In this paper, the grey correlation index curves of the Xianshuihe fault, Longmenshan fault and the western Qinling mountains tectonic area at or near the boundaries of Bayan Har block are extracted. The section variations of Xianshuihe fault, Longmenshan fault and Tazang fault are calculated from GPS velocity field data during 1999-2007, 2009-2015, 2015-2017. We compare and analyze the common characteristics of the fault activity of the block boundary. The results show that the SE-trending movement acceleration began to appear in the east of Bayan Har block in 2009, and that this high-speed characteristic has been maintained for several years. The occurrence of Wenchuan M8.0 earthquake adjusted the stress-strain state of this area, which supports the occurrence of Lushan and Jiuzhaigou M7.0 earthquakes. On the basis of maintaining high-speed movement and high stress-strain state in the east of Bayan Har block from 2015 to 2017, and then accelerating slightly, the remarkable acceleration of tension observed by cross-fault observation of Xianshuihe fault in the boundary of the block from 2016 to July 2017 is related to the Jiuzhaigou earthquake, which is significant for medium-term background prediction.
A geological section of soft-sediment deformation structures has been found in the strata of the first terrace of the north bank of the Yellow river in Pinglu area in Shanxi. There are three types of soft-sediment deformation structures in the observation section: dish structure, liquefied convolute structure, and ball-and-pillow structure. In order to study the triggering factor of the soft-sediment deformation structures in the study area, the three types of soft-sediment deformation structures are given detailed descriptions and their formation mechanisms are analyzed respectively. The criteria of the soft-sediment deformation structure triggered by earthquake factors are summarized. Through comprehensive comparison, it is indicated that the deformation structures in the section owe their genesis to paleoseismic events. The seismic sequence of Pinglu area in southern Shanxi is established. An optical chronology of the sediments in the section brackets the deformation induced by earthquakes at about 1.9±0.2 ka. Based on the influence intensity calculation and seismic data collected in Shanxi province and adjacent provinces, it is concluded that the two earthquakes may be related to the soft-sediment deformation structures in the section.
Before the Jinghe MS6.6 earthquake,significant strain abnormal changes were recorded at Nilka, Balguntay and Xiaoquangou stations. After ensuring the anomaly in the field several times and through argumentation, we affirm that the anomaly is reliable.The relative strain field is calculated based on the records of these three stations.The results show that there is significant acceleration and deflection change in the maximum (small) principal strain and direction before the earthquake.In addition,it is also found that the principal direction is relatively consistent, with the orientation of the focal mechanism solution P axis during the anomaly of the relative strain field.To a certain extent, it is possible that abnormal changes may be related to earthquakes.
In this paper, we take Qianjiangping landslide in 2003 as an example to study landslide movement characteristics based on seismic inversion technology. We first collect seismic waves inspired by the landslide through the China earthquake networks(CEN), then invert for the force-time function of the landslide source, divide landslide sub-events using time-frequency analysis, and finally obtain the dynamics of the sliding body and restore the landslide process. The sliding bed slope, landslide direction, and sliding body displacement derived from seismic inversion coheres with the results from the field survey. We also distinguish a reverse motion from the sub-events analysis. This study helps understand the sliding mechanism of large-scale high speed landslides and is helpful for remote monitoring of landslide disasters.
We use 220 hours of seismic data recorded by globally-distributed seismic station after the MW9.3 earthquake at Japan on 2011-03-11.This paper selects 448 sets of vertical components of seismic waves with higher-quality, based on a certain criterion, and adopts the frequency-domain AR method to estimate the frequency and quality factor for the normal mode 0S0. After determining the weighted averages with signal-to-noise ratio (SNR) as the weights, the estimated results are f=0.814 658 4±5.3×10-7 and Q=5 586±12. The two estimations have higher precision than previous results, which can improve the existing earth models to bring them closer to the real earth.
We use the Venedikov harmonic analysis method to calculate the tidal factor of solid tide of the EW and NS components of the ground tilting observatory station on the Taihang mountain piedmont fault zone from 2002 to 2017. Further, the time series of three characteristic quantities (expansion, shear strain, anisotropy of the medium) of the tidal factor Δγ anomaly and dynamic combination are obtained. The relationship between the three dynamic combination features and the moderate earthquake near the Taihang mountain piedmont fault zone is analyzed. The results show: 1) Tilting factors are less affected by the ocean tide load, and do not show obvious regular changes caused by the change of latitude. The variation of tidal factors may be affected by the change of lateral inhomogeneity of the crust. 2) The dynamic combination feature of the tidal factor has a good correspondence with the ML4.0 earthquakes in the range of 350 km around the observation stations.
