This paper focuses on the data processing analysis of 2020 mount Qomolangma height measurement. First, we detail the process of calculating the 2 important values used to calculate the elevation of the summit of mount Qomolangma, and then we present the height of mount Qomolangma jointly by China and Nepal based on the international height reference system(IHRS): 8 848.86m. Finally, this paper summarizes the characteristics of the achievements, and describes its high accuracy and reliability.
On the basis of the reconstructed single difference residual of carrier phase, we estimate the multipath repetition time of Beidou satellite by using the segmentation idea; we then extract the multipath of single difference residual of carrier phase by regularization method and classical wavelet filtering method respectively to obtain a “clean” single difference residual sequence. The experimental results show that Tikhonov regularization is feasible to correctly extract the multipath signal, the multipath signal is smoother than the original residual measurement, and the estimation method of the regularization parameter is further optimized. After using the optimized Tikhonov regularization method and sidereal filtering, the single difference residual of carrier phase is improved by 40.5% on average. The coordinate residual in E, N and U directions are improved by 24.8%, 26.3% and 42.7%, respectively. The optimized Tikhonov regularization is superior to the traditional wavelet filtering method in both the observation and coordinate domains.
By combining chaotic mapping and adaptive inertial weight, we improve the standard whale algorithm so as to improve the global optimization ability and convergence speed of the algorithm. Aiming at the disadvantage of BP neural network, we use the improved whale algorithm to optimize BP neural network. On this basis, we establish the improved whale algorithm to optimize the BP neural network GPS elevation anomaly fitting prediction model, and the model is verified by two groups of GPS data in different terrain feature engineering. The results show that the BP model optimized by the improved whale algorithm can achieve higher accuracy and stability in GPS height fitting.
To quantitatively analyze the influence of BDS-3 observation multipath error on deformation monitoring accuracy, we select 128 d of BDS-3 monitoring data of a water conservancy project containing 7 stations in 2022, and study the correlation between BDS-3 observation multipath error, deformation monitoring accuracy before and after branch cutting of trees around the monitoring stations. The results show that 1) there is a strong correlation between multipath error and BDS-3 deformation monitoring accuracy, and the correlation coefficients with plane and elevation accuracy are greater than 0.93 and 0.81, respectively; 2) the average multipath error using B1I and B3I observations after tree branch cutting around the monitoring site is reduced from 0.676 m and 0.426 m to 0.329 m and 0.230 m, and the average monitoring accuracy in N, E and U directions reaches 0.9 mm, 0.8 mm, 1.7 mm, and 1.1 mm, 1.0 mm, and 2.2 mm, respectively, which is 63%, 69%, 58%, and 52%, 61%, and 48% higher than that before cutting branches; 3) after changing the surrounding observation environment to weaken the influence of multipath error, the accuracy of using B1I observations is better than that of using B3I observations. Therefore, in the BDS-3 short baseline deformation monitoring application, B1I observations are recommended.
Starting from the system state model, we analyze the influence of scale factor error on the calculation amount and accuracy of integrated navigation. At the same time, based on the characteristics of vehicle motion, we analyze the observability of the scale factor error, and propose a dimensionality reduction state model that only retains the scale factor errors of the heading gyroscope and horizontal accelerometer. The experiments show that: when the scale factor error is greater than 6×10-3, augmenting the scale factor error can help improve navigation accuracy, but the calculation amount increases by about 170%; the reduced-dimensional model can achieve the navigation accuracy of the high-dimensional model, and the calculation amount is only increased by about 70% compared to that without augmenting scale factor error.
The positioning accuracy and reliability of multi-sensor integrated navigation can be improved by making full use of prior constraint information. We extend Kalman filtering under state constraints to traditional federated filtering and propose a federated filtering algorithm under state constraints. When the sub-sensor is abnormal, we use Huber method to adjust the observed noise matrix of the sub-filter based on federated filtering under state constraints. Meanwhile, we introduce adaptive information sharing factor in the information sharing stage to dynamically adjust the fusion weight of the sub-filter and obtain a robust and adaptive federated filtering algorithm with state constraints, which further reduces the impact of inaccurate sub-filter estimates on the fusion results. The method is applied to the multi-sensor integrated navigation system of strapdown inertial navigation system, GNSS and odometer. The simulation results show that the estimation accuracy of federated filter under state constraints is better than that of traditional federated filter, and robust adaptive federated filtering can further improve the accuracy and reliability of navigation and positioning under abnormal observations.
