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12 February 2012, Volume 31 Issue 6
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. 2011, 31(6): 1-5.
On the basis of a 3D viscoelastic finite element model of lithosphere in North China, we simulated numerically the recent annual changing characteristics of tectonic stress field in the region as follows.
1)The maximum principal extensional stress is 3-9 kPa a\+\{-1\} and its azimuth lie in NNWSSE, the maximum principal compressive stress is about 1-6 kPaa-1 and its azimuth lie in NEESWW. The whole North China is under the extensional stress field.
2)The maximum principal extensional stress presents high in the west and low in the east,in general,and the stress of whole NE area is high,and the maximum compressive is high in the NE and SN area.This kind of change is benefical for the enhancement of the fault action in Shanxi and Liaoning areas and many speed up the potencial seismogenic process.
3)Annual cumulative rates of coulomb fracture stress in Tanlu fault belt is of a segmentation pattern that the rate of Jiashan-Guangji segment is highest(6 kPa a-1),in AnshanLiaodong Bay segment it is higher(5 kPa a-1) and others are lower (3-4 kPa a-1). -
. 2011, 31(6): 6-10.By using highfrequency GPS doubledifference precision positioning technology, kinematic and static coseismic deformations caused by Japan Mw9.0 earthquake at nearfield and farfield GPS stations were obtained. The result shows that the maximum kinematic amplitude of IGS station is over 60 cm,postearthquake deformation reached to 30 cm. The kinematic deformation of farfield JLYJ GPS station clearly reflects the displacement waveform caused by seismic surface waves. The spectrum analysis shows that the period of seismic surface waves of JLYJ station caused by kinematic deformation is about 10-17 seconds. The kinematic displacements in
eastwest direction and the vertical direction are much larger than that in the northsouth direction,it shows the deformation of JLYJ station is mainly caused by the Rayleigh wave and its harmonic wave. On the basis of the epicentral distance, the earthquake occurrence time, we can set the Rayleigh wave propagation speed of 3.5 km/s. As the Rayleigh wave changes in a period of 10-17 seconds, so its wavelength of is about 50 km. -
. 2011, 31(6): 11-14.By use of the technology of ionospheric tomography，threedimension ionospheric electronic density in a time length of 21 days prior to Japan March 11,2011 earthquake were reconstructed over the epicenter area, and the electron density anomaly detection was conducted at all ionosphere grid network points for a specific time period. After excluding the effect of solar and geomagnetic activity，the computational results indicate that the abnormal ionospheric electron density decreased at the Universal Time (UT) of 14:00-16:00 on February 28 and
increased at 08:00-14:00 on March 2, 00:00-06:00 on March 3, and 12:00-20:00 on March 4. The occurrence of these anomalies is likely a precursor of the Japan Ms9.0 earthquake. -
. 2011, 31(6): 15-19.On the basis of processing of 9scene repeat track Single Look Complex Envisat ASAR data with Small Baseline (SB) method by 2pass mode, a time series difference interferograms and deformation field and its velocity of L′Aquila Mw6.3 earthquake occurred on April 6, 2009 were obtained. The results show as follows.
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There was an obvious process of displacement and its velocity from slow to speededup is determined from preseismic to postseismic. 2) In the analyzed area of about 54 km×59 km, westward of epicenter shows uplift, and its maximum uplift value is 140mm in the LineOfSight(LOS) and the east to epicenter is subsidence area. However, the head subsidence region is a rupture area, and its majority formed in the course of shocking and subsequence. The maximum settlement reaches to 185 mm. 3)The rupture propagates mainly southeastwards, about 135°, from epicenter, and concentrates on an elliptic area of about 13.4 km×7.6 km. -
. 2011, 31(6): 20-24.In the work,on the basis of geostatistics analysis,with the kinematics method and by use of the 1 068 results of GPS observation in the China continent and its adjacent under the ITRF2007 reference fromwork the distribution characteristics of the horizontal crustal velocity field and the driving mechanism are studied.The influence range and degree of relative action betwen the India,Eurosia,Philippines and Pacific Ocean Plates on the movement and deformation of the China continent and its adjacent region are analyzed as well.
