Since the beginning of the 21st century,major earthquakes have frequently occurred worldwide.To explore the impact of astronomical factors on earthquakes,in this study,the statistical analysis method of correlation is...Since the beginning of the 21st century,major earthquakes have frequently occurred worldwide.To explore the impact of astronomical factors on earthquakes,in this study,the statistical analysis method of correlation is used to systematically analyze the effects of astronomical factors,such as solar activity,Earth’s rotation,lunar declination angle,celestial tidal force,and other phenomena on M≥8 global earthquakes at the beginning of the 21st century.With regard to solar activity,this study focuses on the analysis of the 11-year and century cycles of solar activity.The causal relationship of the Earth’s rotation is not obvious in this work and previous works;in contrast,the valley period of the solar activity century cycle may be an important astronomical factor leading to the frequent occurrence of global earthquakes at the beginning of the 21st century.This topic warrants further study.展开更多
Based on the analysis of coseismic deformation in the macroscopic epicentral region extracted by Differential Interferometric Synthetic Aperture Radar (D-InSAR), and combined with the seismic activity, focal mechanism...Based on the analysis of coseismic deformation in the macroscopic epicentral region extracted by Differential Interferometric Synthetic Aperture Radar (D-InSAR), and combined with the seismic activity, focal mechanism solutions of the earthquake and field investigation, the characteristic of coseismic deformation of MS=8.1 western Kunlunshan Pass earthquake in 2001 was researched. The study shows that its epicenter lies in the northeast side of Hoh Sai Hu; and the seismogenic fault in the macroscopic epicentral region can be divided into two central deformation fields: the west and east segments with the lengths of 42 km and 48 km, respectively. The whole fault extends about 90 km. From the distribution of interferometry fringes, the characteristic of sinistral strike slip of seismogenic fault can be identified clearly. The deformations on both sides of the fault are different with an obviously higher value on the south side. In the vicinity of macroscopic epicenter, the maximum displacement in look direction is about 288.4 cm and the minimum is 224.0 cm; the maximum sinistral horizontal dislocation of seismogenic fault near the macroscopic epicenter is 738.1 cm and the minimum is 551.8 cm.展开更多
On the basis of the airgun source signals recorded by the stations from January,2016 to June,2017,we use cross-correlation detection technology to obtain the characteristics of the stable phase travel time change of e...On the basis of the airgun source signals recorded by the stations from January,2016 to June,2017,we use cross-correlation detection technology to obtain the characteristics of the stable phase travel time change of each station.We used the Yunlong MS5.0 and Yangbi MS5.1 earthquakes as samples.According to regional characteristics,13 stations with high signal-to-noise ratios and complete data were selected(including 3 fixed stations and 10 active source stations).They are divided into four regions,and on the basis of the GNSS baseline data,the characteristics of regional wave velocity changes before and after the earthquake are analyzed.The results show that the station phase travel time change and the regional stress characteristics represented by the GNSS baseline data have good correlation in the short-term.Due to different degrees of regional stress,there are differences in the travel time changes of different stations in the four regions.Before the Yunlong MS5.0 and Yangbi MS5.1 earthquakes,with regional stress adjustment,there is an upward trend in the travel time changes of related stations in the adjacent areas of up to 0.02 s.The difference is that there are differences in the time nodes and duration of the travel time anomalies,and there is a reverse descent process after the Yangbi MS5.1 earthquake.There are different degrees of travel time fluctuations in the relevant stations before and after the two earthquakes,but the fluctuation range before and after the earthquake was small.Compared with the water level change of the reservoir,the adjustment of the regional stress is more likely to have a substantial impact on the travel time changes of the relevant stations.展开更多
