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Crustal thickness and vP/vS ratio of Arxan volcanic group in Xing’an-Mongolia orogenic belt
Zhang Yaxi, Wu Qingju, Zhang Ruiqing, Bai Lanshu
, Available online  , doi: 10.11939/jass.20210070
The Arxan volcanic group is one of the most important volcanic groups in the Quaternary in Northeast China. It is of great significance to obtain information of crustal structure and vP/vS ratios in this area for studying the physical properties of the crust and tectonic evolution beneath the volcanoes. The crustal thickness and average vP/vS in the study area are obtained by the P-wave receiver function and H-κ stacking method. Original waveform data came from temporary broadband seismic stations in the Arxan volcanic area. The results show that the crust thickness is thicker in the northwest and thinner in the southeast, ranging from 33.9 km to 37.9 km. There is a positive correlation between crustal thickness and elevation. The vP/vS ratio ranges from 1.73 to 1.83. There are three high wave vP/vS ratio areas in the study area: Chaihe town-Mingshuihe town, the north of Yimin Doren and Tianchi town. The thin crust and high wave velocity ratio areas beneath Arxan volcanic area may be caused by the upwelling of mantle material and underplating of basaltic magma.
Design on high-precision time-synchronization system for distributed seismic data acquisition
Li Caihua, Teng Yuntian, Zhou Jianchao, Hu Xingxing, Wang Xizhen, Li Xiaojun, Wang Yushi
, Available online  , doi: 10.11939/jass.20210124
In order to solve the time-synchronization problem of distributed seismic data acquisition system, one new high-precision time-synchronization technical system was designed in this paper. In this system, a synchronous timing pulse was transmitted periodically during data communication. Through transmitting time measurement and its transmission delay time correction of synchronous timing pulse, high-precision multi-channel time synchronization were achieved in this technical system. And a time-synchronization technical system designed with high-speed programed chips was used to carry out the time-synchronous test. The result shows that the time-synchronization system can achieve 200 ns time-synchronous error with 2 km optical fiber, which indicates that the time-synchronization system is stable and practical.
Seismic waveforms and their signal-to-noise ratios of borehole observation in Donghai station,Jiangsu Province
Xu Jiren, Li Haibing, Zeng Xiangzhi, Zhao Zhixin
, Available online  , doi: 10.11939/jass.20220195
The Jiangsu Donghai Crustal Activity in Continental Deep Hole National Observation and Research Station (Donghai station for short) is the first deep borehole seismic observation station in China. In order to explore an effective way to observe seismic information with high signal-to-noise ratio in high noise interference areas and to carry out the study on the borehole seismology, this paper analyzed the waveform characteristics and signal-to-noise ratios of waveforms recorded by a seismometer on the ground and three borehole seismometers at different depths underground in Donghai station. The results show that the waveform of a ML0.8 local event cannot be recognized in the seismogram of the seismograph on the ground due to the strong non-seismic noise disturbance around the Donghai station. However, the waveforms of the ML0.8 event can clearly be recognized on the seismograms of the three deep borehole seismographs. Furthermore, the earthquakes with zero magnitude or weaker negative magnitude recorded by the deep borehole seismographs are also more than those recorded by the seismograph on the ground. Meanwhile, the signal-to-noise ratios of waveforms recorded by borehole seismometers at three different depths are much higher than those recorded by the seismometer on the ground; moreover, the average signal-to-noise ratios of waveforms increase with the depths of observation instruments in the borehole. The average signal-to-noise ratio of the waveforms recorded by the seismograph at 1 559.5 m depth underground is 69.20 dB, and that of the seismograph at 2 545.5 m depth is 74.15 dB. Both of the two ratios reached the signal-to-noise ratio value of high fidelity waveform. Therefore, the observation data of seismograph at about 1 500 m depth can effectively avoid the interference on ground and record waveform with high signal-to-noise ratio. Such waveforms provide a real and reliable data for the study on source process and site effect, promoting the development of deep borehole seismology.
