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22 August 2012, Volume 32 Issue 3
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. 2012, 32(3): 1-6.Through whole adjustment calculation of the gravity observations of the northeastern edge of QinghaiTibet plateau, the gravity field variation characteristics in 1993-2003 are analyzed systematically.It is found that significant gravity changes appeared to be concentrated in regions with active faults.By using the calculated results of gravity and leveling data, the characteristics of single layer density time-varying image during 1993-2003 of the northeast edge of QinghaiTibet plateau are studied and it can be recognized that the seismic activity is related with the partial anomaly and high gradient of the variations of crustal density and the bending of its isoline. On the basis of the regional Bouguer gravity anomalies of northeastern edge of QinghaiTibet plateau and artificial seismic profile information, the distribution characteristics of Moho surface are inversed.
Further more,the density deformation of crust and the influence of the displacement on the gravity change of the earth surface is studied as well.The spatial correlation between regional microgravity longterm change and Bouguer gravity anomalies of the northeastern edge of QinghaiTibet plateau are explained. -
. 2012, 32(3): 7-16.Dynamic gravity field variations during the period from 2000 to 2007 in China mainland are decomposed after
the method of multiscale decomposition of wavelet transform. The dynamic gravity field variations of the differentscale wavelet
and the following results are drawn: 1) The firstorder wavelet details are independent of tectonic activities basically.2)The secondorder wavelet details well reflect the uplift of Tibetan Plateau and the preparation of Wenchuan \%M\%s8.0 earthquake.3)The thirdorder wavelet details well
give information about larger scale tectonic activities, such as uplift and eastward mass flow of Tibetan Plateau, Kunlun earthquake and Wenchuan earthquake. 4)The thirdorder wavelet approximations well give information about largescale tectonic activities, such as the collision of India plate with Tibetan Plateau, the subduction of Pacific plate to Eurasian plate and the movement tendency of north China block -
. 2012, 32(3): 17-21.The repetitive leveling data in Liaoning area was sorted out to obtain the vertical deformation rate during 1959—1979, 1979—1997 and 1997—2010. On the basis of the results，the author studied the evolution of vertical crustal deformation, tectonic activity of Liaoning area in 50 years, and the correlation of vertical deformation field with seismic activities. The results show that during 1959 to 1979, the differential change of the vertical deformation rate is the biggest, that reflects the crustal activity is intense, and a Ms7.3 earthquake occurred in Haicheng in this period. During 1979 to 1997 and 1997 to 2010, the differential change of the vertical deformation rate decreased, the crustal activity weakened, and there was no big earthquake occurred in this period. In the period,the differential change of the vertical deformation rate shows that the predominant direction of crust activity of Liaoning area was NNE and NWNWW, and the vertical deformation in different periods was respectively under the control along these directions.
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. 2012, 32(3): 22-26.2001 Kunlun Ms8.1 earthquake ruptured as long as about 400 km. The displacement gradient perpendicular to the strike of rupture belt is significantly greater on the south side than that on the north. This fact cannot be explained by Okada model which is based on elastically homogeneous half space. A horizontally and vertically heterogeneous 3DFEM model is established to generate Green’s functions of slip on 16 segments of the rupture belt with respect to the ground displacement field.With the damping LS(least square) algorithm,the slip distribution of rupture is inversed from observed horizontal displacements of 40 GPS sites, and the result is in good agreement with that from geological field investigation. The ground displacement field rebuilt by the inversed result is close to that observed by GPS, demonstrating different deformation patterns on the two sides of the rupture.
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. 2012, 32(3): 27-30.From the GPS data，we calculated and derived the modern activity characteristics of major faults in the northeast segment of the Baryan Har block. The calculated velocity filed shows that the studied zone rotation clockwise from northwest to southeast, and the rates of the GPS sites decreased from west to east. Besides,we studied the activities of major faults in the studied zone from GPS data, the results show that DiebuBailongjiang fault, GuanggaitouDieshan fault, Xiqinling northern edge fault, Huya fault and LixianLuojiabao fault are of left lateral motion basically and the QingchuanPingwu fault, Chabalinansi fault, and Minjiang fault show an right lateral strikeslip motion characteristic respectively.
