station are used to test the new model. The results show that, by comparison with the higher calculation accuracy, the error probability distribution of the precipitable water vapor is close to the normal distribution and has strong stability.
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jgg. 2019, 39(11): 1142-1147.
We analyze the accuracy of the tropospheric delay in China calculated using ECMWF surface data with the water vapor decline rate and the temperature decline rate provided by the GPT2w model. At first,we analyze the accuracy of meteorological parameters(P,T,e) derived from ECMWF. The results show that the mean RMS are 1.76 hPa, 1.96 K, 1.98 hPa, respectively. Then, we compare the ZTD calculated from ECMWF surface data with bench mark values derived from 6 years(2010 to 2015) of radiosonde data recorded at 75 radiosonde stations in China. To make the result more credible, we also analyze the accuracy of ZTD calculated from radiosonde surface data. The results show that the mean bias value of ZTD derived from ECMWF is 0.07 cm and the mean RMS is 3.72 cm, which is even smaller than radiosonde in the low latitude region. We also assess the accuracy of the ZTD calculated from ECMWF surface data using ZTD time series derived from GNSS stations of CMONOC in 2015. The result shows an average accuracy of 3.41 cm. Through the research, we can draw a conclusion that the accuracy of ECMWF surface data is high enough to be used in the calculating ZTD of stations in China where the meteorological parameters are unavailable and for related GNSS applications.
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jgg. 2019, 39(11): 1148-1152.
Base on the meteorological parameters (temperature (T), air pressure (P), and precipitable water vapor (PWV)), of Beijing Fangshan Station released by the IGS Center and PM2.5 data for the same period, this paper establishes a haze prediction model combining time series network and regression network to predict PM2.5 concentration. The research shows that the fusion network model introducing GNSS meteorological parameters is more adaptable and accurate than the single network model, that it can accurately predict the change of PM2.5 within a certain accuracy range, and that timeliness can reach 3 h. Related studies have verified the feasibility of satellite navigation technology for monitoring and forecasting of haze weather.
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jgg. 2019, 39(11): 1153-1158.
Based on GPS observations from CMONOC, the RIM over China is derived precisely. We introduce a new method of singular spectrum analysis(SSA) to estimate the prediction models of TEC extracted from RIM. A suitable length of original TEC time series of 27 days is selected. By the w-correlation, the RC and window size of prediction model can be also determined. It is found that when the size of window is set as 1/3 of original series, the iteration of the first 5 RC decomposed by SSA has the best effects. The TEC data at center grid point of RIM from 1 to 27 d, 101 to 127 d, 201 to 227 d, 301 to 327 d are extracted respectively, to predict TEC for 7 days by SSA method. Meanwhile, the ARMA prediction model is also found and the models are compared. The results show that, compared with the ARMA model, the relative accuracy of SSA model is improved 10% for 7 days, with better long-prediction and anti-magnetic abilities. Furthermore, the TEC data of 2911 points are predicted by both methods. It is found that the RMSE gradually rose along with the decline of latitude, while the relative accuracy of grids over mid-latitude is slightly higher than other regions. However, regardless of the evaluation index, the SSA prediction model is superior to ARMA model.
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jgg. 2019, 39(11): 1159-1164.
Based on the global atmospheric model and the time series data of CORS location, we calculate the influence of atmospheric load on the crustal deformation at CORS locations using the spherical harmonic coefficient method. The results show that the influence of atmospheric load on the vertical direction of CORS location in the study area is -15.9 to 13.2 mm, and the influence on horizontal deformation is 0 to 2.7 mm. According to the change of RMS value before and after removing the influence of atmospheric load on CORS, it is concluded that removing the influence of atmospheric load on the horizontal direction of CORS time series has little improvement, but has obvious improvement on the vertical direction. According to the least square method, the crustal vertical deformation admittance(regression coefficient) of the study area varies from -0.75 to -0.43 mm/hPa. The research methods and results of this paper can be used for reference in the separation and correction of atmospheric load in CORS.
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jgg. 2019, 39(11): 1165-1170.