Comparative study on grounding resistance measurement method of geo-electric resistivity electrode in geo-resistivity observation
Zhang Yu, Wang Lanwei, Hu Zhe
, Available online  , doi: 10.11939/jass.20210151
When using the traditional three electrode method to measure the underground electrode grounding resistance, there will be a large measurement error, which suggests that the method will not be suitable for the underground electrode ground resistance measurement. In view of this problem, this paper proposes a new method for measuring the electrode grounding resistance by using the geo-electric resistivity observation system, which is so called direct measurement method. Furthermore, the grounding resistances of the underground observation power supply electrodes of Pinggu seismic station of Beijing were measured by using the traditional three-pole method and the direct measurement method. The measurement results show that, compared with the traditional three pole method, the direct measurement method can get more reliable measurement results with less error, and saves man power and measuring time.
Anomaly edge enhancement and topographic correction technology of linear source 3D borehole-to-surface electrical method
Xiong Zhitao, Tang Xingong, Zhang Lianqun, Li Dandan, Yu Junhu
, Available online  , doi: 10.11939/jass.20220074
Based on the finite element method of unstructured grid, the efficient forward modeling of the borehole-to-surface electrical method derived by the linear current source under the condition of the 3D complex geoelectric model was carried out. The effects on the effectiveness and accuracy of the borehole-to-surface electrical method imaging were discussed by obtaining the electric field response derivative to characterize the boundary range of the target body, and using the difference field topography correction technology to eliminate the topographic influence. And the comparison between the numerical solution and the analytical solution verifies the effectiveness of the algorithm in this paper. The model calculation results shows that the spatial position and direction of the roadway with water accumulation cause significant changes in the apparent resistivity, and the extreme value of the apparent resistivity change rate accurately and clearly indicates the boundary position of the roadway. The normalized total horizontal derivative of the electric potential greatly improves the ability of the borehole-to-surface electrical method to identify the complex boundary position of the target body. The influence of topography on the distribution of borehole-to-surface electrical field is also serious, and its apparent resistivity response is approximately symmetrical to the shape of the topography. The difference field technique can effectively weaken the influence of topography on the high-precision imaging of the borehole-to-surface electrical method. The research results have important theoretical and practical significance for improving the data interpretation level and application effect of the borehole-to-surface electrical method.
Estimating of crustal thickness and vP/vS ratio using receiver function,surface wave and gravity data
Ren Zhiyuan, Li Yonghua, Qiang Zhengyang, Shi Lei
, Available online  , doi: 10.11939/jass.20210065
Crustal thickness H and vP/vS ratio are two basic parameters for deciphering the crustal structure. We present an improved technique to constrain crustal thickness, vP/vS ratio and average P-wave velocity by using receiver function, surface wave dispersion and gravity data. Synthetic tests show that the improved method not only can determine the accurate estimate of H and vP/vS ratio , but also give an accurate the average crustal vP. Field data from two stations of South China are analyzed by the improved method, and the results also show the feasibility of the new method in constraining crustal properties.
Global sensitivity analysis of the generalized Pareto distribution model for seismicity in the northeast Tibetan
Ren Mengyi, Liu Zhe
, Available online  , doi: 10.11939/jass.20210112
Because the selected values of input parameters of generalized Pareto distribution (GPD) model are difficult to avoid uncertainty, the input parameters uncertainty of this model may lead to uncertainty in the seismic hazard estimation. In this paper, we selected northeastern Tibetan Plateau as the case studied area, and proposed an uncertainty analysis process and method of seismic hazard estimation based on the global sensitivity analysis. First, we used the GPD seismicity model to obtain the results of seismic hazard estimation. And then, we selected starting time of earthquake catalog and magnitude threshold to be the input parameters of seismicity model. The E-FAST method with global sensitivity analysis function was used to quantitatively analyze the influence of the uncertainties of the two parameters and the interaction between the two parameters on the uncertainty of seismic hazard estimation. The results show that the seismic hazard estimation of the GPD model is more sensitive to the magnitude threshold. With different return periods, the sensitivity degree of seismic hazard estimation to magnitude threshold is different. For different return periods, there are nonlinear effects between the two input parameters on the uncertainty of seismic hazard estimation, and the degree of nonlinear effects is different. The uncertainty analysis process and method proposed in this paper can be applied to the uncertainty analysis of seismic hazard estimation based on other seismicity models.