Aiming at the problem that the traditional synthetic aperture radar interferometry technology is greatly affected by tropospheric delay when monitoring surface deformation, we use the measured meteorological parameters and NCEP meteorological reanalysis data to establish atmospheric correction models respectively. The tropospheric delay correction is performed on the interferogram generated in Yinzhou District to obtain high-precision surface deformation in Yinzhou District from 2018 to 2020. To analyze the effect of different atmospheric correction models on weakening the tropospheric delay effect, we compare the monitoring results with the measured level data in the same period. The results show that the RMSE of the ground meteorological information model, the NCEP meteorological reanalysis data model, and the InSAR monitoring results without atmospheric correction are 2.78 mm, 3.86 mm, and 5.62 mm, respectively. The results further show that the use of the ground meteorological information model to correct the atmospheric phase error has higher monitoring accuracy and can effectively weaken the influence of tropospheric delay on interferometry results.
Based on observation data from the National Geomagnetic Network Center, we study the relationship between the geomagnetic low-point displacement anomaly and earthquakes above 5 magnitude in the mainland of China in the 10 years from 2013 to 2022. The results show good correlation between the geomagnetic low-point displacement anomaly and earthquakes above 5 magnitude. There is high probability of earthquakes with magnitude greater than 5 within 300 km of the anomaly boundary within 2 months after the occurrence of geomagnetic low-point displacement anomaly. The results show that 160 main earthquakes with MS≥5 occurred in mainland China in 2013 to 2022, with an anomaly correspondence rate of 32.4%, the false alarm rate of 67.5%, the false negative rate of 48.1% and the earthquake prediction rate of 55.0%. There is one low-point displacement anomaly before 46 earthquakes, and two or more anomalies before 42 earthquakes. The study also found that superimposing multiple low-point displacement anomaly boundaries before an earthquake on the same base map will form one or more intersection areas, and earthquakes often occur in the intersection area of the low-point displacement boundary. Based on the distribution of active tectonic faults, the occurrence of historical large earthquakes, the potential danger zone of strong earthquakes predicted in the medium and long term and the annual national earthquake danger zone, we further judge the possible earthquake area. This study greatly reduces the range of earthquake location predicted by geomagnetic low point displacement method.
Based on gravity data, with aims to evaluate the effectiveness of Bayesian inference for subsurface target detection in situations where the spatial position and shape of underground targets are unknown, we perform modeling and analysis in terms of regional measurement and line measurement scenarios. The results show that Bayesian method for gravity gradient detection outperforms microgravity detection and can lead to a good parameter prediction quality.
We use the double difference method to accurately locate small and medium-sized earthquakes in the Taiyuan Basin and establish the sub-area of hidden faults in Taiyuan basin. By using the magnitude frequency relationship model reduced by a certain time scale, we fit the empirical evaluation model between the maximum earthquake magnitude Mmax of the hidden fault in Taiyuan basin and the magnitude frequency relationship at/b parameter. After comprehensive analysis, we give the upper limit prediction value of potential magnitude of each active fault zone. To predict the probability of occurrence of potential maximum earthquake magnitudes and moderate-strong earthquake magnitudes for each hidden active fault, we use the Poisson probability model. The results indicate that the Tianzhuang-Wenshui-Fenyang fault area in the central and western parts of the basin, as well as the Sanjia-Hongshan-Pingyao fault area in the southeastern part of the basin, have a higher probability of future earthquakes with MS≥6.5, while the probability level of earthquakes with MS≥6.0 occurring in the future in the Qizishan and Beitian-Wanghu fault areas, mainly composed of NW trending hidden active faults, is relatively low.
