16 August 2013, Volume 33 Issue 4
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jgg. 2013, 33(4): 1-3.
Based on the data obtained since 1951 and the crustal vertical deformation rate calculated from the GPS data obtained from 1999 to 2007, the vertical deformation characteristics in QinghaiTibet block and southern China block, and the relationship between the vertical deformation and both of the occurrence and the development of Wenchuan Ms8.0 earthquake was studied. The results show that Wenchuan Ms8.0 earthquake happened in the vertical deformation rate gradient zone that was the dramatic rising area.The accumulation of deformation strain energy was related with collisions of the IndianEurasian plates, and the vertical uplift of the QinghaiTibet block by strong squeeze in NorthSouth direction at the front edge of the collision of the two plates with the substance movement to the East and SouthEast.
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jgg. 2013, 33(4): 4-8.
Taking the 2008 Gaize earthquake as an example, we use InSAR and MAI techniques to measure line of sight (LOS）and azimuth (AZI）deformations, respectively.InSAR+AZI(model 1）and MultiLOS(model 2）models are applied to reconstruct 3D coseismic deformation fields, Compared with simulations, we discover that the deformations in eastwest,vertical directions of the two models are consistent with each other; however, in northsouth direction, the results of model 1 are tally with the actual situation, while massive distortions occur in that of model 2.
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jgg. 2013, 33(4): 9-12.
Using the GPS observation results of 1999—2007 and 2009—2011 as the constraints, and based on the method of threedimensional finite element, the fault motion and segmentation characteristic of Kouquan fault in Datong basin were analyzed. The results show that the fault is more active in the middle part than the either side. The rightlateral velocity of the fault is 0.8 mm/a and its normal velocity is almost 1.5 mm/a in the middle part of the Kouquan fault.
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jgg. 2013, 33(4): 13-16.
The velocity field of the 296 stations in the SichuanYunnan region has been obtained with the GPS observation data of the CMONOC from 2009 to 2011. Based on the continuous deformation hypothesis, we use the data of the horizontal velocity field to compute the distribution of horizontal strain field in this region by the triangle method. Preliminary analysis indicates that: 1） In SichuanYunnan region, the crustal movement of north and west is stronger than that of south and east. The SichuanYunnan rhombic block is characterized by clockwise rotation. 2） The directions of the principal compressive strain axis and the P axis of the focal mechanism solution show that tectonic stress field in this region is relatively stable in a long term. 3） The high value areas of the principal strain and the maximum shear strain rate are in the Longmenshan fault zone and its surrounding region. In addition to the above areas, the significant highvalue properties of the maximum shear strain rate can be seen in the south of the Xianshuihe fault zone and the northwest segment of the Red River fault zone.
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jgg. 2013, 33(4): 17-21.
Combined the method of curve fitting when calculating a lowerfrequency strain field in a large area with the strain tensor matrix on the earth reference ellipsoid, we put forward a method of calculating strain parameters on reference ellipsoid by using multisurface function. According to the GPS data, we get the QinghaiTibet plateau strain field. The result is in line with both characters of the major tectonic activity within this area and the main direction of P,Taxis from focal mechanism solutions
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jgg. 2013, 33(4): 22-25.
We analyzed 17 M≥6.0 earthquakes which occurred in the mainland of China from 2007 to 2011 by Total Electron Content （TEC） provided by IGS web. We used Principal Component Analysis（PCA） method to detect the TEC anomalies over the epicenter and compared with the method of sliding window statistics. The results show that the PCA analysis is not affected by geomagnetic storm, and broadly consistent with the results of the analysis of the two statistical methods. There are significant abnormalities in the same time and space. Ionospheric TEC anomalies are mainly concentrated in the 0-5 days before the earthquake.
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jgg. 2013, 33(4): 26-30.
Earthquake hazard of Datengxia reservoir in Guangxi region is analyzed using the selfmade software. The whole reservoir is divided into five segments, and eight factors are chosen to calculate the magnitude probability and the corresponding intensity of each segment. The results show that it is possible for the moderatestrong earthquake occurring in Kuwei to Lema and Daduwan to the dam after impoundment, the probabilities are 0.499 and 0.272, respectively. It is less likely to occur earthquake in the three segments between Lema and Daduwan. Under these circumstances, the epicentral intensity of the Kuwei to Lema and Daduwan to the dam segments will reach VI based on the intensity attenuation relationship of reservoir induced earthquake, and the lengths and widths of the isoseismal are 6.7 km, 3.8 km and 5.9 km, 3.3 km, respectively.
