The left-lateral Altyn Tagh Fault(ATF) system is the northern boundary of the Qinghai-Xizang Plateau, separating the Tarim Basin and the Qaidam Basin. The middle section of ATF has not recorded any large earthquakes s...The left-lateral Altyn Tagh Fault(ATF) system is the northern boundary of the Qinghai-Xizang Plateau, separating the Tarim Basin and the Qaidam Basin. The middle section of ATF has not recorded any large earthquakes since1598 AD, so the potential seismic hazard is unclear. We develope an earthquake catalog using continuous waveform data recorded by the Tarim-Altyn-Qaidam dense nodal seismic array from September 17 to November23, 2021 in the middle section of ATF. With the machine learning-based picker, phase association, location, match and locate workflow, we detecte 233 earthquakes with M_L-1–3, far more than 6 earthquakes in the routine catalog. Combining with focal mechanism solutions and the local fault structure, we find that seismic events are clustered along the ATF with strike-slip focal mechanisms and on the southern secondary faults with thrusting focal mechanisms. This overall seismic activity in the middle section of the ATF might be due to the northeastward transpressional motion of the Qinghai-Xizang Plateau block at the western margin of the Qaidam Basin.展开更多
A profile of shallow crustal velocity structure(1–2 km) may greatly enhance interpretation of the sedimentary environment and shallow tectonic deformation.Recent advances in surface wave tomography, using ambient noi...A profile of shallow crustal velocity structure(1–2 km) may greatly enhance interpretation of the sedimentary environment and shallow tectonic deformation.Recent advances in surface wave tomography, using ambient noise data recorded with high-density seismic arrays, have improved the understanding of regional crustal structure. As the interest in detailed shallow crustal structure imaging has increased, dense seismic array methods have become increasingly efficient. This study used a high-density seismic array deployed in the Xinjiang basin in southeastern China, to record seismic data, which was then processed with the ambient noise tomography method. The high-density seismic array contained 203 short-period seismometers, spaced at short intervals(～ 400 m). The array collected continuous records of ambient noise for 32 days. Data preprocessing,cross correlation calculation, and Rayleigh surface wave phase-velocity dispersion curve extraction, yielded more than 16,000 Rayleigh surface wave phase-velocity dispersion curves, which were then analyzed using the direct-inversion method. Checkerboard tests indicate that the shear wave velocity is recovered in the study area, at depths of 0–1.4 km,with a lateral image resolution of ～ 400 m. Model test results show that the seismic array effectively images a 50 m thick slab at a depth of 0–300 m, a 150 m thick anomalous body at a depth of 300–600 m, and a 400 m thick anomalous body at a depth of 0.6–1.4 km. The shear wave velocity profile reveals features very similar to those detected by a deep seismic reflection profile across the study area. This demonstrates that analysis of shallow crustal velocity structure provides high-resolution imaging of crustal features.Thus, ambient noise tomography with a high-density seismic array may play an important role in imaging shallow crustal structure.展开更多
With the development of unconventional shale gas in the southern Sichuan Basin,seismicity in the region has increased significantly in recent years.Though the existing sparse regional seismic stations can capture most...With the development of unconventional shale gas in the southern Sichuan Basin,seismicity in the region has increased significantly in recent years.Though the existing sparse regional seismic stations can capture most earthquakes with ML≥2.5,a great number of smaller earthquakes are often omitted due to limited detection capacity.With the advent of portable seismic nodes,many dense arrays for monitoring seismicity in the unconventional oil and gas fields have been deployed,and the magnitudes of those earthquakes are key to understand the local fault reactivation and seismic potentials.However,the current national standard for determining the local magnitudes was not specifically designed for monitoring stations in close proximity,utilizing a calibration function with a minimal resolution of 5 km in the epicentral distance.That is,the current national standard tends to overestimate the local magnitudes for stations within short epicentral distances,and can result in discrepancies for dense arrays.In this study,we propose a new local magnitude formula which corrects the overestimated magnitudes for shorter distances,yielding accurate event magnitudes for small earthquakes in the Changning-Zhaotong shale gas field in the southern Sichuan Basin,monitored by dense seismic arrays in close proximity.The formula is used to determine the local magnitudes of 7,500 events monitored by a two-phased dense array with several hundred 5 Hz 3 C nodes deployed from the end of February 2019 to early May 2019 in the Changning-Zhaotong shale gas field.The magnitude of completeness(MC)using the dense array is-0.1,compared to MC 1.1 by the sparser Chinese Seismic Network(CSN).In addition,using a machine learning detection and picking procedure,we successfully identify and process some 14,000 earthquakes from the continuous waveforms,a ten-fold increase over the catalog recorded by CSN for the same period,and the MC is further reduced to-0.3 from-0.1 compared to the catalog obtained via manual processing using the same dense array.The proposed local magnitude formula can be adopted for calculating accurate local magnitudes of future earthquakes using dense arrays in the shale gas fields of the Sichuan Basin.This will help to better characterize the local seismic risks and potentials.展开更多
A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaoj...A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaojiang Fault Zone(n-XJFZ).Meanwhile,the stress field of the n-XJFZ was determined by inverting 140 focal mechanism solutions of the small earthquakes within the study area which were recorded in the same period.This determination confirmed a compressive stress in NW-SE orientation and an extensional stress in the NE-SW orientation,with little difference from those released by previous studies.The shear-wave splitting results show a spatial complexity in polarization orientation,different from one site to another.How-ever,the polarization orientations integrated for the subareas suggest that the fault trends seemingly played important roles.All the subareas bear two dominant orientations,N10°E and N90°E,both of which are different from the azimuths of the principal compressive stress,due to the fault distribution.The time delay averaged over the entire region is 4.56 ms/km,close to that of the upper boundary of the generally accepted interval worldwide but larger than those in most of the investigated regions in the Chinese mainland,which probably implies an alignment of more micro-cracks in the n-XJFZ.Interestingly,the 2014 Ms6.5 Ludian earthquake was found to have caused a variation in the time delays of the slow shear waves within the study area though its epicenter was outside.This earthquake resulted in an evident drop of the time delays remaining for 4 months,however,lifted a bit the time-delay level with respect to that prior to the earthquake.展开更多
In this paper, we consider the analysis, implementation, and application of wideband sources using both seismic and acoustic sensors. We use the approximate maximum likelihood (AML) algorithm to perform acoustic direc...In this paper, we consider the analysis, implementation, and application of wideband sources using both seismic and acoustic sensors. We use the approximate maximum likelihood (AML) algorithm to perform acoustic direction of arrival (DOA). For non-uniform noise spectra, whitening filtering was applied to the received acoustic signals before the AML operation. For short-range seismic DOA applications, one method was based on eigen-decomposition of the covariance matrix and a second method was based on surface wave analysis. Two well-known optimization schemes were used to estimate the source locations from the estimated DOAs at sensors of known locations. Experimental estimation of the DOAs and resulting localizations using the acoustic and seismic signals generated by striking a heavy metal plate by a hammer were reported.展开更多
