23 March 2017, Volume 37 Issue 4
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jgg. 2017, 37(4): 331-334.
With two coseismic deformation data sets as constraints, one gained from triangulation data and the other from GPS and triangulation data, the single rectangular fault model of the Tonghai earthquake in 1970 is inferred using a simulated annealing algorithm, and then the slip distribution is inferred using bounded variable least square. The results show that, the length of the outcropping, mainly strike slipping rupture of the single rectangular fault inferred from simulated annealing algorithm,is approximately 100 km; its dipping angle is greater than 80°. The positions and depths of maximum slip in the two slip distribution models inferred from bounded variable least square constrained by the two data sets are basically consistent, while slips in southeast section determined from GPS and triangulation data are larger. Maybe some large errors were introduced by the absence of common stations in coordinate transformation, or the deformation in the southeast section is underestimated.
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jgg. 2017, 37(4): 335-338.
Before the Gaoling earthquake, cross-fault vertical deformation within 100 km ranges on the periphery of the epicenter showed no abnormal changes. Although the earthquake did not cause coseismic deformation of active faults, it led to fault instability. Fault creep intensified under the continuous action of aftershocks, and eventually caused about 3 mm permanent vertical deformation on the Lingkou cross-fault site. We speculate that the occurrence of earthquakes is connected with activities of Weinan tableland front fault.
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jgg. 2017, 37(4): 339-343.
‘Along-track interferometry’method is proposed to obtain along-track displacements from backward and forward interferograms within regions of burst overlap. The azimuth direction displacement component of non-overlap area is measured by interpolation. The experimental results show that the coseismic displacement of the Kaohsiung earthquake is predominantly vertical and east-west direction, and mainly distributes in left and right valves of a blind fault. The left valve uplifts with a maximum vertical displacement of 12 cm, and the right valve drops with a maximum vertical displacement of 8 cm. Meanwhile, they have a displacement westward, to a maximum of up to 6 cm. In addition, the Kaohsiung earthquake has a characteristic of northwest-southeast trend blind fault between the left and right valve.
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jgg. 2017, 37(4): 344-348.
Considering the systematic differences between InSAR monitoring deformation and GPS observation, an integrated deformation analysis model with additional systematic parameters is established for the three-dimensional deformation field, in order to integrate GPS and InSAR data effectively. In this model, systematic parameters are added under the constraint of high accurate deformation derived from GPS to compensate system error in InSAR derived deformation. Both simulated and measured data prove the significance of our method in improving the accuracy of three deformation components, especially in U direction.
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jgg. 2017, 37(4): 349-354.
The present horizontal movement characteristics of the Ordos block is the result of the interaction between the Ordos block movement itself and the whole movement of the mainland of China. The power source of Ordos block is mainly by push from the Qinghai-Tibet block from a NE direction, and the NW extension of the northern margin of the block. The latest GPS velocity field observational evidence from 1999 to 2015 shows that the resultant changeis significant. The velocity field change is more significant in the northeast, northwest, southwest and southeast margins of the block; the left lateral movement speed of the north and south margin is much larger than the right lateral movement speed of the east and the south marginsof the Ordos block. Seismic activity, strain accumulation and release, stress distribution and stress field analysis using the present seismic data since 1970,show that the northern margin of the Ordos block is the main region of strong earthquake activity; this is not only at the block edge, but also in north China. The energy around the Ordos block has accumulated continuously since 2000.This is the longest period since 1970, until the Alashanzuoqi 5.8 earthquake in 2015. The periphery of the block has shown signs of pre-release energy, and there is an abnormal area of stress distribution in the north margin of the Ordos block.
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jgg. 2017, 37(4): 355-360.
On the basis of extensive field geological survey of the Xiannüshan-Jiuwanxi fault, we collect 12 gouge samples, extract the quartz and observe their micro-morphology by SEM. The results show that the Xiannüshan fault is an active fault essentially characterized by stick-slip, and that recent large-scale movement happened in the middle-late Pleistocene period. The Jiuwanxi fault is also an active fault essentially characterized by stick-slip with multi-periodic activities, with early activities much stronger than late ones. Its last activity has taken place during the Pliocene and the middle Pleistocene period. Furthermore, the “V” glyph fracture combination formed by the Xiannüshan-Jiuwanxi fault presents a tectonic pattern which is dominated by the Xiannüshan fault.
