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11 October 2011, Volume 31 Issue 4
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. 2011, 31(4): 1-5.By using the GPS velocity fields of China mainland in three time periods since 1999, the characteristics of crustal dynamic evolution before Wenchuan Ms8.0 earthquake was studied. From the results following knowledges can be drawn.1)The Wenchuan earthquake had taken place in the zone where crustal squeezed movements were blocked obviously. There was a large obstacle existed in the seismogenic zone, and the fault nearby the epicenter was in strong blocking state for many years.2)With the Wenchuan earthquake approaching, the compressive zone in the west to epicenter gradually expanded to east obviously. In some local areas, the direction of principal compressive strain deflected northward, and right lateral shear slip enhanced obviously.3)The sectional features of coseismic deformation
in Whenchuan earthquake and 6.0 or more aftershock distribution were closely related to the sectional movement deformation of the fault and its vicinal zone. -
. 2011, 31(4): 6-9.It is found that some abnormal signals like compressive pulses and tidal distortion of the 4component borehole strain observation at Guza station about a year before the Wenchuan Ms8.0 earthquake in 2008 and even continued to occur occasionally after the earthquake. The S transform was tried to apple to the field in order to carry out a further research into the abnormal signal characteristic from a different perspective. An analysis of 4component borehole strain observation from over 20 stations within 1500 kms from the Wenchuan epicenter showed that only in the observations at Guza station there were significant abnormal signals with the following characteristics: On the basis of the background signals, the signals with period of about 10 to 60 minutes increased before the Wenchuan earthquake and gradually decreased after the earthquake, meanwhile, the most powerful signals were background signals with the power enhanced before the earthquake and weakened after it.
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APPLICATION OF SEISMIC DEFORMATION OBSERVATION TECHNIQUESTO EFFECTIVELY MONITOR EARTHQUAKE PRECURSOR. 2011, 31(4): 10-17.In daily monitoring of seismic crustal deformation, we often found out that there are some abnormal microseisms in the tidal signals. These microseisms called abnormal tremor wave are observed by the broadband digital seismograph.
This article reports a lot of the abnormal tremor waves recorded by DZW gravimeter and VS1 tiltmeter in HUST seismic and tidal station. According to the principle of seismic measuring techniques and observations, we present a unified characteristic curve for seismic crustal deformation observation techniques, analyze and explain them to the roots of different precursory response. The differences of the response to the abnormal tremor waves are mainly decided by the transfer function and the features of the instruments. The seismic crustal deformation instruments are sampling per minute, so the abnormal tremor waves are the aliasing or mapping of the real signals, it can not reflect the true ground motion. Are the abnormal tremor waves before an earthquake related to the earthquake? Is it precursor? We need to analyze and research deeply. This article aims to discuss and expound how to more effectively and accurately obtain earthquake precursor, promote earthquake precursory observation techniques scientific and standardization, breakthrough earthquake monitoring by the bottleneck, and improve the ability of earthquake monitoring and prediction. -
. 2011, 31(4): 18-21.]Through analyzing the anomaly of Ganlin,Wusheng and Gaofengtou mobile short leveling in Yishu fault zone and surrounding NW strike faults and discussing the anomaly mechanism，we think that the three anomalyies are likely caused by crustal stress increasing in this area before and after Wenchuan earthquake.
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. 2011, 31(4): 22-26.During the tenth fiveyear plan, a set of YRY4type componenet borehole strainmeter and a set of TJ2 type volumetric borehole strainmeter were installed in Xuzhou seismostation.At present the observed original plane strain curves from 2008 to 2010, the annual change of plane a systematic comparative study on strain curves, rainfall interference of plane strain curves, pressure interference of plane strain curves and the solid tidal observations is carried out and the respective correlation coefficient and influence coefficient are calcucated as well. This work has practical significance to demonstrate the reliability of the instrumentation, determine the credibility of the information and for correctly understanding of seismic background.