By using the waveform data recorded during the site survey of Lanzhou Seismic Array, the author calculated and analyzed the correlation of the signal and noise between the site pairs and found that the ideal radii of ...By using the waveform data recorded during the site survey of Lanzhou Seismic Array, the author calculated and analyzed the correlation of the signal and noise between the site pairs and found that the ideal radii of the two concentric rings for Lanzhou Seismic Array were 380 m and 1500 m, respectively. According to the radius limit and other requirements, nine sites were chosen to make a seismic array, and then the detection and location ability of the array were estimated.展开更多
Automatic phase picking is a critical procedure for seismic data processing, especially for a huge amount of seismic data recorded by a large-scale portable seismic array. In this study is presented a new method used ...Automatic phase picking is a critical procedure for seismic data processing, especially for a huge amount of seismic data recorded by a large-scale portable seismic array. In this study is presented a new method used for automatic accurate onset phase picking based on the proporty of dense seismic array observations. In our method, the Akaike＇s information criterion （AIC） for the single channel observation and the least-squares cross-correlation for the multi-channel observation are combined together. The tests by the seismic array observation data after triggering with the short-term average/long-term average （STA/LTA） technique show that the phase picking error is less than 0.3 s for local events by using the single channel AIC algorithm. In terms of multi-channel least-squares cross-correlation technique, the clear teleseismic P onset can be detected reliably. Even for the teleseismic records with high noise level, our algorithm is also able to effectually avoid manual misdetections.展开更多
The waveform data recorded during the site survey of the Naqu seismic array in Aug. 2004 were processed by the author. According to the relativity of site pairs in time and frequency domains, the reference values of t...The waveform data recorded during the site survey of the Naqu seismic array in Aug. 2004 were processed by the author. According to the relativity of site pairs in time and frequency domains, the reference values of the inner ring and outer ring were determined. The author evaluated the array deployed for site survey as the primary array, and the results show that the resolution of the primary array is high enough to locate earthquakes precisely.展开更多
The paper proposes the calibration theory and methods for the Shanghai seismic array and analyzes the calibration results. As a result, the calibration results for the seismic array based on 2 typical earthquakes have...The paper proposes the calibration theory and methods for the Shanghai seismic array and analyzes the calibration results. As a result, the calibration results for the seismic array based on 2 typical earthquakes have been drawn; the difference of calibration results between Hokkaido and Honshu region in Japan is investigated. And calibration results of different directions, different epicenter distances and different magnitudes are probed into. The result shows that the location of earthquakes on the Shanghai seismic array is greatly improved.展开更多
The Mesozoic tectonic framework of the eastern South China is mainly controlled by subduction,turning toward,and rollback of the Pacific Plate.Recent studies of receiver function imaging and ambient noise tomography h...The Mesozoic tectonic framework of the eastern South China is mainly controlled by subduction,turning toward,and rollback of the Pacific Plate.Recent studies of receiver function imaging and ambient noise tomography have revealed the“Yshaped”thinnest crustal belt in the eastern South China under the overall extension of the lithosphere.However,the deep dynamic environment and formation mechanisms of the thin crustal belt remain debatable.Here we obtained high-resolution images of the crustal thickness and Poisson’s ratio in the eastern South China Block applying the recently proposed H-κ-c receiver function method,using data recorded by 305 dense portable broadband stations and 219 permanent stations surrounding.Additionally,we discussed the deep dynamic formation mechanism of the“Y-shaped”thinnest crustal belt coupled with two common conversion point stacked images at key locations.Results show that the average crustal thickness of the study area is 33 km(thin crust)and the average Poisson’s ratio is 0.24(low ratio).The overall crustal thinning toward the continental margin is likely because eastern South China was in a back-arc extension environment,which was induced by the rollback of the subducted plate in the Early Cretaceous.The crustal thickness of the“Y-shaped”thinnest crustal belt is<30 km,which is 3-5 km thinner than that outside the zone.The eastern branch is distributed along the trajectory of Nanchang-Ji’an-Ganzhou-Shaoguan-Guangzhou,and the western branch is around the Jianghan-Xiangzhong Basin,both of which intersect in Nanling.The eastern branch of the thin crustal zone indicates the potential location of the Pacific subduction slab breakoff,and the formation mechanism may be related to the interaction of deep-shallow processes,including the upwelling of mantle heat flow through the slab window and transtensional pre-existing faults.We developed a dynamic model that combines subduction-breakoff-rollback processes of the Paleo-Pacific Plate and accompanying deep fluid upwelling to explain the regional extension of the South China lithosphere,the formation mechanism of the thinnest crustal belt,and the distribution of granitic plutons.展开更多
Geological studies show that the southern part of Ailaoshan-Red River shear zone(ALSRRSZ)has experienced complex metallogenic processes and multi-stage non-uniform uplifting,called oblique uplifting since the Cenozoic...Geological studies show that the southern part of Ailaoshan-Red River shear zone(ALSRRSZ)has experienced complex metallogenic processes and multi-stage non-uniform uplifting,called oblique uplifting since the Cenozoic.To detect the deep structure and geodynamic background beneath Daping,Chang’an and other gold and polymetallic deposits in this area,we carried out a high-density short-period seismic array survey in southern Yunnan province.The array used is approximately240 km long with an interval of 500 m between two adjacent stations.Based on the data collected by the array,we used H-κstacking and common conversion point(CCP)methods of receiver functions to reveal the fine crustal structure beneath this array,which was located from Lvchun(western end)to the east and ended in Maguan.The three main conclusions are as follows.(1)The average crustal thickness is approximately 37 km and the Vp/Vsratio is 1.75.However,the thickness and Vp/Vsratio of the Ailao Mountain are rather greater or higher than those of the western Lanping-Simao Basin and eastern South-China block.These results may indicate that the crust is rich in ferromagnesian minerals or has a thermal fluid anomaly after orogenic movement.(2)There are two obvious inclined interfaces beneath the Ailao Mountain in the mid-upper crust,which suggests that strong deformation occurred there during the orogenic period.Some evidences,such as the weak converted-wave Pms phase from the Moho,low P-wave velocities of the upper mantle,high surface heat flow values,and generally developed hot springs,indicate that a strong crust-mantle interaction exists in the southern segments of the Ailaoshan-Red River shear zone.These interactions include a diapir of mantle-sourced magma(stronger in the east than that in the west),lateral collision from the Indian Plate,and the differential uplift caused by the strike-slip movement of the Red River Fault.All of above deep processes led to the Cenozoic oblique uplifting of Ailao Mountain.(3)By combining the location of the deposits on the surface,characteristics of the average crustal Vp/Vsratio,hypocenters of the small earthquakes along the research profile,Moho shape,and horizontal variations of the Pms phase amplitudes,we speculate that the Ailaoshan Fault was the upgoing conduit for metallogenic magma and played a significant role in the Cenozoic development of the multiform metal deposits around the Ailao Mountain area.展开更多