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jgg. 2017, 37(4): 361-364.
A pair of Radarsat-2 and TerraSAR-X were employed to monitor the change of Hawaii volcano national park and its surrounding areas. Compared with the results obtained by offset-tracking technology, this fully demonstrates the ability of sub-band interferometry in deformation monitoring. In addition, comparing deformation obtained by the two kinds of data, the results show TerraSAR-X, with its higher resolution and wider bandwidth, can get more accurate results. Then the sub-band interferometry technology is applied to a pair of PALSAR of mine of Tangdong, to extract the azimuth deformation. Compared with GPS monitoring data obtained in the same time, it further validates ability of sub-band interferometry in deformation monitoring.
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jgg. 2017, 37(4): 365-368.
Sentinel-1A IW mode SAR image has a width of 250 km with low noise and a short revisit period. However, the TOPS image mode causes large Doppler frequency variations, which sets very stringent co-registration requirements in interferometry processing. In this paper, TOPS SAR image co-registration and burst merge are presented, and a process flow chart of deformation monitoring with TOPS SAR image is stated. Consistent deformation, with descending and ascending images of the Menyuan earthquake in Qinghai province, demonstrates the validity of the presented method.
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jgg. 2017, 37(4): 369-373.
In this paper,based on research from July 2014 to July 2015 from the International GNSS service (IGS) orbit combination theory, GPS combined orbit is computed by an independent algorithm, using the precise orbit of IGS analysis centers. This method has advantages over the combination method of GEO/IGSO/MEO orbit of the Beidou navigation system.According to the experiment, the maximum three-dimensional root mean square(RMS) accuracy difference of combined orbit is up to 4 mm, using the analysis of the Scripps Institution of Oceanography (SIO). The precision of the combined orbit increases nearly fifty percent by using SIO since GPS week 1 807.When using the different methods to eliminate the difference of coordinate reference frame, the accuracy of combined orbit dramatically changed, and the result using the rotation parameter of SINEX is better than that of using that of ERP. Finally, the combined orbit is calculated from 2014 July to 2015 July. Compared with IGS combined orbit, it is found that the three-dimensional difference is less than 3 mm, the mean RMS is 1.50 mm and the weighted mean RMS is 1.16 mm, according to the satellite accuracy code, proving the algorithm’s accuracy and stability.
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jgg. 2017, 37(4): 374-379.
This paper proposes a new geometry-free and ionosphere-free triple-frequency ambiguity resolution(NGIF-TCAR). The new method can aid wide-lane ambiguity and narrow-lane ambiguity to eliminate ionospheric residuals by assigning pseudorange observation different weight value. Both wide-lane and narrow-lane ambiguity are affected by observation noise, and can be success fully fixed by rounding off the average float ambiguity over several epochs. The new method can effectively achieve the long baseline ambiguity rapid resolution by using the measured GPS/BDS of medium and long baseline triple-frequency data.
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jgg. 2017, 37(4): 380-384.
We propose a source localization algorithm using received signal strength that does not need to know the source transmit power and the path-loss exponent. The algorithm first employs a double differential method to eliminate the source transmit power related parameter and path-loss exponent of the path-loss model. Then, least squares criteriaare used to estimate the location of the source node. The location accuracy of the algorithm is evaluated and compared with other source node localization algorithms by simulation data.
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jgg. 2017, 37(4): 385-389.
Common mode error(CME), a major source of error correlated spatially in regional GPS solutions, should be removed to enhance signal-to-noise ratio in GPS coordinate time series. Principal component analysis (PCA), which is widely used for CME extraction, decomposes the time series of the GPS network into a group of modes, where each mode consists of a common temporal function and corresponding spatial response based on second-order statistics. Since the probability distribution function of GPS time series is sometimes no-Gaussian, the second-order statistic cannot fully capture its stochastic characteristics. In this paper, we assume that CME is stochastic independent with other error sources, so an independent component analysis (ICA) is introduced to analyze it. The performance of ICA is validated and compared with that of PCA through a simulated example.
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jgg. 2017, 37(4): 390-393.