Application of generalized extreme value distribution based on profile likelihood estimation in long term earthquake prediction
Zhao Yibin, Zhang Yanfang, Wang Fuchang, Ren Qingqing
, Available online  , doi: 10.11939/jass.20210067
To describe the uncertainty of strong earthquake prediction, we introduced the profile likelihood estimation into parameter estimation of extreme value model for earthquake prediction. It elaborated the profile likelihood estimation principle and numerical algorithm of shape parameters and earthquake return level in generalized extreme value distribution. Meanwhile, a model of generalized extreme value distribution was created and was used to analyze the seismic risk of the East Kunlun seismic belt. The results showed that profile likelihood estimation and maximum likelihood estimation generated basically the same effect in point estimation of shape parameters and return level as well sd the estimation of confidence interval of earthquake return level within 10 years. However, in the confidence interval estimation of moderate and long interval earthquake return level, the asymmetric confidence interval of return level obtained through the profile likelihood estimation can more accurately express the uncertainty of predicted magnitude of a strong earthquake and more effectively predict the outcome.
Study on shallow S-wave velocity structure in Chongqing area
Dong lei, Shen Xuzhang, Chen Lijuan
, Available online  , doi: 10.11939/jass.20210113
Based on the teleseismic waveform data recorded at permanent stations in Chongqing and its adjacent area from January 2011 to October 2018, the shallow S-wave velocity structure beneath the stations of Chongqing and its surrounding area is calculated by the method to constrain shallow structure based on direct P-wave amplitude in receiver functions. The results indicated that, the velocity structure of shallow S-wave in Chongqing is obviously related to the basin mountain structure, the low velocity anomaly in the basin corresponds to the characteristics of sedimentary layer, and the Daba mountain and Dalou mountain regions show relatively high velocity anomalies. The S-wave velocity of Huayingshan fault is higher than that of sedimentary layers on both sides of the fault, implying that the sedimentary layers in Sichuan basin are thin in the middle and thick on both sides. The Dianjiang MS4.4 earthquake and the Shizhu MS4.5 earthquake located in the east Sichuan detachment structure area are related to the obvious low velocity anomaly. The Rongchang MS4.7 and MS4.8 earthquakes have no obvious characteristics of high or low velocities, which may be related to water injection. The Wulong MS5.0 earthquake occurred on the high velocity body side that is conducive to strain accumulation of the high and low velocity junction. Finally, we discussed the seismogenic environment of five earthquakes in Chongqing since 2010.
Rupture process of the MS6.9 Menyuan,Qinghai, earthquake on January 8, 2022
Dai Danqing, Yang Zhigao, Sun li
, Available online  , doi: 10.11939/jass.20220032
Based on the waveform data observed by the near field strong-motion stations, the earthquake rupture process can be quickly and stably inverted. This paper collected waveform data recorded by the strong-motion stations reconstructed in Qinghai during the implementation of the National Rapid Intensity Report and Seismic Early Warning Project. Based on these data, the rupture process of the Qinghai MS6.9 earthquake on January 8, 2022 was inverted by the iterative deconvolution and stacking method (IDS). The rupture model from inversion show that the rupture extends from the initial rupture point to a unilateral rupture in the southeast-east direction, with a duration of about 14 seconds (mainly focus on 2−8 seconds), a maximum slip of 3.6m, and a rupture length of about 20 km. The rupture extends longitudinally from the deep to the shallow, which is consistent with the surface rupture found in the field investigation. The spatial distribution of aftershock sequences shows significant segmentation characteristics, indicating complex tectonic transitions in the rupture zone. There is still the possibility of strong earthquakes in this area in the future.
