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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes/issues, but are citable by Digital Object Identifier (DOI).
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Discussion the interaction between hot spots and mid-ocean ridge from the axial morphology and the variation of subsidence rate on both sides of the Southwest Indian Ridge
Wang Hao, Tan Pingchuan, Ruan Aiguo
, Available online  , doi: 10.11939/jass.20220186
Based on high resolution seafloor bathymetry map, we divided the Southwest Indian Ridg(SWIR) (11.88°E—66.75°E) into six different regions. In each region, we estimate the variation of the morphology of the axis, and the basement subsidence curve over the flanks of the spreading ridge, which can be used to indicate the spreading process of the SWIR and how it was affected by the hot spot. The result shows that: ① For the entire SWIR, axial uplift accounts for 13.38%, axial rift accounts for 82.8%, and flat transitional shape accounts for 3.82%, areas at 19°E, 36°E, 41.2°E, 43.7°E, 50.4°E, 64.5°E have focus magmatic ridge representing axial ridge uplift; ② The area between the Eric Simpson-Indomed transition faults (39.4°E—45.77°E) shows axial valley with anomalous shallow bathymetry and asymmetrical anomalous low basement subsidence rates between north and south. Therefore, we believe that the area between the Eric Simpson-Indomed transition faults has been significantly affected by the hot spots. Compared to the subsidence rate north of the spreading ridge, the anomalous low subsidence rate in the south indicates that the interaction between the hot spots and the ridge is characterized by the hot spots flowing upward from the south of the SWIR to the bottom of the lithosphere, and then interact with the lithosphere.
Removing tilt noise from the vertical component data of ocean bottom seismograph:A case study on the data from the Pankun test in the South China Sea
Wu Yuechu, Yang Ting
, Available online  , doi: 10.11939/jass.20220163
Based on the correlations between the noise data of the horizontal and the vertical components, we can remove the tilt noise from the vertical component by using the transfer function of the horizontal-to-vertical component. Using the data from the 2019−2020 Pankun OBS South China Sea test, this paper describes the theory and process of this method. It compares the seismograms before and after removing the tilt noise and highlights the improvement of the dispersions of Rayleigh surface waves. The results show that removing tilt noise can improve the signal-to-noise ratio of seismograms for the OBs data in the low-frequency range, resulting in surface waves more conducive to imaging the deep structure of the oceanic lithosphere. This study also shows that although the tilt angle (1.0°) of the seismometer of Pankun OBS is much smaller than the tolerance of the tilt angle of the instrument (2.5°), the bottom currents still generate a significant level of tilt noise on OBS data. Therefore, the leveling system of the instrument is a crucial component affecting the OBS data quality.
Research progress on detection of carbon leakage by ocean bottom seismometer
Wei Yao, Niu Xiongwei, Yu Jiahui, Gong Wenfei, Dong Chongzhi, Wei Xiaodong, Ruan Aiguo
, Available online  , doi: 10.11939/jass.20220187
Marine carbon geological storage is an important strategy to slow the global warming. However, Marine carbon geological storage may pose a risk of carbon leakage, so it is necessary to monitor the carbon storage structure and seafloor carbon leakage. One of the effective monitoring means is ocean bottom seismometers (OBS) multi-wave component seismic detection. This paper presents an example of reservoir structures and fluids within the seafloor crust using OBS detection technology. The content mainly includes two-dimensional and three-dimensional array OBS experiments, and the methods include traveltime inversion, anisotropy analysis and microseismic methods. OBS multi-component seismic detection has the advantages of wide range, large depth, high signal-to-noise ratio, and large offset. However, there is still room to improve the resolution of reservoir and leakage models established by 2D and 3D OBS inspections. The observation accuracy can be improved by using a dense array, or a more reasonable array method can be used to obtain the best resolution. As the goal of carbon neutrality draws nearer, the need for carbon sequestration in countries is imminent. Therefore, it is particularly necessary to develop OBS seabed carbon leakage monitoring technology as soon as possible to ensure the implementation of carbon sequestration programs.
