Using the FG5 absolute gravimeter, absolute gravity values are determined at three base gravity sites in Lushan and one datum site in Jiujiang seismic station to determine the Lushan calibration baseline.Further, twenty-five sites are determined using seven CG-5 relative gravimeters with two return measurements. The results show that the accuracy of gravity values at all of the base sites is better than  ±5.0 μGal.The application of FG5 absolute gravimeter along with several relative gravimeters to construct short calibration baselines is a new and modern approach which has scientific significance as well as economic value.

This paper analyses the ionospheric disturbances triggered by the 25 April 2015 Nepal earthquake, using data from 6 IGS GPS stations in the Nepal area. The results show that there are ionospheric disturbances with different frequencies (3 mHz and 4 mHz) above the Nepal area after the earthquake. We deduce that the disturbances with a frequency of 3 mHz within 1 000 km are generated by AGW(acoustic gravity wave) produced by vertical motions of the earth’s surface, and the disturbances with a frequency of 4 mHz, which can reach over 2 000 km, are caused by the Raleigh wave’s upward propagation. Furthermore, we invert the epicenter in the light of the observed disturbance location and empirical disturbance velocities, combining the two kinds of disturbance signals to validate our results. The inverted epicenter accords well with the real position.

Using a three-dimensional corner point method and space objects rotating geometric transformations, the relationship between the fault disclination and gravity changes in the earth’s surface is established. The influence of gravity changes on fault depth and dip is discussed by rotating basis points on the left endpoint. The results show that gravity changes are significantly correlated with depth of fault. Gravity changes gradually reduce with the increasing depth of fault in single disclination, or W1,W2 and W3 modes respectively. Fault dips in different modes have different responses. Surface gravity distribution is related to the disclination mode and rotating basis point.

Altimeter gravity anomalies, geoid and vertical deflection are used to calculate oceanic vertical gravity gradient anomalies. The correlation between the gravity gradient anomalies and bathymetry is analyzed. Taking islands in Midwest Pacific Ocean as examples, the bathymetry model is inversed in 20~200 km wavelength; results show that the relative precision of the bathymetry model is 714%. In seamount distributed areas, the relative precision is lower.

This paper studies the resolution of the digital terrain model, the selection of reference surface, and their influence on the calculation of speed and precision by RTM. The results show that:1) When using DTM2006.0 as a reference surface, RTM and RET2012 have similar results for mainland areas, while the precision of RTM is not as fine as that of RET2012 and RET2014 for coastal areas; 2) Considering computational efficiency and accuracy, we can use the 7.5″ SRTM for the inner zone with a radius of 50 km, the 15″ SRTM for the outer zone with a radius of 200 km, and choose the RET2012 model data as a reference surface to construct the residual terrain model at the east area of our country.

According to the distribution of lithospheric plates and their known evolution, the author analyzes the basic characteristics of plate motion as well as a variety of geodynamic mechanisms proposed by predecessors, specifically mantle convection. The author proposes that the earth dynamics of crustal movement comes from "unsynchronized action" caused by the "pole-fleeing" of the earth’s rotation and the change of the radius of gyration, and that the earth dynamics are also affected by the inherent laws of the rigid lithospheric plate, such as stress balance, inertia and elasticity. In addition, the role of regular tidal and the occasional meteorites are additional stress factors on plate movement.

Based on GPS horizontal velocity data from 1999-2007 and 2009-2013, mainly from the crustal motion observation network of China(COMMON), using the GPS velocity profiles, and combing with the principal strain rate field near the west Qinling fault, this paper analyzes the motion and deformation along different segments of the west Qinling fault. The results show that from 1999-2007, the characteristic of the whole fault is left strike slip with compression; among all four segments, the Guomatan has the highest activity, and the Tianshui-Baoji segment has the lowest. The principal strain rate along the whole west Qinling fault derived from GPS measurements shows that the principal compression strain rates are apparently greater than the principal strain rates. However, strain rate values are obviously different: the compression strain rate of the Guomatan and Yuanfeng segments are greater than the Zhangxian and Tianshui-Baoji segments. Compared to data from 1999-2007, the results during 2009-2013 show that the Zhangxian segment becomes more active, and has a relatively large tensile strain rate. These changes in the Zhangxian segment maybe caused by the Minxian-Zhangxian MS6.6  earthquake on July 22, 2013. The characteristics of principal strain rate of all segments of the west Qinling fault are the same as the results derived from the GPS velocity profiles. After comprehensive analysis of the remote and near field deformation characteristics acquired by the GPS velocity profiles and GPS principal strain rate field, we find that the whole west Qinling fault may be in a locked state, showing strain accumulation to a certain extent; among the four segments, the Tianshui-Baoji segment has the lowest activity, and this feature may show that this segment is at the highest locked state.

In this paper, we take rock-based GNSS continuous stations as referents, and inspect the observed deformation variations in both horizontal and vertical components of every soil-based GNSS continuous station. Observations show that severe subsidence stations must be corrected, slight subsidence stations should be corrected depending on the research goals, and no correction is needed on non-subsidence stations for continuous GPS observations. We also present some methods for subsidence correction on GNSS station observations.