This paper has discussed the effective resistivity ellipse and the paradoxical phenomenon of anisotropy. Two cases have been discussed, namely: there are three measuring lines at arbitrary angles with one another and...This paper has discussed the effective resistivity ellipse and the paradoxical phenomenon of anisotropy. Two cases have been discussed, namely: there are three measuring lines at arbitrary angles with one another and there are two mutually perpendicular measuring lines and an additional measurement of the transversal effective resistivity. For these cases, the paper has given the methods for quantitatively calculating the parameters of georesistivity anisotropy. The formulae given include those for calculating the azimuth (of the principal axis of minimum resistivity ρ 1, the average resistivity ( ρ 1ρ 3) 1/2 , (ρ 2ρ 3) 1/2 , and the anisotropy coefficient λ=(ρ 2/ρ 1 ) 1/2 . As a case history, the data observed by the Datong geoelectricity station have been processed with reference to the results of in situ resistivity measurement in media subjected to shear. The results of analysis have led to the following understandings. Before and after the Datong M S6.1 earthquake on October 19, 1989, the abnormal rise of NE trending georesistivity and abnormal fall of NW trending georesistivity observed at the Datong and Yangyuan stations were caused by the pure shear acting on the medium. The major principal compression was in NE direction, which made an acute angle with the strike of the seismic fault plane, and thus there was a greater shear stress but very small normal stress so that the fault was likely to slide but the earthquake was only of moderate magnitude. The states of stress in medium were the same before and after earthquake and therefore the georesistivity precursor was of the same sign as that of co seismic variations.展开更多
The continuous GPS observation at the fiducial stations in the Crustal Movement Observation Network of China (CMONOC) recorded the crustal movement of Chinese mainland before and after the great Kunlun Mountain earthq...The continuous GPS observation at the fiducial stations in the Crustal Movement Observation Network of China (CMONOC) recorded the crustal movement of Chinese mainland before and after the great Kunlun Mountain earthquake of M=8.1 on November 14, 2001, especially the horizontal crustal movement in the western part of China. Based on the datum defined by a group of stable stations with small mutual horizontal displacements for a few years, the time series of horizontal displacements at fiducial stations were obtained. Significant anomalous horizontal displacements had appeared at the fiducial stations in the western part of China since early November 2000 and several earthquakes with the magnitudes about 6.0 had occurred in Yunnan and Sichuan Provinces. The northward components of the horizontal displacement at the fiducial stations in west China had decreased signifi-cantly and even changed in the opposite sense since mid April 2001. After the earthquake, the northward dis-placements still decreased and there were significant westward displacements. The process of the crustal move-ment in the western part of Chinese mainland (in reference to east China) suggests that the main force source for this earthquake came from the northward pushing of the Indian plate. The great earthquake released a large amount of energy, as a result, the action applied by the Indian plate to Chinese mainland diminished significantly and after the great earthquake, the seismic activity in Chinese mainland decreased considerably until the end of 2002.展开更多
Following the theory and definition of the Corioli force in physics, the Corioli force at the site of the M=8.1 Kunlun Mountain Pass earthquake on November 14, 2001, is examined in this paper on the basis of a statist...Following the theory and definition of the Corioli force in physics, the Corioli force at the site of the M=8.1 Kunlun Mountain Pass earthquake on November 14, 2001, is examined in this paper on the basis of a statistical research on relationship between the Corioli force effect and the maximum aftershock magnitude of 20 earthquakes with M7.5 in Chinese mainland, and then the variation tendency of aftershock activity of the M=8.1 earthquake is discussed. The result shows: a) Analyzing the Corioli force effect is an effective method to predict maximum aftershock magnitude of large earthquakes in Chinese mainland. For the sinistral slip fault and the reverse fault with its hanging wall moving toward the right side of the cross-focus meridian plane, their Corioli force pulls the two fault walls apart, decreasing frictional resistance on fault plane during the fault movement and releasing elastic energy of the mainshock fully, so the maximum magnitude of aftershocks would be low. For the dextral slip fault, its Corioli force presses the two walls against each other and increases the frictional resistance on fault plane, prohibiting energy release of the mainshock, so the maximum magnitude of aftershocks would be high. b) The fault of the M=8.1 Kunlun Mountain earthquake on Nov. 14, 2001 is essentially a sinistral strike-slip fault, and the Corioli force pulled the two fault walls apart. Magnitude of the induced stress is about 0.06 MPa. After a comparison analysis, we suggest that the aftershock activity level will not be high in the late period of this earthquake sequence, and the maximum magnitude of the whole aftershocks sequence is estimated to be about 6.0.展开更多