Short duration events on OBS recordings in the Northwest Sub-basin of the South China Sea
Wang Yizhi, Yang Ting, Liu chenguang, Liu Dan, Wu Yuechu
, Available online  , doi: 10.11939/jass.20220175
Based on the analysis of the data on broadband ocean bottom seismographs deployed in the Northwestern sub-basin of the South China Sea from October 2019 to May 2020. We detected more than 150 000 short duration events (SDEs) at each OBS station by using STA/LTA algorithm. The characteristic of SDE signals is analyzed. According to different signal characteristics, these SDEs are classified as consecutive short duration events (C-SDEs) and random short duration events (R-SDEs). The possible generation mechanisms for C-SDEs and R-SDEs are analyzed, respectively. We infer there are active sources of C-SDE signal in the Northwest Sub-basin of the SCS. The source may be caused by human activities, such as air gun firing or low frequency hydroacoustic communication signals. The R-SDE sources appear close to the OBS stations, likely generated by the ruptures due to gas escape from seafloor sediments. R-SDEs on OBS recordings indicate persistent gas escape from the sedimentary layer in the northwestern sub-basin of the SCS.
Anisotropic structure and dynamic implications of the upper mantle in the South China Sea
Xue Mei, Li Lin, Yang Ting, Liu Chenguang, Hua Qingfeng, Xia Shaohong, Huang Haibo, Le Ba Manh, Huo Da, Pan Mohan
, Available online  , doi: 10.11939/jass.20230054
The South China Sea (SCS) is located at the intersection of the Eurasian, Pacific, and India-Australia plates. It is the largest marginal sea in a series of marginal seas in the northwest Pacific Ocean. Many models have been proposed for the opening of the SCS, such as the extrusion model driven by the collision of the Indian Plate and the Eurasian Plate, and the slab pull model related to the subduction of the proto-SCS. This study aims to constrain the models of opening the SCS through the anisotropic structure of the central basin of the SCS and its surroundings. Based on the seismic data recorded by ten ocean bottom seismometers recovered from two passive seismic experiments conducted by Tongji University in the central basin of the SCS in 2012 and 2014, three different shear wave splitting methods are used to obtain the XKS splitting results of the central basin for two global earthquakes and the S phase splitting results provided by 20 regional earthquakes surrounding the SCS. The SKS splitting results demonstrate the presence of strong anisotropy with the NE fast direction in the central basin of the SCS, which may be related to mantle flow along the ocean ridge during seafloor expansion and the mantle flow dragged by the subduction of the proto SCS plate. Strong anisotropy is also observed in the upper mantle surrounding SCS, and the anisotropy observed in different azimuths is different. The fast directions obtained are consistent with previous SKS-splitting results, GPS, and plate motions, and importantly correspond well to the regional tectonics or mantle convection models. The anisotropic results are consistent with the expected results of the extrusion model driven by the collision of the Indian Eurasian plate and the slab pull of proto-SCS. The anisotropy results are inconsistent with the ideal upwelling driving model of the mantle plume. Unfortunately, due to the limited splitting observations in the central basin, the anisotropic results cannot confirm or falsify the "Atlantic-type" seafloor spreading model, the backarc spreading model, and the plate-edge rifting model. To verify the above models, further observations are needed.
The microseisms caused by Typhoon Hagupit and Typhoon Bavi
Sun Dongjun, Liu Fang, Wang Peng, Yu Haiying, Wang Chengrui
, Available online  , doi: 10.11939/jass.20220183
Typhoon-induced waves can usually enhance the microseisms energy, the generation mechanism and source locations of microseisms are controversial. We calculated the power spectral density and polarization analysis of the continuous waveform data of seven wide-band seismic stations on the coast or inland from July 1 to September 1, 2020. The variation of power spectral density in different frequency bands during typhoons has been quantitatively discussed, and the distribution of noise sources at SSE, DYS, HUH, TPS and QHS seismic stations were studied. The results show that the power spectral density of double-frequency microseisms significantly increased by Typhoon Hagupit and Typhoon Bavi, especially the long period double-frequency microseisms. The single frequency and microseisms with period ≥20 s increased inconspicuously. The short period double-frequency microseisms recorded at SSE, DYS, HUH, TPS, and QHS seismic stations are affected by different sources in the adjacent sea area. The sources of the long period double-frequency microseisms are consistent, pointing to the south-south-west direction, which may be affected by the source area of the South China Sea or further south. The single frequency microseisms are affected by different noise sources along the coastline.