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. 2011, 31(4): 27-31.On the basis of the mobile gravity data in western area of Yunnan province during 1992-2000, the dynamically evolutional characteristics of geoid are researched. The results show that the changes of geoid are closely relative to fault activity, and the variations of local geoid are related with the preparation and occurrence of earthquake of Ms≥6.0
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. 2011, 31(4): 32-36.Crustal strain field derived from the data from GPS observation network of Fujian area,the intensity accumulation rate
of deformation velocity calculated from acrossfault vertical deformation and tensile or compression of each station based on acrossfault vertical deformation and other deformation observations are calculated, and then, based on these, the deformation characteristics in the periods:2005—2006, 2007—2008 and 2009—2010 in Fujian area are studied. It shows that there are two areas ,XiamenLongyanDongshan and the junction of Zhenghai and Shaxian Nanri island, with stronger tectonic activity, tendency accumulation, higher accumulation intensity, dominated mainly by compressive points, might be the zone with high risk of mediumstrong earthquakes. -
. 2011, 31(4): 37-40.In order to study the present movement state of Shandong and surrounding blocks, GPS data from the Crustal Movement Observation Network of China (CMONOC) and the Continuous Observation GPS Network of Shandong Province was used and thus analyzed the baselines between GPS stations on different blocks. Using the K-L best straight line fitting and Slide Fourier method, we got the baselines changes by year cycle, and analyzed the trend of baselines crossing different blocks. In addition,we obtain the present crustal movement characteristics of Shandong and surrounding blocks, and analyzed the influence of Japanese earthquake of 9.0 on Shandong area.
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. 2011, 31(4): 41-46.The continuous and precise data were recorded by variety precursor instruments in the Hubei LocalEarthquakeprecursor Observing System during the 2009-2010 solar eclipse.
After the careful processing and analysis for observations, three significant variations all related to the solar eclipse are found. Firstly,the geomagnetic anomaly valleys appeared before the eclipse starting. Secondly,during the total and annular solar eclipse, there were some differences between geomagnetic components and between microchanging geomagnetic anomaly phenomena. Before and after the total solar eclipse, there were clear features with shorttime and synchronization on the geomagnetic horizontal component. However, during the annular solar eclipse, geomagnetic declination component shows transitiontype change characteristics with trended and lagged. Thirdly,the solar eclipse made the tilt and strain of crustal deformation observations shorttime pulsate. -
. 2011, 31(4): 47-51.The correlation and product spectra between the gravity earth tide for over 13 000 hours observed with SGC053 at Jiufeng station and the barometric pressure were analyzed.It is shown that the barometric pressure is the main factor leading to gravity change. And the atmospheric pressure admittance is -3.116 nms -2/mbar.
The atmospheric pressure admitlance is depended on the frequency.
According to the 7 product spectral lines, atmospheric pressure admittances was fitted with linear. The frequencydependent atmospheric pressure admittance function is y=7.036x+2.524. The freqDep admittance correction is almost consistent with constant admittance correction. The difference between the corrected results with the two methods is less than ±(1-2) nms -2. -
. 2011, 31(4): 52-55.To analyze the long-term stability of some points of 2000 National Basic Gravity Network, the absolute gravimeter, FG5/240, was applied to the absolute gravity measurement for two benchmark points of 2000 National Basic Gravity Network, which are located in the Yongxing island and at Zhengzhou station, and the observation accuracy was proved to be better than 5×10 -8 ms -2. As a result, the differences between the observation values and the reference values at the two points of 2000 National Basic Gravity Network are obtained.
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. 2011, 31(4): 56-59.On the basis of the highprecision global gravity model(EGM2008),combined with multialtimeter data(Geosat/GM data,ERS1/168 data and Envisat data),the gravity anomalies grided in 2′×2′ over China sea and its vicinity (0°N～42°N，102°E～138°E) are determined with the method of deflection of the vertical and inverse Vening Meinesz formula.Compared with the shipboard gravimetry over the South China sea,the results show that the standard error of the gravity anomalies computed with the altimeter data is ±9.43× 10 -5 ms -2. To remove gross error of the residual deflection of the vertical by selecting different criterias, the gravity anomalies computed with the altimeter data and shipboard gravity anomalies were compared and analyzed,the accuracy of residual deflection in the vertical range of 3″~ 5″ is better.
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. 2011, 31(4): 60-62.The correction of Astronomical Atmospheric Refraction(AAR) is one of the important topics in astronomy and geodesy.On the basis of the literature 1 and 2,series expansion theory of AAR was restudied, a new series expansion was provided. The new expansion can expanded to the arbitrary order and times items, and reached the submilliarcsecond theoretical accuracy. In addition, the phase atmospheric refractive index near the ground had been extracted from the expansion, as a single unknown parameter,so, new expansion can be adapted to different observation wavelengths processing of optical technology. Finally, the new series expansion making tangent of visual zenith distance as a argument is given. This work will completely replace the formula in AAR table of Pulkovo Observatory. This method can also be applied to the theory of ray tracing.