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. 2012, 32(3): 31-35.On the basis of analysis of the faultcrossing deformation observation data on Shanxi fault zone, this paper discussed the deformation characteristics of the zone. According to the longterm trend analysis, tensional deformation has been the main deformation of both the north and the south part of the Shanxi fault. On the middle part
shearing is the main deformation. The time subsection results indicates that from 1989 to 2000, faulting inverse inheritance turning changes appeared in three stations:Xiadazhi, Daixian, Guangsheng temple,in the central part of Shanxi fault zone. In the same time, the absolute value of the fault’s vertical movement rate significantly reduced, which reflectes a locking condition of the fault activity in Xiadazhi, Daixian, Guangsheng temple area. In addition, the faultcrossing deformation observation data and GPS strain rate field results indicate that the Shanxi fault deformed mainly with a near NW tensional deformation. However, as the different observation dimension, the value between them are not be comparable. -
. 2012, 32(3): 36-40.By use of the data from three IGS stations located in the area of \%M\%w9.0 Japanese earthquake, the total ionospheric electronic content (TEC) values in four days before and after the earthquake were obtained.There was an explicit ionospheric disturbance phenomenon
on that day by analyzing and comparing the computational results. The TEC disturbance phenomenon can be found from different satellite data, which become insignificant with increased distance between the stations and epicenter. A fourday average TEC values before and after the earthquake are computed. The results indicate a significant increase of mean TEC for a few hours after the earthquake. -
. 2012, 32(3): 41-44.Deep borehole strainmeter was installed in Beijing Baishan in October 2008, it has accumulated a lot of observations which provides the basis for the reliability analysis. We analyzed system reliability from stability of the reference component, harmonic tidal factor, and correlation analysis of the plane strain calculated by perpendicular component. In the conclusion, Beijing Baishan deep borehole strainmeter has high consistency and reliability,
it can provide reliable and credible observations for geophysics research and earthquake prediction. -
. 2012, 32(3): 45-49.A new model is established for estimation of zenith tropospheric delays from regional CORS data which does not require any meteorological data and only related to the time and position of the station. By compared with the inverse distance weighting method and the remove and recovery method using measured data from Guangxi CORS, the results show a significant improvement on the calculated accuracy with new model, that the average accuracy is about 8.5mm, especially in the rainy day. Besides, the average accuracy of the new model used to estimate the surface PWV values of CORS station is about 1.5 mm.
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. 2012, 32(3): 50-54.CEI can receive within the same beam the downlink signals transmitted from two colocated GEOs at two receivers of a baseline simultaneously. By doing the crosscorrelation for each GEO, the precise CEI differenced phase can be obtained. And then the differential CEI measurement of the two GEOs can be constructed to cancel major common errors. The principle of relative orbit determination is analyzed. The method to solve unknown phase ambiguity and its precision are investigated. It is pointed out that the strategy of enlarging the length of baseline gradually can ensure the reliability of computed phase ambiguity as well as the filter accuracy of relative orbit. EKF simulations of two colocated GEOs have proved that differential CEIalone can be used to determine relative orbit.
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. 2012, 32(3): 55-58.The relation between the local coordinate system can be solved and the practical 3D coordinate system with the 3D datum transform model, and then by using the relation between the center coordinate of shield tail and link can be obtained, finally,the coordinate of the center of shield head can be solved based on the center of link and the distance of jack. The results show satisfactory when it is used in shield guiding in practice.
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. 2012, 32(3): 59-63.Since the 1950s, hundreds of ground fissures have occurred in Shanxi Graben basin, which is especially obvious in Yuncheng basin. The intensive ground fissures hazard seriously constrained the urban construction and economic development of the studied area—Yuncheng city. By thoroughly analyzing the geological tectonic background of this area, we focused on the influences of new tectonic activity, ground subsidence caused by excessive water withdrawn, rainfall, stratum and geomorphology conditions on the ground fissures, and predicted the activity of ground fissures by combining BP neural network with GIS, and finally verified it with the known fissures information.
A very satisfying conclusion is summarized and it will play a directive role in the prevention and mitigation of ground fissures disaster in this region. -
. 2012, 32(3): 64-67.Selecting the typical land subsidence area of Xi’an city as investigation subject, the influence of construction load on land subsidence was simulated from construction density, plot ration and distance between buildings with finite element model of elastic dynamics based on effective stress principle. The results show that the size of buildings and plot ration as well as the dispersion among buildings have diverse influence on land subsidence, while the load of city construction is one of the main factors that lead to the Xi’an land subsidence in the recent years.
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. 2012, 32(3): 68-71.In order to transform coordinates from WGS84 to CSCG2000 for GPS engineering control network, the ITRF displacement velocity of the stations must be solved accurately. The displacement velocity data are necessary to obtain the velocity field in GPS crustal deformation monitoring network. On the basis of continual observations of CSCORS stations, we discussed two algorithms for calculating the displacement velocity:the weighted interpolation algorithm and dividing coordinates difference by time difference.
