Crustal deformation is the most direct phenomenon of the earthquake preparation, occurrence and adjustment process. This paper briefly reviews the development history of the crustal deformation observation, summarizes the development set up of its related physical model about earthquake forecast, and then introduces the current application of the deformation data in the earthquake domain. In the future, we suggest to pay more attentions to two aspects: 1) in geodesy surveying domain, we should dense observations in typical tectonic zones first, and then construct the universal geodetic model with multi-source data; 2) in research domain, we should develop the methods to obtain the stress/strain field in high-resolution, construct the relationship between the stress/strain field and the earthquake process, study and obtain the crustal viscosity structure distribution in high accuracy, strengthen to research the deformation mechanism of the active tectonic block, promote study of the reliable method and model to invert fault slip rate, locking degree, and slip deficit distribution, and strengthen recognition of the pattern and mechanism of abnormity phenomena in the continuous observation for typical areas. In general, the core issue is to provide effective observational constraints and establish quantitative mechanical models for the fault deformation mechanism, which is the key to understanding the earthquake process and promoting the physical forecast of strong earthquakes.

We analyze the 3-D deformation observed by GPS(1990~2015) and precise leveling (1980~2014) in Weihe basin. The results show the horizontal movement rates are 4.3~11.6 mm/a and the directions change in the vicinity of 107.8° and 110.5° E from SEE in western, to SE in central, and E in eastern basin. The vertical movement in more than 30 years shows priority to inherited movement at the rates -4.6~6.2 mm/a relative to ITRF2008. There are obvious differential movements between the basin and mountain, the different block in the basin. The Ordos block moves upward at a rate of 3 mm/a as a stable block within a differential rate of 1 mm/a. With respect to central Ordos, Weihe basin is undergoing subsidence at a rate of 5 mm/a, while at Qinling the subsidence rate is about 4 mm/a. The upward and downward movements present four quadrants: Xi ’an and Gushi sag, while Lishan and Xianyang uplift. The big differential movement and quake-hit area appear in the intersection of faults or blocks. The activities of the faults in the western and southern basin are stronger than those in the eastern and northern regions, based on the observations in the cross-faults. Based on the data of leveling profiles on a long timescale, the major activities of the Qishan-Mazhao, Qinling, Huashan and Weihe faults are normal slip. The rates are up to 5 mm/a in the central Weihe fault which is divided into Xi ’an sag and Xianyang uplift, while the slip rates of other faults are within 3 mm/a.

Using GPS observation data of the 1999, 2001, 2004 and 2007 phases of the China crustal movement observation network, interpolation is applied to gain the boundary conditions of a 2-D element discontinuous model, which is used to simulate the slip rates of the fault system in Longxi area and undertake uncertainty analysis over it. The study determines that the NNE direction movement of Longxi block had been hindered by Orods and Alxa blocks. Haiyuan fault, Laohushan fault, and northern Xiqinling fault show a left-hand strike slip characteristic, and the slip rates are about 3.5 mm/a, 2.2 mm/a and 1.9 mm/a respectively, which means that the tectonic stress has been accumulating in the key tectonic section rapidly.

Based on the observational data of GPS regional stations in Yunnan area from 2011 to 2016, this paper uses GAMIT/GLOBK software to process observed data, utilizing a high-precise data processing strategy. After deducing the coseismic effect and region Euler uniform rotation vector with the GPS horizontal velocity field relative to the Eurasian plate, we get the regional GPS horizontal velocity field and use it as input data. Finally, using the multi-scale spherical wavelet model that can be decomposed and selected according to the density of GPS stations, we obtain the GPS strain field in Yunnan province at resolution scales 6, 7, 8 and 9. Based on historical MS5 earthquakes in Yunnan province, and the faults such as Xiaojiang and Honghe faults, we analyze the spatial distribution characteristics of the strain field. The results show that, in the integrated solution processing of regional strain field, the spherical wavelet method can adapt to the density change of the stations, and estimate surface strain field with multi-scale. Using multi-scale spherical wavelet to get integral solution strain field is an effective method, showing robust results. The results are in good agreement with historical earthquakes and regional fracture properties. The analysis results of principal strain, dilatation and shear strain are coincidence, regular, and in good agreement with regional historical seismic information and the active faults in the areas. From the result of principal strain rate, dilatation and maximum shear rate in the Yunnan area, which is shown by the spherical wavelet analysis: a) the Honghe fault may be a tectonic fault with important tectonic significance. Strain characteristics indicate that the Yunnan area is divided into two characteristic areas by the Honghe fault; b) the Ludian, Tengchong, Puer, Dali areas may present more intense seismic activity; c) the Songming area in Xiaojiang fault zone shows a high anomaly in multi-scale strain characteristics, and the seismic monitoring activities of this area in the later stage should be a focus for further research.