We invert the focal mechanism of the 2021 Yangbi 6.4 earthquake by the CAP method. Based on the focal mechanism of M≥3.0 earthquakes in Yunnan province from 2015 to 2022, the spatial distribution of the stress tensor variance before and after the earthquake is inverted by the superimposed stress field inversion method. We then use the focal mechanism of M≥3.0 earthquakes in Yunnan from 2013—2022 to further analyze the temporal evolution characteristics of focal mechanism parameters. The results show that the Yangbi 6.4 earthquake is a right-lateral strike-slip earthquake, moment magnitude is MW6.03, moment depth is 5.8 km, for nodal surface I, strike is 39°, dip angle is 75°, slip angle is -16°; for nodal plane II, strike is 133°, dip angle is 75°, slip angle is -164°. The spatial evolution of the stress tensor variance shows that the stress tensor variance near the earthquake area undergoes a process of “low value-significant increase-drop before the earthquake to form a new low value-significant increase after the earthquake.” The temporal evolution of the stress tensor variance shows that the stress tensor variance near the Yangbi 6.4 earthquake area reaches its highest value one to two years before the earthquake, then continues to decline, and then turns and trends back up after the lowest value, with an overall positive “V” shape. Earthquakes occur during a positive “V” turn followed by an upturn in trend. The spatiotemporal evolution of stress tensor variance is consistent.
Based on GPS displacements, we apply the finite fault method to inverse the slip distribution of the 2022 Taiwan MW6.9 earthquake. The results show that the earthquake ruptured to the surface, and the slip is dominated by strike-slip with a reverse component. It mainly extends along the fault in the NNE direction. There are two rupture concentrated areas, and the total released seismic moment is about 5.73×1019 Nm. Based on the analysis of the GPS observations and dislocation theoretical model, we infer that the coseismic deformation generally conforms to the regional tectonic movement characteristics of the east coast of Taiwan island. The subduction of the Eurasian plate by the Philippine sea plate is the main source of power for the Central Range fault activity.
This paper takes the Menyuan MS6.9 earthquake in 2022 as an example, fitting the coseismic strain observations of four component borehole strainmeters at 1sps sampling rate from 17 stations with the coseismic strain simulations obtained by using qssp software forward calculation; we then analyze their correlation. The results show that the north-south and east-west P-wave waveforms of 17 stations fit well, and the average correlation coefficients are 0.835 and 0.842, respectively, reaching a high correlation, indicating that the borehole strain observation data can better reflect the seismic fracture information, which further verifies that borehole strain observation data can be used to study the seismic fracture process in theory.
We take the typical surface rupture caused by the Luhuo M7.9 earthquake in 1973 as an example. Based on the UAV SfM method, we obtain high resolution and high precision topographic and geomorphic data in the region. We extract the quantitative parameters of dislocation by LaDiCaoz and introduce the relevant technical process in detail. The results show that: 1) The horizontal dislocation and vertical dislocation of typical ridge dislocations in Luho Zhajiao village area measured by LaDiCaoz are 6.3(+0.5/－0.7) m and 0.4(+0.1/－0.1) m. The analysis shows that the amount of horizontal dislocation is the cumulative result of 3 strong earthquakes at least. 2) UAV SfM method can obtain high resolution and high precision topographic and geomorphic data in a small area efficiently, conveniently and at a low cost. The data quality can satisfy the fine structure study of active faults and quantitative parameter extraction, which has a broad application prospect in the high altitude of western Sichuan. 3) Using LaDiCaoz for dislocation extraction can further reduce the error of measurement results caused by human factors, and the reliability of dislocation results can be verified, realizing the semi-automatic extraction of active fault dislocation.
To effectively grasp the reactivation characteristics and deformation laws of an ancient landslide, based on the on-site investigation results of the landslide area, we analyze the reactivation deformation characteristics, and then use the WPT-ROA-RVM-CT model for landslide deformation prediction. The results show that after heavy or continuous rainfall, the surface cracks of landslides are relatively developed, with tensile and shear properties. The landslide exhibits obvious displacement characteristics, that is, the deformation of the middle and rear edges of the landslide are significantly greater than that of the front edge. The deformation direction has a counterclockwise variation, fully indicating that the reactivation deformation characteristics of ancient landslides are significant. Meanwhile, through deformation prediction, the WPT-ROA-RVM-CT model is verified to have high prediction accuracy. Through extrapolation prediction, we find that the subsequent deformation rates of landslides are all positive and large, indicating that the subsequent deformation of landslides will further increase, with a significant risk of instability. Therefore, disaster prevention and control research need to be carried out as soon as possible.
