16 April 2018, Volume 38 Issue 4
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jgg. 2018, 38(4): 331-337.
Based on about 30 years mobile cross-fault short leveling data for at the surroundings of Ordos block up to the end of 2016, we compute the vertical synthetic norm of grey relation degree, annual velocity and trend accumulation rate.We analyze the characteristics, level and time-space differences of the tectonic activities. Furthermore, we consider possible relationships with the gestation-occurrence and the influence of strong earthquakes inside the monitoring area and great earthquakes outside the monitoring area. The results showed that: (1) the characteristics of fault activity are basically consistent with the geological data; (2) anomalies are found inside and outside the study area before most earthquakes with magnitude over Ms5.8 and the Wenchuan great earthquake; (3) vertical tectonic activitiesare faster in the western Weihe basin and the northern Liupanshan tectonic region, while slower in the central Weihe basin, the Haiyuan fracture and the southern Liupanshan tectonic region. Long-term energy accumulation is relatively obvious in Shanxi fault belt and the northern west Qinling tectonic region. Both ends are relatively active, while the center locked from Liupanshan tectonic region to the western Weihe basin, particularly in recent years.
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jgg. 2018, 38(4): 338-343.
Based on elastic dislocation theory and lithosphere layered viscoelastic model, we analyze the influence of the co-seismic and post-seismic stress of the Yushu earthquake on the Zaduo earthquake. Additionally, we discuss the stress influence of Yushu and Zaduo earthquakes on the major active faults about seismic risk in the study area. The result shows that the co-seismic stress increased 1.476 kPa on the epicenter of the 2016 Zaduo earthquake. During the 6 years between the two earthquakes, post-seismic Coulomb stress enhanced regional stress in the area, and released stress in the stress shadow; the epicenter of the Zaduo earthquake is always located in the area of enhanced stress. When the Zaduo earthquake occurred, the Coulomb stress increased 3.902 kPa on the epicenter of the Zaduo earthquake. The results of different models show that the occurrence of Yushu earthquake promoted the occurrence of Zaduo earthquake. The co-seismic rupture of Zaduo earthquake only affected the stress state of a small area around the epicenter, which made a high stress area in the northwest of Zaduo fault zone. The co-seismic and post-seismic effect of Yushu earthquake significantly enhanced the stress state of the Yenuoka-Jielong segment, Batang-Luoxu segment, Dangjiang segment, the middle segments of Batangxiang and Wudaoliang-Qumalai faults. The northwest seismic gaps of Ganzi-Yushu fault, including the Yenuoka-Jielong and Batang-Xianggu segments, retain arelatively high seismic hazard.
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jgg. 2018, 38(4): 344-350.
We chose the continuous waveform data of 40 days from 169 seismograph stations within 800 km from the epicenter of the Wenchuan earthquake as the research object and analyze the probable abnormal signals. Two kinds of obvious and ubiquitous abnormal signals are found: (1) spindle anomalies, which are found in ~63% of stations, with duration of 1.5 days to 2 days, absolute values of the amplitudes around ~1 700 count and dominant frequency of 0.2~0.3 Hz, and (2) jump anomalies, which are observed in ~15% of stations, with more in north-south component, duration around 2 000 s, amplitudes of ~2 000 count and dominant frequency of 0.1~0.2 Hz. It is indicated that the formation of spindle anomaly is more likely due to the influence of typhoon, and that the jump anomaly may be have the mechanism of the new precursor theory of solitary wave. The results are helpful in understanding the seismogenic process and capturing earthquake precursors.
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jgg. 2018, 38(4): 351-355.
Ambient noise tomography is a powerful method to image the structure of the crust and upper mantle with better resolution. We use the nearest neighbor algorithm to map S wave velocity based on the ambient noise phase speed tomography of the Qingling-Dabie orogenic belt. With depths of 6～38 km S wave velocity, we build the partition velocity model, and apply it to the seismic localization of the June 16,2017 Zigui M4.3 and the February 23,2017 Zigui M3.8 earthquakes. The results show that the average error of the partition model issmaller, and the seismic localization results of the partition model is closer to the results from the Three Gorges digital seismological network. So, the partition velocity model is more reasonable than the one-dimensional velocity model in seismic localization.
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jgg. 2018, 38(4): 356-361.
Based on SPT-N data of seismic safety evaluation controlled drillings and the results of seismic ground motion parameter zonation in the urban area of Wuhan, the possibility of liquefaction of soil layers in rare earthquakes is determined by the method of code. The liquefaction index and the sites coordinates are used to draw the map of liquefaction potential in the urban area of Wuhan. The map initially predicts the possible liquefaction areas and severity levels, and also shows that the right bank of the Yangtze river contains both greater distribution area and stronger liquefaction potential than the left bank. Comparison analysis on the liquefaction data of four historical earthquakes illustrates that the possible liquefied sites in Wuhan urban area are characterized by shallow groundwater table, wide distribution and large buried depth of liquefied soil layers.
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jgg. 2018, 38(4): 362-365.