The observation of the fault-zone trapped waves was conducted using a seismic line with dense receivers across surface rupture zone of the M=8.1 Kunlun Mountain earthquake. The fault zone trapped waves were separated ...The observation of the fault-zone trapped waves was conducted using a seismic line with dense receivers across surface rupture zone of the M=8.1 Kunlun Mountain earthquake. The fault zone trapped waves were separated from seismograms by numerical filtering and spectral analyzing. The results show that: a) Both explosion and earthquake sources can excite fault-zone trapped waves, as long as they locate in or near the fault zone; b) Most energy of the fault-zone trapped waves concentrates in the fault zone and the amplitudes strongly decay with the distance from observation point to the fault zone; c) Dominant frequencies of the fault-zone trapped waves are related to the width of the fault zone and the velocity of the media in it. The wider the fault zone or the lower the velocity is, the lower the dominant frequencies are; d) For fault zone trapped waves, there exist dispersions; e) Based on the fault zone trapped waves observed in Kunlun Mountain Pass region, the width of the rupture plane is deduced to be about 300 m and is greater than that on the surface.展开更多
After the 2015 M_S8. 1 Nepal earthquake,a strong and moderate seismicity belt has formed in Tibet gradually spreading along the northeast direction. In this paper,we attempt to summarize the features and investigate t...After the 2015 M_S8. 1 Nepal earthquake,a strong and moderate seismicity belt has formed in Tibet gradually spreading along the northeast direction. In this paper,we attempt to summarize the features and investigate the primary mechanism of this behavior of seismic activity,using a 2-D finite element numerical model with tectonic dynamic settings and GPS horizontal displacements as the constraints. In addition,compared with the NEtrending seismicity belt triggered by the 1996 Xiatongmoin earthquake,we discuss the future earthquake hazard in and around Tibet. Our results show that: the NE-directed seismicity belt is the response of enhanced loading on the anisotropic Qinghai-Tibetan plateau from the Indian plate and earthquake thrusting. Also,this possibly implies that a forthcoming strong earthquake may fill in the gaps in the NE-directed seismicity belt or enhance the seismic hazard in the eastern( the north-south seismic zone) and western( Tianshan tectonic region) parts near the NE-directed belt.展开更多
文摘Since the beginning of the 21st century,major earthquakes have frequently occurred worldwide.To explore the impact of astronomical factors on earthquakes,in this study,the statistical analysis method of correlation is used to systematically analyze the effects of astronomical factors,such as solar activity,Earth’s rotation,lunar declination angle,celestial tidal force,and other phenomena on M≥8 global earthquakes at the beginning of the 21st century.With regard to solar activity,this study focuses on the analysis of the 11-year and century cycles of solar activity.The causal relationship of the Earth’s rotation is not obvious in this work and previous works;in contrast,the valley period of the solar activity century cycle may be an important astronomical factor leading to the frequent occurrence of global earthquakes at the beginning of the 21st century.This topic warrants further study.
文摘Based on the analysis of coseismic deformation in the macroscopic epicentral region extracted by Differential Interferometric Synthetic Aperture Radar (D-InSAR), and combined with the seismic activity, focal mechanism solutions of the earthquake and field investigation, the characteristic of coseismic deformation of MS=8.1 western Kunlunshan Pass earthquake in 2001 was researched. The study shows that its epicenter lies in the northeast side of Hoh Sai Hu; and the seismogenic fault in the macroscopic epicentral region can be divided into two central deformation fields: the west and east segments with the lengths of 42 km and 48 km, respectively. The whole fault extends about 90 km. From the distribution of interferometry fringes, the characteristic of sinistral strike slip of seismogenic fault can be identified clearly. The deformations on both sides of the fault are different with an obviously higher value on the south side. In the vicinity of macroscopic epicenter, the maximum displacement in look direction is about 288.4 cm and the minimum is 224.0 cm; the maximum sinistral horizontal dislocation of seismogenic fault near the macroscopic epicenter is 738.1 cm and the minimum is 551.8 cm.