Conjugate earthquake and measurement of friction coefficient in crustal medium
Wang Anjian, Chen Yuntai
, Available online  , doi: 10.11939/jass.20210111
Anderson’s theory indicates that the conjugate rupture phenomenon of earthquake can be explained by Coulomb’s criterion, and there is a simple quantitative relationship between the angle of fault plane and the friction coefficient of underground rock. Based on the author’s method of calculating the friction coefficient of the medium through conjugate earthquakes, this paper systematically analyzes 19 domestic and foreign earthquakes with “X”-shaped or incomplete “X”-shaped (“L”-shaped) conjugate rupture characteristics. Analyze and compare with the source mechanism, regional stress axis direction and other data to determine the conjugate fault plane, and then determine the angle of the conjugate plane and calculate the internal friction coefficient of the rock. The research results further confirm that the conjugate fracture of natural earthquakes is in good agreement with the laboratory rock fracture, and the Coulomb criterion and Anderson theory are also valid at large scales. It is shown that the internal friction of the underground medium is determined by the conjugate angle. The coefficient is a useful supplement to the cognition of the characteristics of the underground medium.
A new method for expressing seismic hazards
Zhang Meng, Pan Hua
, Available online  , doi: 10.11939/jass.20210106
The aim is to find a way to express seismic hazard with high accuracy, a wide range of exceedance probabilities and a convenient application. We reviewed several commonly used methods for seismic hazard expression, and the "characteristic coefficient method" based on a new function fitting the seismic hazard curve is proposed. The results show that the new function could effectively fit the seismic hazard curve, with a significant improvement compared to the extreme value function, and can adequately express the seismic hazard of a site. In addition, it is found that the parameter k (referred to as the characteristic coefficient in the paper), which characterizes the shape of the curve in this function, is related to the seismic environment faced by the site, that is, the hazard contribution for sites of low values of k essentially coming from the near field, while the contribution of sites for high values of k from long distances cannot be ignored.
Rupture process of the January 2022 Menyuan,Qinghai MS6.9 earthquake revealed by inversion of regional broadband seismograms
Zhu Yinjie, Luo Yan, Zhao Li
, Available online  , doi: 10.11939/jass.20220148
Based on regional broadband waveform records, we investigate the rupture process of the January 2022 Menyuan MS6.9 earthquake by using the finite fault inversion method, and then combined with the geological knowledge and aftershock relocation results to determine the actual rupture fault., The inversion results show that the Menyuan earthquake occurred on a WNW-trending strike-slip fault. The rupture mainly occurred on both sides of the hypocenter, with a bilateral rupture characteristic. The maximum ruptures on the two sides of the hypocenter occurred at 2 s and 9 s. In terms of rupture scale, the depth of obvious rupture and the length of surface rupture are about 16 km and 20 km, and the maximum slip of 1.5 m occurs at about 6km. The seismic energy is mainly released in the first 15 s. The total seismic moment released is 1.23×1019 N·m, equivalent to MW6.67. The dip angle of the seismogenic fault plane is 84.6°, almost vertical. Due to the large range of rupture, the surface projection of obvious rupture is up to 34 km.
An estimation model of high frequency attenuation coefficient of ground motion for local site
Lang Ziping, Yu Ruifang, Xiao Liang, Fu Lei, Zhou Jian
, Available online  , doi: 10.11939/jass.20220053
When using the stochastic finite fault method for ground motion simulation, how to select reasonable parameters to describe the near-surface high-frequency attenuation characteristics of a specific local site has important practical significance for evaluating the correctness of ground motion simulation results. In the prediction of ground motion parameters of engineering sites, how to quickly determine the value of this parameter is an urgent problem to be solved in practical applications. Firstly, the correlation that between the high-frequency attenuation coefficient κ0 of the site and the average shear wave velocity vS30 was analyzed; Then, based on the 546 κ0 coefficients calculated by domestic and foreign scholars, the root mean square value of κ0 in a certain time window was used to discuss its variation trend with the increase of the average shear wave velocity vS30.The results showed that although κ0 had obvious regional differences, its root mean square value showed a decreasing trend with the increase of vS30In order to obtain a reasonable κ0 estimation model, the linear function, polynomial function, logarithmic linear function and log-log linear function were used to preliminarily fit the relationship between the root mean square value of κ0 and vS30. The results show that the logarithmic linear function can be better describe the relationship between κ0 and vS30. Finally, based on the 477 data obtained from the screening, the model parameters were fitted by the least square method, and a practical model of κ0- vS30 suitable for engineering applications was obtained. The analysis of the applicability of the model shows that the κ0 estimation model constructed in this study can reasonably estimate the high-frequency attenuation of ground motion when predicting site ground motion parameters.
