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15 May 2020, Volume 40 Issue 5
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jgg. 2020, 40(5): 441-445.Based on the waveform records of the Minxian-Zhangxian MS6.6 and Menyuan MS6.4 earthquakes recorded by Gansu and Qinghai seismic network, we calculate the peak velocities in three components of the two earthquakesby the FFT method. We discuss the geographical distribution characteristics of the peak velocity ratio between components. The results show that the Minxian-Zhangxian earthquake is characterized by thrusting and sinistral dislocation, and the energy of the south-north component is obviously greater than that of the east-west component when we compare the two horizontal directions. The Menyuan earthquake is a thrusting earthquake with slight left-lateral strike-slip, and the energy of two horizontal components is equal. Based on the distribution characteristics of aftershocks of these two earthquakes and the research results of other scholars, we infer that the seismogenic fault of Minxian-Zhangxian earthquake should be a secondary fault which is parallel to Lintan-Tangchang fault, and the seismogenic fault of Menyuan earthquake should be a secondary fault on the northwest side of Lenglongling fault, but controlled by the activity of Lenglongling fault.
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jgg. 2020, 40(5): 446-451.Based on the data of 30 s sampling rate of 28 GNSS continuous tracking stations in Yunnan in 2014, we extract the maximum shear strain grid time series from the 3 months before the earthquake as the time scale and 1 month as the window length. For the maximum shear strain time series after the trend term is removed, two standard deviations are set as the abnormal threshold. Taking the 2014 Yingjiang 6.1, Ludian 6.5 and Jinggu 66 earthquakes as samples, the relationship between the maximum shear strain grid timing anomaly and the M≥6.0 earthquake during the earthquake incubation is analyzed. The results show that the anomalous distribution of GNSS maximum shear strain grid time series in Yunnan has a good correlation with Yingjiang 6.1, Ludian 6.5 and Jinggu 66 earthquakes in 2014. The maximum shear strain anomaly grid, in the short-term before the earthquake, is concentrated in the vicinity of the epicenter, and there is a phenomenon of pre-earthquake enhancement and rapid disappearance after the earthquake. The area where the maximum shear strain anomaly grid distribution is relatively concentrated can be used as a reference index for the future occurrence of M≥6.0 earthquakes. The maximum shear strain comprehensive index value prediction results show that the number of predicted earthquakes is 3, and 3 earthquakes are successfully predicted, 0 are missing, and 1 is falsely reported (the indicator appears without earthquake), and the accuracy rate is 75%. From a spatial point of view, the three earthquake epicenters are located at the edge of the anomalous grid, indicating that the edge of the maximum shear strain anomaly may be more dangerous.
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jgg. 2020, 40(5): 452-456.Based on the relationship between seismic energy and Benioff strain, the catalog of all seismicity from Yunnan seismic network between 1990 and 2016 as well as the catalog of M≥5.0 seismicity from China seismological network between 1969 and 2016 are used in this paper. The time series of seismic strain release in the Yunnan and its neighboring area, and then the continuous wavelet transform method,are used to analyze the earthquake period and discuss its characteristics and causes. The results show that the seismic activity in Yunnan contains long periods of about 1, 400 d(11 a) from 1990 to 2016. It also contains short periods of 12 d and 32 d in 2008. Furthermore, it contains short periods of about 400 d(1 a), 1 400 d(4 a) and 6 a as well as long periods of about 16 a and 27 a from 1969 to 2016.
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jgg. 2020, 40(5): 457-463.The GM(1,1) power model can be used for the prediction of settlement that tends to be stable or has a trend of S-type. However, the GM(1,1) power model has some shortcomings, including the inherent defects of grey modeling, no applicability for non-equal interval data, and the complexity of solving parameters. In combination with the power function transformation and the unbiased GM(1,1) model or the unequal interval unbiased GM(1,1) model, we establish the unbiased GM(1,1) power model and the unequal interval unbiased GM(1,1) power model. Based on the Matlab program, we take the minimum relative mean error of the fitting results as the optimization objective, and advance the solving method of optimization parameters. Meanwhile, we propose an alternative method of Origin fitting function SRichards2. The application results of engineering examples show that the two methods have a good fitting effect and can be used in settlement prediction. Considering the application effect and the modeling characteristics of the two methods, we recommend the Origin fitting function SRichards2 is recommended for manual data processing, and the unbiased GM(1,1) model and non-equal interval unbiased GM(1,1) model for special optimization objectives or automatic monitoring design.
