15 August 2024, Volume 44 Issue 8
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jgg. 2024, 44(8): 771-775.
This paper introduces the research progress, standardized test and experimental observation on seismic station of the JCZ series ultra broadband seismometer JCZ-360. The results show that the JCZ-360 ultra broadband seismometer can effectively suppress the influence of external atmospheric pressure, external magnetic field interference and temperature change on the instrument. Its performance is more stable and noise level is lower at the ultralow frequency terminal. The JCZ-360 ultra broadband seismometer can not only observe full-band seismic waves, but also record information such as solid tides and free oscillation of the Earth. It has the comprehensive observation ability of traditional seismic and traditional geophysical field.
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jgg. 2024, 44(8): 776-782.
Based on NGA database and using genetic programming techniques, we give a set of prediction equations for PGA, PGV and PGD. On the basis of the explicit prediction formula, the reliability test and model comparison are carried out by establishing the correlation between ground motion parameters and key seismological parameters such as magnitude, fault distance, fault mechanism, and site shear wave velocity within 30 meters. The results show that: 1) Compared with the traditional decay relation-like prediction equations based on nonlinear regression techniques, genetic programming techniques do not need to specify the equation form of the decay relation, can model the complex behaviors of PGA, PGV and PGD, and give explicit formulas to meet engineering needs. 2) Compared with the Campbell-Bozorgnia attenuation relationship, the prediction effect of PGA and PGV based on the genetic programming techniques is slightly better; the RMSE and MAE of the PGD prediction model are 5.47 and 1.64, respectively, which are significantly smaller than those of the Campbell-Bozorgnia model, which are 45.98 and 4.61. 3) The obtained ground motion prediction equations are characterized by magnitude effect, site amplification effect, and saturation effect of near-field large earthquakes, but fail to reflect the soft-soil damping effect, and the maximum site amplification coefficients of PGA, PGV and PGD are about 1.42, 2.53 and 2.64.
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jgg. 2024, 44(8): 783-786.
We compare and analyze the scale factors of long baseline calibration and datum solution of 5 CG-6 relative gravimeters, and process the data of gravity network in Guizhou of CMONOC in 2022 and 2023 using different scale factors. The results show that the scale factors of CG-6 relative gravimeters vary over time, and the precision of processing results is better by using the datum solutionscale factor.
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jgg. 2024, 44(8): 787-792.
The traditional Kalman filter(KF) of GNSS/SINS integrated navigation system is optimal under the minimum mean square error(MMSE) criterion and under the Gaussian hypothesis. However, when the measurement noise is disturbed by heavy tail pulse noise, the filtering performance of KF is seriously degraded. To solve this problem, we propose a maximum entropy Kalman filter(MCKF) for integrated navigation system. First, we establish the state equation and measurement equation of MCKF. Then, using the principle of maximum entropy, we establish a Kalman filter based on the maximum entropy criterion, and design its filter iteration flow. Finally, we simulate the GNSS/SINS integrated navigation system in the environment of mixed Gaussian noise and heavy tail pulse noise, respectively. The simulation results show that KF performs better than MCKF under mixed Gaussian noise interference, MCKF has better filtering performance than KF under the interference of heavy tail pulse noise, and MCKF is equivalent to KF when the kernel bandwidth tends to infinity.
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jgg. 2024, 44(8): 793-796.
We proposed an adaptive spatiotemporal filtering method for GNSS coordinate time series, which dynamically subdivides the filtering region into several subregions, facilitating the extraction and elimination of common mode errors under specified thresholds. We conduct a case study on 184 vertical GNSS coordinate time series from CMONOC. The results of three groups of randomized experiments show that the average RMS values of the station sequences after adaptive PCA spatiotemporal filtering are reduced by about 39.7%, 38.4%, and 39.7% on average compared with that before the filtering, and the filtering effect is better than that of the overall PCA spatiotemporal filtering method. Analysis of pre- and post-filtering site noise characteristics reveals that, compared to traditional PCA filtering, our method resulted in an additional attenuation of approximately 17.8% in power-law noise amplitudes within site residual time series.