In this paper, SBAS-InSAR is used to obtain high resolution ground subsidence information for the Beijing region. A spatial-temporal analysis of the ground subsidence in the region during the years of 2007 to 2010 is performed utilizing eighteen ENVISAT ASAR images. The results show that subsidence in the Beijing region is severely uneven; that multiple subsidence funnels formed in Changping district, Shunyi district, Tongzhou district, etc. are interconnected and have an eastward expansion trend; that the subsidence velocities in most areas are in the range of -150 mm/a to 10 mm/a and the maximum subsidence is over 400 mm; and that ground subsidence is influenced by groundwater exploitation and urbanization significantly.

The first-order forecast effective measure cannot consider the standard deviation of the accuracy and the weight is always unchanged. In this paper, a new combination forecasting model is proposed based on the second-order forecast effective measure and the induced ordered weighted geometric averaging operator (IOWGA). This model predicts the second-order forecast effective measure as an objective function and determines the weight based on the value’s accuracy. We use an example to illustrate this method. Experimental results show that the proposed model has high forecasting precision, which could be widely used in deformation forecasting or analysis.

In this paper, 17 scenes TerraSAR-X radar images acquired from August 2013 to August 2014 are used by the small baseline subset (SBAS) InSAR method to obtain the surface deformation series during the operation of underground gas storage (UGS) in Hutubi (HTB). We combine these data with data from injection/production pressure wells, using multi-point source Mogi model to simulate the deformation field of UGS in Hutubi. The results show that the deformation characteristics of the whole UGS area is a discontinuous distribution, and the deformation peak value along satellite line of sight (LOS) is 10 mm and -8 mm during gas injection and gas production respectively. The retrieved deformation sequences conform to injection/production pressure changes very well. Based on the multi-point source Mogi model, we simulate the deformation process of HTB UGS and apply an adaptive forward search method to obtain the radius and depth of point source. The simulated results indicate that when the injection/production average pressure of HTB UGS is 18 MPa and 15 MPa, LOS deformation is up to 7 mm and -4 mm respectively; surface deformation is related to the density of gas injection/production wells. The UGS gas distribution is not uniform, indicating that the structure of underground gas storage is complex.

In order to weaken the influence of GPS errors in vibration monitoring results affected by measurement noise and multipath etc. in the deformation monitoring of buildings, a combined algorithm based on PCA and lifting wavelet transformation is proposed. The PCA spatial filtering method is used to separate the common-mode error, which eliminates the inter-station correlated error. Then, the lifting wavelet transformation is used to de-noise the building structure vibration signal, which is then used to extract structural vibration signals. Taking a tall building in Hong Kong as an example, the results show that the algorithm can effectively improve the accuracy of deformation monitoring.

In this paper, with the derivation of code observation equation, the structure and influence factors of inter system bias are analyzed. We discover that all factors for low precision navigation can be treated as related to satellite number. A new inter system bias parameter estimation solution is proposed. Finally, the new solution is applied to multi-GNSS positioning, providing reliable positioning information for real-time low precision users when only 4 multi-GNSS satellites are visible.

We propose a new method which modifies users’ tropospheric corrections based on the height information of stations and users. We use data from six CORS stations in America and seven stations in the SatRef network in Hong Kong to analyze our method. Results show the method can modify tropospheric correction bias in vertical directions effectively, that the method performs well while the elevation difference is above 100 m, bringing the precision of tropospheric correction to the cm level.

We propose a tomographic approach using multi-epoch observations based on GPS data from Hong Kong CORS, and analyze the influences under different weather conditions. The results show that the RMS and error statistics of our proposed approach are better than the traditional method. In addition, tomographic results vary according to weather conditions. However, whatever weather conditions prevail, the proposed approach is superior than the traditional method.

In this paper, we analyze the effect of offset outliers on the accuracy of SAR registration. In order to solve this problem, we adopt an algorithm that combines the LTS and selecting weight iteration. Then, we use ENVISAT ASAR data in Nantong as an example and choose the quality of the interferogram fringe and the distribution of the coherence as the index to test the robustness of our method. The results indicate that the proposed method is able to reject the offset outliers effectively and eliminates their effect on the accuracy of SAR registration. Thus, our method can improve the accuracy of SAR registration reliably.

Using the gPhone gravimeter digital observation data recorded at Beijing seismic station, we detect spherical modes of   0S0-0S60 of the earth free oscillation stimulated by the M8.1 earthquake that occurred on April 25,2015 in Nepal. In our process, the method of power spectral density(PSD) is used．In comparison with the periods of free oscillations of the PREM model, the observed periods coincide well with the theoretical values.The results verify that gPhone gravimeter can detect the earth’s free oscillation.

Robust trend estimation is employed for some outliers in the free fall absolute gravimeter. We compare gravity as obtained by ordinary least square estimation and by robust trend estimation. The results show that we can reject outliers by adjusting the weighting factors of the time-distance pairs, thus improving measurement accuracy.

The BDS/GPS data quality checking software DataQC, which supports the RINEX 2 and 3 formats, was developed by analyzing the data quality module of TEQC. The main indexes include data integrity rate, multipath value, signal to noise ratio, cycle slips and so on. The DataQC also supports the estimation functions of ionosphere TEC and receiver differential code bias. The TEC estimated results of both systems are consistent with GIM in magnitude and trend.

This paper describes and analyzes the design and implementation of the events database platform for the tracking and analysis of earthquake precursors. At present, the platform has been deployed in a wide range of national earthquake precursor networks. Its advantages are its easy-to-use complete functions, and the ease with which functions are extended.Large numbers of event analysis records and special reports are generated by the platform, providing for the earthquake analysis forecast consultation and network maintenance management.