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jgg. 2020, 40(5): 457-463.We analyze the deformation characteristics during the surveillance period using two newest crustal deformation monitoring data of Baihetan and Wudongde reservoir area in 2018-2019. We analyze the levelling and gravity data using the relative benchmark, and analyze the distance measurement data of valley width and cross-fault using the relative coordinates of the projection surface. The results show that: 1)There is a settling zone with a range of 16 km in the central region of the left bank upstream of Baihetan reservoir area, and the levelling branch line of the right bank upstream of Wudongde reservoir area has a larger uplift.The rest of the two reservoir areas are relatively stable, and the vertical variables are less than 5 mm. 2)The changes of gravity field in the two reservoir areas are basically stable, the gravity field has no significant abnormal changes, and the large changes in the gravity value of individual points are caused by the changes of the surrounding environment. 3)The changes of the relative coordinates of each point of four valley width nets in the two reservoir areas are not large, but relative contraction is shown in four valley width nets, and the contraction value is 1－2 mm. 4)There are five cross-fault sites in the two reservoir areas that are relatively stable, and there are no significant signs of vertical or horizontal activity during the monitoring period. There is a certain differential vertical movement accompanied by a horizontal compression movement on both sides of the fault in the surveillance area of Luozuo site in Wudongde reservoir area. The results can provide background information for the study of the deformation after reservoir impounding and the earthquakes induced by reservoirs.
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jgg. 2020, 40(5): 470-475.To determine the influence of different sorting algorithms on the decorrelation performance of ambiguity in the ambiguity resolution, we theoretically analyze the natural ascending sorting method, the sorted QR decomposition method and the perturbed ascending sorting strategy. Secondly, based on simulated data and measured data, we compare and analyze the three algorithms in five aspects: decorrelation time, search time, overall time consumption, bootstrapping success rate, and condition number. The results show that decorrelation efficiency is negatively correlated with the degree of compression of the search ellipsoid. The higher the degree of compression of the search ellipsoid, the lower the decorrelation efficiency. For different sorting algorithms, the key to improve decorrelation performance is to reduce the decorrelation time and conditional variances are ordered in a certain direction to improve search efficiency.
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jgg. 2020, 40(5): 476-481.Based on the GNSS coordinate time series of nearly 9 years of 22 tide stations in China’s coastal areas, we use the maximum likelihood estimation method to analyze the noise characteristics and establish the optimal noise model for each station. Finally, we estimate station speed by considering the colored noise.Compared with the speed and error estimated by considering pure white noise model and GLOBK result, the results show: 1)All of the GNSS time series of coastal tide stations contain colored noise. The east and vertical coordinate mainly includes white noise+flicker noise,and the north coordinate mainly includes white noise+flicker noise and white noise+first-order Markov noise+ random walk noise.2)The values of white noise and flicker noise in the north and east coordinates of the three coastal areas show the law that the noise is more southward, the values of white noise and flicker noise of the vertical coordinates in south China sea are the largest.3)The speed error that considers colored noise is 5 to 10 times greater than considering only white noise and GLOBK result.4)When estimating the speed of the GNSS of tide station,the noise type should be judged first,and the color noise should be considered to estimate the speed.
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jgg. 2020, 40(5): 482-485.The impact of ERP prediction error on LEO autonomous orbit determination is analyzed with the orbit data from Luojia-1A satellite. The test results indicate that ERP have a significant impact on the tangent and normal direction, with less impact on the radical direction. With 10-days prediction, the impact on the tangent direction reaches a decimeter level, which will have a major impact on the precise orbit determination.
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jgg. 2020, 40(5): 486-490.The traditional ionospheric anomaly detection method in ground-based augmentation system (GBAS) cannot take detection accuracy and sensitivity into account, so we apply the least mean square (LMS) adaptive filter with single-channel and variable step size to suppress the high-frequency noise of code-carrier divergence. On the basis of the standard two-channel LMS adaptive filter, we construct a single-channel LMS adaptive filter using delayed detected signal as reference input by utilizing the short-time correlation of the detected signal and the non-correlation of quantized noise. And at the same time, we improve the Sigmoid function to make the adaptive filter converge fast in the early stage and maintain high stability after the filter converges. The experimental results show that under the same satellite elevation and ionospheric time gradient, the detection time of ionospheric anomaly can be reduced by using the LMS adaptive filter, and the method can also achieve anomaly detection when the ionospheric time gradient is small, which verifies the effectiveness of the proposed algorithm.