This article summarizes the site selection, instrument configurations and installation of temporary seismic network deployment, and analyzes the initial seismic characteristics of the 2022-06-01 MS6.1 Lushan earthquake ambient noise and the aftershock sequence from the network. The results show that after the temporary seismic stations were deployed, the density of seismic stations in earthquake region is improved, and that the joint network with the permanent seismic stations improves the azimuthal coverage of the seismic stations and the spatial resolution of the scientific research. Under the influence of nearby cultural noise sources, the temporary stations generally show higher noise level than the nearby permanent station, and the noise level is significantly higher than the average value of NHNM and NLNM; some stations are close to or higher than the NHNM value. The high-frequency noise presents a prominent diurnal variation characteristic related to human activities, that is, seismic noise level increases during the daytime, and decreases at night. Affected by this, the number of earthquakes recorded by temporary seismic network during the daytime is significantly less than nighttime, and the number of small earthquakes recorded is significantly reduced. The results from hypoDD relocation show that the aftershocks are mainly distributed in the north of the Xiaoguanzi fault, with a northeast distribution, about 10 km long in the northeast and about 6 km in the northwest. The magnitude of completeness MC of aftershock sequence calculated by maximum curvature method is 1.2, the MC increase from 1.1 in the nighttime to 1.4 in the daytime, and this mean the seismic monitoring capacity of the seismic region during the daytime is weakened. We also observed that the aftershock sequence after a medium-strong earthquake decays rapidly with time, and the number of aftershocks within 5 days is about 80% of the total aftershocks, especially those within 2 days after the mainshock. In order to better understand the development process of earthquakes, it is necessary to ensure the rapid and effective deployment of seismic stations to give play to the effectiveness of seismic stations.
Based on theoretical analysis, we propose the concepts of apparent azimuth and apparent declination of ground tilt, and introduce the procedure of calculating the apparent declination. We use the observed data of five measurement components of the water pipe tiltmeter from 1987 to 2021 in Beijing Yanqing Xibozi and Gansu Lanzhou Shilidian stations as examples. In turn, we calculate the results for the apparent declination of the 715 measured component observations of the national ground tilt network in 2020. Results from two typical stations show that: the Xibozi station NS direction angle of apparent declination PNS=－0.1°; EW direction angle of apparent declination PEW=9.6°; NE direction angle of apparent declination PNE=12.4°; the Shilidian station NS direction angle of apparent declination PNS=0.3°; EW direction angle of apparent declination PEW=－22.5°; the maximum apparent deflection angle of 2 stations is 23.2°, the minimum value is －36.0°. From the statistical mean of the 5 components, the maximum value of the apparent deviation angle is 12.4°, the minimum value is －22.5°, and the range is 34.9°. Both stations show that the number of apparent deflections in the NS direction is relatively small, while the number of apparent deflections in the EW direction and NE directions is relatively large. The calculation results of the observed data from the national earth tilt network indicate that there are 266 components with an apparent deviation angle PS<10°, accounting for 37.20%, the number of components with an apparent deviation angle of PS<22.5° is 445, accounting for 62.24%, and the number of components with PS>45° is 111, accounting for 15.52%; the number of components with apparent deviation angle dispersion error MPS<10° is 247, accounting for 34.55%, the number of MPS<22.5° is 446, accounting for 62.38%, and the number of components with MPS>45° is 43, accounting for 6.01%. Based on the results of this study, we recommend that the initial azimuth angle of the measurement component with an apparent deviation number greater than 20° should be emphatically checked; also we should carefully screen the observation data of the measurement component with an apparent deviation angle dispersion error MPS>20°.
To better suppress the influence of power frequency interference on the observation signal, based on the analysis of the source of power frequency interference, the classification of power frequency interference and the influence of power frequency interference on the observation, we compare and analyze the commonly used power frequency common mode interference and power frequency serial mode interference suppression methods, so as to suppress the power frequency serial mode interference in the design of DCY-I geoelectric field observation instrument by using the method of oversampling and multi-level digital filtering. We use the two-level floating ground method to suppress the power frequency common mode interference, which can play a good suppression effect on the power frequency interference.
We propose a time accuracy measurement method for low-sampling data acquisition equipment. We introduce the measurement principle and data acquisition process of this method, and give results of the time accuracy for a low-sampling data collector equipment with an example of earthquake department. The results show that this method can improve the time measurement accuracy of low-sampling data acquisition equipment to milliseconds. This method can be used in the test of timing accuracy of geophysical observation data collector with linear relationship between input and output.