In this paper, a three-dimensional finite element model is established for northwest Yunnan province. The tectonic stress field of the area is simulated by using 2009~2016 GPS velocity field data as the displacement boundary condition of numerical simulation. The results show that: Chuxiong to the northwest of Yunnan province shows overall tensional stress; in the area circled by Eryuan-Heqing, Honghe, Chenghai faults, the internal tensile stress is significantly lower than that of the outside; the low value area, especially around the boundary fault, is often in areas of frequent crustal faulting; the north of Qujiang fault and the south of Lüzhijiang fault present a tensional stress concentration zone, which will be focused on in the future.

Based on the slip model of the 2017 MS7.0 Jiuzhaigou earthquake and the uniform viscoelastic semi-infinite space model, we examine the co-seismic and post-seismic Coulomb failure stress change (ΔCFS) induced by this earthquake and investigate its influence on the surrounding area. We find that the co-seismic ΔCFS increased by 148 kPa at both ends of the rupture zone of the north segment of Huya fault, which is over the stress threshold (10 kPa). In the next 50 years, the ΔCFS continues to increase, but the value is only between 3~5 kPa. The co-seismic ΔCFS increases only 0~3 kPa on the south part of the Huya fault, and the post-seismic shows roughly no changes. The northwest part of Tazang fault has a 5~33 kPa co-seismic ΔCFS increase, which is also over the threshold, and continues to be enhanced in the next 50 years. The ΔCFS on the west part of Xueshan fault is promoted by 6.15 kPa, which is less than the threshold, caused by the co-seismic, but shows little influence in the future. All these segments of the faults, with ΔCFS increases over 10 kPa, signal the raising earthquake activity, and the need for enhanced monitoring. Respectively, this earthquake released the stress on the eastern part of Xueshan fault, the Zhouqu segment of Bailongjiang fault, the northern part of Minjiang fault and the north part of Longriba fault. The seismic activity of these regions may decrease within a short time. The Qingchuan fault, which is far away from the epicenter, and other remote areas, are weakly influenced; co-seismic and post-seismic stress changes are negligible.

Using the seismic waveform data recorded by regional seismic network of Xinjiang and the method of CAP, we calculate the focal mechanism of 50 earthquakes with magnitude MS≥3.0 occurring in Hutubi during from Jan.15,2010 to Jan. 2,2017. Then, we analyze the types and the regional features of the focal mechanism of earthquakes in Hutubi. Based on the data of the above focal mechanism solutions, we invert the stress field of Hutubi area using MSATSI software. The result shows that the main compressional stress P axis is near NNE, indicating that the region stress field is mainly under action of the level extrusion of NNE. The horizontal compression is more obvious in the eastern part of the study area. Stress field is more significant for NNE direction during 2010 to 2016, but does not change the general characteristics of the maximum principal stress axis in the region, indicating that the study area may be mainly affected by a stable stress field of NNE.

The Taihu segment of the Tanlu fault zone lies on the east side of the Dabie mountains. It is the tectonic boundary between the Dabie mountains and the foreland basin, and the linear features of the faults are clear on remote sensing images. Geological surveys and trench work were carried out in the Taihu-Tongcheng area. In the Taihu trough we find a soft fault gouge in the fault zone, and the fault extends upward into the middle Pleistocene clay. Test results of OSL and ESR show that faults have strong activity in the middle Pleistocene.The fault profile of the Honglaowu in Tongcheng shows that the fault has broken the early Pleistocene gravel layer, and the fault gouge developed in the lower part of the fault. ESR sample test results also show that the fault has a strong activity in the middle Pleistocene. According to comprehensive analysis, it is concluded that the Taihu segment of the Tanlu fault zone still has a strong activity in the early Pleistocene, and the latest activity is the middle Pleistocene (Q2), which is a tectonic background factor mainly composed of small and medium-sized seismic activity in the study area.