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jgg. 2020, 40(5): 491-495.This paper is based on the three typhoon events of “Soudelor”, “Megi” and “Haitang” in Taiwan from 2015 to 2017. We use ground-based GPS data to retrieve the atmospheric rainfall (PWV), and carry out preliminary analysis of the relationship between PWV and rainfall during typhoon.Second,we use cross-wavelet and wavelet coherence to further analyze the temporal and spatial variation of PWV and rainfall. The results show that: during the typhoon, the PWV generally rises and then decreases, and the volatility is severe. When the rainfall occurs, the PWV must change drastically. In the research time domain, PWV has a strong positive correlation with rainfall, and the correlation coefficient reaches 0.7; PWV changes in pre-existing rainfall, and heavy rainfall occurs 0-3 h after PWV changes. Studying the temporal and spatial variation characteristics of PWV and rainfall provides a good reference for short-term rainfall forecasting.
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Model Establishment and Accuracy Analysis of Atmospheric Weighted Mean Temperature in Guizhou Regionjgg. 2020, 40(5): 496-501.Based on the meteorological data of the two radiosonde stations in Guiyang and Weining from 2014 to 2016, the overall, local and seasonal atmospheric weighted mean temperature models of Guizhou are constructed by the one-dimensional linear regression method. Model accuracy is analyzed. The results show that the accuracy of Guizhou model is higher than that of the Bevis, national, and subtropical monsoon climate models.Meanwhile, the establishment of Guizhou local and seasonal models contribute to further improve accuracy. Compared with the Bevis model, the local model inversion has higher PWV accuracy and is in better agreement with actual precipitation.
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jgg. 2020, 40(5): 502-506.To understand the quaternion, this paper defines a non-exchange product between two vectors parallel or vertical to each other, names it as the Glassman product, and promises this non-exchange product meet the commutative law. Furthermore, this paper derives the specific expression of the Glassman product between any two vectors, and then leads to the conception of the quaternion and its operation rules. In theory, this paper proves that any quaternion can be represented as the Glassman product between two vectors, and the Eulerian equation of the rotating vector can be represented by the orthogonal transformation of the unit quaternion either.
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jgg. 2020, 40(5): 507-511.Since the mass of one observation will affect the residual of multiple observations, this paper improves the iterative method of bifactor robust estimation as follows: if the maximal standardized residual is tested as mass or obvious suspicious mass, the bifactor equivalent weight is only constructed for the observation with mass, while the weight of other observations remains unchanged. In addition to the two cases above, the bifactor equivalent weight can be constructed for all observations at the same time. The calculation steps can also be simplified based on the improved equivalent weight construction method. Simulation calculation and analysis are carried out using the observation data of a GPS network. The results demonstrate that the method can improve calculation efficiency when containing a small amount of masses, and improve the accuracy of parameter estimation when containing more masses.
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jgg. 2020, 40(5): 512-516.In this paper, we propose a biased estimation method based on Neumann series to solve the ill-conditioned least squares problem. The biased estimation formulas established by the proposed method can include the existing least squares estimation, ridge estimation and generalized ridge estimation formulas. Using the proposed method, we can establish the essential relationship between biased estimation and unbiased estimation. In addition, we can derive a series of new biased estimations from the proposed method. In the series of biased estimates, there are solutions that are closer to the true value than ridge estimates or generalized ridge estimates. An ill-conditioned system of equations is taken as an example to verify the proposed method. The results show that when the observation vectors contain noise, the errors between the results obtained by least squares estimation and the true values are very large. However, the results of biased estimates at all levels are closer to the true values. Moreover, the results of biased estimates at two and three levels are closer to the true values than the corresponding ridge estimates. It is shown that the method proposed in this paper provides a new way to solve the ill conditioned least squares problem.
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jgg. 2020, 40(5): 517-521.We analyzed the thermochemical structure of north China Craton(NCC) from gravity and topography data. After calculating the free air gravity anomaly, Bouguer gravity, isostatic gravity, residual topography, residual gravity and the corresponding inverted density, we find that: 1) there is excess buoyancy in central and eastern parts of NCC; 2) more buoyant newly-formed lithosphere indicate that high temperature is dominant in bivariate function of temperature and chemical composition; 3) as much as 50-60 percent of old original Craton lithospheric material may still stay in the present-day ENCC lithosphere, thus supporting the episodic and multi-staged delamination numerical studies.