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jgg. 2024, 44(8): 797-803.
This paper introduces the methods and steps for estimating multi-GNSS multi-frequency code biases and validates the effectiveness of estimating inter-frequency code biases using a multi-GNSS ionospheric modeling approach. We compute daily solutions for various code biases using MGEX network observations from January 2019 to July 2023. We further analyze the accuracy of various code biases. The results indicate that the multi-GNSS multi-frequency OSBs calculated in this paper exhibit an average weekly stability ranging from 0.07 to 0.26 ns. Among them, the average weekly stability of BDS-2 and BDS-3 multi-frequency OSBs are 0.17 to 0.26 ns and 0.13 to 0.21 ns, respectively. The consistency of various types of DCBs with products from DLR and CAS can be maintained within 0.3 ns. This research is not dependent on external post-processing products and can calculate code biases with both a rapid turnaround time and high precision.
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jgg. 2024, 44(8): 804-809.
Based on the satellite orbit characteristics of BDS GEO, IGSO, and MEO, we use multi-point hemispherical grid model(MHGM) and sidereal filtering(SF) method to establish a multipath error correction model for a mixed constellation of BDS. After applying the model to correct multipath errors, the post-fit carrier phase residuals for BDS precise point positioning(PPP) are significantly reduced, and the positioning accuracy in E, N, and U directions is improved by 41%, 37%, and 38%, respectively, with an overall increase in convergence speed of 31%.
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jgg. 2024, 44(8): 810-814.
Acoustic positioning technology can transfer the position reference frame maintained by GNSS into the ocean. Domestic GNSS-acoustic seabed positioning experiments typically involve the cooperation of multiple hardware devices. However, the observation data outputted by different devices may suffer from time stamp jumps. While time stamp jumps can be resolved through redundant observations, there is currently no effective solution for cases without redundant observations. Therefore, we propose a time stamp jump correction method based on parameter search. By constructing a search space for time stamp deviations and using the unit weight variance of acoustic positioning results as a criterion, the time stamp jump in observation data is searched numerically. The proposed method is validated using measured sea trial data. The results show that the parameter search method successfully detects a time stamp jump of approximately 1 second in acoustic device data and improves the accuracy of acoustic positioning from decimeter-level to millimeter-level by correcting the data time stamps.
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jgg. 2024, 44(8): 815-819.
We use observation data from 5 GNSS/MET stations in Shanghai from July 21 to August 8, 2021 to invert atmospheric precipitable water vapor(PWV) by GAMIT software, and study the relationship between PWV and rainfall in Shanghai and the spatial distribution characteristics of PWV during typhoon “In-Fa”. The results show that the correlation between GNSS PWV and sounding PWV is above 0.9. Before the formation of precipitation, PWV undergoes three obvious rise processes and the precipitation generation time is about 60 h ahead of typhoon landfall. PWV sharp change will cause a sharp rise or fall in precipitation. After the precipitation, PWV gradually drops below 40 mm. Before typhoon landfall, PWV is basically above 75 mm; PWV above 80 mm is mainly distributed in southern and central areas of Shanghai. After typhoon landfall, PWV is above 80 mm, and higher value areas can reach 90 mm. After the typhoon moved away, the PWV value dropped below 85 mm. The expansion and progression of the high-value area to the northwest is basically consistent with the typhoon path.
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jgg. 2024, 44(8): 820-826.
We select 38 views of Sentinel-1A SAR images, and obtain the surface subsidence results within 5 km along the Qufu-Heze section of the Lunan high speed railway using SBAS-InSAR technology for the period from February 2019 to November 2022. We analyze the distribution characteristics and patterns, and use the PSO-BP model to predict the subsidence of some feature points. The results show that the annual average deformation rate is between －20 and 15 mm/a, the maximum subsidence velocity is 25.46 mm/a, and the maximum lifting velocity is 17.43 mm/a within 0.1 km along the high speed railway; the RMSE of the subsidence prediction value obtained by the PSO-BP model ranges from 5.8 to 12.4 mm, which can predict the surface subsidence well.
