15 September 2024, Volume 44 Issue 9
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jgg. 2024, 44(9): 881-885.
Based on the mechanism of deformation anomaly, we analyze the correlation of several anomalies before the earthquake. Combined with observation facts and experiments, we explore the possible organic connections between them. The explanations are given uniformly from the mechanism for the anomalies before and after the earthquake, such as the severe drought before the earthquake, the heavy rain after the earthquake, the sand jetting and ground collapse during the earthquake, as well as ground sound and light, the ionosphere anomaly before the earthquake, the atmospheric electrostatic anomaly before the earthquake, and the electromagnetic wave anomaly before and during the earthquake. We consider that these anomalies are all related to the formation, expansion and rapid disappearance of micro-crack expansion bodies near the seismic source before the earthquake.
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jgg. 2024, 44(9): 886-891.
This article introduces the method of factor analysis. It conducts comprehensive analyses on 16 seismic activity parameters of the small and medium-sized earthquake sequences in the Pingyuan earthquake area. The results show that the current comprehensive factor W was in the highest value range of this quiet episode. Further research of the single factors reveals that the underground medium in the Pingyuan earthquake area might have undergone some changes. In the future, seismic activity in north China may increase.
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jgg. 2024, 44(9): 892-898.
Based on the mobile geomagnetic observation data of four consecutive periods from 2020 to 2023 in the border area of Hebei and Shandong, this paper analyzes the temporal and spatial variation characteristics of the regional lithospheric magnetic field and its relationship with the Pingyuan MS5.5
earthquake on August 6, 2023. Combined with the laboratory results of rock magnetism and the theory of fault meta-instability, it discusses the meta-instability characteristics before the plain earthquake and the seismogenic mechanism.The results show that:1) The spatial and temporal variation characteristics of the lithospheric magnetic field in the study area have obvious anomalies before the Pingyuan MS5.5 earthquake. There is always a weakening area of the horizontal vector near the epicentre from 2020 to 2023, and with the passage of time, the weakening area with horizontal vector gradually approaches the epicentre; there is always a 0 value line of the total geomagnetic intensity, magnetic declination and vertical component near the epicentre. 2)The time series variation of the observation points near the epicentre in 2020-2021 is highly consistent, which better reflects the synergistic activity state of the faults near the observation points, and may be used as one of the characteristics to identify the sub-instability stage of the faults.3) By analyzing the relationship between stress and magnetic field intensity, it can be seen that the total intensity of geomagnetic field in the middle and eastern segment of Linnan fault and the north-eastern segment of Liaocheng-Lankao fault increases, and the crustal stress should be in a release state; the total intensity of geomagnetic field in the western segment of Linnan fault and Tangyi fault decreases, and the crustal stress should be in an accumulation state. The stress release of the former can promote the stress accumulation of the latter, which may lead to the instantaneous increase of the shear stress of the latter and instability when it exceeds its strength, thus triggering the plain earthquake. -
jgg. 2024, 44(9): 899-904.
We use the catalog of modern earthquakes in the Beijing-Tianjin-Hebei region from 1980 to 2022 as a statistical sample. To grid the study area, we use the incompletely centralized Voronoi segmentation method based on spatial segmentation. Based on the Poisson model, the probability model of earthquake risk is established, and we conduct the probability prediction of small and medium earthquakes at the medium-term scale of the study area. The results show that the calculated probability of relatively high value region has a certain correlation with the occurrence of earthquakes with MS≥3.0, which can provide a reference for medium and long term earthquake prediction.
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jgg. 2024, 44(9): 905-909.