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. 2011, 31(6): 25-31.The vertical crust deformation of northeast margin of QinghaiTibet block before and after Wenchuan \%M\%s8.0 earthquake has been analyzed with the regional leveling and faultcrossing leveling data. The results show that within 10 years before the earthquake the regional vertical deformation has a certain diversity with
regional feature. In detail, that the tectogenesis for degressive Qilian mountain and anabatic aislebasin in Hexi area reflected by the vertical deformation is counterinheritance motion; that the tectogenesis in XijiHaiyuan Guyuan area reflected by the vertical deformation is balanced motion, and on the west to ZhangxianWudu of LanzhouTianshuiWudu area, Minshan’s rise is obviously increasing and accompanied with high gradient belt. It could be inferred that the pressure from the Tibetan plateau is relatively weakened in the north direction and clearly increased in the east direction. Monitoring data show that the vertical deformation of northeast margin of QinghaiTibet has an extensive inverted variation from Aug. to Oct. in 2008 after Wenchuan Ms8.0 earthquake. The Xiahe and Hezuo area of Minshan uplift shows rapid counterinheritance sinking relative to Linxia from 2006-2008. It could be inferred that the pressure eastward from the Tibetan plateau is weakened due to Wenchuan Ms8.0 earthquake.The monitoring data in 2010 show that the crustal vertical deformation of northeast margin of QinghaiTibet is decresing, and that Hezuo area is counterinheritance sinking relative to Linxia from 2008-2010, nevertheless, the differential morement between Hezuo and Linxia is decreasing. It could be inferred that regional tectogenesis reflected by the vertical deformation, including Minshan uplift, has been to stable state. -
. 2011, 31(6): 32-38.By use of the wavelet analysis, the electromagnetic radiation data of the Yushu earthquake magnitude 7.1 in Qinghai province near Dujiangyan, Jiange, Jiangyou stations in Sichuan and Ersha station in Zhengzhou before and after the event,
were studied in the different scales of wavelet detail decomposition and then it is found that there are anomalous information before the earthquake, and had interpretated preliminarily. The results show that, the first, the details of the wavelet decomposition show
abnormal electromagnetic wave signal of low frequency before the earthquake portion of the earlier time; epicenter close to the station, the information that appears anomay in high frequency band; a little far from the epicenter of the station, the anomay in low frequency band information. The second,along with the epicentral distance increases, the smaller the radiation energy, the anomalies appear later. -
. 2011, 31(6): 39-42.Preseismic ionospheric TEC anomalies of Wenchuan earthquake on May 12th 2008 and Yushu earthquake on April 14th 2010 were studied by using CODE GIM (Center for Orbit Determination in Europe, Grid Ionospheric Model) data. By considering the sun and geomagnetism activity levels (Dst index and Kp index),the ionospheric anomalies were analyzed with median of TEC 10 days earlier as basic values and 1.5 fold standard deviation as error limit. The results show that TEC anomalies before both the earthquakes can be detected.
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. 2011, 31(6): 43-48.
Controlled by absolute gravity data, mobile gravity data of western Yunnan network from 1985 to 2010 are processed with adjustment of average accuracy of 12×
10 -8 ms -2.The characteristics of single point gravity variation curve are with seasonal fluctuation and trend movement(up or down) in longterm. The gravity dynamic variation of some points is consistent with preparation process of Lijiang Ms7.0 earthquake. The annual change rate of gravity from longterm observation can reflect the trend variation of gravity field in a time period. The annual change rates of gravity in 1985-1995 and 1996-2003 might reflect the energy accumulation and release before and after the Lijiang Ms7.0 earthquake. Since 2003, the rising velocities of gravity are over 10×10 -8 ms -2/a along the Jianchuan fault, HeqingEryuan fault and the northern segment of Red River Fault Zone. On the basis of the initial fault movement model, the forward simulant annual changing rates of gravity are similar with the measured values. It indicates that fault movement has great contribution to the gravity field change. The annual fault movements inversed by annual change rate of gravity are consistent with the geological results, and basically reflect its active characteristics
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. 2011, 31(6): 49-53.The postseismic deformation,observed by precise leveling,of Ms7.2 Xingtai earthquake in 1966, Ms7.8 Tangshan earthquake in 1976, Ms7.8 Tonghai earthquake in 1970, Ms7.6 Luhuo earthquake in 1973 and Ms7.0 Gonghe earthquake in 1990 each shows typical characteristics of decaying exponential. Considering both the effects of fault creep on the brittle creeping fault zone (BCFZ) and viscous flow below BCFZ,we estimate the effective relaxation time of the five great earthquakes with leastsquare method. The inversion results show that the difference of relaxation time between eastern and western China is very significant. The effective relaxation time of Tangshan earthquake is the longest (10.3 years), and the time of Xingtai earthquake is the second longest (4.4 years), while the effective relaxation time of Tonghai, Luhuo and Gonghe earthquake are about 2 years only. The significant difference may be caused by different upper crustal depth and viscosity of lower crust and upper mantle between eastern and western China.