A semi-parametric model is presented to improve the assumptions made for the REHSM and RELSM models, enabling them to have wide applicability and interpretability. Analysis of the velocity field data of the recent GPS observations in the Bohai sea area show that it is feasible and reasonable to use the new model to analyze crustal deformation.
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jgg. 2018, 38(4): 366-369.
The main work of this paper,is to develop ATL COM components and a DLL dynamic link library that can resolve baseline of BDS and GPS, and embed COM components and DLL in web. Through several groups of experiments of different observation times and baseline lengths for processing, the analysis results show that the baseline calculating library has good encapsulation, embeddedness and universality, and can greatly reduce development time of developers.
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jgg. 2018, 38(4): 370-373.
In this paper, a three-dimensional ionosphere model-NeQuick2 is introduced. We firstly evaluate the precision of Klobuchar and NeQuick2 using global ionosphere maps and then perform the SADODS simulation experiments in different methods, using different ways to eliminate the influence of ionosphere. The results demonstrate that the orbital accuracies using NeQuick2 are improved by 0.2 m compared to the traditional method using modified Klobuchar.
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jgg. 2018, 38(4): 374-380.
Based on the results of GPS/BDS dual systems joint orbit determination, the orbit quality variation characteristics of new and old satellites are given, and the impacts of different attitude control modes on POD are analyzed. For the defects of the solar radiation pressure (SRP) model, we propose two modified POD strategies and discuss their availability. The results show that when the acute angle between sun vector and orbit-plane is less than 4 degrees, the yaw attitudes of old IGSO and MEO satellites are switched and significant orbit quality degradation is observed, while the orbit quality of the IGSO-6 satellite is stable. The ECOM SRP model is suitable for the IGSO-6 satellite, but not for old BDS satellites. Both modified POD strategies can improve the orbit accuracy of BDS satellites to some extent.
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jgg. 2018, 38(4): 381-385.
This paper separates and distills the multipath model from three directions residual coordinate of X,Y,Z based on complete empirical mode decomposition (CEEMD). We use the repetition characteristics of multipath to correct the coordinate sequence for the next day. The results show that, CEEMD can effectively extract the multipath error correction model from residual coordinate, and the RMS of coordinates sequence after correction is much smaller than before. This signifies that the method weakens the influence of multipath error to a certain extent. Furthermore, the processing result is superior to the traditional moving average de-noising method and EMD.
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jgg. 2018, 38(4): 386-389.
In this paper, we discuss the effects on the accuracy of solutions of GPS/BDS long baseline, on the commonly used equalization model, the height angle model, and the Helmert posterior variance estimation model. We use data of the ZHJJ and QLA measuring stations (Sichuan CORS network). The results show that: (1) a BDS/GPS combination system can achieve long baseline high-precision solutions; (2) the solution accuracy of the Helmert posterior variance estimation random model is highest, and can achieve horizontal and vertical accuracy of 140 km long baseline solution in BDS/GPS combination system better than 8 mm and 10 mm respectively; (3) the performance of the equivalent entitlement model and the height angle random model is equivalent in solving BDS/GPS long baseline single epoch.
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jgg. 2018, 38(4): 390-393.
The paper analyzes the characteristics of AODE in broadcast ephemeris for different orbit of BDS from 2013 to 2015. According to the AODE distribution of IGSO and MEO, the signal-in-space accuracy based on different AODE is analyzed in the paper. The results show: AODE of satellites is in period and is consistent with the orbit. For IGSO satellites, the average AODE is about 1.7 hours, reaching to a maximum of 7 hours. Considering orbit alone, the URE of different AODE varies 0.5 m at the worst. For MEO satellites, the average AODE is about 11 hours, and the maximum reachedis two days. Considering orbit alone, the URE of different AODE varies 0.9 m for the worst. During 2013 to 2015,the average URE of IGSO satellites are 0.81 m, 0.84 m and 1.11 m; for MEO satellites they are 0.84 m, 0.82 m and 1.04 m.
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jgg. 2018, 38(4): 394-398.
In the traditional mode, kinematic precise point positioning (PPP) technique uses the kinematic sequential least squares algorithm to carry on the epoch recurrence solution. However, because of coordinate parameter’s temporal characteristics, the epoch is not inherited, which makes the kinematic PPP algorithm losea priori position information constraints. Aiming at this problem, this paper discusses a kinematic precise point position algorithm which takes real-time position prediction information into account. It uses prediction residual information to determine the adaptive factor of each coordinate component. We analyze the positioning accuracy and the correlation with the sampling interval. Finally, the numerical simulation results show that the proposed method effectively improves the accuracy of high-frequency dynamic data processing, which has application value for the monitoring of slow deformation.
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jgg. 2018, 38(4): 399-401.