The second method can be used for the continually observational GPS network, but for GPS engineering control network only the interpolation algorithm can be used. The displacement rates of CSCORS stations in three periods had been computed accurately and it is found that the displacement rates are nonlinear.The examples show that the displacement rates computed by two different methods are consistent, thus the weighted interpolation method can be adopted to solve the rates of stations in GPS engineering control network. -
. 2012, 32(3): 72-75.Considering the real significance of the recommendation of “northward extending coverage area”, and that the position report service and short message service by using RDSS offer great societal benefits, we put forward the suggestion in favor of northward extending the RDSS service coverage area of the 2nd generation BEIDOU/COMPASS navigation satellite system, and adding RDSS function to IGSO satellite belong BEIDOU constellations.In addition, the necessity and feasibility of the suggestion are dealed with.
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. 2012, 32(3): 76-79.A new combination method based on the frequency spectrum analysis and the grey model
is proposed to forecast the ionosphere TEC. First, the grey model is established based on the residuals calculated by the frequency spectrum analysis and then to calculate the next epochs’ residuals and add them to the forecast results from the frequency spectrum analysis. The results indicate that the forecast accuracy is about 0.53 TECU and the RMS error of forecast values is about 0.65 TECU. Forecast accuracy is related to longitude and latitude rather than the length of the used historical data. Compared with existing methods, this method is of higher accuracy with fewer data and has simplicity for promising application in ionosphere TEC short-term forecast. -
. 2012, 32(3): 80-85.The kinematic orbit determination of LEO satellite software named GNSS_LEO_KPP is developed, and the
observation data of GRACE_A and GRACE_B satellites in 7 days from DOY220/2011 to DOY226 / 2011 are calculated. Compared with the JPL precise orbits, the accuracy of final kinematic orbit can reach 10—20 cm.
The results show that: the priori orbit quality has a certain level of impact on the final kinematic orbit quality, so we could use the iterative loop kinematic orbit as a prior orbit, and the final kinematic orbit accuracy can be maintained in decimeter or subcentimeter level. -
. 2012, 32(3): 86-89.Aim at the problem of quality control and node choice in modeling local marine geomagnetic field based on multisurface function, a fitting method with combining robust trend surface and orthogonal least squares is proposed. In order to control the influence of some outstanding points to surface fitting, a robust fitting of the trend surface by using an equivalent weight is adopted and the adaptive node choosing method is proposed based on the effect of every node on the curve fitting calculated by using the orthogonal least squares as well. The results show that this method is more effective in accuracy and stability than normal method.
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. 2012, 32(3): 90-93.The TLS fitting and estimation residuals will be upward with the increasing in the amount of observed data in the process of TLS fitting and estimation. In order to curb the trend, the adaptive regression is introduced to the TLS fitting and estimation. The appropriate regression model is used to analyze the residuals handled by gray method. The results of residual analysis is combined to the results of TLS fitting and estimation to weaken the impact of residuals. The experimental results confirm the feasibility of the method.
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. 2012, 32(3): 94-96.
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. 2012, 32(3): 97-101.An equivalent weight robust ridge estimation model is derived according to the idea of robust estimation for correlated observations, and then the Lcurve method is introduced to this model for the solution of ridge parameters. In the iterative process, equivalent weight matrix may be non positive definite so it can not be unitized through classical Cholesky decomposition. According to the characteristic of bifactor model, an algorithm of equivalent weight matrix decomposition is proposed to solve this problem, then the Lcurve method can be successfully used in this process. The calculated example manifests that this model can effectively eliminate the influence of coefficient matrix’s morbidity and gross errors.
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. 2012, 32(3): 102-105.The simulation technique of triplefrequency GPS data by using uncombined precise point positioning(PPP) algorithm is proposed. Through solving GPS dualfrequency observation data, the errors of observational environment including troposphere and ionosphere delay are calculated, and then the data of L5 frequency are simulated according to the errors calculated. By the comparison with the measured L5 observation data,it is obtained that the difference between the simulated carrier and the observed carrier is less than 0.2 cycles, and the fluctuation is small enough that verifies the algorithm. Consequently, the simulation technique using PPP could reflect the actual measuring environment and play a significant role in the relevant triplefrequency algorithm.
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. 2012, 32(3): 106-109.The model for optimum selection of the test quantities of triplefrequency cycle slip combinations is investigated according to the theory of multifrequency cycle slip detection.