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. 2011, 31(6): 54-57.By processing the observation data of the GPS network in Chongqing from February,2008 to October,2010, the following data were obtained: the coseismic displacement of 12 GPS stations in this area, the time series of crossfault baseline length before and after Wenchuan earthquake, the horizontal movement field of Chongqing GPS stations related to WUHN and the horizontal movement rates of Chongqing under the regional NNR frame. The results show that the maximum of the coseismic horizontal displacement in Chongqing is 24 mm, and the minimum is 7 mm.After that event, the crustal movement in Chongqing has been steady as a whole.
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. 2011, 31(6): 58-62.China Geodetic Coordinate System 2000 (CGCS2000) can only provide static coordinate of stations based on ITRF97, epoch at 2000,using nationallevel CORS data,we have established the CGCS2000 plate motion model, which provides highaccuracy velocity field to realize stations’ epoch reduction from 2000 to current epoch.
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RELOCATION OF EARTHQUAKES OF YUBEI AREA AND ADJACENTREGION WITH DOUBLE DIFFERENCE LOCATION ALGORITHM. 2011, 31(6): 63-68.The earthquakes that occurred in the area of Yubei and adjacent region from 1985 to 2008 were relocated with the double difference method and the results of 497 earthquakes were obtained. The result shows that the distribution of relocated epicenters appear zonal,while the earthquakes in a part of areas get close to tectonic belts. The most hypocenter depths in the area distribute mainly within the upper and middle crust. The average hypocenter depth is 13.3 km and the seismogenic layer ranges from 10 km to 20 km.
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. 2011, 31(6): 69-72.When the data coverage is dense, some algorithms need to solve large size matrix, thus the computation time is proportional approximately to the cube of the number of data constraints,it makes the process very slow. Focusing on this problem, the moving curvature is introduced in interpolation. Only the nearest data points are chosen for interpolating by twodimensional spline based on the moving Green’s function. The examples show that the interpolation accuracy of the proposed method is higher than that of two other methods. No matter how many data points there are, this method can be implemented fast. It is not necessary to split the data into subsets which can be modeled individually, or to blend the subsets together into a final model. Comparing with the global solution, this algorithm can greatly reduce the computation time.
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. 2011, 31(6): 73-78.As focusing on present domestic INS technology and GNSS data processing technology, the feasibility for carrying out inertial gravimetry experiment with domestic inertial navigation system is discussed. The results from the analysis show that, although GNSS observation and data processing have not big issues presently, it is still hard to reach 1×10\+\{-5\}ms\+\{-2\} gravity accuracy by use of the inertial navigation system. However, with the technical progress of the domestic inertial system, the day for inertial gravimetry with domestic inertial navigation system is approaching.
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. 2011, 31(6): 79-83.A reasonable geomagnetic adaptable matching area can improve the navigation accuracy effectively.
The selection of geomagnetic adaptable matching area based on geomagnetic field character and on geomagnetic character parameter information entropy are compared.Through a particular case,it is shown that the selection based on geomagnetic character parameter information entropy is more effective and more appropriate as the standard of the selection of geomagnetic adaptable matching area. -
. 2011, 31(6): 84-88.How to detect the cycle slip is always the key to data preprocessing for satellite orbit determination. The method of LCPC combination, Multidifference combined Polynomial fitting for cycle slip detecting is analyzed,and then the test of orbit precision determination using COMPASS observations is made. It shows that，as for the observations of COMPASS receiver, the accuracy of orbit determination will be improved by choosing the methods of cycle slip detecting and data preprocessing rationally.