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jgg. 2013, 33(4): 31-35.
The paper studies the different coseismic changes of water level caused by the M85 Sumatra earthquake on Sep.12 in 2007, the M90 Japanese earthquake on Mar.11 in 2011 and the M80 Wenchuan earthquake on May.12 in 2008 and local earthquakes in the Three Gorges area between Sep and Nov in 2008 through the Three Gorges well network, the mechanism is explained. Corresponding relationship between coseismic changes of water level and parameters of teleseism and local earthquakes is deduced.
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jgg. 2013, 33(4): 36-38.
According to the requirements of the project, we undertook research on the activity of QingshankouHuangpi Fault. In this study, we measured gaseous mercury in soil and electromagnetic field along 4 lines accrosing the Fault by XG4 digital mercury analyzer and very low frequency analyzer. The measure data indicate that contenents of intensity of gaseous mercury in soil and electromagnetic is closely related to fault activity. In the active sections of the fault, abnormality of gaseous mercury in soil and electromagnetic field are much higher than that in the stable sections.The results mean that the two methods above can be used not only to confirm the location of faults,but also can be used to analize intensity of an active fault.
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jgg. 2013, 33(4): 39-43.
Combining with horizontal geoelectric field data in Hongshawan, Huangyangchuan and Songshan stations in Gansu province, the vertical geoelectric field data of three years observed in the three stations are studied. The results showed that:1）The obvious and stable annual periods of sinusoidal shape were found from vertical geoelectric field data in the three stations, but the value and the phases of an annual variation period are different.2）The impending anomalies before the earthquakes recorded by the vertical geoelectric field from Hongshawan station agreed with the earthquake occurrence in time and space. But whether the anomalies were caused by the earthquakes, a further research is needed.
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jgg. 2013, 33(4): 44-47.
The yearly rate of gravity change owing to elevation changes and underground material transfer were calculated using 10 years measurement results of absolute gravity and GPS at Jixian datum. The results show that the technology of monitoring tiny vertical crust movement using highprecision absolute gravimeter is rapid, efficient and no error accumulation. In addition, the loss of underground water of Jixian is serious in recent years.
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jgg. 2013, 33(4): 48-51.
The vertical crustal movement velocity field in Hebei is calculated using the GAMIT/GLOBK software with GPS observational data of the firststage stations of Hebei CORS network in the past four years. The results show that the mainly vertical crustal movement is a downward motion and that southeast plain region is a serious settlement area in Hebei. The cumulative subsidence in the past three years is more than 150 mm in part areas. And the vertical descent rate in November is faster than that in April. The larger difference of rate has more than 10 mm/a. The model of vertical crustal movement velocity field in Hebei is established based on the method of multiquadric functions and 6′×6′grid velocity is calculated and the isoline map of vertical movement velocity is drew.
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jgg. 2013, 33(4): 52-55.
An orbit gravity field was simulated through the EGM2008 with ultrahighdegree, and then the gravity field was approximated by polynomial fitting with divided segmentation of the orbit. According to the different segmentations and polynomial fittings, a test was done which focuses on the precision, data storage and calculation speed of the polynomial fitting. The results show that: comparing with traditional methods, the computing speed of the orbit gravity field by the segmentation polynomial fitting approximation improves 3 orders of magnitude, and data storage is less than 100 floating point numbers.
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jgg. 2013, 33(4): 56-60.
〗In this contributions we defined the model of mixed structured total least squares according to the mixed least squarestotal least squares and proposed an iterative algorithm for the mixed structured total least squares problems, which solving by the nonlinear least squares adjustment theory. Three numerical examples are given at last,where assumes the errors of elements in observation vector equal ,greater and lesss than the error of independent elements in coefficient matrix ,respectively. It’s shown that the method represented in this paper would be able to estimate the parameters theoretically closer to the true value and attain the more precise mean square error of weight unit than least squares and mixed least squarestotal least squares, especially when the coefficient matrix which holds more errors than observation vector.