This article gives a description of our first study on ground rotational motion and its pre-liminary results. The ground rotational motions around vertical axis were obtained using near-field translational records of ...This article gives a description of our first study on ground rotational motion and its pre-liminary results. The ground rotational motions around vertical axis were obtained using near-field translational records of a temporal seismic array with observational distances of 1.8 to 2.7 km. The sources used are explosions with explosive of 500 kg for each. Ground rotational velocities were calcu-lated using the space derivatives of the horizontal components of translational velocities from the array. The peak ground rotational velocities （PGRV） are approximately 30 to 57 ？rad/s. Our results are very close to those from Wassermann et al. （2009）, who used both a seismic array and a rotational sensor to record an explosion in Germany and obtained PGRV values of about 50 ？rad/s. Their explosives are 150 kg, only one third of ours, but their observational distance is 250 m, much less than ours.展开更多
The special seismic tectonic environment and frequent seismicity in the southeastern margin of the Qinghai-Tibet Plateau show that this area is an ideal location to study the present tectonic movement and background o...The special seismic tectonic environment and frequent seismicity in the southeastern margin of the Qinghai-Tibet Plateau show that this area is an ideal location to study the present tectonic movement and background of strong earthquakes in China's Mainland and to predict future strong earthquake risk zones. Studies of the structural environment and physical characteristics of the deep structure in this area are helpful to explore deep dynamic effects and deformation field characteristics, to strengthen our understanding of the roles of anisotropy and tectonic deformation and to study the deep tectonic background of the seismic origin of the block＇s interior. In this paper, the three-dimensional （3D） P-wave velocity structure of the crust and upper mantle under the southeastern margin of the Qinghai-Tibet Plateau is obtained via observational data from 224 permanent seismic stations in the regional digital seismic network of Yunnan and Sichuan Provinces and from 356 mobile China seismic arrays in the southern section of the north-south seismic belt using a joint inversion method of the regional earthquake and teleseismic data. The results indicate that the spatial distribution of the P-wave velocity anomalies in the shallow upper crust is closely related to the surface geological structure, terrain and lithology. Baoxing and Kangding, with their basic volcanic rocks and volcanic clastic rocks, present obvious high-velocity anomalies. The Chengdu Basin shows low-velocity anomalies associated with the Quaternary sediments. The Xichang Mesozoic Basin and the Butuo Basin are characterised by low- velocity anomalies related to very thick sedimentary layers. The upper and middle crust beneath the Chuan-Dian and Songpan-Ganzi Blocks has apparent lateral heterogeneities, including low-velocity zones of different sizes. There is a large range of low-velocity layers in the Songpan-Ganzi Block and the sub-block northwest of Sichuan Province, showing that the middle and lower crust is relatively weak. The Sichuan Basin, which is located in the western margin of the Yangtze platform, shows high-velocity characteristics. The results also reveal that there are continuous low-velocity layer distributions in the middle and lower crust of the Daliangshan Block and that the distribution direction of the low-velocity anomaly is nearly SN, which is consistent with the trend of the Daliangshan fault. The existence of the low-velocity layer in the crust also provides a deep source for the deep dynamic deformation and seismic activity of the Daliangshan Block and its boundary faults. The results of the 3D P-wave velocity structure show that an anomalous distribution of high-density, strong-magnetic and high-wave velocity exists inside the crust in the Panxi region. This is likely related to late Paleozoic mantle plume activity that led to a large number of mafic and ultra-mafic intrusions into the crust. In the crustal doming process, the massive intrusion of mantle-derived material enhanced the mechanical strength of the crustal medium. The P-wave velocity structure also revealed that the upper mantle contains a low-velocity layer at a depth of 80-120 km in the Panxi region. The existence of deep faults in the Panxi region, which provide conditions for transporting mantle thermal material into the crust, is the deep tectonic background for the area＇s strong earthquake activity.展开更多
The Xiaojiang faults,striking north-tosouth(NS),and the Honghe faults,striking north-to-west(NW),are first-order block boundaries that intersect to form a concentrated stress zone at an acute angle in the southern par...The Xiaojiang faults,striking north-tosouth(NS),and the Honghe faults,striking north-to-west(NW),are first-order block boundaries that intersect to form a concentrated stress zone at an acute angle in the southern part of the Sichuan-Yunnan rhombic block(SYB).It is also a crucial zone for material escaping from the Tibetan Plateau(TP)due to the collision between the Indian Plate and the Eurasian Plate.In December 2017,the Institute of Earthquake Forecasting of the China Earthquake Administration(CEA)deployed a linear temporary seismic broadband array,the Honghe-Xiaojiang temporary Seismic Array(HX Array),across first-order block boundaries in the southern SYB.By using the waveform data of small earthquakes recorded by stations in the HX Array across Xiaojiang faults from 2017 to 2019,and by permanent seismic stations of the China National Earthquake Networks from 2012 to 2019,this paper adopts the systematic analysis method of shear-wave splitting(SWS),SAM method,to obtain preliminary results for seismic anisotropy in the upper crust.The study area can be divided into two subzones according to the spatial distribution of the directions of polarization of the fast shear-wave(PFS)at the stations:the northern zone(zone A,where the HX Array is located)and the southern zone(zone B,to the south of the HX Array).The results show that the directions of the PFS at stations in zone A were highly consistent,dominant in the NE direction,correlated with the in-situ principal compressive stress,and were seemingly unaffected by the Xiaojiang faults.The directions of the PFS as recorded at stations in zone B were more complicated,and were dominant in the NS direction parallel to that of the regional principal compressive stress.This suggests the joint influence of complex tectonics and regional stress in this narrow wedge area.By referring to the azimuthal anisotropy derived from seismic ambient noise in the southeast margin of the TP,the NS direction of the PFS in the middle and lower crust,and its EW direction in the upper mantle,this paper concludes that azimuthal anisotropy in the upper crust differed from that in the lower crust in the south segment of Xiaojiang faults,at least beneath the observation area,and azimuthal anisotropy in the crust was different from that in the upper mantle.The results support the pattern of deformation of ductile flow in the lower crust,and the decoupling between the upper and lower crusts as well as that between the crust and the mantle in the study area.The crustal directions of the PFS appeared to be independent of the Xiaojiang faults,suggesting that the influence of the South China block on the SYB passed through the Xiaojiang faults to the Yimen region.The results of this study indicate that anisotropic studies based on data on the dense temporary seismic array can yield clearer tectonic information,and reveal the complex spatial distribution of stress and deformation in the upper crust of the south segment of Xiaojiang faults.展开更多
