In this paper, the anomalies of fault deformation before the Jan. 21th, 2016 Menyuan Ms6.4 earthquake, and their variations after the quake, are synthetically analyzed. To do so, we use the data of across-fault short-leveling at the Qilian Mountain fracture zone, additional data observed in the several days after the quake, as well as the aid of observational curves and time-space evolution of the anomalies and the index of feature intensity. The results show that, in 2015, the group short-term anomalies of fault deformation appear in the middle-eastern segment of this fracture zone and display an obvious increasing trend, mainly revealing abrupt change characteristics. These anomalies are related to the Menyuan earthquake to some degree, which have medium-short-term or short-term precursory features. Moreover, observational data after the earthquake reveal the faults’ deformations are mainly turning features, suggesting that the co-seismic deformations are not very significant.

The across-fault data of the Qilianshan-Haiyuan fault zone presents obvious precursory anomalies before the Menyuan Ms6.4 earthquake. We study deformation phenomena and activities of faults around Qilianshan before the earthquake. Based on the latest across-fault data in the northeastern margin of Tibet plateau, and by using a variety of methods, including temporal curve analysis, the fault rate of the synthetic analysis method, and the vertical deformation rate, this article extracts anomaly characteristics and reveals fault activity from different angles and scopes. The results are as follows: (1) Within 150 km epicentral distance, multiple sites present typical short-term anomalies, which are mainly accelerated and extensional changes; within 150-300 km, the anomaly type gives priority to trend variation. (2) The spatial distribution of anomaly stations shows that anomaly stations, concentrated in the middle of Qilianshan fault, have the tendency to migrate to the east and concentrate in the middle-eastern region. At the same time, the anomaly in Haiyuan has increased. These phenomena are extremely similar to those before 2003 Minle Ms6.1 earthquake. (3) From 2014, the synthetic rate of Qilianshan  fault deviates from the value of the normal far away, which means strain is easy to accumulate here. Further, according to results of vertical deformation trend accumulation rate, the earthquake epicenter is located in the high value area of deformation accumulation.  So the occurrence of the earthquake had a certain degree of inevitability.

The relative gravity data from 2011 to 2015 in Hexi area are processed to analyze the dynamic evolutional characteristics in temporal and spatial domains of the gravity field before the Menyuan M6.4 earthquake. The results show that the gravity field alternated wavelike with positive and negative gravity during the study period, which supports that crust tectonics present accumulating strain. The Menyuan M6.4 earthquake occurred in the high negative gravity variation area. A high gradient formedin regions,and the positive and negative variations of gravity amount to 110μGal. Specifically, a borderline of positive and negative gravity is located to the south of the epicenter, along the north edge of the Qilianshan and Lenglongling faults.

Based on the precise orbit and satellite clock corrections products of BDS, GPS, GLONASS and Galileo generated by the PANDA software package of Wuhan University, we analyze the positioning precision and the convergence time of kinematic PPP in 7 modes, including BDS-only, GPS-only, combined BDS and GPS, combined BDS and GLONASS, combined GPS and GLONASS, combined BDS, GPS and GLONASS, and combined BDS, GPS, GLONASS and Galileo, by processing data from MGEX.  The results illustrate that: 1) The convergence speed of BDS kinematic PPP was very slow and the precision could reach the centimeter level after convergence.  2) The precision in the north component of GPS/BDS kinematic PPP is worse than that of GPS-only ones but the convergence speed and the positioning precision improves in the East and Up components.  The convergence speed and the precision of GPS/GLONASS and GLONASS/BDS kinematic PPP are also improved.  3) The precision in the plane and vertical direction can reach 1 cm and 3 cm after 20 minutes, respectively.  The introduction of Galileo satellites hardly changed the convergence time and precision.

In view of the problem of multi-mode fusion, the BDS/GPS/GLONASS combined PPP’s (precise point positioning) function and random models are given.  Based on extended Kalman filter (EKF), the BDS/GPS/GLONASS combined PPP algorithm is realized.  Both static and kinematic PPP are tested using observational data, and the results show that: 1) In static PPP, the convergence time of BDS is about 80 min and the positioning accuracy of BDS is about 3 cm in horizontal, 6 cm in vertical.  Compared to GPS PPP, the combined PPP has a similar accuracy, and the convergence time is consistent with the convergence time of single system, which is applied in combined PPP and converges faster.2）In kinematic PPP, the convergence time of BDS is about 105 min, and a position accuracy of 7 cm in horizontal and 12 cm in vertical can be achieved.  Compared to single system PPP, both the convergence time and accuracy of combined PPP are improved.