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. 2011, 31(6): 89-93.With the use of Continuous Operating Reference Station(CORT) technology in geodesy of large scale,it plays a key role in station distribution and data processing of the thirdorder GPS geodetic network. This technology not only accelerates the construction speed, increases the network flexibility, but also ensures the initial control and calculation accuracy. Compared with the previous situation, the CORT
distribution density increased to 10 times totally, in key areas increased to 100 times. The observing means also have very great changes. On basis of the station of Chinese crustal motion network and CORT, the calculation and accuracy statistics of the thirdorder GPS geodetic network had been carried out in different areas. By contrast, the latter has the higher accuracy of thirdorder GPS geodetic network. -
. 2011, 31(6): 94-99.For the rational use of geometric and physical information of slope, and in order to control the influence of outliers on deformation parameter estimation, a constrained filtering model using mechanical state information of slope is given. At the same time, the algorithm
utilizes the useful information in constrained equation to accurately determine
the equivalent weights of measurements, thus the relevant adaptive robust constrained filtering algorithm is given.By a pratical example,it is proved that this algorithm can improve the reliability of state parameter estimation. -
APPLICATION OF SIMULTANEOUS ITERATIONS RECONSTRUCTION TECHNIQUE FOR 3D WATER VAPOR TOMOGRAPHY SYSTEM. 2011, 31(6): 100-103.Simultaneous iterations reconstruction technique(SIRT) is one of the several reconstruction algorithms of the ART family. It is used widely for tomography technique because of its convenience in dealing with large sparse matrix.
Thus SIRT is carried out to reconstruct the three dimension distribution of water vapor by simulation. The results show that SIRT can work effectively in water vapor tomography, get rapid convergence, and implement more easily than inversion. -
. 2011, 31(6): 104-108.Based on the common reference stations in STRF and ITRF, standard transformation between the two reference systems is realized by solving the Euclidean similarity of seven parameters, and the seven transformation parameters are derived from the time series of SLR core station in the period of 1983-2008. The results are proved reliably by statistic analysis of transformation parameters.
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. 2011, 31(6): 109-112.As comparing with the ITRF2000, the ITRF2005 make a lot of improvement on solution generation, datum definition and realization and so on, so there is a certain frame difference between the ITRF2000 and ITRF2005, furthermore, it would affect GNSS data processing. So in this work, the differences of the results including station coordinates, baseline length and horizontal velocity field were analyzed. After transformation, the differences of position are at millimeter level, the differences of baseline length are less than 1mm. The differences of horizontal velocity fields decreases with the reduction of studied area. For large regions, the differences are less than 1mm/a and a systematic difference of about 2 degrees in direction. For medium regions, the differences and direction are not significant.
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. 2011, 31(6): 113-116.To improve the accuracy of GPS height transform from geodetic height to normal height, General Regression Neural Network（GRNN）was used for fitting. The X and Y coordinates of the control points were employed as the inputs of GRNN, and the elevation anomaly were the outputs of the neural network.We adopted experimental data for training the network, then, took the trained network as a model to complete the abnormal height prediction. The results show that the GRNN method is feasible and has the high accuracy of the GPS height transform.
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. 2011, 31(6): 117-120.An inequality constrained rank deficient adjustment model is proposed and on its basis the algorithm which is simple and easy to implement
is designed. In the algorithm the reference condition is treated as a virtual observation and by using iterative Gaussian elimination to distinguish active or inactive constraints based on KuhnTucker condition, and then the inequality constrained model is transformed into equality constrained rank deficient adjustment model. In addition,an example of level network is given to prove the feasibility and correctness of this algorithm. -
. 2011, 31(6): 121-123.In view of that the EMD (Empirical Mode Decomposition, referred to as EMD) in dealing with nonlinear, nonstationary signal, and artificial neural network (Artificial Neural Networks, referred to as ANN, also known as neural network) can deal better with the nonlinear problems,we propose a new way combining these two methods for dealing with the signal prediction.Firstly,
by using EMD to decompose the simulation signal with noise into several IMF(Intrinsic Mode Function, referred to as IMF) components and a tendency and then in two ways to deal with the endpoint problem in the decomposition process. The results show that the two methods can be good to solve the endpoint problem, then for each component using RBF (Radial Basis Function) neural network to predict separately, and reconstruct the final prediction results. Compared with the use of neural networks to predict directly without being processed with EMD and real data, this method has a higher prediction accuracy. -
. 2011, 31(6): 124-127.The influence of lowelevation satellite signals on the resolution accuracy was analysed by use of the Bernese software to calculate tropospheric refraction error and the positioning of the elevation error under different satellite elevation angles.It is concluded that with cutoff elevation angle of 5 degree the good accuracy can be reached.
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. 2011, 31(6): 128-131.In the Virtual Reference Station (VRS) technology, atmospheric refraction error is the main factor affecting the accuracy of the longdistance RTK.However, the elevation difference between the reference plane and the roving station will cause the deviation of tropospheric error in the system and then the accuracy of troposphere correction will be lowered.A new tropospheric error model based on neural network, taking into account the space troposphere error, is presented. The accuracy of tropospheric delay model is within 5 cm, in spite of interpolation points in the network or out of network.