Curie depth in Greenland area
Chu Wei, Xu Ya, Zhang Jian, Zhang Qianwen, Lu Shupeng, Hu Qixin
, Available online  , doi: 10.11939/jass.20220167
This paper estimates the Curie depth in Greenland area based on the global magnetic anomaly data by using the centroid method. For further analysis we introduce the latest heat flow data, crustal structure and ocean age, which helps to deepen the understanding of thermal structure in the studied area. When the magnetic body satisfies different distribution assumptions, the different theoretical formulas and correction factors for calculating the Curie depth are summarized. Among these distribution assumptions, we apply the fractal distribution assumption to the Greenland area. The result shows that the Curie depth ($ {h}_{{\rm{b}}} $) in the studied area is within 40 km, with an average depth of about 20 km and an estimation error of about 2.7 km. Based on $ {h}_{{\rm{b}}} $, we calculate the distance $ {h}_{{\rm{m}}} $ from topography to Curie depth and the distance $ {h}_{{\rm{c}}} $ from the top crystalline basement to Curie depth. Besides, we correct surface heat flow to obtain $ {Q}_{{\rm{s}}} $ according to different crustal types. We find that $ {Q}_{{\rm{s}}} $ is approximately inversely proportional to $ {h}_{{\rm{m}}} $, which proves that the result is reasonable. Further analysis shows that $ {h}_{{\rm{b}}} $ in the studied area is generally shallower than Moho depth, while in part of the northern Greenland, $ {h}_{{\rm{b}}} $ is deeper than Moho. In the ocean, $ {h}_{{\rm{c}}} $ increases with the age of the ocean crust.
Study on seismicity characteristics of fault zones in Fujian area based on automatic seismic detection method
Liu Fang, Sun Dongjun, Zhou Yijian, Zhu Ailan, Wei Wei, Piao Jian
, Available online  , doi: 10.11939/jass.20220188
Driven by the tectonic loading of Taiwan and Taiwan Strait, there are several large Quaternary fracture zones in the Fujian area, with strong historical and current seismicity. We build a comprehensive seismic catalog with a new automatic workflow called PALM (phase picking, association, location, matched filter), which combines STA/LTA and matched filter. PALM is applied to 10 month’s continuous data starting from 2015 in 88 stations from the Fujian Earthquake Agency. We recognized 919 template events and finally relocated 2 243 events after matching filter, among which 1 991 events with magnitude greater than ML1.0, and greatly expanded the catalog from Fujian Earthquake Agency in the range of ML1.0−1.5. The depth of relocated earthquake events are distributed between 0 and 20 km, with most of them occurred within 10 km. The seismicity is concentrated along Changle−Zhao’an fault and Yong’an−Jinjiang fault and showed obvious segmental activity. We detected more earthquakes than catalog from Fujian Earthquake Agency and the seismicity was stronger in the southwest section and weaker in the northeast section. The depth distribution along the fault zone became shallower from south to north, which was consistent with the change of Moho depth. Besides, we can see a highly clustered feature of seismicity at northwest section and slightly dispersed at southeast segment in Yong’an−Jinjiang fault, which forms a conjugate shape with Changle−Zhao’an fault. The repicked and relocated events in Fujian area was consistent with the characteristics of crust horizontal deformation, which was stronger in southern and eastern while weaker in northern and western.