Single Tikhonov regularization tends to over-smooth solutions. TV regularization effectively resists noise. Therefore, in this paper, we regularize the ill-posed problem by incorporating both Tikhonov and TV regularization, and give the iterative algorithm. Two numerical experiments are carried out to demonstrate the efficiency and performance of the hybrid regularization method.
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jgg. 2017, 37(4): 394-396.
It is imperative to consider analysis accuracy and computational time of every algorithm. When it is used to analyze random error, the computational time of total variance is very long. Aimed at this problem, this essay analyzes the Allan variance and the total overlapping Allan variance approaches. Three sampling modes are put forward. We find the origin of long computational time of total variance, based on which half overlapping total variance is proposed. Finally, the new algorithm is tested with a static experiment of inertial measurement unit including optic-fiber gyro. The result shows that analysis accuracy of half overlapping total variance is the same as with total variance, but computational time of half overlapping total variance is less than total variance.
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jgg. 2017, 37(4): 397-402.
The quality of atmosphere de-aliasing models significantly impact the precision of GRACE temporal gravity field models. Improvement of atmosphere de-aliasing models will benefit the exact signal extraction of Earth mass changes from GRACE satellites. As spherical harmonic analysis is the main process to convert atmosphere pressure into atmosphere de-aliasing models, this paper deduces five kinds of spherical harmonic analysis formulae that can be adapted to the computation of atmosphere de-aliasing models based on the analytic integral formulae. Simulated data,with or without white noise,are used to verify the validity and effectiveness of five spherical harmonic analysis methods by closed loop processes. Five atmosphere de-aliasing models are calculated based on the combination of ERA-interim surface pressure data and five spherical harmonic analysis approaches. Using the comparison of inter-satellite range rate residuals and cumulative geoid height errors, we verify that different spherical harmonic analysis methods can lead to variability of range rate residuals up to 0.6 nm/s and that the first Neumann method has the highest precision. It can be recognized that the impact of five spherical harmonic analysis methods on the state-of-the-art GRACE satellite gravity field recovery could be negligible, while the first Neumann method is recommended to compute atmosphere de-aliasing models for future satellite gravity missions with laser ranging measurements.
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jgg. 2017, 37(4): 403-406.
Based on CMONOC mobile gravity data from 2000, zero drift characteristics of 18 LCR-G relative gravimeters are studied. The results show that zero drift rate of gravimeter may sometime shave a significant change, up to 10 μGal/h. Based on different processing methods of zero drift correction, the results of traditional and improved adjustment models are compared. Given the same priori error, the posterior error of the traditional adjustment model is 39 μGal, and its average accuracy of gravity value is 26.5 μGal; however, for the improved adjustment model, its posterior error is 16.5 μGal and the average accuracy of gravity value is 11.2 μGal. The accuracy of the improved model is much higher than that of the traditional adjustment model. The comparison shows that computing the zero drift correction by circuit in the data preprocessing can effectively eliminate the error of significant change of zero drift. The improved model is superior to traditional adjustment model that assumes the zero drift as a constant.
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jgg. 2017, 37(4): 407-410.
Based on the grid value of the coefficient term of relative gravimeter resolved from long baseline and absolute point calibration, we calculate mobile gravity data from 2014 to 2016 in south-central Shanxi province network using the classical adjustment method. Then we get the images of gravity field change in 0.5 a scale. It turns out that the evolution of gravitational field occurs in three stages, which are the regional negative gravity anomaly,the local gravity anomaly and the earthquake occurrence, in the study region before the Yuncheng earthquake.
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jgg. 2017, 37(4): 411-415.
Taking Lushan earthquake as an example, we compare the spectral characteristics of seismic signals recorded by gravimeter and seismometer in the same seismic stations. The results show that the P-waves recorded by the two instruments are basically the same when the epicenter distance is greater than 2 000 km, but there is a slight difference in magnitude. The results of P-wave spectrum analysis indicate that the gPhone gravimeter cannot record some high frequency information, and the main frequency range of seismic waves recorded by the gPhone gravimeter and CTS-1 seismometers are quite concentrated in the 0-0.3 Hz range when the epicenter distance is greater than 2 000 km.
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jgg. 2017, 37(4): 416-419.