Waveforms generated by the 50t explosion of project Brightlight （ I ） were recorded by HILR array. Using array techniques, the author performed identification, f-k analysis, velocity spectrum analysis, etc. of the w...Waveforms generated by the 50t explosion of project Brightlight （ I ） were recorded by HILR array. Using array techniques, the author performed identification, f-k analysis, velocity spectrum analysis, etc. of the weak signals. The analysis results show that the signal-to-noise ratio after beamforming was obviously enhanced, and the signal could be clearly shown. The energy from this explosion was mainly concentrated in the 1 -8Hz range from f-k analysis. The velocity spectrum gave clear positions of event phases, which could not be seen in the original weak signals. The maximum energy distribution obtained by the Beaman method is close to the theoretical value in the azimuth-slowness domain.展开更多
Using the arrival times of 197 earthquakes well recorded by the Beijing Seismic Network and the China-Germany cooperative Yanqing Digital Seismic Array in the period from October of 2001 to December of 2005, we accura...Using the arrival times of 197 earthquakes well recorded by the Beijing Seismic Network and the China-Germany cooperative Yanqing Digital Seismic Array in the period from October of 2001 to December of 2005, we accurately relocate these earthquakes by the joint-inversion program for hypocentral position and 3-D velocity structure The distribution of hypocenters shows that there are two major seismic active belts in the northwestern Beijing. The first belt stretches from Qinghe, Wenquan to the NW direction and the second extends from Nankou, Changping to the ENE direction.展开更多
A rapidly deployable dense seismic monitoring system which is capable of transmitting acquired data in real time and analyzing data automatically is crucial in seismic hazard mitigation after a major earthquake.Howeve...A rapidly deployable dense seismic monitoring system which is capable of transmitting acquired data in real time and analyzing data automatically is crucial in seismic hazard mitigation after a major earthquake.However,it is rather difficult for current seismic nodal stations to transmit data in real time for an extended period of time,and it usually takes a great amount of time to process the acquired data manually.To monitor earthquakes in real time flexibly,we develop a mobile integrated seismic monitoring system consisting of newly developed nodal units with 4G telemetry and a real-time AI-assisted automatic data processing workflow.The integrated system is convenient for deployment and has been successfully applied in monitoring the aftershocks of the Yangbi M_(S) 6.4 earthquake occurred on May 21,2021 in Yangbi County,Dali,Yunnan in southwest China.The acquired seismic data are transmitted almost in real time through the 4G cellular network,and then processed automat-ically for event detection,positioning,magnitude calculation and source mechanism inversion.From tens of seconds to a couple of minutes at most,the final seismic attributes can be presented remotely to the end users through the integrated system.From May 27 to June 17,the real-time system has detected and located 7905 aftershocks in the Yangbi area before the internal batteries exhausted,far more than the catalog provided by China Earthquake Networks Center using the regional permanent stations.The initial application of this inte-grated real-time monitoring system is promising,and we anticipate the advent of a new era for Real-time Intelligent Array Seismology(RIAS),for better monitoring and understanding the subsurface dynamic pro-cesses caused by Earth's internal forces as well as anthropogenic activities.展开更多
The seismic waveform of the Yutian Ms7. 3 earthquake, Xinjiang on February 12, 2014 was recorded clearly and completely by the Digital Seismic Networks of Xinjiang, Qinghai, Tibet, and Xinjiang Hotan array, so the met...The seismic waveform of the Yutian Ms7. 3 earthquake, Xinjiang on February 12, 2014 was recorded clearly and completely by the Digital Seismic Networks of Xinjiang, Qinghai, Tibet, and Xinjiang Hotan array, so the method of joint location by regional seismic network and seismic array can be used to accurately determine the earthquake source location. The following technologies were used in the process of location： （ 1 ） We selected seismic stations equally located around the epicenter of the Ms 7. 3 earthquake with an average interval of about 15 degrees in the initial location. （2） The recording waveforms of Yutian seismic station were rotated to the radial and tangential directions to precisely obtain the arrival time of S-waves to determine the epicentral distance. （ 3） The velocity model was used in the determination of location of the epicenter, based on the historical records of earthquakes in the area within a radius of 1.0 ° from the source as the center, and the velocity model is obtained after re-fitting and calibration. （4） Based on the waveform records of the Hotan seismic array, the method of waveform beaming was used to determine the azimuths and perform the correction of the epicenter location with these azimuths. （5） The deterministic method was used to measure the source depth. Finally, it is concluded that the Yutian Ms 7. 3 main shock hypocenter location is 36. 197°N, 82. 467°E, focal depth 12km and original time 17：19：48. 2 μm. February 12, 2014.展开更多
Vibration due to moving traffic loads is an important factor which induces frozen soil damage; this paper analyzed these vibration characteristics of frozen soil foundation under track loads. Firstly, seismic observat...Vibration due to moving traffic loads is an important factor which induces frozen soil damage; this paper analyzed these vibration characteristics of frozen soil foundation under track loads. Firstly, seismic observation array （SOA） technology was applied to monitor the three dimensional dynamic characteristics of frozen soil under movable track load in a per- mafrost region and seasonal frozen soil area. Secondly, a numerical simulation for the response of frozen soil under movable track load was performed based on finite element analysis （FEA）, The results show that dynamic characteristics of frozen soil in perpendicular and parallel direction of the track are obviously different. In the direction perpendicular to the track, the vertical acceleration amplitude had an abrupt increase in the 9-10 m from the track line. In the direction parallel to the track, the acceleration in vertical and horizontal direction had a quick attenuation compared to the other direction. Lastly, various parameters were analyzed for the purpose of controlling the dynamic response of frozen soil and the vibration attenuation in frozen soil layer.展开更多
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP, 2019QZKK0701-02)the National Natural Science Foundation of China (Grant 42104102 and 42130807)。
文摘The left-lateral Altyn Tagh Fault(ATF) system is the northern boundary of the Qinghai-Xizang Plateau, separating the Tarim Basin and the Qaidam Basin. The middle section of ATF has not recorded any large earthquakes since1598 AD, so the potential seismic hazard is unclear. We develope an earthquake catalog using continuous waveform data recorded by the Tarim-Altyn-Qaidam dense nodal seismic array from September 17 to November23, 2021 in the middle section of ATF. With the machine learning-based picker, phase association, location, match and locate workflow, we detecte 233 earthquakes with M_L-1–3, far more than 6 earthquakes in the routine catalog. Combining with focal mechanism solutions and the local fault structure, we find that seismic events are clustered along the ATF with strike-slip focal mechanisms and on the southern secondary faults with thrusting focal mechanisms. This overall seismic activity in the middle section of the ATF might be due to the northeastward transpressional motion of the Qinghai-Xizang Plateau block at the western margin of the Qaidam Basin.