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jgg. 2020, 40(5): 522-528.Using 516 local earthquake events recorded by 82 permanent stations from 2008 to 2018, we apply the double-difference tomography method to relocate seismic events and invert the 3-D seismic velocity structure of Maoshan fault zone and adjacent areas. We analyze the relationship between two destructive earthquakes and velocity structure. The tomography results show that the residual of seismic relocation is significantly reduced and horizontal resolution in most study areas can reach 0.2°. The P wave velocity structure has significant heterogeneities. The rate of change between the speed after the inversion and the initial velocity model is about ±10%. The Maoshan fault zone exhibits high velocity features at both ends, and the middle section exhibits low velocity structures. The 1974 MS5.5 earthquake occurred in the low velocity of deep metamorphic rocks in the Liyang earthquake source area, while the 1979 MS6.0 earthquake occurred on the boundary between the deep metamorphic and shallow metamorphic rocks. The reason for the two earthquakes may be that the stresses easily accumulate in the low velocity body and the boundaries with large velocity gradients.
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jgg. 2020, 40(5): 529-533.Analysis of 672 aftershocks, stress background and deep background of the Xingwen MS5.7 earthquake, shows that it was caused by the northeast-southwest buried fault. The horizontal maximum principal stress of the northwest-southeast direction continues to squeeze and caused Xingwen MS5.7 earthquake. Three other earthquakes and the Xingwen MS5.7 earthquake are linearly arranged in a northeast direction. Combining focal mechanism solution with the stress direction suggests that the other three earthquakes are also related to the buried fault.
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jgg. 2020, 40(5): 534-539.A series of earthquakes occurred in Songyuan area, Jilin province between October 31 and November 23, 2013, including five MS≥5 earthquakes. The largest one, of MS5.8,occurred November 23, 2013. By calculating the correlation coefficients of the spectral amplitude of these five MS≥5 earthquakes in Songyuan area in 2013, it is found that the focal mechanisms of the first and fifth earthquakes are similar, while those of the second, third and fourth earthquakes are similar. Statistical analysis on these five earthquakes and compared with tectonic earthquakes and collapsed earthquakesshows that the displacement source spectrum of Songyuan swarm in 2013 presents the characteristics of early attenuation and fast attenuation compared with tectonic earthquakes. Characteristic parameters of time-domain and frequency-domain, such as waveform complexity and spectral ratio, are also quite different from those of tectonic earthquakes, but more in line with the characteristics of collapsed earthquakes.
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jgg. 2020, 40(5): 540-545.Research on the instrument principle, transfer function and observation data of the vertical pendulum tilt meter (VPT) in the 2-60 s band shows that the VPT can record the signals in this band. As the band is a transition band, the response of ground motion on the observed data is weakened about 20-40 dB. The VPT’s frequency band is improved in order to expand the signals of the 2-60 s periods in pass-band. The results show the same as other fixed deformation observations with 1 Hz samplings. After transforming the observation into the expression of acceleration, the amplitude-frequency characteristics coincide with global seismic background noise model, which would be a new way to analyze the VPT data. The improved VP vertical pendulum has a slightly better effect on the body phase recording of earthquakes with long distance and medium magnitude than before. However, due to the influence of ground micro-tremor, we need more refined methods to improve the recognition effect in identifying non-ground micro-tremor.
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jgg. 2020, 40(5): 546-550.This article briefly introduces GRACE RL06 time-varying gravity field model data from CSR, GFZ and JPL institutions, and compares and analyzes the calculation models of RL06 and RL05 data. Using the RL06 and RL05 time-varying gravity field model data from 2004-01 to 2014-11, we analyze the RL06 and RL05 data from three aspects: the global land storage change inversion results, the time-variable gravity field model degree variance, and the C20 term time series. We perform a comparative analysis. The experimental results show that the quality and accuracy of RL06 data is improved significantly. The de-stripe effect of results using RL06 data is better and the signal-to-noise ratios of results are larger. The degree variance of RL06 data is smaller than degree variance of RL05 data in high degree. The C20 time series of RL06 data is closer to SLR data. The quality of CSR RL06 is best in CSR, GFZ and JPL RL06 data. The signal-to-noise ratios of global terrestrial water storage inversion results with using CSR RL06 data is largest and degree variance of CSR RL06 data is largest under the same conditions.