This paper applies the finite difference travel time inversion and time-term method to model the upper crustal velocity structure and the crystalline basement structure beneath Yibin-Jinchuan profile. The tomographic and time-term method results show that: the basement depth of the Sichuan basin in the southeastern section is about 3~5 km, the unconsolidated sedimentation is very thick, and the shallow velocity is very low. In the northwest section the burial depth of the crystalline basement is gradually reduced by 0~3 km, partly exposed on the surface, and the shallow velocity increases obviously relative to other segments. The crystalline basement depth beneath the profile is obviously heterogeneous. The velocity structure gradual variations obviously correlate with the faults of Longquanshan mountain, Mingshan-Chengdu and the area of Longmenshan mountain. The velocity structure and the interfacial morphological characteristics of the crystalline basement provide seismic evidence for the studies of seismogenic mechanism and earthquake risk assessment in this area.

In order to study the effect of GPS/BDS combined orbit determination(OD) on Beidou navigation satellite system(BDS) orbits in different cases, GPS/BDS combined and BDS-only OD experiments are conducted respectively, adopting different lengths of OD arc and different distributions of ground  tracking network. Precision and accuracy of OD results of these two methods are compared thoroughly by orbit overlapping arc difference, difference with MGEX products and satellite laser ranging(SLR) residuals. The results show that, with the regional tracking network, GPS/BDS combined OD can noticeably improve the precision and accuracy of BDS IGSO/MEO satellite orbits for 1-day solution but only have marginal improvement on that of all types of BDS satellite orbits for 3-day solution. With the global tracking network, combined OD can improve the precision in along-track and cross-track directions of BDS IGSO/MEO satellite orbits for both 1-day and 3-day solutions but have minimal improvement on the accuracy in radial direction. Furthermore, combined OD barely has an effect on the precision and accuracy in all directions of BDS GEO satellite orbits.

With the prominence of the strategic position of the Antarctic and Arctic and the development of the polar regions, people’s demand for polar navigation and positioning gradually increased. Based on the constellation structure of the current BDS system (BD2), complete BDS system (BDS) and GPS system, this paper evaluates the number of visible satellites, DOP value and positioning accuracy of the BD2, BDS system in the polar research stations (Yellow river station, Kunlun station, Zhongshan station, Great Wall station) and the Arctic circle. BDS, GPS and its combination system in the north and south pole positioning performance are compared and analyzed. The simulation results show that the current BDS system (BD2) only partially covers the polar regions, the ability to provide navigation and positioning to the polar regions is limited, and the positioning accuracy is greater than 30 m in a wide range. The positioning accuracy of the complete BDS system (BDS) in the polar region is comparable to that of the GPS system, the number of visible satellites can reach about 13, PDOP value can reach 1.6, and the positioning accuracy is better than 8 m. The PDOP value of GPS/BDS combination system in the polar region can reach 1.4, and the positioning accuracy is better than 6.0 m.

Beidou-3 experimental satellites are equipped with Ka band inter-satellite link(ISL) equipment, which provides satellite-ground orbit determination and time synchronization observation means of ISL mode. The mathematical model of synchronous observation of time-division satellite-ground two-way ISL mode is derived. Taking the satellite-ground data of ISL as a sample, the feasibility of time synchronization in ISL system is analyzed and compared with L band observations. The results show that the fitting parameters of clock offset in ISL system are consistent with those of L band. The fitting accuracies within 7 days, 3 days, 1 day and 1 hour are respectively 1 ns, 0.85 ns, 0.2 ns and 0.2 ns, which, especially for 1 day fitting, are better than those of L band. At the same time, the clock offset prediction accuracy of the next day is analyzed by using seven-day measurements of the satellite ground clock offset. The prediction error of ISL satellite clock offset is within 2 ns. Finally, the satellite-ground and inter-satellites combined observation is carried out. The error in 2 days observation is 0.52 ns. The feasibility of ISL observation is verified.