基金supported by the China Geological Survey Project“Deep Geological Survey of the Qin-Hang Belt”(No.DD20160082)the National Natural Science Foundation of China(No.41574048)
文摘A profile of shallow crustal velocity structure(1–2 km) may greatly enhance interpretation of the sedimentary environment and shallow tectonic deformation.Recent advances in surface wave tomography, using ambient noise data recorded with high-density seismic arrays, have improved the understanding of regional crustal structure. As the interest in detailed shallow crustal structure imaging has increased, dense seismic array methods have become increasingly efficient. This study used a high-density seismic array deployed in the Xinjiang basin in southeastern China, to record seismic data, which was then processed with the ambient noise tomography method. The high-density seismic array contained 203 short-period seismometers, spaced at short intervals(～ 400 m). The array collected continuous records of ambient noise for 32 days. Data preprocessing,cross correlation calculation, and Rayleigh surface wave phase-velocity dispersion curve extraction, yielded more than 16,000 Rayleigh surface wave phase-velocity dispersion curves, which were then analyzed using the direct-inversion method. Checkerboard tests indicate that the shear wave velocity is recovered in the study area, at depths of 0–1.4 km,with a lateral image resolution of ～ 400 m. Model test results show that the seismic array effectively images a 50 m thick slab at a depth of 0–300 m, a 150 m thick anomalous body at a depth of 300–600 m, and a 400 m thick anomalous body at a depth of 0.6–1.4 km. The shear wave velocity profile reveals features very similar to those detected by a deep seismic reflection profile across the study area. This demonstrates that analysis of shallow crustal velocity structure provides high-resolution imaging of crustal features.Thus, ambient noise tomography with a high-density seismic array may play an important role in imaging shallow crustal structure.
基金supported by the National Natural Science Foundation of China under grants 41874048 and 41974068supported by the National Key Research and Development Projects 2018YFC0603500。
文摘With the development of unconventional shale gas in the southern Sichuan Basin,seismicity in the region has increased significantly in recent years.Though the existing sparse regional seismic stations can capture most earthquakes with ML≥2.5,a great number of smaller earthquakes are often omitted due to limited detection capacity.With the advent of portable seismic nodes,many dense arrays for monitoring seismicity in the unconventional oil and gas fields have been deployed,and the magnitudes of those earthquakes are key to understand the local fault reactivation and seismic potentials.However,the current national standard for determining the local magnitudes was not specifically designed for monitoring stations in close proximity,utilizing a calibration function with a minimal resolution of 5 km in the epicentral distance.That is,the current national standard tends to overestimate the local magnitudes for stations within short epicentral distances,and can result in discrepancies for dense arrays.In this study,we propose a new local magnitude formula which corrects the overestimated magnitudes for shorter distances,yielding accurate event magnitudes for small earthquakes in the Changning-Zhaotong shale gas field in the southern Sichuan Basin,monitored by dense seismic arrays in close proximity.The formula is used to determine the local magnitudes of 7,500 events monitored by a two-phased dense array with several hundred 5 Hz 3 C nodes deployed from the end of February 2019 to early May 2019 in the Changning-Zhaotong shale gas field.The magnitude of completeness(MC)using the dense array is-0.1,compared to MC 1.1 by the sparser Chinese Seismic Network(CSN).In addition,using a machine learning detection and picking procedure,we successfully identify and process some 14,000 earthquakes from the continuous waveforms,a ten-fold increase over the catalog recorded by CSN for the same period,and the MC is further reduced to-0.3 from-0.1 compared to the catalog obtained via manual processing using the same dense array.The proposed local magnitude formula can be adopted for calculating accurate local magnitudes of future earthquakes using dense arrays in the shale gas fields of the Sichuan Basin.This will help to better characterize the local seismic risks and potentials.
基金This study is supported by the National Key R&D Program of China(No.2018YFC1503400)the National Natural Science Foundation of China(No.41804088).Some of the figures were made using the Generic Mapping Tools(Wessel et al.,2013).
文摘A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaojiang Fault Zone(n-XJFZ).Meanwhile,the stress field of the n-XJFZ was determined by inverting 140 focal mechanism solutions of the small earthquakes within the study area which were recorded in the same period.This determination confirmed a compressive stress in NW-SE orientation and an extensional stress in the NE-SW orientation,with little difference from those released by previous studies.The shear-wave splitting results show a spatial complexity in polarization orientation,different from one site to another.How-ever,the polarization orientations integrated for the subareas suggest that the fault trends seemingly played important roles.All the subareas bear two dominant orientations,N10°E and N90°E,both of which are different from the azimuths of the principal compressive stress,due to the fault distribution.The time delay averaged over the entire region is 4.56 ms/km,close to that of the upper boundary of the generally accepted interval worldwide but larger than those in most of the investigated regions in the Chinese mainland,which probably implies an alignment of more micro-cracks in the n-XJFZ.Interestingly,the 2014 Ms6.5 Ludian earthquake was found to have caused a variation in the time delays of the slow shear waves within the study area though its epicenter was outside.This earthquake resulted in an evident drop of the time delays remaining for 4 months,however,lifted a bit the time-delay level with respect to that prior to the earthquake.