The Mascon data published by different research institutions are introduced briefly in this paper. Pesults of terrestial water storage variation which calculated y Mascon data, GLDAS model data and spherical harmonic coefficients method are compared in global and regional scales. The results show that Mascon data of different institutions have consistency. Signal-to-noise ratio and spatial resolution of terrestrial water storage variation results are improved by the Mascon method compared with the spherical harmonic coefficients method. More true signals of regional mass variation are kept. Time series of regional terrestrial water storage variation results which calculated by Mascon data are more relevant to GLDAS model results compared with the results of the spherical harmonic coefficients method. The signal-to-noise ratio of global surface mass variation inversion results by Mascon data are larger than results of spherical harmonic coefficients method. The JPL Mascon results are maximal.
To improve the accuracy of quasigeoid/geoid determination based on GPS/leveling, we present a new approach to fit quasigeoid/geoid called semi-free position point mass, based on the gravity field approximation principle. Compared with the traditional point mass model, the plan coordinates of the new model are stationary, while the depths are free. The method is established by a kind of iterative algorithm using the relationship between the nearest points. The gravity parameters are fitted in multi-band by several mass-points under the known data-points with different depths. Three experiments are conducted in different test zones where the data conditions vary. The results show that applying the model to quasigeoid/geoid fitting is feasible, and achieves higher accuracy than Kriging and Co-Kriging method in the test zones.
In order to solve the problem of low efficiency in calculating vertical deviation in large-scale and high-resolution regions by using the super-high-order earth gravity field model, this paper presents an array dimension-lifting and zoning methods based on OpenMP multi-core parallel technology. Experiments show that the acceleration ratio of this method to calculate vertical deviation is up to 5.6 times, which greatly improves the calculation efficiency of super-high order vertical deviation, and provides ideas for solving similar fast calculation problems in data processing of gravity field.
First, we use wavelet to transform decomposition and reconstruction of ZTD time series of IGS stations in China, and then compare low-frequency trend and high-frequency cycle terms of ZTD with annual precipitation, analyzing their relationship with annual precipitation, and analyzing the causal relation with climate data. The results show that the low-frequency trend is the same as the trend of annual precipitation, there is a good correspondence between the high-frequency cycle terms and the annual precipitation variation, and the peak of high-frequency annual cycle terms corresponds to the peak of annual precipitation.
In this paper, we propose a segmentation-based overlapping window fitting algorithm that divides the segmentation window into boundary, overlapping, and inner areas. By weighted averaging the fitting values of the overlapping area of the front and back windows, the fitting value between windows changes continuously. Using GNSS ionospheric data, three algorithms of epoch-by-epoch sliding window, independent segment window and overlapping window are compared. In the ionospheric fitting calculation of G01 at NKLG station with 400 epoch windows, the epoch-by-epoch method consumes 121.618 s, while the independent and overlapping subsection methods only use 0.396 s and 0.985 s, respectively, and the calculation efficiency is 307 times and 123 times that of the former. The results show that the proposed algorithm takes account of both computational accuracy and execution efficiency, and is a good method to deal with time series with large amount of data, and continuous and drastic changes.
BDS precise clock offset data from 2013-01-01 to 2018-05-01 are provided by WHU and GFZ. These data are used to evaluate the long-term performance of BD-2 on-board atomic clocks by phase, frequency, drift rate, frequency accuracy and stability. The results show that the phase data are not so continuous or stable and the phase modulations are frequent; the frequency drift rate maintains in 10-18-10-17/s; the frequency accuracy is stable in 10-11; the frequency stability in ten-thousands is about 10-14-10-13, and MEO satellites are more stable than GEO or IGSO satellites. Furthermore, according to the relationship between clock switching and frequency drift rate, accuracy and stability, the BD-2 satellite clocks switching information is verified and deduced.
We advance an analytical method of CORS height time series based on K-means clustering EEMD. Aiming at the problem of low signal-to-noise ratio and partial mode mixing in signal decomposition of traditional EEMD, we add positive and negative white noise EEMD to improve signal decomposition SNR. Based on the K-means clustering method, we cluster the various IMF components decomposed in the EEMD iterative process. The experience results show that the method improves the SNR by more than 3%, and the decomposition accuracy based on index of orthogonality increases by more than 26%. The clustering results can solve the problem of mode mixing of the approximate year, half-year and two years periodic signals in the IMF.