Galileo signal in space error and standard positioning performance analysis provides reference for use and the next construction.  First, broadcast ephemeris orbital accuracy and clock accuracy, as well as URE, are analyzed by using precise orbit and clock file as reference.  The results show the RMS of along-track error is less than 2 m, cross-track error is less than 1 m, radial error is less than 0.5 m, clock error is less than 3 ns, and the value of URE(1σ) is 0.82 m.  Second, the Galileo satellite’s visibility and the value of PDOP are studied, and each part of UEE is calculated using the measured data.  Finally, the standard positioning performance of the Galileo system is analyzed and its three-dimensional positioning accuracy (1σ) is found to be around 3.8 m-6.4 m.

Ionosphere-free combination sets are proposed in this paper based on three ionosphere-free combination types.  Considering both position and ambiguity-fixed RMSE as evaluation indices, the optimal ionosphere-free combination sets are selected in double and triple frequency modes.  Computation and analysis results show that the evaluation index of 16 combination sets are equivalent in the double-frequency model, but could not get the ambiguity-fixed in single epoch due to the pseudo-range noise being more than 0.02 m.  In the triple-frequency model, there are significant differences in 2 196 independent combination sets; when the pseudo-range noise is under 0.6 m, optimal combination set can get the ambiguity-fixed in single epoch.  Moreover, combination set 2-Ⅱ has better performance than both the TCAR/CIR and matrix transformation methods.

Although the baseline is short, tropospheric delay cannot be fully eliminated by double difference method if the height difference of two stations is very large. Residual tropospheric error will have an impact on the baseline solution. A semi-parametric model is proposed to solve the short baseline with large height difference. Actual experimental results show that, the semi-parametric model can separate residual tropospheric error and improve calculating precision of baseline better than the least squares estimation.

In high-precision GPS analysis, the surface temperature and pressure of GPS sites are used to derive a priori zenith tropospheric delay.  By comparing the different estimates of site position obtained using the global model of pressure and temperature GPT and GPT2 respectively, we find that the deviation of a priori zenith tropospheric delay due to the site pressure deviation cannot be absorbed completely by the delay parameters.  Further, it will cause the deviations of site position estimates, especially for the vertical component; these deviations also depend on site latitude and elevation-dependent data weighting used in the data analysis.  The site temperature deviations will not affect the site position estimates clearly.  However, statistical analysis based on a large amounts of data show that the accuracy of position estimates decreases with the increase of site temperature.  Taking the results of regional network in 2013 as an example, when site temperature increases from 0 ℃ to 30 ℃, the repeatability of daily solutions occupied 4 d decreases from about 1 mm to about 2 mm, and from about 3 mm to about 6 mm for the horizontal and vertical components, respectively.

Instead of astronomical geodetic points, we proposed to put the baseline field, which has similar site conditions, forward.  This paper analyzes the principle of starting from the observed error, then examines the measurement accuracy requirements and equipment selection.  We use the GPS and industrial electronic theodolite in astronomical geodetic surveying and improve the methods of observation.  After establishing the gyrotheodolite azimuth calibration device based on the baseline field, we do an experiment that shows that the accuracy can satisfy the specification requirements.  Furthermore, the uncertainty analysis of the calibration device is given.

If there are no ideas of the locations of gross errors, selecting weight iteration method runs the first adjustment with equal weight. It leads to gross errors transferred to other observations. The robust estimation will fail because of incorrect weight. The first order minimum norm has the ability to resist gross errors, but is not optimal under Gaussian distribution. Combined two methods above, which the first order minimum norm is used to determine the location of gross errors, and then selecting weight iteration method reduces weight of those gross errors, we propose a novel robust estimation. The novel method is validated by a level net data processing.

Considering the low contrast and severe noise features of wall crack images, this paper proposes a crack detection algorithm based on tensor voting and target tracking.  On the basis of image binarization, the idea of clustering with tensor voting is used to highlight the linear target of the image.  Then feature points are chosen on the highlighted linear target, and locations of cracks on the image are obtained through feature points tracking.  Finally, the concept of re-cast is utilized to capture the original information of cracks.  Test results show that this algorithm can detect cracks correctly on wall images and has high detection rate along with some degree of universality.

Using PANDA software, all data of continuous stations of crustal movement observation network of China (CMONOC) are calculated to obtain continuous single day coordinates, while the corresponding horizontal velocity field is built through QOCA software.  Analysis demonstrates that the precision of horizontal positioning of PANDA software reaches 2 mm, while differences root mean square (RMS) between the horizontal velocity field calculated by QOCA software and the horizontal velocity field published by China Earthquake Administration are 1.12 mm/a and 0.95 mm/a in east-west and south-north directions respectively.  Ultimately, based on calculated velocity filed results, the main characteristics of spatial distribution of crustal horizontal movement of the Chinese continent are described.

This paper analyzes the GPS section deformation and strain accumulation of the Eastern Haiyuan fault and the Western Liupanshan fault with three episodes of GPS velocity field data, recorded between 2007-2013.  We undertake a comparative analysis of three properties: compression, tension and slip.  The results show that, first, the Eastern Haiyuan fault and the Western Liupanshan fault have the same movement style.  Second, in the past 10 years, these active faults’ main campaign feature is mainly a left rotation, and pressure changes are minor.  In terms of the relative motion differences rate between the upper and the under plates, the measure range is 2.0-5.5 mm/a in the slip direction, and 0.5-3.0 mm/a in the vertical direction.