基金Supported by NSF CENS program (CCR-0121778), NSF (EF-0410438), and ST Microelectronics in USA.
文摘In this paper, we consider the analysis, implementation, and application of wideband sources using both seismic and acoustic sensors. We use the approximate maximum likelihood (AML) algorithm to perform acoustic direction of arrival (DOA). For non-uniform noise spectra, whitening filtering was applied to the received acoustic signals before the AML operation. For short-range seismic DOA applications, one method was based on eigen-decomposition of the covariance matrix and a second method was based on surface wave analysis. Two well-known optimization schemes were used to estimate the source locations from the estimated DOAs at sensors of known locations. Experimental estimation of the DOAs and resulting localizations using the acoustic and seismic signals generated by striking a heavy metal plate by a hammer were reported.
文摘By using the waveform data recorded during the site survey of Lanzhou Seismic Array, the author calculated and analyzed the correlation of the signal and noise between the site pairs and found that the ideal radii of the two concentric rings for Lanzhou Seismic Array were 380 m and 1500 m, respectively. According to the radius limit and other requirements, nine sites were chosen to make a seismic array, and then the detection and location ability of the array were estimated.
基金National Natural Science Foundation of China (Grant No. 40234043).
文摘Automatic phase picking is a critical procedure for seismic data processing, especially for a huge amount of seismic data recorded by a large-scale portable seismic array. In this study is presented a new method used for automatic accurate onset phase picking based on the proporty of dense seismic array observations. In our method, the Akaike＇s information criterion （AIC） for the single channel observation and the least-squares cross-correlation for the multi-channel observation are combined together. The tests by the seismic array observation data after triggering with the short-term average/long-term average （STA/LTA） technique show that the phase picking error is less than 0.3 s for local events by using the single channel AIC algorithm. In terms of multi-channel least-squares cross-correlation technique, the clear teleseismic P onset can be detected reliably. Even for the teleseismic records with high noise level, our algorithm is also able to effectually avoid manual misdetections.
基金The research was under the construction of the Naquseismic array of Chinese Digital Seismography Observation Networkin National 10th Five-Year Program.
文摘The waveform data recorded during the site survey of the Naqu seismic array in Aug. 2004 were processed by the author. According to the relativity of site pairs in time and frequency domains, the reference values of the inner ring and outer ring were determined. The author evaluated the array deployed for site survey as the primary array, and the results show that the resolution of the primary array is high enough to locate earthquakes precisely.
基金the State Key Marine Geological Laboratory of Tongji University,China
文摘The paper proposes the calibration theory and methods for the Shanghai seismic array and analyzes the calibration results. As a result, the calibration results for the seismic array based on 2 typical earthquakes have been drawn; the difference of calibration results between Hokkaido and Honshu region in Japan is investigated. And calibration results of different directions, different epicenter distances and different magnitudes are probed into. The result shows that the location of earthquakes on the Shanghai seismic array is greatly improved.
基金geological survey project of China Geological Survey(Grant Nos.12120114067701,DD20179357,and DD20160082)the National Natural Science Foundation of China(Grant No.41574092)supported by the National Natural Science Foundation of China(Grant Nos.91962110,41774113,42174069,41874055,and 42104099).
文摘The Mesozoic tectonic framework of the eastern South China is mainly controlled by subduction,turning toward,and rollback of the Pacific Plate.Recent studies of receiver function imaging and ambient noise tomography have revealed the“Yshaped”thinnest crustal belt in the eastern South China under the overall extension of the lithosphere.However,the deep dynamic environment and formation mechanisms of the thin crustal belt remain debatable.Here we obtained high-resolution images of the crustal thickness and Poisson’s ratio in the eastern South China Block applying the recently proposed H-κ-c receiver function method,using data recorded by 305 dense portable broadband stations and 219 permanent stations surrounding.Additionally,we discussed the deep dynamic formation mechanism of the“Y-shaped”thinnest crustal belt coupled with two common conversion point stacked images at key locations.Results show that the average crustal thickness of the study area is 33 km(thin crust)and the average Poisson’s ratio is 0.24(low ratio).The overall crustal thinning toward the continental margin is likely because eastern South China was in a back-arc extension environment,which was induced by the rollback of the subducted plate in the Early Cretaceous.The crustal thickness of the“Y-shaped”thinnest crustal belt is<30 km,which is 3-5 km thinner than that outside the zone.The eastern branch is distributed along the trajectory of Nanchang-Ji’an-Ganzhou-Shaoguan-Guangzhou,and the western branch is around the Jianghan-Xiangzhong Basin,both of which intersect in Nanling.The eastern branch of the thin crustal zone indicates the potential location of the Pacific subduction slab breakoff,and the formation mechanism may be related to the interaction of deep-shallow processes,including the upwelling of mantle heat flow through the slab window and transtensional pre-existing faults.We developed a dynamic model that combines subduction-breakoff-rollback processes of the Paleo-Pacific Plate and accompanying deep fluid upwelling to explain the regional extension of the South China lithosphere,the formation mechanism of the thinnest crustal belt,and the distribution of granitic plutons.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFC0600302)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0701)the National Natural Science Foundation of China(Grant Nos.41774097,41674064,41704042&41574082)。
文摘Geological studies show that the southern part of Ailaoshan-Red River shear zone(ALSRRSZ)has experienced complex metallogenic processes and multi-stage non-uniform uplifting,called oblique uplifting since the Cenozoic.To detect the deep structure and geodynamic background beneath Daping,Chang’an and other gold and polymetallic deposits in this area,we carried out a high-density short-period seismic array survey in southern Yunnan province.The array used is approximately240 km long with an interval of 500 m between two adjacent stations.Based on the data collected by the array,we used H-κstacking and common conversion point(CCP)methods of receiver functions to reveal the fine crustal structure beneath this array,which was located from Lvchun(western end)to the east and ended in Maguan.The three main conclusions are as follows.(1)The average crustal thickness is approximately 37 km and the Vp/Vsratio is 1.75.However,the thickness and Vp/Vsratio of the Ailao Mountain are rather greater or higher than those of the western Lanping-Simao Basin and eastern South-China block.These results may indicate that the crust is rich in ferromagnesian minerals or has a thermal fluid anomaly after orogenic movement.(2)There are two obvious inclined interfaces beneath the Ailao Mountain in the mid-upper crust,which suggests that strong deformation occurred there during the orogenic period.Some evidences,such as the weak converted-wave Pms phase from the Moho,low P-wave velocities of the upper mantle,high surface heat flow values,and generally developed hot springs,indicate that a strong crust-mantle interaction exists in the southern segments of the Ailaoshan-Red River shear zone.These interactions include a diapir of mantle-sourced magma(stronger in the east than that in the west),lateral collision from the Indian Plate,and the differential uplift caused by the strike-slip movement of the Red River Fault.All of above deep processes led to the Cenozoic oblique uplifting of Ailao Mountain.(3)By combining the location of the deposits on the surface,characteristics of the average crustal Vp/Vsratio,hypocenters of the small earthquakes along the research profile,Moho shape,and horizontal variations of the Pms phase amplitudes,we speculate that the Ailaoshan Fault was the upgoing conduit for metallogenic magma and played a significant role in the Cenozoic development of the multiform metal deposits around the Ailao Mountain area.