In order to solve the inefficient problem in calculating station coordinates with double-difference positioning, GNSSer PPP mode is introduced to speed up the solution process by multicore parallel operation. The precision of velocity field model is reduced due to the random signal contained in the station velocity, so least-squares collocation is used to estimate the random signal, and the Helmert estimation of variance components is introduced to adjust the unreasonable relationship between the noise covariance matrix and the signal covariance matrix. Then, a more accurate velocity field model can be established. Taking the continuously operating reference stations of the CMONOC in Xinjiang from 2011 to 2017 as an example, GNSSer PPP mode is used to obtain the coordinate time series to improve the efficiency of the calculation. The reliability and efficiency of GNSSer are verified. It is also confirmed that the PPP can obtain the velocity information, which is substantially consistent with the double-difference positioning, the difference is within 1.5 mm/a. The established horizontal velocity field grid model in Xinjiang shows that the movement velocity in Xinjiang is 27.1-34.8 mm/a, and the overall trend is north to east. From southwest to northeast in Xinjiang, the direction of motion is deflected from north to east.
Based on GPS Doppler velocity determination, we compare the error sources between stand-alone GPS velocity and relative GPS velocity, and analyze the influence of these errors on accuracy using GPS broadcast ephemeris. Then, experiments are carried out with static and low-dynamic data. The results show that in static environments the baseline distance is about 600 km, the accuracy of standalone velocity and relative velocity both can achieve a level of cm/s using raw Doppler, and the RMS of stand-alone velocity is lower than that of relative velocity. The accuracy of stand-alone velocity and relative velocity can achieve a level of mm/s using carrier phase-derived Doppler, and the RMS of relative velocity is lower than that of stand-alone velocity. In low-dynamic environments, the accuracy of stand-alone velocity and relative velocity both can achieve a level of dm/s using raw Doppler, and they can achieve a level of cm/s using high-frequency carrier phase-derived Doppler.
We propose a station selection method for pseudolite system based on weighted horizontal dilution of precision. This method gives different weights to each station according to the relative position of station and receiver, reducing the possibility that stationsthathave large measurement error areselected to participate in positioning. We analyze the mathematical models of pseudo-rangemeasurementerror, and the WHDOP expression is analyzed in detail. Station selection based on the contribution of WHDOP is designed. The simulations reveal that the method can select stations efficiently and accurately, thereby reducing the calculation amount of the receiver and improving the positioning accuracy of the system.
Using C# language and the .net framework 4.5, 6 kinds of design principles and 6 kinds of design patterns are applied to cope with the recurrent problems appearing in the development of GNSS data processing software.The data processing software of GNSSer is developed, and the purpose of unifying and bridging the gap between the analysis, design and implementation of the object-oriented method in the process of GNSS data solving is achieved. This is easy and flexible to maintain, extend and reuse.
We use singular spectrum analysis to extract the corresponding components and compute the correlation coefficients, under the influence of factors. The results show that the trend term of dam deformation mainly relates to water level and aging factor. For seasonal terms, the temperature factor contributes more than water level. Experimental results of dam deformation show that SSA can extract the trends and periodic signal effectively and is useful to forecast dam deformation. Then, recurrent forecasting method of SSA is used for the prediction of dam deformation. Compared with Gaussian process and multiple-regression analysis, the results show that SSA is an effective method with a higher predictive accuracy for analyzing and forecasting dam deformation.
In this paper, the zero drift characteristics of the newly introduced four CG-6 relative gravimeters are studied.The results show that the static zero drift rate, mixed zero drift rate, and dynamic zero drift rate of the four gravimeters are less than 8 mGal/h, which meets the technical specifications given by the manufacturer. However, in a long period of time, the zero drift of each instrument has different degrees of nonlinear characteristics, indicating that the zero-drift rate is unstable. Therefore, in long-term field observation and subsequent data processing, it is not appropriate to use the zero-drift rate as constants are solved and zero drift corrections are made.
In order to study the variation characteristics of strain field in Sheshan area, three sets of annual strain rate, maximum shear strain rate and their responses are obtained using the borehole-lined model formula, the variation and difference values of observed data from 2013 to 2018 of Sheshan station, and three strain conversion methods, including no correction, change correction and difference correction. Three sets of surface strain annual rate, maximum shear strain annual rate change and strain main direction calculation results were obtained.It is found that the difference value is more effective in calculating the main direction of strain and extracting the characteristic curves of annual strain rate and maximum shear strain rate.
We design a laser acquisition system based on linear CCD and FPGA. The system chose the FPGA chip EP2C5T144C8N(FPGA) to be the master chip. Verilog language and C# language are used to design the system software to implement the driver of linear CCD sensor and analog-digital conversion, real-time imaging and processing of the acquired data. The experimental results show that the linear system can satisfy the demand of LDI’s detection.