Based on the seismic observation data of 7 temporary seismic stations in the hot dry rock area of Matouying and the pressurized water injection data of M1 well from 2022-06 to 09, we study the relationship between seismic activity, water injection pressure and water flow; we further study the focal mechanism of induced earthquakes and analyze their influence on the surrounding stress field. The results show that 201 earthquakes may be induced by water injection operation, and the focal depth is mainly concentrated in 0-4 km. This area is also a safe area with small ground confining pressure, and the probability of moderate and strong earthquakes is small. The changes of water flow and water pressure not only affect the temporal and spatial distribution characteristics of induced earthquakes, but also affect the frequency of seismic activity. When the stress accumulates to a certain level to induce earthquakes, the water flow, water pressure and earthquake frequency show a positive correlation. The relationship between the amount of water injected and the earthquake magnitude is not obvious, and the pressure is linearly correlated with the induced earthquake magnitude. When the continuous water injection volume reaches 11 821 m3 and the pressure reaches 23.46 MPa, the fault instability may induce earthquake. The focal mechanism of the maximum induced earthquake is strike-slip type, and the principal compressive stress is NNW, which has a certain deviation from the stress distribution in North China. It can be seen that the mining of M1 well has an effect on the local stress distribution. According to the migration rule of earthquake epicenter, there are new ground cracks.
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jgg. 2024, 44(9): 910-918.
Based on the data of fault location, velocity structure and 292 focal mechanisms in Tangshan area, we carry out the spatial grid division of stress field inversion, and retrieve the whole and major fault stress fields in Tangshan area by using grid search method. The results show that: 1) Before and after the 2011 MW9.0 Tohoku earthquake, the overall regional tectonic stress field in Tangshan area rotated slightly clockwise, and the stress state changed from strike-slip to positive strike-slip, which may be mainly caused by the spatial location change of the focal mechanism solution. 2) The Tohoku earthquake in Japan made the plunge angle of σ1-axis in some areas of Tangshan change from steep to horizontal, and the stress field has a small clockwise rotation. 3) At present, the overall regional stress field in Tangshan area is characterized by σ1-axis NEE-SWW direction, σ3-axis near NS direction, and R value is 0, which is consistent with previous research results. It shows that the stress field in Tangshan area has been adjusted to the state before the 1976 Tangshan MW7.8 earthquake, and the stress state is partial tensile. 4) At present, 6-20 km of Weishan-Fengnan, Douhe, Luanxian-Leting fault sections and 11-20 km of Douhe fault section are strike-slip stress states; The stress state of 0-10 km of Douhe fault section is positive strike-slip. 6-20 km of Leizhuang, Chenguantun and Lulong fault segments, 0-5 km of Weishan-Fengnan fault segments are positive fault type stress states. The σ1-axis directions of the above faults are consistent with the principal strain direction and the fast wave polarization direction of shear wave splitting in this region. 5) The Tangshan area is in a relatively unified NNW-SSE tensile action, but the Guye and Luanxian areas are in NEE-SWW compressive action.
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jgg. 2024, 44(9): 919-925.
This article is based on the detection results of the Jiaocheng fault zone in different projects, and through systematic analysis and organization, uses three methods: geological exploration trough profile method, empirical statistics method, and numerical simulation method, to evaluate the risk of surface rupture and the width of the coseismic surface rupture zone in the northern section of the fault zone during the occurrence of the maximum potential magnitude MS7.2 earthquake. We analyze the reliability of the results obtained by the three methods was analyzed, and a weighted comprehensive average method was proposed to calculate the width of the coseismic surface rupture zone of the fault. On the basis of considering the accuracy of detection methods, the range of avoidance zones for the Jiaocheng fault zone during project site selection is determined to be on both sides of the fault zone, with an extension of 15.0 m on the west side of the F11 trace to 86.9 m on the east side of the F21 trace. This result has certain reference significance for land planning and utilization along the Jiaocheng fault zone. The method can provide reference for similar research.
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jgg. 2024, 44(9): 926-931.