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jgg. 2013, 33(4): 61-64.
Four images for ALOS PALSAR of the track 474 before and after Wenchuan earthquake are processed by the software ROI_PAC, and then the tropospheric and ionospheric delay are corrected
by ERAInterim data and NeQuick model. The sedimentation is compared with that derived from five GPS observations, the results show that the mean value of the differences between the sedimentation derived from DInSAR and that from GPS observations is 0.104 m, which is 0.057 m when the sedimentation derived from DInSAR which the tropospheric and ionospheric delay are corrected. This illuminates that the accuracy of the sedimentation from DInSAR is improved after the tropospheric and ionospheric delay are corrected. -
jgg. 2013, 33(4): 65-68.
Using the GDR data recorded by the Jason1, Jason2 and Envisat altimetry satellites for three years, and on the basis of the geoid calculated by the GOCO02S gravity field model which is combined with GOCE and GRACE, the mean dynamic topography is calculated over China sea and neighbour using Pointwise approuch. The results show that different trends are reflected from mean sea surface and mean dynamic topography, which are consistent with the known results respectively
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jgg. 2013, 33(4): 69-72.
After reviewing the prediction of LOD based on the LS+AR model, the influence of different cycle term on prediction accuracy is analyzed by using different combination of the main cycle terms. The results show that longterm cycles of 18.6year and 9.3year, the shortterm cycle of onethird year have great impact on LOD prediction accuracy. Therefore, it is recommended that the above three cycle terms should be taken into account in highaccuracy LOD prediction except for annual and semiannual cycle terms
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jgg. 2013, 33(4): 73-78.
Time system and coordinate system are the reference datum for navigation and positioning, any form of navigation and positioning are carried out within a certain amount of time and coordinate frame. This paper detailed study spatio tempora unification among Beidou Satellite Navigation System （BDS）, GPS and GLONASS, introduces the time frame and coordinate frame of the three navigation systems. Gives spatio tempora unification conversion model and parameters. On the basis of the theory, puts forward the spatio tempora unification method in practical application of multimode navigation and positioning. Based on the Visual C++ platform write multimode combinations positioning program, calculate and analyze BDS/GPS/GLONASS three system receiver data, experimental results show that, multimode fusion positioning have better accuracy and reliability. Verify the correctness and feasibility of spatio tempora unification transformation thought and method in practical application.
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jgg. 2013, 33(4): 79-82.
An improved Geometry Clipmap algorithm is presented, in which we increase the number of topographic data scheduling module, reconstruct the organization of the note, and introduce the progressive texture update technology. The experiments show that new algorithm improves the work efficiency and display effect of flight simulation system.
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jgg. 2013, 33(4): 83-87.
On the basis of the morphological expansion and corrosion principle, we put forward a method and flowprocess in landuse parcels generalization which is suitable to fast engineering application, combining with the general law of map generalization and minimum cartographic area, distances between patches and width of the parcel on landuse map. A typical case study of the difficult part of long and narrow patches proves that it is efficient to obtain the generalization goal using this method.
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APPLICATION OF MINIMUM CLOSED LOOPS SEARCHING
ALGORITHM IN DETECTING INSAR PHASE UNWRAPPING ERRORSjgg. 2013, 33(4): 88-91.Based on the Minimum Spanning Tree （MST） method, we improved the searching algorithm for minimum closed loops in consideration of multiple connected graphs. A tree and some redundant branches are built up according to the nodes and the length of edges. The minimum spanning condition was satisfied by sequentially selecting the redundant branch which can construct the minimum loop. The independent condition was satisfied by keeping onetoone correspondence between the redundant branch and minimum loop. Finally, we applied the algorithm to detect InSAR phase unwrapping errors which greatly improved the efficiency of InSAR data processing.
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jgg. 2013, 33(4): 92-95.
An estimation method of contamination rate based on entropy was proposed. It is useful for gross error statistic to avoid limited error selection. Two models of data main distribution were suggested to investigate contamination rate and the estimation methods of contamination rate based on entropy were given out. A numerical simulation was performed to analyze the influence of entropy truncation error on data contamination rate estimation. It is less influence for entropy truncation error to contamination rate estimation based on entropy. When truncation error is 0.01, the variation of contamination rate estimate is only 1%. The examples show that the estimation method of contamination rate based on entropy is reliable and superior to the traditional estimation.