基金supported by the National Natural Science Foundation of China (Nos. 90814001, 40974053, 41074069)
文摘This article gives a description of our first study on ground rotational motion and its pre-liminary results. The ground rotational motions around vertical axis were obtained using near-field translational records of a temporal seismic array with observational distances of 1.8 to 2.7 km. The sources used are explosions with explosive of 500 kg for each. Ground rotational velocities were calcu-lated using the space derivatives of the horizontal components of translational velocities from the array. The peak ground rotational velocities （PGRV） are approximately 30 to 57 ？rad/s. Our results are very close to those from Wassermann et al. （2009）, who used both a seismic array and a rotational sensor to record an explosion in Germany and obtained PGRV values of about 50 ？rad/s. Their explosives are 150 kg, only one third of ours, but their observational distance is 250 m, much less than ours.
基金supported by China earthquake scientific array exploration Southern section of North South seismic belt(201008001)Northern section of North South seismic belt(20130811)+1 种基金National Natural Science Foundation of China(41474057)Science for Earthquake Resllience of China Earthquake Administration(XH15040Y)
文摘The special seismic tectonic environment and frequent seismicity in the southeastern margin of the Qinghai-Tibet Plateau show that this area is an ideal location to study the present tectonic movement and background of strong earthquakes in China's Mainland and to predict future strong earthquake risk zones. Studies of the structural environment and physical characteristics of the deep structure in this area are helpful to explore deep dynamic effects and deformation field characteristics, to strengthen our understanding of the roles of anisotropy and tectonic deformation and to study the deep tectonic background of the seismic origin of the block＇s interior. In this paper, the three-dimensional （3D） P-wave velocity structure of the crust and upper mantle under the southeastern margin of the Qinghai-Tibet Plateau is obtained via observational data from 224 permanent seismic stations in the regional digital seismic network of Yunnan and Sichuan Provinces and from 356 mobile China seismic arrays in the southern section of the north-south seismic belt using a joint inversion method of the regional earthquake and teleseismic data. The results indicate that the spatial distribution of the P-wave velocity anomalies in the shallow upper crust is closely related to the surface geological structure, terrain and lithology. Baoxing and Kangding, with their basic volcanic rocks and volcanic clastic rocks, present obvious high-velocity anomalies. The Chengdu Basin shows low-velocity anomalies associated with the Quaternary sediments. The Xichang Mesozoic Basin and the Butuo Basin are characterised by low- velocity anomalies related to very thick sedimentary layers. The upper and middle crust beneath the Chuan-Dian and Songpan-Ganzi Blocks has apparent lateral heterogeneities, including low-velocity zones of different sizes. There is a large range of low-velocity layers in the Songpan-Ganzi Block and the sub-block northwest of Sichuan Province, showing that the middle and lower crust is relatively weak. The Sichuan Basin, which is located in the western margin of the Yangtze platform, shows high-velocity characteristics. The results also reveal that there are continuous low-velocity layer distributions in the middle and lower crust of the Daliangshan Block and that the distribution direction of the low-velocity anomaly is nearly SN, which is consistent with the trend of the Daliangshan fault. The existence of the low-velocity layer in the crust also provides a deep source for the deep dynamic deformation and seismic activity of the Daliangshan Block and its boundary faults. The results of the 3D P-wave velocity structure show that an anomalous distribution of high-density, strong-magnetic and high-wave velocity exists inside the crust in the Panxi region. This is likely related to late Paleozoic mantle plume activity that led to a large number of mafic and ultra-mafic intrusions into the crust. In the crustal doming process, the massive intrusion of mantle-derived material enhanced the mechanical strength of the crustal medium. The P-wave velocity structure also revealed that the upper mantle contains a low-velocity layer at a depth of 80-120 km in the Panxi region. The existence of deep faults in the Panxi region, which provide conditions for transporting mantle thermal material into the crust, is the deep tectonic background for the area＇s strong earthquake activity.
基金This work was supported by the National Natural Science Foundation of China(No.41730212)the National Key R&D Project of China(No.2017YFC1500304)the Basic Research Project of Institute of Earthquake Science,CEA(No.2017IES010202).
文摘The Xiaojiang faults,striking north-tosouth(NS),and the Honghe faults,striking north-to-west(NW),are first-order block boundaries that intersect to form a concentrated stress zone at an acute angle in the southern part of the Sichuan-Yunnan rhombic block(SYB).It is also a crucial zone for material escaping from the Tibetan Plateau(TP)due to the collision between the Indian Plate and the Eurasian Plate.In December 2017,the Institute of Earthquake Forecasting of the China Earthquake Administration(CEA)deployed a linear temporary seismic broadband array,the Honghe-Xiaojiang temporary Seismic Array(HX Array),across first-order block boundaries in the southern SYB.By using the waveform data of small earthquakes recorded by stations in the HX Array across Xiaojiang faults from 2017 to 2019,and by permanent seismic stations of the China National Earthquake Networks from 2012 to 2019,this paper adopts the systematic analysis method of shear-wave splitting(SWS),SAM method,to obtain preliminary results for seismic anisotropy in the upper crust.The study area can be divided into two subzones according to the spatial distribution of the directions of polarization of the fast shear-wave(PFS)at the stations:the northern zone(zone A,where the HX Array is located)and the southern zone(zone B,to the south of the HX Array).The results show that the directions of the PFS at stations in zone A were highly consistent,dominant in the NE direction,correlated with the in-situ principal compressive stress,and were seemingly unaffected by the Xiaojiang faults.The directions of the PFS as recorded at stations in zone B were more complicated,and were dominant in the NS direction parallel to that of the regional principal compressive stress.This suggests the joint influence of complex tectonics and regional stress in this narrow wedge area.By referring to the azimuthal anisotropy derived from seismic ambient noise in the southeast margin of the TP,the NS direction of the PFS in the middle and lower crust,and its EW direction in the upper mantle,this paper concludes that azimuthal anisotropy in the upper crust differed from that in the lower crust in the south segment of Xiaojiang faults,at least beneath the observation area,and azimuthal anisotropy in the crust was different from that in the upper mantle.The results support the pattern of deformation of ductile flow in the lower crust,and the decoupling between the upper and lower crusts as well as that between the crust and the mantle in the study area.The crustal directions of the PFS appeared to be independent of the Xiaojiang faults,suggesting that the influence of the South China block on the SYB passed through the Xiaojiang faults to the Yimen region.The results of this study indicate that anisotropic studies based on data on the dense temporary seismic array can yield clearer tectonic information,and reveal the complex spatial distribution of stress and deformation in the upper crust of the south segment of Xiaojiang faults.