Geodynamical simulation of the effects of ridge subduction on the scale of the seismogenic zone south of Chile Triple Junction
Guo Changsheng, Sun Pengchao, Wei Dongping
, Available online  , doi: 10.11939/jass.20210192
Earthquakes are much more frequent to the north of Chile Triple Junction than to the south, where the thermal anomaly is also more significant. To study the effects of ridge subduction on the thermally defined seismogenic zone, two-dimensional finite element models were established based on the geology of Chile Triple Junction, the process of ridge subduction was simulated, and the effects of the initial slab dip and the convergence rate on the seismogenic zone were compared. The results show that the width of the seismogenic zone decreases during the ridge subduction, inducing earthquakes to occur much less to the south than to the north of Chile Triple Junction. By comparing the observed data in the vicinity of the profiles with the numerical simulation results, we find that the numerical simulation can roughly reflect the width of the interplate seismogenic zone and the surface heat flow in the area of Chile Triple Junction. At the same convergence distance, a larger convergence rate comes with a wider seismogenic zone and the deeper the downdip limit of the seismogenic zone, the higher the surface heat flow in the vicinity of the trench. Compared with the convergence rate, factors such as slab dip have little effect on the surface heat flow. In the process of ridge subduction, larger the slab dips leads to narrower seismogenic zones. When the effect of shear heating is included in the simulation, the width of the seismogenic zone in the process of ridge subduction can shrink to about 15 km and the depth of the seismogenic zone is small. Such a narrow and shallow seismogenic zone makes it hard for earthquakes to occur and for the Wadati-Benioff plane to be observed in some areas south of Chile Triple Junction.
Seismic monitoring of typhoons based on seismology
Zhu Xinhui, Fang Sunke, Lin Jianmin
, Available online  , doi: 10.11939/jass.20220191
Typhoons are one of the most destructive meteorological disasters all over the world. However, because of the lack of in situ observations under such extreme weather conditions during the typhoon’s passage, typhoon monitoring and forecasting are still not able to meet the needs of typhoon prevention and mitigation. In recent years, a new method of typhoon monitoring based on seismological observations and techniques has emerged and developed, utilizing typhoon-generated seismic noise as a proxy. This paper reviews the recent progress in study of typhoon-induced microseisms, including the generation mechanisms, source location distribution, and its potential implications on typhoon monitoring and ocean wave parameter inversion. Future prospects on seismic monitoring of typhoons are provided and discussed. This newly emerging method may provide interdisciplinary support to traditional observation and investigation of typhoons.
Relative motions for cross-fault sites of the 1999 MW7.6 Taiwan Chi-Chi earthquake
Xu Longjun, Lü Miao, Zhang Heng, Yu Yue, Xie Lili
, Available online  , doi: 10.11939/jass.20220170
Based on the strong motion data of the 1999 MW7.6 Chi-Chi (Jiji) earthquake in Taiwan region, the relative motion time histories of sites across the fault are studied. In order to obtain accurate residual displacement of near-field ground motion, a base-line correction method using variable step-size grid search is proposed. Through the correction of the initial time of the ground motion history, relative motion histories between the hanging-wall and footwall stations of the Chi-Chi earthquake are obtained. The results show that the fling-step effect of the ground motion is significant, the average slip velocity of the fault plan can be as high as 1.4 m/s; the relative motion between the fault plans is similar to the motion characteristics of the fault ground motions, while the amplitudes are even larger; the residual displacements of the fault are about 80% of the maximum inter-plan relative displacement.