By selecting 16 iGMAS station observation data for 10 days from January 23, 2018, the observation data quality of third-generation Beidou satellite (BDS-3) and the orbit accuracy of BDS-3 satellites satellite are evaluated using BDS-only precise orbit determination (POD). In the data quality analysis, two stations with different receiver types are selected to evaluate the signal-to-noise ratio (SNR), pseudorange noise and multipath error for Beidou new and old signals, comparing them with GPS Block ⅡF and Galileo FOC satellite. The pseudorange noises of all stations are calculated and analyzed. The results show that the signal-to-noise ratio of B1I and B3I for BDS-3 satellite is slightly stronger than those of BDS-2 satellites. The noise multipaths are considerable between BDS-2 and BDS-3 satellites, both of which are at the magnitude of 0.1m. BDS-3 satellites do not have satellite-induced code pseudorange variations. As to the new signals, the B1C/L1/E1 SNR is strongest for GPS satellites, and the Galileo is equivalent to the BDS satellite. The SNR among three GNSS systems in B2a/L5/E5a and B2b/E5b frequencies are basically equivalent. In terms of noise and multipath, B1C/L1/E1 GPS is superior to BDS and Galileo, with the magnitude of 0.1m. B2a/L5/E5a and B2b/E5b are basically the same, both at the magnitude of 0.1m. In BDS-only POD tests, strategies with/without GEO satellite and ECOM five or nine parameters were respectively compared, and the satellite laser ranging data are used for independent check. The results show that the orbits with GEO satellite and selecting ECOM five parameters can receive the best accuracy. The average orbit determination precisions of C19 satellite with 7 overlapping arcs are 32, 16 and 8 cm in along, cross and radial directions, respectively.
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jgg. 2019, 39(11): 1171-1177.
We perform multi-GNSS precise point positioning(PPP) testing on MGEX stations based on the ISC products released by the iGMAS Product Integration and Service Center(ISC), the GBM products released by the Helmholtz-Centre Potsdam-German Research Centre for Geosciences(GFZ), and the GBM-300 s products based on re-sampling of GBM clock products. This paper analyzes the positioning accuracy, convergence rate, ZTD accuracy and station clock accuracy of 15 MGEX stations around the world from January 1 to January 15, 2018. The experimental results show that the 3D positioning accuracy and convergence rates of Beidou PPP based on the ISC products are better than GBM products for 0.89mm and 24 min; the ZTD accuracy and station clock accuracy of the Beidou PPP based on the ISC products are better than GBM products for 0.3 mm and 0.02 ns; the difference between the ZTD accuracy and the station clock of the GPS, GLONASS, Galileo PPP and the four system combination PPP based on the ISC products, as compared with that based on the GBM products is less than 1.5 mm and 0.05 ns. However, the positioning accuracy of the PPP based on ISC products is lower than that based on GBM products for 2 to 3 mm in the Up direction and the convergence rate of the PPP based on ISC products is slower than that of GBM products for 5 to 20 min. This paper analyzes the accuracy and service reliability of iGMAS products, and gives suggestions for the improvement of iGMAS product performance.
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jgg. 2019, 39(11): 1178-1181.
In this paper, we use the theory of numerical analysis and design a method of ground track point calculation based on GCRS-ITRS transformation. Based on the earth ellipsoid model and the IERS2010 standard, combined with the mature basic library of Standards of Fundamental Astronomy (SOFA),under the enviroment of C++, the method can satisfy the requirements for real-time and accuracy.
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jgg. 2019, 39(11): 1182-1187.
We propose a new method for ill-posed problems in the large rotation angle three-dimensional coordinate transformation based on the unit quaternion. This method constructs a rotation matrix by unit quaternion, which avoids complex trigonometric function derivations, is easy to linearize, and has a more concise coefficient matrix. Considering the ill-posedness of the normal equation matrix, the ridge parameter and the functional matrix are introduced, which reduces the adverse effects caused by the ill-posedness of the equation, and generates a stable equation solution. At the same time, the estimated value of the solution when the equation is iteratively solved is closer to the true value than the traditional iteration method by correcting characteristic value. The algorithm is verified by simulation and measured data, showing that the algorithm has the characteristics of fast convergence, no initial value of conversion parameters, global convergence, unbiased solution and easy program implementation. It provides a new way for general coordinate transformation.