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. 2011, 31(4): 63-65.Least Squares Spectral Analysis (LSSA) has been shown more suitable than Fourier analysis for analyzing time series with spikes, gaps, datum shrifts (offsets) and other disturbances in a variety of applications in geodesy and geophysics. To detect the weak superconducting gravimetric signals, a methodology of product spectrum based on weighted LSSA is presented,which can take consideration the correlations among the signals and highlight the potential spectra power of high resolution in the common figures as well as weaken or eliminate the power of noise. A data set of superconducting gravimeter observations at the Canada Superconducting Gravimeter Installation (CSGI) has been assembled for analysis to show its efficacy.
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. 2011, 31(4): 66-70.On the basis of deducing the universal expressions in an orthogonal curvilinear coordinate system of the displacement gradient matrix and the strain tensor matrix of displacement vectors, we further derive the universal expression of the conversional matrix between two partial coodinates in random different orthogonal curvilinear coordinate systems,meanwhile, indicats that this conversional matrix also belongs to the orthogonal matrixes so that the strain tensor matrixes are similar matrixes. With this understanding,the after deply analysis of the geometric and physical natures of the strain tensor matrixes, discovers the invariant code mystery of crustal deformation hidden in these matrixes, which is, whatever the orthogonal curvilinear coordinate system is, the strain tensor matrix has a unique and invariant principle strain characteristic polynomial and by its corresponding strain eigenvalue equation we can derive the principle strains with their directions at any crustal particle,then the matrix can be turned into a diagonal matrix by putting the principle strains values as its diagonal elements, and the matrix trace equals the body strain, the matrix determinant equals a product of the principe strains. All these geometric and physical quantities are the crustal deformation invariants at the spot.
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. 2011, 31(4): 71-75.The algorithm of eliminating gross errors in robust estimation and gross error detection IQR criteria, and the orthogonal polynominal interpolation algorithm were studied. The experimental object is GPS singleday height time series of CORS fiducial stations in China from March 1, 1999 to December 31, 2009 lasting nearly 11 years. Through the gross error detection and interpolation tests of three selected base stations, the result shows that robust estimation is more effective than the IQR criterion to detect and remove gross error. When the interpolation being carried out by use of cubic spline function if the number of epoch is continuously short of over 5~10,then the result of interpolation will distorted easily.However,the result from fitting by use of loworder orthogonal polynomial will be stable,as usuall,the ideal result can be achieved with fitting two or three times.When the epoches are continuously short of three months the curve after fitting with orthgonal polynomial will still be basically consistent with the trend of the sequence,i.g. the result of intergolation is good.
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. 2011, 31(4): 76-79.
The selfconsistency problem of the point mass model method for approximating the Earth’s external gravity field is discussed. Considering the fact that the disturbing gravity cannot be obtained through direct measurement at altitudes above the Earth’s surface, a solution which made for studying the approximation accuracy of the point mass model method is proposed.
That a test of internal and external consistency accuracy based on the ground and airborne gravity observations of Australia was made. Numerical results show that the internal consistency accuracy is10 -8 ms -2, and the external consistency accuracy of the point mass model method at the altitude of 655 m is ±3×10 -5 ms -2 .
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. 2011, 31(4): 80-83.The effects of the station amount, observation time and station distribution on the estimated satellite clock biases were analyzed.The results show that,general speaking,the increment of station amount and observation time is conducive to improve the estimated accuracy of satellite clock bias. However, the increment of station amount will increase the timeassuming,
in order to ensure the accuracy and the property of realtime, it is useful to select the appropriate station distribution and amounts, which are conducive to the real time estimation of satellite clock biases and their application.Realtime precise point positioning (PPP) tests show that, compared with the PPP positioning based on the IGS final precise clock, due to the effect of low precision of estimated clock bias in the initial phase, it makes the parameter convergence of PPP positioning require more time -
. 2011, 31(4): 84-89.According to the fact that the points in two transformational coordinate systems are all affected by random errors, which make the observation vector and coefficient matrix in error equations both include errors, and even, these observations and elements in coefficient matrix may be heteroscedastic and correlated.We employ the weighted total least squares solution to calculate the parameters of ITRF transformation. To demonstrate the performance and efficiency of the application of WTLS solution in coordinate transformation, the simulation and real experiments are implemented. The results show that the WTLS solution is correct and more reasonable.