DING Lisha, XIE Jianbo, WU Huadeng, LIAO Yifan, YE Shishan, LU Zijin, MA Jiemei, LV Zhonghang
, Available online  , doi: 10.11939/jass.20220146
Observation exploits the spectral statistical characteristics of strong motion ambient noise through acceleration RMS density function, for estimating the quality of records from and status of the real-time strong motion station. Since then, the monitoring capability analysis method of the strong seismic station has been outlined, which is the acceleration RMS average model, the minimum mode and the probability interval of ambient noise of a strong-motion station are compared with the frequency-amplitude lines, which estimated from the regional earthquake events with epicenteral distance of 70~150 km from each station and magnitudes range from M7.0 down to M2.0. This procedure not only shows the dynamic performance of the strong motion station, but also demonstrates the monitoring quality directly. Through this method, we get : The monitoring capability analysis method can be used to estimate the probability of the different magnitude regional seismic events recorded by strong motion station, so as to evaluate the monitoring capability of station. Affected by the environmental noise of the station, each station can clearly observe different earthquake magnitudes from the others. And the different lower limits of noise recorded by different stations is due to the interaction of instrument self-noise of accelerometers and environmental noise. The acceleration RMS minimum model of strong motion station can be used as the estimation of optimal monitoring capability of the station and is a comprehensive index of self noise of the accelerometer and noise of the observation environment. The data from the Pearl River Delta Early Warning Network in Guangdong, China.
New progress in seismic oceanography
Song Haibin
, Available online  , doi: 10.11939/jass.20230014
Ocean multi-scale dynamic processes are the focus of current oceanography research. Seismic oceanography can obtain high-quality data with a resolution of 10 m on hundreds of km section, so it can analyze the sub-mesoscale dynamic phenomenon at the edge of an eddy (such as the beautiful spiral arm found in the Arctic Ocean seismic section study) and the vertical amplitude structure of the internal solitary waves, and can combine the internal solitary wave waveform change with the mixing parameter distribution. This paper reviews the new insights and advances of these studies. At the same time, the common offset section prestack migration method makes full use of the multiple coverage characteristics of multi-channel seismic method to obtain the temporal variation of seismic images, thus adding a key tool to seismic oceanography for revealing the spatio-temporal evolution of the ocean internal structure. Therefore, the new space-time perspective provided by seismic oceanography will play an important role in the study of ocean multi-scale dynamic processes.
Strong ground motion simulation for the 2014 MW6.1 Ludian,Yunnan earthquake
Liu Yijun, Li Xiaojun, Zhao Xiaofen, Xu Chao, Wen Zengping
, Available online  , doi: 10.11939/jass.20220216
Considering the complex source rupture process from Zhang Yong (2015), the hybrid broadband simulation method was applied to synthesize the ground motions for the Ludian earthquake based on kinematic source model. The simulation results of representative sites were compared with the observed strong motion recordings, and impacts from three different source rupture models on strong ground motions were analyzed. The results show that for moderate earthquakes with limited fault dimension, the differences of strong ground motion characteristics among different source rupture models with the similar seismic moment are not obvious in the far fields, but are distinct in the near-fields. In addition, the distributions of intensity measurements of ground motions are given, and it is found that source rupture model plays an important role in the spatial distribution pattern of strong ground motions and strong ground motion characteristics. Therefore, the elaborate source rupture models are very important to estimate the strong ground motion characteristics and seismic hazard analysis in the near field.
Ocean bottom seismograph orientation and crustal structure of the Woodlark Rift
Gao Jia, Yu Youqiang
, Available online  , doi: 10.11939/jass.20220091
The Woodlark Rift in southeastern Papua New Guinea is a young continental rift and develops within the collision zone between the Australian and SW Pacific Plates, which offers an ideal location to explore the crustal structure beneath the incipient rift under a convergent setting. However, the sea water layer makes it difficult to collect high-quality seismic data, and the common step is to deploy the ocean bottom seismographs (OBSs) in a free-fall way. Therefore, mis-orientation of horizontal components of the OBS usually leads to failure of applying the inversion techniques such as the receiver function to the three-component waveforms. In this study, we employed both P-wave and Rayleigh-wave polarization analyses to determine all available OBS orientations, and then used the recorded teleseismic waveforms to conduct a receiver function study on the crustal structure beneath the Woodlark rift. The number of the receiver function traces has greatly increased after the orientation corrections and the crustal structures can be better constrained based on the results from P-wave polarization analysis. Contrasting crustal structures were revealed beneath the Kiribishi Basin and the Goodenough Basin where the rift axis is located. The crust beneath the Goodenough Basin is deciphered to thin towards the rift axis with an average of (33.3±2.42) km, while a much thinner crust is observed beneath the Kiribisi Basin with a mean value of (24.1±5.44) km. High vP/vS ratios were determined at all stations, which may be attributed to the Papuan ultramafic body and dehydration melting of subducted slab segments.