This paper discusses the application of the NAKAI fitting model to precursory data processing, realizes solid tide observation data compensation value and continuation, and analyses the probability resulting from adding the data continuation module to the China seismic precursory station network data process system.  The result shows that, based on the NAKAI model, we can compensate and continue solid tide data with great results, and that adding the data continuation module in the data process system is both possible and effective.

Based on the function relationship between gravity coefficient and the Earth orientation parameters (EOP), we estimate second-degree spherical harmonic gravity changes ΔC21 and ΔS21 from 1980 to 2013.  Comparison of the ΔC21 and ΔS21 provided by SLR, shows that they agree well with each other.  Moreover, we find a 6-year periodicity exists in ΔC20 provided by SLR.  Otherwise the amplitude is just 1/10, as compared with the 6-year signal of LOD.  This indicates that the 6-year periodicity of LOD is not excited by the atmospheric and oceanic hydrologic motion and the Earth’s body, although the exact mechanisms are still not understood.

Based on the gravity observation data with high precision and GPS, the Gravity Anomaly in Yichuan-Tai’an profile is analyzed in this paper.  The Bouguer anomaly is obtained by data correction, and the residual gravity anomaly is obtained by Gaussian low-pass filter.  We profile the crustal density structure.  Fitting the data along the profile of Bouguer gravity anomaly with the constraint of the Zhucheng-Yichuan deep seismic sounding (DSS) velocity profile, the profile density of crust structure is obtained.  The study results show that the trend anomalies mainly reflect the change of the crustal thickness in this section, and Taihang mountain gravity is a cascade with abrupt change of the crustal thickness.  A further investigation on the residual gravity anomaly is presented by the comparison of our data with other results in the literature.  The results indicate that the residual gravity anomaly mainly reflects the geological structure and shallow low density geological body.  The residual gravity anomaly and the geological structure have a good correspondence, and the amplitude reflects the basic characteristics of the geological body with clearer detail than does the Bouguer gravity anomaly.

In this paper, wavelet neural network is used to forecast the gravity data of the unmeasurable zone.  In the experiment, the forecast precision of gravity data in different landforms is analyzed, contrasting two dimensional inputs with longitude and latitude, and three dimensional inputs with longitude, latitude and altitude.  It is found that the use of wavelet neural network can achieve high forecast precision of gravity data in the unmeasurable zone, especially with three dimensional inputs.  This is conducive to process the high-precision gravity reference map using interpolation methods.

In this paper, we use several stations’ high-rate GNSS observations of the strong earthquakes in Japan on March 11, 2011 and in Wenchuan May 12, 2008 to get the displacement waveforms during the events by means of Precise Point Positioning.  From the first-difference displacement waveforms, we get the high-rate GNSS velocity time series, then we use their S transform spectrums to identify seismic phases and pick up the arriving times.  The pickup results are applied for the inversion of the epicenter location and the origin time.  Compared with the data published by USGS, the difference of the Japanese earthquake epicenter location is about 16 km, the origin time difference is about 0.7 s; the epicenter location difference of Wenchuan event is about 4 km, and origin time difference is about 0.4 s. 

The nonlinear least square method is introduced to fit the calibration data sampled in seconds of quartz horizontal pendulum tiltmeter.  The scale value of the tiltmeter is obtained by iterative calculation using the Levenberg-Marquardt algorithm.  Simulation and filed experimental results indicate that the scale value calculated by nonlinear least square method is consistent with the tiltmeter’s original.

In this paper, the environment around Jixian seismostation and instrument work state is investigated with respect to the water tube tilt-meter’s accelerated incline to north direction from 1st April.  Results are as follows: (1) The sensor at the north end was replaced at 31st March in 2014.  Similarly, the accelerated incline to western direction began after replacing the sensor at western end in April 2009, which confirms that replacement of the sensor will influence water tube measurement to some extent.  (2) Yuqiao reservoir to the south of Jixian seismostation discharged from April 1st to 11th with a velocity as high as 50 m3/s, the maximum rate over the past years.  Short term accelerated incline to the north began when reservoir discharged fast.  (3) The average discharge rate drastically exceeds the reservoir threshold calculated using a 3D concentrated load model and the calculated incline data in a horizontal direction is consistent with the real change of water tube data and vertical pendulum tilt-meter at Xiaoxinzhuang cave, which confirms the influence of reservoir using quantitative method.  (4) Water tube continued accelerated inclining to north until mid-May, though Yuqiao reservoir was storing after April 11th.  Duration and range of anomaly exceed the real change time and calculated result.  Therefore, the accelerated incline to the north direction from April 1st in 2014 reflects influence of sensor replacement and discharge of Yuqiao reservoir.