基金sponsored by the Yunnan Youth Seismology Science Fund Project(2018k08)the National Natural Science Foundation of China(41574059,41474048)the Science and Technology Special Fund,Yunnan Earthquake Agency(ZX2015-01,2018ZX04)
文摘On the basis of the airgun source signals recorded by the stations from January,2016 to June,2017,we use cross-correlation detection technology to obtain the characteristics of the stable phase travel time change of each station.We used the Yunlong MS5.0 and Yangbi MS5.1 earthquakes as samples.According to regional characteristics,13 stations with high signal-to-noise ratios and complete data were selected(including 3 fixed stations and 10 active source stations).They are divided into four regions,and on the basis of the GNSS baseline data,the characteristics of regional wave velocity changes before and after the earthquake are analyzed.The results show that the station phase travel time change and the regional stress characteristics represented by the GNSS baseline data have good correlation in the short-term.Due to different degrees of regional stress,there are differences in the travel time changes of different stations in the four regions.Before the Yunlong MS5.0 and Yangbi MS5.1 earthquakes,with regional stress adjustment,there is an upward trend in the travel time changes of related stations in the adjacent areas of up to 0.02 s.The difference is that there are differences in the time nodes and duration of the travel time anomalies,and there is a reverse descent process after the Yangbi MS5.1 earthquake.There are different degrees of travel time fluctuations in the relevant stations before and after the two earthquakes,but the fluctuation range before and after the earthquake was small.Compared with the water level change of the reservoir,the adjustment of the regional stress is more likely to have a substantial impact on the travel time changes of the relevant stations.
文摘This paper has discussed the effective resistivity ellipse and the paradoxical phenomenon of anisotropy. Two cases have been discussed, namely: there are three measuring lines at arbitrary angles with one another and there are two mutually perpendicular measuring lines and an additional measurement of the transversal effective resistivity. For these cases, the paper has given the methods for quantitatively calculating the parameters of georesistivity anisotropy. The formulae given include those for calculating the azimuth (of the principal axis of minimum resistivity ρ 1, the average resistivity ( ρ 1ρ 3) 1/2 , (ρ 2ρ 3) 1/2 , and the anisotropy coefficient λ=(ρ 2/ρ 1 ) 1/2 . As a case history, the data observed by the Datong geoelectricity station have been processed with reference to the results of in situ resistivity measurement in media subjected to shear. The results of analysis have led to the following understandings. Before and after the Datong M S6.1 earthquake on October 19, 1989, the abnormal rise of NE trending georesistivity and abnormal fall of NW trending georesistivity observed at the Datong and Yangyuan stations were caused by the pure shear acting on the medium. The major principal compression was in NE direction, which made an acute angle with the strike of the seismic fault plane, and thus there was a greater shear stress but very small normal stress so that the fault was likely to slide but the earthquake was only of moderate magnitude. The states of stress in medium were the same before and after earthquake and therefore the georesistivity precursor was of the same sign as that of co seismic variations.
基金The National Development and Programming Project for Key Basic Research (95-13-03-07).
文摘The continuous GPS observation at the fiducial stations in the Crustal Movement Observation Network of China (CMONOC) recorded the crustal movement of Chinese mainland before and after the great Kunlun Mountain earthquake of M=8.1 on November 14, 2001, especially the horizontal crustal movement in the western part of China. Based on the datum defined by a group of stable stations with small mutual horizontal displacements for a few years, the time series of horizontal displacements at fiducial stations were obtained. Significant anomalous horizontal displacements had appeared at the fiducial stations in the western part of China since early November 2000 and several earthquakes with the magnitudes about 6.0 had occurred in Yunnan and Sichuan Provinces. The northward components of the horizontal displacement at the fiducial stations in west China had decreased signifi-cantly and even changed in the opposite sense since mid April 2001. After the earthquake, the northward dis-placements still decreased and there were significant westward displacements. The process of the crustal move-ment in the western part of Chinese mainland (in reference to east China) suggests that the main force source for this earthquake came from the northward pushing of the Indian plate. The great earthquake released a large amount of energy, as a result, the action applied by the Indian plate to Chinese mainland diminished significantly and after the great earthquake, the seismic activity in Chinese mainland decreased considerably until the end of 2002.