Time problems of recorded data in artificial source ocean bottom seismometer exploration and cause analyses
Bai Kunlin, Fan Chaoyan, Wan Kuiyuan, Zhang Chenglong, Xia Shaohong
, Available online  , doi: 10.11939/jass.20220206
Artificial source seismic exploration based on ocean bottom seismometer (OBS) is one of the most effective methods to study the structure of crust and mantle, the seismogenic structure and the submarine mineral resources. In modeling velocity structure, the precise time measurements of recorded data by OBS are the key to ensure the reliability of velocity structure. However, in practical work, OBS placed at the seafloor directly, which is unable to acquire accurate time with the satellite navigation system in time, leads to time error of the recorded data, and its oscillation frequency of the quartz is easily affected by temperature, pressure, instrument properties, etc. Therefore, it is necessary to analyze the reasons of clock errors in the process of data processing, to obtain the exact time. The common time errors in Chinese artificial source OBSs data processing were briefly summarized in this study, focusing on the processing of profile OBS2020-1 and combining the other previous correction examples. OBS time problems were classified and corrected, through checking the data record format, calculating the time error between the adjacent data files, comparing the difference of profiles obtained by different processing methods, analyzing whether the initial time and sampling time are abnormal, using resample and other methods. The analysis shows that most of the time error commonly existing in the data records of Chinese OBS can be solved, and the method provided in this paper can avoid “stair” , “incline” , even “missing” of the events in OBS seismic profiles caused by improper handling. It ensures the integrity of the effective seismic phase, and effectively solves the problem of time error of OBS data to improve the quality and utilization of data. This study establishes a good foundation for traveltime tomography, and provides a reference for the processing process and methods of artificial source OBS in the future.
Discussion on the magnitude overestimation of the 1920 Haiyuan earthquake
Liu Jing, Xu Jing, Ou Qi, Han Longfei, Wang Zijun, Shao Zhigang, Zhang Peizhen, Yao Wenqian, Wang Peng
, Available online  , doi: 10.11939/jass.20220051
The great 1920 Haiyuan earthquake, resulting in tremendous casualties, ranks as one of the largest and most devastating earthquakes in China. This significant event marks the start of investigating earthquakes through modern scientific approaches in China. Recent studies show that the moment magnitude of the 1920 Haiyuan earthquake is MW7.9±0.2, prominently smaller than the widely known and often cited magnitude M81/2. This paper reviews the re-calibration and conversion of different magnitude types in the early developing phase of seismometers and analogue seismographs. Similar to the 1920 Haiyuan earthquake, the magnitude of many large shallow earthquakes that occurred in this period are systematically over-estimated due to factors such as developing technology, sparse instrumentation and data, and diverse calibration functions. The moment magnitude, linked to physical parameters of earthquake rupture, is the best magnitude scale. For magnitude is the most commonly used parameter in describing an earthquake’s size and energy and is an essential factor in seismic hazard assessment, bias and errors in magnitude conversion have significant consequences in understanding the spatio-temporal pattern of historical seismicity and the reliability of various products of seismic potential and hazard evaluation. We thus advocate citing revised moment magnitude MW7.9 for the 1920 Haiyuan earthquake in future studies and re-evaluating the magnitude of historical earthquakes in general. With a revised magnitude, the 1920 Haiyuan earthquake is similar in size to the 2008 Wenchuan earthquake (MW7.9, MS8.0) and the 2001 Kunlun earthquake (MW7.8, MS8.1).
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.
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.