Joint inversion of multi-station receiver functions and gravity data for imaging Moho variations and average crustal vP/vS ratios
Hao Aowei, Zhang Haijiang, Han Shoucheng, Gao Lei
, Available online  , doi: 10.11939/jass.20210179
Crustal thickness and vP/vS ratio are two important parameters for understanding crustal structure and composition, which can help to study regional tectonics. Receiver function analysis has been widely used for determining crustal thickness and vP/vS ratio by the H-κ method or the H-κ-c method. However, it can only acquire average crustal thickness and vP/vS ratio below each seismic station, but cannot constrain their lateral variations among seisimic stations due to their sparse and irregular distribution. On the other hand, the gravity data has been widely used to derive the Moho variaitons, which has a good coverage and resolution laterally but poor resolution vertically. Therefore, in this study we have developed a new joint inversion method of receiver functions and gravity data to simultaneously invert for variations of Moho depths and average crustal vP/vS ratios in a region. The method takes advantage of complementary strengths of receiver functions and gravity data, and can simultaneously fit all receiver functions and gravity data in the region. The synthetic tests show that the proposed joint inversion method produces more reliable results than only receiver function analysis, especially for the crustal thickness.
A transfer function based on Laplace transform to improve the accuracy of narrow-frequency velocity recording
Sun Yixuan, Xu Guolin
, Available online  , doi: 10.11939/jass.20210182
Affected by the flat response range of the narrow-band seismograph, the narrow-band recording has the problem of low-frequency component distortion, which limits the usable range of the seismic recording. To solve this problem, the authors deduce an improved transfer function based on the Laplace transform and bilinear transform to realize the correction from narrow-band seismic records to broadband seismic records. The Japanese Hi-net velocity records are used as an example for correction, and the corrected velocity records are compared with the same KiK-net acceleration integral velocity records. The results show that the original velocity records are distorted at low frequencies, while the corrected waveform is consistent with the KiK-net acceleration integral velocity records. The analysis shows that the improved transfer function can effectively solve the distortion of the low-frequency components in the original velocity records, which effectively widens the usable range of low-frequency. Compared with the N.Nakat-corrected velocity recording method, the velocity recording corrected with the transfer function given in this paper is more accurate in terms of amplitude and waveform.
3-D P and S wave velocity and Poisson’s ratio structures and seismic activity in Shandong area
Fan Jianke, Ding Zhifeng, Guo Huili, Su Daolei, Zhang Bin
, Available online  , doi: 10.11939/jass.20210077
Shandong area is located in eastern China, where faults develop and earthquakes occur frequently. Therefore, high resolution velocity structure is quite necessary for better understanding causal mechanism of earthquakes. Based on abundant P and S wave arrival times recorded at stations in and around Shandong area, high resolution 3-D P wave velocity (vP), S wave velocity (vS) and Poisson’s ratio structures are obtained. The results reveal that, the hypocenter of the 2020 Changqing (M4.1) earthquake is located in the transition zone where seismic velocity and Poisson’s ratio change drastically in the horizontal direction. This suggests that the 2020 Changqing (M4.1) earthquake may be caused by the sinistral strike-slip movement of the Changqing fault affected by the regional stress field. Occurrence of the 2003 Laoshan (M4.1) earthquake and Laoshan, Rushan and Changdao earthquake swarms may be strongly affected by fluids. These fluids invaded along pre-existing faults or cracks in relatively intact rock bodies, and induced faults to act or cracks to break up, which caused the occurrence of middle and strong earthquakes and earthquake swarms.