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jgg. 2013, 33(4): 96-99.
In the transformation from national referenceellipsoidcentric coordinate to national geocentric coordinate, the lack of precise geodetic elevation of control points in referenceellipsoidcentric coordinate makes the rectangular space coordinates of control points contain error. And this factor has an impact on final conversion accuracy. Up to late the 3D space coordinate model based on least squares has not taken into account the
influence. In this paper,we discuss the method of 3D space coordinate transformation based on total least squares, besides, compare the methods of coordinate transformation based on total least squares and least squares used known data.The result shows that the accuracy of the former is better than the later. -
jgg. 2013, 33(4): 100-103.
The altitude angle of satellite is analyzed, and the influence of vertical deflections on altitude angle of satellite and tropospheric refraction corrections for GPS surverying is researched. The coordinates of stations are calculated using precise point positioning mode. The result shows that the influence of vertical deflection on station coordinate cannot be ignored.
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jgg. 2013, 33(4): 104-106.
A new strategy derived from robust estimation to improve the convergence time of precise point positioning is presented, and the 24 1hour data are processed to test the strategy. The results show that robust estimation is effective to improve the convergence time of precise point positioning, it also shows the success rate of robust estimation is better than that of least squares. The positioning results show that robust estimation is significant to improve the positioning accuracy of small spans, and could reduce the affection of the observations which their ambiguities aren’t convergent effectively.
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jgg. 2013, 33(4): 107-111.
Aiming at the poor performance of short term prediction of navigation satellite clock error, a variable weight combined ARIMA and ANN method is proposed, which combines the virtues of ARIMA and ANN. To improve the accuracy of prediction, an additional momentum term is used to modify the weight of the neural network and a sequence relative nearness degree is used to modify the weight of models. The clock data of 4 typical GPS satellites are chosen and respectively used in ARIMA, ANN and variable weight combination models to forecast short term clock error. The results show that the accuracy of variable weight combination model is superior to the other models, especially in the field of rubidium clock, the error of which is half of the other models.
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jgg. 2013, 33(4): 112-116.
On the basis of quadratic polynomial, the model of leastsquares collocation to estimate satellite clock bias is established by considering the random part of satellite clock bias. To determine the covariance function of this model, the paper selects the empirical function and combines the experiments of clock bias data comparing to the covariance function fitting of leastsquares collocation, then obtains reasonable value ranges of the parameter for the model’s covariance function. Finally, the model is certified to have a good performance in the shortterm prediction of clock bias and can be also served as a new interpolation method by comparing with common algorithms of clock bias prediction and interpolation.
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jgg. 2013, 33(4): 117-119.
A forecasting software titled GMRCFS has been developed based on the GM（1,1） residual error model of grey system, and deformation of Geheyan dam has been predicted by five GPS monitoring sites on June 10 to November 28 in 1998. The results show that the GM（1,1） residual error model has high accuracy, it could satisfy the demand of dam deformation forecasting if a step size is chozen reasonably.
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jgg. 2013, 33(4): 120-123.
Tropospheric delay density is resolved with the groundbased GPS monitoring network data in USA solved by the GAMIT/GLOBK software based on tropospheric slant path total delay virtualized by backprojection method. Tropospheric delay 3D feature is analyzed by the method of tomography.The result shows that zenith total delay solved by two methods is small, the maximum error is less than 5 mm, and the mean square is 4.1 mm.
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jgg. 2013, 33(4): 124-127.
The PS point cloud segmentation and orbital ramp correction based on the Delaunay Triangulation and Tarjan’s algorithm was proposed in order to amend the estimation errors of orbital ramp correction during the PSInSAR processing. The PSInSAR results of Kashi prefecture recorded by the Envisat satellite of European Space Agency show that: Comparing with the traditional methods, this algorithm could eliminate the orbital errors effectively and avoid the errors caused by the notunicom unwrapping area. And the algorithm is applicable to the areas with continuous distribution of PS points in the entire images and could be coverd basically.
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jgg. 2013, 33(4): 128-132.