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. 2011, 31(4): 90-93.On the basis of the HilbertHuang Transform(HHT) method and according to the assumption of the background noise signal continuity in time domain, an adaptive algorithm of seismic signal denoising is presented. The algorithm, as used to analyze the seismic wave , has certain positive results.Through the analysis following conclusions can be drawn.1)According to the background noise signal characteristics, the algorithm can effectively remove the lowfrequency noise signal from the original signal. 2)By the use of the adaptive algorithm we can decompose the signal and denoising, and avoid the time resolution and frequency resolution problem. 3)The algorithm has the flaw for dealing with highfrequency interferenc，and so needs to be improved.
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. 2011, 31(4): 94-98.A new idea that by transforming the meridian arc length formula into two other forms was put forwand, which are expressed by the elliptic integrals of the second kind, they were named as “FormⅠ” and “FormⅡ”. In “FormⅠ”, the meridian arc length formula is represented as the sum of a rational function and the elliptic integrals of the second kind by the geodetic latitude parameter, which establishs the function relations between the meridian arc length and the elliptic integrals of the second kind. Analogously, taking the reduced latitude as an independent variable, the “FormⅡ” formula give a simpler form of the meridian arc length formula in terms of the elliptic integrals of the second kind. On these bases of theoretical analysis, the computer program is compiled in MATLAB by calling the Elliptic E(x, k) Function to calculate the meridian arc length. It was proved that this method improved greatly the accuracy and efficiency of previous calculation. Moreover, the meridian arc length of CGCS2000 was also calculated based on the principle that provided. The results
indicate that the “FormⅠ” and “FormⅡ” formula are simpler and more suitable for series expansions and the realization on computer than the classical form. Furthermore, it perfects the meridian theory. -
. 2011, 31(4): 99-102.The model of GPS triplecarries phase combination observations was deduced, and errors of combination observations were analyzed. Based on the theory of fuzzy clustering analysis, the combination observations obtained by the longer wavelength criterion are analyzed and are classified by using the selfadaptive clustering algorithm based on dissimilarity matrix. The condition which each calss suit to
has been analyzed and proved with the method for the integer ambiguity resolution based on matrix transformation by using measurements of L1 and L2 carriers and simulations of L5 carrier. The result shows that using the fuzzy clustering method not only the optimization combination can be achieved but also the workload for enumerating all possible combinations to filter the better combination will be decreased. -
. 2011, 31(4): 103-106.Both the characteristics of Lagrange interpolation and Neville interpolation are compared with each other.
It is concluded from the results that the highorder interpolation is not good enough for highprecise applications.Finally, a new interpolation method which based on high/low orders to solve this problem is put forth. -
. 2011, 31(4): 107-111.In order to avoid the distortion of the real situation reconstruction, and on the basis of related theory of noise removing, some researches are taken and three noise elimination algorithms for terrestrial 3D laser scanning data with priori information, utilizing the points labled with height as the priori information are presented,
elevation of interpolation, fitting plane or trend surface with Leastsquare method being compared, and choice of proper threshold to eliminate noise. The experimental results indicate that points labled with height can be used as standard of noise elimination for the entity features are well preserved. -
. 2011, 31(4): 112-115.For the incomplete surveying data caused by various factors, traditional adjustment can not be achieved. It is harmful to the accuracy of the surveying, even leads to abandoned observation data. Through EM algorithm, we can take the potential information which is helpful to improve the accuracy of data processing effectively. EM processing algorithm for incomplete surveying data is proved. The results show that the surveying accuracy is improved by using the EM algorithm to process the incomplete data. The results are extremely similar to the adjustment results with complete data and significantly better than the results without adjustment.
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. 2011, 31(4): 116-118.The vertical deviation of a local height datum from the geoid is essential and fundamental for the transformation of regional datums and the unification of the global height datum. The value of the gravity potential of Qingdao Dagang tidal station is acquired by using 936 GPS leveling point data and EGM2008 geopotential model, which is 62 636 852.85±0.07 m 2/s 2 , in turn ,a vertical deviation of 0.32 m of Chinese height datum from the geoid is obtained.