In view of the non-linearity and non-stationary characteristics of satellite clock bias(SCB) time series, as well as the interference between trend and noise components that may affect the accuracy of prediction, this paper proposes a SCB prediction model(SSA-ANFIS) based on singular spectrum analysis(SSA) and adaptive neuro-fuzzy inference system(ANFIS). This paper first uses SSA to decompose and reconstruct the first-order difference sequence of clock bias, obtaining the trend component and the residual component. Then, it uses the ANFIS model to predict the reconstructed components, and superimposes and restores the predicted results to obtain the final predicted clock bias value. Finally, through experiments, this paper compares the proposed model with GM, QP, LSTM and ANFIS models. The results show that SSA-ANFIS model can effectively improve the prediction accuracy of the single model. Compared with the LSTM and ANFIS models, its prediction accuracy increased by 25.7%-40.7% and 39.4%-45.7%, respectively.
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jgg. 2024, 44(9): 932-936.
We propose a gait recognition model that fuses long short-term memory(LSTM) and convolutional neural network(CNN), the model can automatically extract activity features and classify them using a small number of model parameters, and we utilize this model for user identification. The experimental results show that the recognition accuracy of the model is about 97.68 % and the loss value is about 0.05, which significantly improves the recognition rate compared to other models.
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jgg. 2024, 44(9): 937-944.Based on the Sentinel-1 ascending image from January 2021 to June 2023, we use the StaMPS-SBAS method to obtain the surface deformation of the core production area of Liaohe Oilfield. Based on the deformation rate results, we use the composite dislocation, Mogi and Okada models to invert the reservoir parameters, comparing our results with existing research. The results show that the LOS deformation rate in the study area is －165.84 to 54.52 mm/a, and the maximum cumulative settlement(LOS direction) during the research period is about 400 mm. There are three significant subsidence areas in the area, namely Shuguang oil production plant, Huanxiling oil production plant and Jinzhou oil production plant. Shuguang oil production plant has a subsidence deceleration trend, while the other oil production plants have a subsidence acceleration trend. There are obvious differences in the reservoir parameters inverted by different models. Compared with the Okada and Mogi models, the reservoir depth inverted by the composite dislocation model (1 665.21 m) is the closest to the actual (about 1 600 m). Moreover, the deformation simulated by the composite dislocation model is most consistent with the observed deformation.
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jgg. 2024, 44(9): 945-950.
To monitor land subsidence in Suzhou city during the rapid construction of subway, this paper focuses on the temporal analysis of ground deformation in Suzhou central area with PS-InSAR, using TerraSAR-X and Sentinel-1 data in 2010-2020 combined with leveling observation data. The results show that the ancient city area of Suzhou is stable relatively, and the maximum settlement points are in Yangshan with the settlement rate exceeding -20 mm/a. The subsidence trend has slowed down in Suzhou central area, with a significant reduction in the subsidence range, and several small uplifted areas have appeared particularly in the east of Caohu, and the north of Taiyang road. The settlement of buildings nearby the subway accelerate significantly with the influence of subway construction, especially for new buildings, whose own short-term sedimentary settlement is superimposed with the settlement of subway construction, resulting in the subsidence rate exceeding -10 mm/a.
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jgg. 2024, 44(9): 951-958.
This paper proposes a noise reduction algorithm combining adaptive variational mode decomposition and KSVD dictionary learning. In this method, we fully retain the effective information in the monitoring sequence by denoising the sub-sequences after the decomposition of the monitoring sequence, and consider the features in the residual sequence. We take the deformation monitoring data of a dam as an example. The results show that the proposed method can effectively retain the effective information in the monitoring sequence, and is more suitable for dam deformation prediction under complex conditions than the traditional noise reduction method, and can further improve the generalization ability of the prediction model.
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jgg. 2024, 44(9): 959-971.