The tropospheric delay is a main error source for the global satellite navigation and positioning, and the EGNOS model can be used to calculate the zenith tropospheric delay.The Zenith Tropospheric Delay (ZTD) data observed from 48 International GNSS system (IGS) sites which distributed in Asian area are used to assess the effectiveness and accuracy of ZTD calculated from EGNOS model in 20092011, and the application of the EGNOS model is also analyzed in Asian area. The results show:1) relative to IGS observed ZTD, the bias and Root Mean Square(RMS) for ZTD calculated from the EGNOS model are -0.18 cm and 5.98 cm respectively in Asian area, and the bias and RMS are 0.81 cm and 6.13 cm respectively in China.2) The bias and RMS show a obvious seasonal variation. The bias generally shows the largest value in the summer and the smallest values in the autumn, while the RMS shows the largest value in the summer and the smallest values in the winter.3) The relation between the bias and the altitude or latitude is not obvious, but the RMS decreases with the increasing altitude or latitude, and the bias and RMS show a relative smaller valves in high latitude of the northern and western areas.4)The daily bias and RMS at low latitude of southern area and eastern area in the summer have a relatively larger variation.
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jgg. 2013, 33(4): 133-136.
〗A new selenoid (lunar geoid) is derived using the lunar gravity model CEGM02 and topography model LRO_LTM02, which approximates the physical surface as closely as possible. The estimated gravity potential value of this selenoid is 2 822 327.8±16.2 m2/s2, denoted as W0 in usual. A triaxial level ellipsoid whose surface gravity potential equals W0 above is calculated and used as a reference ellipsoid, and its semimajor axis, polar flattening, equator flattening and longitude of semimajor axis are 1 737 462 m, 1/2 579, 1/6 863 and -76.8 ″, respectively. Based on this reference ellipsoid, the gravity decreases about 60×10-5ms-2 from the equator to the poles, while the variation along the equator is about 25×10-5ms-2. The selenoid undulations are in the range of -325.9 m to 389.1 m.
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jgg. 2013, 33(4): 137-141.
According to the noise characteristics, an integrated noise correction method based on wavelet filtering and the Principal Compoment Analysis (PCA) is proposed. The experiment data shows that the combined method is superior to a single filtering method, the former can effectively weaken the multipath effect and high frequency random noise.
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jgg. 2013, 33(4): 142-145.
Based on the variance components estimation, the receivers DCB and VTEC residual values are calculated by the pseudorange data with carrier phase smoothing and the vertical electronic content (VTEC) and the DCB of satellites. By using 35 IGS stations data, the DCB of 40 IGS receivers are estimated. The results show that the accuracy of DCB can be better than 1 nanosecond compared with the DCB provided by the IGS.
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jgg. 2013, 33(4): 146-150.
The method of establishing the mean freeair gravity anomaly reference field with rare gravity data has been studied based on the Airy and Heiskanen isostatic theory. The numerical model of the mean freeair gravity anomalies has been established using the regional highresolution topographic data; then for the problem that the systematic errors existed in the computational area, a few of gravimetric points have been chosen as constraint points in order to eliminate errors. Finally, the comparisons have been made among the gravity field model of EGM2008 and interpolation using separate points. As a result, the method could get better precision than two other methods as well as could reduce workloads in gravity measurement in the fields, the method is suitable for establishing the mean freeair gravity anomalies in difficult conditions.
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jgg. 2013, 33(4): 151-154.
The paper analyzed the relative calibration and absolute calibration of four component borehole strain observation. By the theorem “sum of vertical components must be equal”, we can only obtain the ratio of site scale value of 3 sensors and the sensor which is as a constant element, but we cannot get site scale value, so it cannot solve relative calibration. By the relationship between tides and component strain observation value, the coupling coefficient can be calculated, but calibration of the elastic parameters cannot solve the problem of the absolute calibration of strain.
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jgg. 2013, 33(4): 155-159.
Data sharing services from six international research organizations are summarized with the geographical distribution maps of highrate sites drawn. And the temporal characteristics of observation data are analyzed. This can provide important data resource for seismic activity monitoring research. Finally, an example is illustrated to show the application of highrate GNSS sharing data in the seismic research.