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The Joint Detection Method of Active-Passive Surface Wave Based on MASW and SPAC and Its Applicationjgg. 2024, 44(8): 827-832.
In this paper, the interior layer of Dushan substation in Guizhou province is taken as the research object. We generate a composite dispersion curve by superimposing the dispersion energy of multichannel analysis of active surface waves(MASW) and spatial auto correlation(SPAC) of passive surface waves. The curve has a wider frequency band, which can not only ensure the resolution of the surface layer and avoid the formation of a large exploration blind area, but also effectively improve the inversion depth and obtain a more refined shear wave velocity model. The model can be given geological significance in combination with the drilling data. The results show that the combination of MASW and SPAC is beneficial to the fine imaging of the strata from the surface to the deep layer, and to understand the lithological structure characteristics of the strata. Compared with drilling, this method has low field construction cost and high efficiency, and it can provide an important reference for the detection of unfavorable geological bodies in complex urban areas.
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jgg. 2024, 44(8): 833-840.
To obtain high-quality original seismic data of the Wuwei basin of the lower Yangtze block, we conduct experimental research based on the reflection seismic data from 2019 to 2020, such as high density wide line acquisition technology, excitation technology, and tomographic static correction technology. We summarize a set of collection and construction parameters suitable for shale gas seismic exploration in the Wuwei basin, and apply these parameters to the newly deployed seismic exploration work in the research area. We obtained seismic data with high signal-to-noise ratio. By performing Kirchhoff pre-stack time migration on the data, we obtain a high-resolution and high-precision time-domain reflection profile. The target layer(Permian) on the profile has strong reflection wave energy and continuous in-phase axes, which can basically clarify the geological structure framework of the area. This can provide reliable seismic imaging data for the drilling and deployment of shale gas in the Wuwei basin.
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jgg. 2024, 44(8): 841-846.
To study the applicability of the H/V spectral ratio method for determining the predominant period of laterite sites, we conduct systematic microtremor measurement on different classifications of laterite sites and process the microtremor measurement data using different combinations of horizontal components in the H/V spectral ratio method to get the HVSR curves. We analyze the HVSR curves to obtain the predominant period of the sites, and then determine the site classifications and divide the site geotechnical types. Finally, we verify the applicability of the microtremor H/V spectral ratio method for determining the predominant period of laterite site by borehole exploration. Moreover, using the combination of the sum of east-west and north-south vectors as horizontal components in the microtremor H/V spectral ratio method can obtain the predominant period of the site more easily and accurately.
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jgg. 2024, 44(8): 847-852.
Based on lithologic characteristics, samples age, sporo-pollen and sedimentary cycle analysis of the controlled drill in northern Taiyuan basin, as well as the known data of sporo-pollen assemblage and strata lithology of late Cenozoic in Taiyuan basin, we divide the Quaternary strata in Taiyuan basin. The Quaternary strata from top to bottom in Taiyuan basin is divided into: from 0 to 31.6 meter is the Holocene; from 31.6 to 95.5 meter is the late Pleistocene, which is further divided into the early(31.6 to 47.8 meter), the middle(47.8 to 78.2 meter) and the late(78.2 to 95.5 meter) periods; from 95.5 to 186.16 meter is the middle Pleistocene; from 186.16 to 250.42 meter is the early Pleistocene. On this basis, we analyze the evolution characteristics of the Quaternary in Taiyuan basin based on the color and particle size features of sediment and sporo-pollen analysis results.
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jgg. 2024, 44(8): 853-856.