The characteristics of subway stray current on geo-electrical resistivity observation
Wang Lanwei, Zhang Yu, Zhang Xingguo, Hu Zhe
, Available online  , doi: 10.11939/jass.20210197
The geo-electrical resistivity observation is one of the most important methods in the study of earthquake precursor, and the characteristics of the stray current during subway operation in the geo- resistivity observation are useful for analyzing the geoelectric observation data and the anomaly variation before earthquake. Based on the study on the generation mechanism, the quantitatively results of the influence of stray current on geo-electrical resistivity observation were given in this paper. The result shows that the effect distance can reach dozens or even to a hundred kilometers. Through monitoring the stray current in some geo-electrical resistivity observation stations around cities, such as Beijing Tongzhou station, Tianjin Qingguang, Baodi and Tanggu stations, Jiangsu Jiangning station and Liaoning Xinchengzi station, the amplitude and frequency range of the stray current signal as well as its spatial distribution characteristics were analyzed. It shows that the amplitude of the signal ranges from several to tens millivolt, and the period range is mainly from 50 s to 200 s. Due to the influence of stray current, the signal-to-noise ratio is decreased by 10 to 30 dB, and the accuracy of the observation data is more than 20 times worse than the specified requirement. According to the characteristics of the stray current propagation, several methods which can be used to suppress the signal were proposed in this paper, and it will provide a foundation for the identification of anomaly information from the observation data and anti-interference technology study.
Shallow velocity structure and seismogenic environment in the Zigui section of the Three Gorges Reservoir region of China
Hu Jintao, Xie Jun, Wei Zigen, Jin Chao
, Available online  , doi: 10.11939/jass.20210194
After the impoundment of the Three Gorges Reservoir in 2003, shallow earthquakes occurred frequently, which had a great impact on local productions and lives. The study of shallow velocity structure is of great significance for shallow seismic disaster assessment and disaster prevention and reduction in Zigui area. In this paper, based on the vertical component continuous waveform records of 24 mobile seismic stations in Zigui area from June to July of 2020, the empirical Green’s functions between stations are obtained by cross-correlating of the ambient seismic noise, the Rayleigh wave group velocity dispersion curves of 0.6−5 s are extracted, and the inversion for the three-dimensional S-wave velocity model is obtained within 6 km near the surface of the region. The results show that the S-wave velocity of Zigui basin and its south adjacent area is significantly lower than that of the eastern fault area, which is consistent with the structural evolution and sedimentary characteristics of different structural blocks in the studied area; an earthquake with MS4.2 occurred on the vertical high-velocity and low-velocity junction area of the study area in 2014. The S-wave velocity decreases obviously near the Yangtze River region in the fault zone, indicating that the Yangtze River water penetrates into the fault area. Therefore, the frequent occurrence of earthquakes in Zigui area is related to the water load and water infiltration of the Three Gorges reservoir.
Applicability of the Next Generation Attenuation-West2 ground-motion model to the components of near-fault velocity pulse-like ground motions
Zhao Xiaofen, Wen Zengping, Xie Junju, Xie Quancai
, Available online  , doi: 10.11939/jass.20210176
The traditional ground-motion models (GMMs) do not account for pulse effects and may therefore fail to estimate seismic hazards and risk at near-fault sites, where pulse-like ground motions are expected. Thus, the applicability of the newest generation NGA-West2 GMMs to the near-fault velocity pulse-like ground motions need to be tested. The near-fault strong ground motions are quantitatively identified by considering the uncertainty of pulse orientation and using wavelet method from recent earthquake since 2013 to form a new pulse database. Based on the new pulse database, long-period pulses are extracted from the original pulse records by using wavelet method. Based on a quantitative analysis of the epsilon parameter, we quantitatively test the applicability of the NGA-West2 ground-motion model to the near-fault velocity pulse-like ground motions. The results show that the four NGA-West2 models are more suitable for describing the residual recordings at the studied period, but underestimate the pulse original ground motions especially around the pulse period. We noted that, during the four NGA-West2 models, the applicability of the CB2018 to the residual ground motions is the best. This study provides an excellent opportunity to quantitatively evaluate the NGA-West2 GMMs and to update these models in the near future, and also provides a basis for incorporating pulse effects into near-fault probabilistic seismic hazard analysis and seismic design.