We propose a phase prediction method based on carrier open-loop tracking to solve the problem of carrier phase discontinuity in the case of short-time occlusion of GPS signals. The prediction method realizes the open-loop tracking of carrier phase by accurately predicting the doppler of the lost-locked channel, and focuses on improving the influence of the receiver clock drift on the doppler estimation accuracy. The performance of the proposed method is evaluated based on the software receiver. The test results show that the probability of carrier phase error less than 1/4 cycles is more than 90% when the partial GPS signal is interrupted by 15 s.

Using the multiplicative algebraic reconstruction technique(MART), the accuracy of ionospheric electron density in the cells without any rays traversing them depends on the initial value, which is generated by empirical model. To solve the above problem, an improved algebraic reconstruction technique is presented in the paper. In this algorithm, a basic scale is calculated as the proportion of observed STEC and reconstructed STEC in some iteration. According to the spatial correlation of electron density, scaling factors are calculated as a function of basic scale and the distance from the center of cell and GPS ray for each cell in the reconstruction area. So, the ionospheric electron density of each cell will get closer to the ground truth. Numerical experimental and actual observation tests prove that the new algorithm is superior to the original MART.

Effected by parameter value, the accuracy of the finite element method in simulation of tunnel excavation will be reduced. The BP neural network and numerical simulation method are used to analyze the mechanics parameters of tunnel surrounding rock. The study shows that, comparing measured and simulated values, the reliability of the inversion parameters is proved, the maximum minimum principal stress and the change of the displacement of the tunnel are obtained, and the corresponding value of the settlement of the vault is calculated by the strength reduction method, and the self-stability coefficient of the surrounding rock of the tunnel is obtained by the discrete point fitting, and the tunnel circumference is analyzed.

This paper introduces the basic principle of strapdown airborne gravity vector measurement, and uses wavenumber correlation filtering (WCF) and specific force linearity correction method to compensate the horizontal and vertical components of gravity disturbance. It then evaluates the internal accuracy. The test data of the domestic strapdown airborne vector gravimeter is processed and analyzed to verify and evaluate the performance of airborne vector gravimeter. The results show that after applying wavenumber correlation filter for the horizontal component of gravity disturbance of the six repeatlines, the average internal accuracy of the east and the north components increases from 9.77 mGal and 9.18 mGal, to 5.95 mGal and 3.83 mGal, respectively, with half-wavelength resolution of 7.5 km. After linear correction for the vertical component of specific force, WCF method is used to process the vertical component of gravity disturbance of the repeatlines. The average internal accuracy of the vertical component of gravity disturbance is improved from 1.27 mGal to 0.59 mGal.

Considering shortcomings of conventional search methods in airborne gravity measurement data processing, such as slow search speed, low correct rate and poor applicability, a new method, the ‘sliding window search method’ is proposed. The main line point is regarded as the search center and the main and sub line points are searched in a certain width of search box. The adjacent measuring points detected in the main and auxiliary lines form a line segment, and the intersection and discrepancy are determined. Through practical examples, the sliding window search method is discussed and analyzed from the aspects of search time and accuracy. The results show that the proposed method is simple and efficient, the searching efficiency of cross-point is improved and the workload is reduced significantly.

We examine structure strong motion observation records from the Ludian MS6.5 and Yao’an MS6.0 earthquakes, as recorded by a structure seismic response array in Yunnan province. Fourier spectrum analysis shows that 1.7 Hz is the natural frequency of the first vibration mode, and 2.1 Hz is the natural frequency of the second, which is a torsional mode. Comparing strong motion records of the two earthquakes, we infer that the torsional vibration of Ludian is much stronger than Yao’an. In addition, we establish a 3D finite element model using SAP2000, selecting strong motion records as input motion to simulate the seismic performance of structure. Time history analysis shows that the structure’s performance is consistence with Fourier spectrum analysis. In summary, we think that the input motion angle is an important aspect to the torsional vibration of structure.

We investigate the data characteristics of volume borehole strain observatory in Anhui province including 12 sets of TJ-Ⅱ volume borehole strainmeters. The comprehensive analysis of the volume strain summarizes the three typical characteristics, including the continuous- drift-upward annual change pattern, water- level-synchronization annual change pattern, and no significant annual change. Based on the internal precision of the data, drilling environment, installation situation, interference factor, and image feature of the output data, etc., three typical characteristics are closely related to strainmeter, borehole, and installation quality.