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jgg. 2019, 39(11): 1188-1193.
The random error of MEMS gyroscope has become the main factor affecting system navigation accuracy, and there is a universality problem in modeling, so we propose an error compensation method of cubic Kalman iterative estimation. The Allan variance is adopted to identify the random error parameters of MEMS gyroscope. Combining the trailing property of MEMS gyroscope output data autocorrelation and partial correlation function, we design a Kalman filter model of MEMS gyroscope error based on time series ARMA. The test environment is set up with 6 MEMS inertial measurement units of the same model, and the verification experiment is carried out. The results show that the error coefficients of the MEMS gyroscope after the filtering process are significantly reduced, and the filtering effect is enhanced with the increased filtering. Meanwhile, the 6 sets of MEMS test equipment show the consistency of the error reduction trend. The comparison of results of attitude errors caused by gyroscope show that the filter method proposed in this paper is helpful for navigation.
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jgg. 2019, 39(11): 1194-1197.
In this study, we reanalyze the wave records from temporary seismic monitoring stations and the 4 to 5 permanent stations closest to the epicenter in the head region of Xiluodu Reservoir. The focal depth of the relocated earthquakes is compared with the network catalogue, and there is a clear deviation. The focal depth determined by the temporary stations and the permanent stations closest to the epicenter can explain the cause of the earthquake and the mechanism of the reservoir induced earthquake. It can provide references for other hydropower projects in the study of reservoir induced seismicity, and how to use seismic observation data to determine more credible seismic focal depth.
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jgg. 2019, 39(11): 1198-1201.
To study the geochemical characteristics of the gas in the soil layer and the tectono-geochemical background, which was reflected by fault gas in the south Anyang fault zone, two periods field measurement are used to analyze the concentration distribution of soil H2 and Rn in the one observation line of Zong village. The results show that the distributions of H2 and Rn concentration in the first phase range from 0.66 to 58.56×10-6 and from 15 to 123 kBq·m-3, respectively. The background values of H2 and Rn concentration are 6.87 ×10-6 and 52.49 kBq·m-3, respectively. The concentration distribution range of H2 and Rn in the second phase range from 0.36 to 29.73×10-6 and from 28.2 to 103 kBq·m-3, respectively, with background values of 0.89 ×10-6 and 47.49 kBq·m-3, respectively. In two phase measurement, a strong anomaly of H2 and Rn appears at 210 to 300 m, with anomalous values located near the fault zone, which could effectively indicate the fracture location. It is feasible to use fault gas H2 and Rn to detect the location of concealed faults in this area.
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jgg. 2019, 39(11): 1202-1206.
Several fault gas continuous observation points along the Maoshan fault line are planned to establish a fault gas observation network. Taking Maoshan Zhukuang as an example, this paper analyzes the fault gas characteristics of the site by combining the results of fault gas selection with geological, artificial earthquake and short leveling across faults. This helps to determine the location of continuous fault gas observation points, and to provide reference for subsequent fault gas network selection.
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jgg. 2019, 39(11): 1207-1210.
This paper presents a practical application of the aerial photo technique using an unmanned aerial vehicle to inspect cable PE appearance in Tianxingzhou river bridge. First, we design a detail scheme including the flight and inspection based on the structural characteristics of the bridge and the distribution pattern of the bridge cables. Then, high-definition (HD) images of the cable PE appearance are acquired densely by the HD camera of the unmanned aerial vehicle. Finally, the working status and health condition of the bridge cable can be evaluated effectively by analyzing the acquired HD images. Compared to the traditional inspection techniques, such as the hanging basket and rope climbing robot, the aerial photo technique using unmanned aerial vehicle has advantages, including ease, effectiveness and strong maneuverability.