The traditional method of geoid-quasigeoid separation is difficult to meet the accuracy requirements in mountainous regions with complex terrain. We use a strict formula to calculate the geoid-quasigeoid separation in the mount Qomolangma area and analyze spatial changes. The results show that the total correction using the strict formula varies from －3.270 m to －0.119 m, the potential correction reaches 1.272 m, and the gravity gradient correction reaches －0.138 m. The magnitude of these corrections is large enough and needs to be taken into account in mountainous areas. The strict method and the approximate method both have a certain correlation with height, and the former produces smoother results than the latter. Under the influence of Bouguer gravity anomaly and terrain changes, some local features of strict method are negatively correlated with height.
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jgg. 2024, 44(8): 857-866.
By fusing the observation data with the model，data assimilation provides an effective solution for realizing accurate mapping of physical and mathematical models to solid Earth as much as possible. We review the application and research status of data assimilation method in various branches of solid Earth geophysics, and make a preliminary discussion on the urgent problems of data assimilation method in solid Earth geophysics.
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jgg. 2024, 44(8): 867-872.
Using high resolution remote sensing images, we accurately extract the water body boundary of the head area of the Three Gorges reservoir. A precise discretized numerical model is constructed for the water body to simulate and calculate the gravity effect of the head area of the Three Gorges reservoir at different storage and release water levels. We finely preprocess the continuous observation data of the gPhone 101 gravity gravimeter at Zigui station in 2017 and the gPhone 113 gravity gravimeter at Maoping station in 2019 to 2021. The results show during the water storage process from 145 m to 175 m, the simulation values of gravity change on the bank at different storage levels (distance is 5 m) are 0 to 28 μGal, 0 to 47 μGal, 0 to 60 μGal, 0 to 97 μGal, 0 to 170 μGal, and 0 to 210 μGal, respectively. There is an effect of 10 to 20 μGal within 2 km from the bank at the time when the storage level is elevated by 5 m. When the water storage level increases 30 m, there is an effect of 30 to 40 μGal within 5 km from the bank. The gravity residuals mainly reflect the hydrological gravity effect information, the gravity residuals at Zigui station recorded about 40 μGal of gravity change, and the gravity residuals at Maoping station recorded about 50 μGal of gravity change. The gravity change trend and the water level change show very good consistency, verifying the accuracy of the model simulation results, and provides a reference for the stability monitoring of the head area of the Three Gorges reservoir and its banks.
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jgg. 2024, 44(8): 873-880.
Aiming at the shortcomings of the seafloor topography inversion based on gravity data in irregular shape sea area (e.g. the sea-land boundary area), such as the implementation difficulty, we propose the improved gravity-geologic method (iGGM) and regression analysis method (iGA) based on the approximate linear relationship between seafloor topography data and gravity data, combined with depth soundings and gravity anomaly data, to predict seafloor topography in the area. We select the range of 2°×2°(6°N~8°N, 115°E~117°E) in the south China sea as the study area. Using iGGM and iRA, and compared with the SCS_Grid model (gridded acoustic bathymetric data in the study area) and topo_23.1 model, etc., we construct the SCS_iGGM and SCS_iRA seafloor topography models. The experimental results show that the overall statistical results of the SCS_iGGM and SCS_iRA are similar to the SCS-DTU18 model, SCS-ETOPO1 model and SCS_topo_23.1 model in the sea-land boundary sea area, and the correlation coefficient is higher than 0.99. The external checking results in the study area shows that the accuracy of the SCS_iGGM and SCS_iRA is comparable. Compared with the SCS-DTU18 model, SCS-ETOPO1 model and SCS_topo_23.1 model, the accuracy of the SCS_iGGM and SCS_iRA models are improved by about 76%, 70% and 53% respectively. Combining the sea gravity anomaly and ship depth soundings to establish seafloor topography model, either in terms of the seafloor topography data recovery capacity, or the quality of model construction, is better than the seafloor topography model that relies only on ship depth soundings data.