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. 2011, 31(6): 132-135.The 2D Vondrak filter combined with the multisurface function was used in the height anomaly fitting.The experimental result shows that it is a practicable method in the height anomaly fitting.Compared with the multisurface function fitting method,the accuracy have been greatly improved to 76.4% at most.The standard error has decreased up to 54.72%.
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. 2011, 31(6): 136-139.OpenGL is the premier environment for developing interactive 3D graphics applications, which is used widely in remote sensing, flight simulation, satellite orbit visualization and other fields. For users to understand directly the movement of current vehicles in real time in multiangle, multilevel ways, GNSS simulation software needs realtime 3D visualization of moving vehicles. The method how to use OpenGL to realize the flight simulation visualization and show the result according to output the of GNSS simulation such as pitch angle,yaw angle and speed is presented , which has a good visual effect.
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. 2011, 31(6): 140-144.On the basis of SpaceWise Least Square method, three numerical methods including Cholesky decomposition, Preconditioned conjugate gradient and Open MultiProcessing parallel algorithm are applied into the determination of gravity field with satellite gravity gradiometry data. The results show that, Cholesky decomposition method has been unable to meet the requirements of computation efficiency when the computer hardware is limited. Preconditioned conjugate gradient method can improve the computation efficiency of huge matrix inversion, but it also brings a certain loss of accuracy. The application of Open MultiProcessing parallel algorithm could achieve a good compromise between accuracy and computation efficiency.
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. 2011, 31(6): 145-150.Multipath error and random noise are two important error sources in highrate GPS positioning. In order to characterize and mitigate these errors, and improve the accuracy of highrate GPS positioning, the Principal Component Analysis (PCA) and Karhunenloeve Expansion (KLE) are introduced to evaluate the random noise level of the time series of coordinate on some days, extract and mitigate the multipath error from coordinates time series of multiple days. The data processing, comparison and analysis based on real data show that the principal component coefficients ratio of PCA can effectively reflect the random noise level of the time series of coordinates on certain day, meanwhile, the multipath error of the time series of coordinates on many days can be extracted and mitigated with introduction of PCA. Compared to PCA, the KLE approach performs slightly weaker on accurate improvement,but the random noise and local anomaly can be suppressed by KLE better since it is not sensitive to the random noise.
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. 2011, 31(6): 151-154.The decoherence phenomena such as LowSNR radar signal, shadows and layover caused by topography etc, causing phase data discontinuous, makes the result of unwrapping phase inaccurate or completely wrong.
On the basis of the analysis of influencing factors to weighted choice, a new method to choose the weightes according to the measure of confidence in frequency domain was developed. The experiments show the defect of subestimate to the slope of least squares method can be well overcome.It is proved that this method has good rational and stable performance. -
. 2011, 31(6): 155-158.5 Burris relative gravimeters were tested by static and dynamic surveying on short calibration line of Lushan and Wuhan gravity datum station, the processed data shows that the observation accuracy of Burris gravimeter is better than 15.0×10 -8 ms -2, the static and dynamic zero drift are very small and present linear, the repeated STD is better than 5.0×10 -8 ms -2.
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. 2011, 31(6): 159-163.Through the calculation of the gravity disturbance with the EGM2008 spherical harmonic model the gravity disturbance graph of a certain area wasgenerated .Since the model of strapdown inertial navigation error under the condition of gravity disturbance was established, then the influence of the horizontal component of gravity disturbance on the error of strapdown inertial navigation system can be proved by a simulation.The simulation results show that gravity disturbance can cause the velocity and the position error with the Schuler period oscilation, when there is 12.5×10 -5 ms -2 gravity disturbance, it will cause position error of 160 m.
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. 2011, 31(6): 164-169.The drillinghole deviation problem is explored through theoretical and numerical analysis.First,the finite element modeling to different deviation(zero to half of hole radium) established and relatively dispalcement fields are obtained.Then,the correlation of deviation value and mean diaplacement error(MDE) is developed.When the deviation is located at 0.2 level,the MDE components at radical and circumferential direction is less than 15% and 10% respectively,when it is located at 0.4 level,the relatively error will exceed to 30% and 25%,if it is exceed to 0.5 level,the present law is invalidated and had to be improved.