The SuperSTAR accelerometers on GRACE satellites, which directly and precisely measure the non-gravitational forces, need to be calibrated by evaluating the scale and bias parameters. In this paper, the characteristics of pulse thrusting signal included in the accelerator observations are analyzed and their effect on accelerator calibration is discussed. Research based on the situ data of acceleration in April 2008 demonstrates that maximum effect of pulse thrusting on the calibrated scale parameter reaches 0.02, the calibrated bias parameter comes to 10-7 m·s-2, the calibrated acceleration amounts to 10-9 m·s-2, 10-10 m·s-2 on the Y and Z axis respectively.
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jgg. 2018, 38(4): 402-406.
In this paper, the range, angle and registration error are analyzed. The error entropy model was constructed according to the concept of information entropy. The reliability index of deformation extraction was determined according to the relationship between error entropy and error limit. Eventually, the effectiveness of the method was validated according to the simulating and real landslide.
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jgg. 2018, 38(4): 407-413.
In this paper, firstly, we introduce the basic principle and the key technology of BEMD method; Secondly, the model test proves that the bi-dimensional intrinsic mode function (BIMF) at all levels and the residue by BEMD method, which own their practical geological meaning; Lastly, the BEMD method is innovatively applied to deal with the mobile gravity anomalies of differential dynamic variation of the period of 2015-09~2016-09 so as to obtain the multi-scale decomposition and the extracted anomalies at all levels are analyzed, and then we reconstruct the local and region anomalies with BIMFs and residue, and the results show that the weak anomalies in the region area at a certain frequency range decomposed by BEMD method, can be enhanced relatively, the regional anomaly characteristics become more obvious, and then we can propose the suggestion about the earthquake trend according to the features of abnormal changes.
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Extraction of GRACE Time-Varying Gravity Field Signal Based on Improved Principal Component Analysisjgg. 2018, 38(4): 414-421.
According to the problem that signal leakage exists and noise reduction by de-striping is not sufficient in the approach of principal component analysis, we propose an improved method of extracting the signal using the principal component analysis directly from spherical harmonic coefficient. First, the principal component analysis is performed on the spherical harmonic coefficients to extract the main modes. Then, the appropriate filtering method and parameters are selected according to their own noise characteristics in different modes. Finally, the signal extraction is carried out. The GRACE temporal earth gravity field models of 2005-01~2013-12 (108 months) released by CSR are used to extract the equivalent water height signals, and the data of June and December 2006 are compared with unmodified principal component analysis. The results show that the modified method is effective and could both eliminate striping noise and reduce signal leakage.
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jgg. 2018, 38(4): 422-425.
Based on observations from GPS,EDM and leveling, the deformation of three stations with different depth and shapes is analyzed. The stations are in Yangling, Shaanxi, where the depth of soil is more than 100 m. Comparing the changes of the distance and subsidence between the three stations and GNSS continuous station SNYL, we can choose a better and more reasonable construction design for soil-based stations. The results show that stations with an 8 m depth, which is built directly with soil modulus, has better indicators than others, being more stable and using fewer workers, less material and reduced cost. The station with a 3 m depth is better than that with 5 m depth. The experimental results can provide the design foundation for the same standard of soil-based stations in the western area of China.
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jgg. 2018, 38(4): 426-432.
Analyzing the effect of precipitation on data observed by horizontal pendulum tiltmeters at Yunxian station, we found: in spring and winter, as it accumulatively comes to 15 mm, precipitation effects ground tilt amount; in summer and autumn, when the cumulative value of rainfall reaches the driving rainfall,there is a good correlation between rainfall and slope. In the middle of the rainy season, the relationship is not obvious.Due to the vertical pendulum observation curve, there is strong correlation between rainfall accumulation and the value curve.We use the unary linear regression method to rule out of rainfall interference.
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jgg. 2018, 38(4): 433-436.
Based on geothermal observation data from 2012 to 2015 in different strata in Huailai, combined with MAPSIS, MapInfo, SPSS and other software to analyze the data, several conclusions can be drawn. Analyzing the east, west, south, north data of the temperature detectors in wells, we can get the approximate position of the hot water pipe nearby. In general, the changing trends of geotemperature in four directions are almost similar. According to the figure of geothermal curve of the multiple depth, combined with the analysis tables, the conclusion could be drawn that under 3.2 meter, the geotemperature near the wells is not affected by the weather on the whole, with only slow annual change. The geothermal curve of 5.0 meter deep is more stable. Considering economy and convenience, the best depth of geothermal observation is 5 meter.
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jgg. 2018, 38(4): 437-440.
Due to long working life, aging of components, creep of material, and other factors, it is necessary to carry out in-situ static physical calibration periodically to understand borehole strain meterperformance. At present, the static physical calibration method with piezoelectric ceramics has many disadvantages,including hysteresis, creep and linearity, so the accuracy of calibration is poor with large errors.To make the in-situ linear calibration of the RZB-type borehole strain meter,a linear calibration mechanism was designed. Based on a ceramic motor as the core, a grating sensor as the feedback and the RS485 bus, the mechanism can remotely realize the in-situ linear calibration to master instrument function. Some simulation experiments for in-situ linear calibration are performed in the laboratory,and the calibration data of the full-scale sensor show that: the calibration resolution is better than 2 μm and the linearity is better than 1%.