基金Key Project of Disaster Reduction of Jiangxi Province during the tenth Five-Year Plan (JX105-05).
文摘Following the theory and definition of the Corioli force in physics, the Corioli force at the site of the M=8.1 Kunlun Mountain Pass earthquake on November 14, 2001, is examined in this paper on the basis of a statistical research on relationship between the Corioli force effect and the maximum aftershock magnitude of 20 earthquakes with M7.5 in Chinese mainland, and then the variation tendency of aftershock activity of the M=8.1 earthquake is discussed. The result shows: a) Analyzing the Corioli force effect is an effective method to predict maximum aftershock magnitude of large earthquakes in Chinese mainland. For the sinistral slip fault and the reverse fault with its hanging wall moving toward the right side of the cross-focus meridian plane, their Corioli force pulls the two fault walls apart, decreasing frictional resistance on fault plane during the fault movement and releasing elastic energy of the mainshock fully, so the maximum magnitude of aftershocks would be low. For the dextral slip fault, its Corioli force presses the two walls against each other and increases the frictional resistance on fault plane, prohibiting energy release of the mainshock, so the maximum magnitude of aftershocks would be high. b) The fault of the M=8.1 Kunlun Mountain earthquake on Nov. 14, 2001 is essentially a sinistral strike-slip fault, and the Corioli force pulled the two fault walls apart. Magnitude of the induced stress is about 0.06 MPa. After a comparison analysis, we suggest that the aftershock activity level will not be high in the late period of this earthquake sequence, and the maximum magnitude of the whole aftershocks sequence is estimated to be about 6.0.
基金Joint Earthquake Science Foundation of China (201001).
文摘The observation of the fault-zone trapped waves was conducted using a seismic line with dense receivers across surface rupture zone of the M=8.1 Kunlun Mountain earthquake. The fault zone trapped waves were separated from seismograms by numerical filtering and spectral analyzing. The results show that: a) Both explosion and earthquake sources can excite fault-zone trapped waves, as long as they locate in or near the fault zone; b) Most energy of the fault-zone trapped waves concentrates in the fault zone and the amplitudes strongly decay with the distance from observation point to the fault zone; c) Dominant frequencies of the fault-zone trapped waves are related to the width of the fault zone and the velocity of the media in it. The wider the fault zone or the lower the velocity is, the lower the dominant frequencies are; d) For fault zone trapped waves, there exist dispersions; e) Based on the fault zone trapped waves observed in Kunlun Mountain Pass region, the width of the rupture plane is deduced to be about 300 m and is greater than that on the surface.
基金funded by China Comprehensive Geophysical Field Observation in North China of Earthquake Scientific Research(201508009)
文摘After the 2015 M_S8. 1 Nepal earthquake,a strong and moderate seismicity belt has formed in Tibet gradually spreading along the northeast direction. In this paper,we attempt to summarize the features and investigate the primary mechanism of this behavior of seismic activity,using a 2-D finite element numerical model with tectonic dynamic settings and GPS horizontal displacements as the constraints. In addition,compared with the NEtrending seismicity belt triggered by the 1996 Xiatongmoin earthquake,we discuss the future earthquake hazard in and around Tibet. Our results show that: the NE-directed seismicity belt is the response of enhanced loading on the anisotropic Qinghai-Tibetan plateau from the Indian plate and earthquake thrusting. Also,this possibly implies that a forthcoming strong earthquake may fill in the gaps in the NE-directed seismicity belt or enhance the seismic hazard in the eastern( the north-south seismic zone) and western( Tianshan tectonic region) parts near the NE-directed belt.