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. 2011, 31(4): 119-122.Geometry free model for resolving GPS ambiguity is a linear model which does not take baseline components as unknown parameters. For the Geometry free model, the code observation is almost used in ambiguity resolution directly , and although the observation time span is very short, the design matrix will not have characteristics of multicollinearity,so that the geometry free model is very useful in ambiguity resolution. In this paper, the expressions for triple frequency float ambiguities and covariance matrix for the geometry free model have been deduced by use of the Kronecker product. The phenomena that the expression of covariance matrix is independent from the geometry between the receiver and satellites but only relates with code and phase noise and number of epochs , and the Ztransformation martrix
Z is independent of the geometry between the receiver and satellites and number of epochs but only relates with code and phase noise is discovered by analysing the expression. Furthermore, the success rate of ambiguity resolution for single frequency, dual frequency and triple frequency is computed respectively. At last,the conclusions that only a few epochs need fixing ambiguities for dual frequency and triple frequency, and especially for triple frequency only one epoch needs fixing ambiguities are drawn. -
. 2011, 31(4): 123-126.The causes of aliasing in GRACE mission is investigated, the impact on the static as well as timevarying gravity field is analysed, and a method for analyzing aliasing problems relative to ocean tide and atmosphere is proposed. Through comparing different methods for reducing aliasing error, it is pointed that gravity field mearsuring mode with combination of satellite costellations is the most effective one at present. The results will be able to provide references for the development of next generation gravity satellite missions in China.
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. 2011, 31(4): 127-131.Establishing mobile stations is the most reliable way for researching surface subsidence and building damage. At present, the processing in later stage of field observations is mostly with offset method or other traditional methods to converse the observations to the strike direction and tendency direction, thus station’s layout and data processing are subject to greater limitations, the calculation accuracies of movement and deformation of the surface are significantly affected. For the Shortcomings of traditional data processing of observation station, a new method of data processing of observation station is introduced with practical engineering example.
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. 2011, 31(4): 132-134.The precision of orbit determination and clock error computation of PANDA(Position And Navigation Data Analysis) is verified through experiments. The high frequency GPS observation data during Wenchuan earthquake is processed by kinematic precise point positioning with the PANDA products of orbit and clock error. The results indicate that the advantages of using PANDA for high frequency kinematic precise point positioning are good in real time and of high accuracy.
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. 2011, 31(4): 135-138.On the basis of the ionospheric gridcorrection data which are tested by widearea precise realtime positioning system.
The ionospheric delay of the signal puncture point over the reference station is estimated by using two weighting methods.
Futher more the estimated ionospheric grid delay of the signal puncture point has been compared with those tested in the actual measurement. For the stations located in different positions,in the middle or highlatitude the grid correction is better than that in lowlatitude. This result reveals that it is concerning to the characteristics of the ionosphere, but caused by weighted interpolation correction scheme. -
. 2011, 31(4): 139-143.The principle,calculation method of correlation coefficient, and its significance test were described. Focusing on integrated navigation RAIM model, the integrated navigation RAIM method based on correlation analysis theory was probed, testing process of single and multiple gross errors detection was presented. By simulating the 12 GPS and Galileo navigation satellite positioning system, outliers were added to single and two satellites, respectively. Simulation results show that the correlation coefficient of observations’ influence vector and residual error can locate and remove satellites which contain gross errors, improving the navigation positioning accuracy.
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. 2011, 31(4): 144-148.The recognition and selection of highcoherence PS points is a premise that guarantees the highprecision of permanent scatterers. The characteristics and flaws of all kinds of selection methods,such as amplitude stability, phase stability, timing sequence correlation and amplitude dispersion index threshold were analyzed. The recognition strategy of PS points is brought forward based on the union and intersection of time sequence correlation coefficient threshold and amplitude dispersion index threshold. The basic principle of point target check method is expounded and the corresponding model is given, in addition, its effectiveness and superiority is verified.
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. 2011, 31(4): 149-153.On the basis of the 6 JERS1 SAR images, the time series of deformation in Tengchong volcanic area were obtained by SBASDInSAR technique through separating the linear deformation phase, the nonlinear deformation phase, the atmospheric phase screen and the DEM residual error phase. Compared with the GPS measurement results, SBASDInSAR technique can detect the crustal deformation at the precision of subcm level. The deformation of the DanzhaGaotian fault is obviously different between the two sides,which may relate the chamber below. The deformation pattern of the Dayingshan area indicates that there is probably an buried fault underground.
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. 2011, 31(4): 154-159.In order to extract information including thin layer’s position and thickness, from reflected wave data of Ground Penetrating Radar (GPR) in multilayered situation, a spectral inversion algorithm realized in frequency domain is presented. Through analysis of electromagnetic wave propagation in multilayer media, generalized reflection coefficients are derived. After dividing the coefficients into pairs followed by decomposing the pairs into even and odd components, a cost function is established to connect reflection coefficients’ spectrum and \{layer’s\} parameters before inversion is carried out. Some simulations show that accurate inversion results can still be expected when thickness of the layer is less than tuning thickness, which therefore improves resolution of thin layers.