Furthermore,taking the smallest variance of cycle slip as the standard, and the wavelength of phase combination as the constrain condition
a linear independent carrier phase combinations are selected as cycle slip test quantities. By use of the triplefrequency GPS observation data from IGS, the performance of the cycle slip detection combinations is tested. The results show that the combinations proposed could effectively detect cycle slips on every frequency. Consequently, it can play a significant role in the practical triplefrequency GPS data preprocessing. -
. 2012, 32(3): 110-115.By analyzing the electromagnetic spectrum data observed by DEMETER satellite during the time interval between March 2006 and February 2009, it is found that the characteristics of electric field power spectrum of global ionosphere in DEMETER altitude are as follows：the 50-300 Hz frequency band about earthquake ionospheric effect are the dominant frequency the closer,the distance to seismic spatial position, the more significant seismic anomaly; indifferent hemispheres of the earthquake, abnormal azimuthal direction is different.The studies on the events in northern hemisphere in geomagnetic summer show that the anomaly corresponding marine quakes occured in geomagnetic summer the frequency spectrum anomaly of geomagnetic field basically were positive and these land negative and corresponding the quakes in different hemisphere were significantly different:these in
the northern hemisphere were positive and meridional, and negative anomaly of north but negative anomaly opposite in the southern hemisphere, the negative anomaly were northeast and positive ones southwest. -
. 2012, 32(3): 116-120.According to the theory of the elliptic integral of the second kind and Lagrange inversion theorem, we present a new method to solve the inverse problem of Meridian arc length, which is expressed by Taylor Series generated from the cosine function of reduced latitude. It gives a analytical solution for this problem. Numerical calculations are used to illustrate the accuracy of the method and the results show that it is applicable and useful in practice.
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. 2012, 32(3): 121-124.A new ephemeris calculation method based on Doppler integration
is proposed in order to detect and repair cycle slips. This method use ephemeris data to calculate Doppler integration between neighboring epochs accurately. In the condition of static observation, with this method we can detect and repair cycle slips from singlefrequency observation data of large sampling interval easily, without Doppler observations of receiver.The example of IGS observation data shows that with this new method the single cycle slip and continuous cycle slips from IGS data of 180 seconds sampling interval can be detected and repaired easily. -
. 2012, 32(3): 125-128.The transformation method of high accuracy for a threedimensional space rectangular coordinate system based on the use of robust estimation theory is discussed. The method can overcome the low accuracy of individual public point coordinates or very large which will give the latge effect on coordinate transformation error the parameters, and calculate the accurate coordinate transformation parameters, so as to achieve the high accuracy of coordinate transformation. Through the analysis of an example shows that this method is practical and effective
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. 2012, 32(3): 129-134.The timefrequency analysis method base on EMD(empirical mode decomposition) for GPS height time series is put forward.Taking two national CORS stations’ GPS height time series as an example, each intrinsic mode function is decomposed and the contribution rate of variance is also calculated. The problem of identifying father distinguishing the periodical signals and the trend is emphasizerd. The results indicate that it is only meaningful to distinguish the periodical and the trend signal on certain length of time series’ section. The trend based on EMD or EEMD presents with large curvature while the traditional form of periodical fitting function only linear form.
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. 2012, 32(3): 135-138.To estimate the effects of set and drop numbers on FG5 absolute gravity measurement, different set and drop numbers
were taken in a test and the result of absolute gravity accuracy and gravity value were calculated and analyzed. The results show that
when the sets is 13, 1 set/hour and 100 drops/set then the FG5 absolute gravity measurement can satisfy the 5.0×10 -8 ms -2 accuracy requirement. -
. 2012, 32(3): 139-151.The geoscience has focused on the explorations of the Earth’s deep interiors and its dynamics for a long time. In the past twenty years the study in this area reached a new stage and a series of new discoveries had been published. In this article, we review the main results obtained from the studies so far and explore its developments in the future.
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. 2012, 32(3): 152-159.]The progresses in the nextGeneration American GRACE FollowOn and European E.MOTION satellite gravity measurement missions are respectively introduced for the sake of providing a reference for the nextgeneration satellite gravity measurement mission in China. Finally, the research significances and scientific objectives of the nextgeneration PostGRACE satellite gravity measurement mission in China are expatiated in detail. We propose that the software platforms of precise orbit determination and satellite gravity recovery should be established as soon as possible, the error analyses of key payloads of gravity satellite should be developed in advance, and the mission requirements of satellite gravity measurement should be carried out as early as possible.