According to the high consistency between the observed and theoretical data of the crustal deformation incremental value, we take the ratio of daily change amplitudes as a factor to detect scale changes. The method is used on most tidal deformation observation data in which the correlation coefficient is higher than 70%. Only one day’s data is needed to detect both the grid change and the graded change of the scale. Correcting data leads to different results, indicating that it is important to detect the change of scale and correct the data before analysis.
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jgg. 2017, 37(4): 420-424.
According to the observation data of gPhone101# gravimeter in Zigui during 2012-06-2014-08, the corrected gravity residuals reflect the gravimetric response caused by reservoir impound changes. For different impound stages, gPhone101# gravity residual shows different response characteristics. Thirty meters elevation fluctuations of water level can cause a 70 μGal gravimetric response. A gPhone can detect the gravimetric response of Three Gorges Reservoir area effectively. However, local rainfall hydrological effects are also important contributors to gravimetric response and should not be neglected when we detect the influences of impound.
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jgg. 2017, 37(4): 425-428.
In this paper,we use observation data for Tianshui geomagnetic station(TSY), Lanzhou geomagnetic station (LZH), Qianling geomagnetic station(QIX), and Chengdu geomagnetic station(CDP), based on multi-scale wavelet decomposition, extraction of time of low-point on vertical compenent,and variation process of low-point shift on time. The results show that the low-point shift continues to lag the vertical compenent on Tianshui geomagnetic station (TSY) from May to July 2013.The range of variation lies beyond the normal state, but other stations do not present this abnormal phenomenon. This process shows localized features at Tianshui station; the Minxian-Zhangxian 2013-07-22 M6.6 earthquake occurrence is on down-point time of low-point shift peak, showing the correlation between the anomaly and the earthquake. This may be a reflection of seismogenics in the geomagnetic field. These results have an important reference value in the study of the seismogenic process, mechanism dynamics process of geomagnetic low point shift, and exploration on earthquake prediction.
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jgg. 2017, 37(4): 429-432.
The negative feedback seismometer transfer function of the feedback model is broken down into low-end and high-end of the frequency characteristics of the two parts. The low-end of the frequency characteristics of the second-order high-pass filter transfer function reveals low-frequency cutoff spreading methods: reduce mechanical natural angular frequency ω0, increase the inertial mass, increase the high frequency end of angular frequency ω0, reduce sensitivity Sv, increase the feedback coil resistance, reduce the diameter of the wire, use higher resistivity material coil, use a weaker magnetic field. We use the negative feedback downhole seismometer experiment to test the low end of its expansion and the theoretical derivation of consistency.
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jgg. 2017, 37(4): 432-435.
Using the SZW-1A digital thermometer, we survey the relationship of water temperature to depth and analyze short-term stability in Xin 11 Well, located in Hongyanchi, Xinjiang, China. We take the observational step as 10 meters, continue at one week for each point, take the average value as the water temperature, and compute the standard deviation of every point after the water temperature is stable. We determine the inflection point of gradient-depth is 400 m, the inflection point of stability-depth is 470 m, the interface of rocks is 380 m, and the borehole casing is 378 m. We conclude that, from the relationship of gradient-depth and stability-depth, the open borehole belongs to a weak permeability section and is inflected by low-temperature water, which comes from shallow circulating water.
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jgg. 2017, 37(4): 436-440.
Using a portable hydrogen analyser, field measurements are performed to determine hydrogen (H2) concentrations in the soils of the north China plain, Loess plateau, Changping district, Haiyuan fault zone, and Beiluntai fault at the edge of south Tianshan. The factors affecting soil gas H2 concentration, such as the sampler type, test hole depth, soil characteristics, and fault characteristics, and the mechanisms of their influence are discussed in terms of a gas diffusion equation. The results show that: (1) the soil gas H2 concentration is mainly affected by the time lapse between the hole drilling and measurement, test hole depth, and sampler shape; (2) the measured soil gas H2 concentration agrees well with the analytical solution of the gas diffusion equation, and the curve shape is closely related to the degree of H2 enrichment in the soil and the soil density; and (3) the soil gas concentration in the fracture zone is largely affected by tectonism, the fault slip rate, the degree of fault locking, the development degree of fractures between the hanging wall and footwall, and the degree of fracture locking, because these factors can alter the H2 upward transport channels and degree of surface enrichment.