In recent years, high-precision time-varying gravity observation technology on land has developed rapidly. In addition to the continuous improvement of absolute gravity equipment such as quantum gravimeters, the layout of gravity observation network in Chinese mainland has also become increasingly perfect. A microgal-level time-varying gravity field observation network with a resolution better than 100 km has been built in the main active tectonic regions within Chinese mainland. This paper begins with the technology and method of terrestrial time-varying gravity observation. We first introduce the concept of land time-varying gravity observation, the classification of gravity instruments, and the construction and development of the high-precision gravity observation system in Chinese mainland, as well as the problems and optimization suggestions for this system. Then, we introduce the time-varying gravity technology methods and model products, and their applications in various fields. Finally, we discuss issues related to the data products and applications of land time-varying gravity and propose a design and layout plan for the next-generation land gravity observation system that aims to address the scientific questions of the China seismic experiment site and deep earth science. As a crucial part of the national geophysical monitoring network, terrestrial time-varying gravity observation generates high-precision model products that can not only aid in the study of deep crustal dynamics but also provide crucial data support for geophysical navigation and national defense.
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jgg. 2024, 44(9): 972-977.
At present, the seismic stations need to use two sets of acquisition systems to monitor and record weak signals and large seismic signals. To address this problem, this paper proposes a data acquisition method that automatically switches acquisition modes. When monitoring weak signals under normal conditions, the acquisition system uses small-signal channel ADCs for graded sampling, and when large earthquakes and giant earthquakes occur, the system automatically switches to use large-signal channel ADCs for sampling. Experiments show that the dynamic range of the acquisition system reaches 128 dB for single AD data acquisition at 100 Hz sampling, and 158 dB for double AD data acquisition at 100 Hz sampling.The improved data acquisition method effectively improves the dynamic range of seismic signal acquisition, and improves the performance of the data acquisition system to a certain extent without increasing the hardware cost.
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jgg. 2024, 44(9): 978-984.
We propose a random noise suppression method CEEMD-PCA based on principal component analysis (PCA) optimized complementary ensemble empirical mode decomposition (CEEMD) for DSQ water tube tiltmeter signal. The method incorporates eight IMF component quality evaluation indexes, such as correlation coefficient, distribution entropy, MSE, R2, SSE, RMSE, MAE, MAPE; it implements dimensionality reduction and compression of the index value matrix with the help of principal component analysis to transform it into a new parameter that can represent the characteristics of all different types of indexes, and constructs a comprehensive IMF component quality evaluation function to complete the original noise-containing signal according to the score ranking results. We complete the linear reconstruction of the original noisy signal according to the score ranking results. The results of both simulated and measured signal denoising experiments show that the CEEMD-PCA model outperforms the classical models such as Kalman filter, 70 th-order low-pass FIR filter, etc., improves the signal-to-noise ratio of the original signal, and accurately completes the signal reconstruction, which can better retain the effective components.
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jgg. 2024, 44(9): 985-990.
On August 23, 2023, the seismic instrument system of the Hongyanhe Nuclear Power Plant successfully recorded a M4.6 earthquake in Pulandian, Dalian. This is the first complete strong earthquake record around the nuclear power plant area in China. We analyze the seismic data recorded by the system, and the data playback shows that the seismic recorded data was clear and complete, and the peak value of the free field monitoring data is consistent with the calculation result of the seismic attenuation empirical formula. Comparing the peak acceleration values of seven monitoring points data, the result shows that the nuclear power plant building has an amplification effect on seismic acceleration signals, and the amplification coefficient is positively correlated with building elevation. The conclusion of spectral analysis of peak acceleration data shows that predominant frequency points of seismic response data in nuclear power plant buildings are mainly concentrated in the range of 10 to 20 Hz, and seismic acceleration signals in the range of 10 to 20 Hz also have certain destructive effects on the building. This conclusion is inconsistent with the seismic triggering filtering range (1 to 10 Hz) specified in NB/T 20076-2012 seismic instrument criteria, due to the fact that the seismic trigger recognition algorithm of the seismic instrument system is set in a filtering range of 1 to 10 Hz. This defect will reduce the performance of the seismic instrument system’s depth safety defense.