基金The Basic Science Research Project of Commonweal of Nation Level (DQJB06A02 ),ChinaThe Brightlight (Ⅰ) Project from Institute of Geophysics,CEA
文摘Waveforms generated by the 50t explosion of project Brightlight （ I ） were recorded by HILR array. Using array techniques, the author performed identification, f-k analysis, velocity spectrum analysis, etc. of the weak signals. The analysis results show that the signal-to-noise ratio after beamforming was obviously enhanced, and the signal could be clearly shown. The energy from this explosion was mainly concentrated in the 1 -8Hz range from f-k analysis. The velocity spectrum gave clear positions of event phases, which could not be seen in the original weak signals. The maximum energy distribution obtained by the Beaman method is close to the theoretical value in the azimuth-slowness domain.
文摘Using the arrival times of 197 earthquakes well recorded by the Beijing Seismic Network and the China-Germany cooperative Yanqing Digital Seismic Array in the period from October of 2001 to December of 2005, we accurately relocate these earthquakes by the joint-inversion program for hypocentral position and 3-D velocity structure The distribution of hypocenters shows that there are two major seismic active belts in the northwestern Beijing. The first belt stretches from Qinghe, Wenquan to the NW direction and the second extends from Nankou, Changping to the ENE direction.
基金supported by the National Natural Science Foundation of China (under grants 41874048,41790464,41790462).
文摘A rapidly deployable dense seismic monitoring system which is capable of transmitting acquired data in real time and analyzing data automatically is crucial in seismic hazard mitigation after a major earthquake.However,it is rather difficult for current seismic nodal stations to transmit data in real time for an extended period of time,and it usually takes a great amount of time to process the acquired data manually.To monitor earthquakes in real time flexibly,we develop a mobile integrated seismic monitoring system consisting of newly developed nodal units with 4G telemetry and a real-time AI-assisted automatic data processing workflow.The integrated system is convenient for deployment and has been successfully applied in monitoring the aftershocks of the Yangbi M_(S) 6.4 earthquake occurred on May 21,2021 in Yangbi County,Dali,Yunnan in southwest China.The acquired seismic data are transmitted almost in real time through the 4G cellular network,and then processed automat-ically for event detection,positioning,magnitude calculation and source mechanism inversion.From tens of seconds to a couple of minutes at most,the final seismic attributes can be presented remotely to the end users through the integrated system.From May 27 to June 17,the real-time system has detected and located 7905 aftershocks in the Yangbi area before the internal batteries exhausted,far more than the catalog provided by China Earthquake Networks Center using the regional permanent stations.The initial application of this inte-grated real-time monitoring system is promising,and we anticipate the advent of a new era for Real-time Intelligent Array Seismology(RIAS),for better monitoring and understanding the subsurface dynamic pro-cesses caused by Earth's internal forces as well as anthropogenic activities.
基金funded by the Special Project of the Department of Earthquake Monitoring and Prediction,China Earthquake Administration(1309010)Seismic Network Youth Special Project,China Earthquake Administration(20140330,20130201)
文摘The seismic waveform of the Yutian Ms7. 3 earthquake, Xinjiang on February 12, 2014 was recorded clearly and completely by the Digital Seismic Networks of Xinjiang, Qinghai, Tibet, and Xinjiang Hotan array, so the method of joint location by regional seismic network and seismic array can be used to accurately determine the earthquake source location. The following technologies were used in the process of location： （ 1 ） We selected seismic stations equally located around the epicenter of the Ms 7. 3 earthquake with an average interval of about 15 degrees in the initial location. （2） The recording waveforms of Yutian seismic station were rotated to the radial and tangential directions to precisely obtain the arrival time of S-waves to determine the epicentral distance. （ 3） The velocity model was used in the determination of location of the epicenter, based on the historical records of earthquakes in the area within a radius of 1.0 ° from the source as the center, and the velocity model is obtained after re-fitting and calibration. （4） Based on the waveform records of the Hotan seismic array, the method of waveform beaming was used to determine the azimuths and perform the correction of the epicenter location with these azimuths. （5） The deterministic method was used to measure the source depth. Finally, it is concluded that the Yutian Ms 7. 3 main shock hypocenter location is 36. 197°N, 82. 467°E, focal depth 12km and original time 17：19：48. 2 μm. February 12, 2014.
基金supported by the National High Technology Research and Development Program of China (863, 2008AA11Z104)
文摘Vibration due to moving traffic loads is an important factor which induces frozen soil damage; this paper analyzed these vibration characteristics of frozen soil foundation under track loads. Firstly, seismic observation array （SOA） technology was applied to monitor the three dimensional dynamic characteristics of frozen soil under movable track load in a per- mafrost region and seasonal frozen soil area. Secondly, a numerical simulation for the response of frozen soil under movable track load was performed based on finite element analysis （FEA）, The results show that dynamic characteristics of frozen soil in perpendicular and parallel direction of the track are obviously different. In the direction perpendicular to the track, the vertical acceleration amplitude had an abrupt increase in the 9-10 m from the track line. In the direction parallel to the track, the acceleration in vertical and horizontal direction had a quick attenuation compared to the other direction. Lastly, various parameters were analyzed for the purpose of controlling the dynamic response of frozen soil and the vibration attenuation in frozen soil layer.
