In this paper,characteristics of spatial and temporal variation of linear fitting goodness before some moderately strong earthquakes(Ms≥5.0)in the eastern part of China(east of longitude 180)are studied according to ...In this paper,characteristics of spatial and temporal variation of linear fitting goodness before some moderately strong earthquakes(Ms≥5.0)in the eastern part of China(east of longitude 180)are studied according to the famous Gutenberg-Richter’s relation expressed as lgN=a-bM,by using the moderate and small events that occurred in and around the source area.The results show that the linear goodness of fitting varies abnormally prior to these moderately strong earthquakes.In the early stage of the earthquake preparatory process,distribution of the energy released through small events in and around the source area is isostatic and the fitting goodness approximates 1,while the distribution of the energy turns to be isostatic before moderately strong earthquakes,leading to the obvious decrease of the linear goodness of fitting.This phenomenon could be a medium term anomaly and a medium term criterion for moderately strong earthquake prediction.展开更多
The uncertainty of potential seismic regions for moderately strong earthquakes has a great effect on the results of seismic hazard analysis in weak seismicity regions,so it is the basement of seismic zoning and seismi...The uncertainty of potential seismic regions for moderately strong earthquakes has a great effect on the results of seismic hazard analysis in weak seismicity regions,so it is the basement of seismic zoning and seismic hazard assessment for engineering sites by correctly dividing the potential seismic regions for moderately strong earthquakes.By taking Northeast and North China as examples,the authors compiled and systematically analyzed a large amount of basic data and then suggest the principles and methods of potential seismic regions for moderately strong earthquakes based on a great number of case studies.The practical division of potential seismic regions in the Changchun and Jilin areas shows that these principles and methods show better suitability.Moreover,the authors also discuss in this paper the progress obtained and put forward some problems that should be solved in the future.展开更多
In this paper,approaches are developed to delineate the potential seismic source regions of moderately strong earthquakes that do not have clear seismotectonic settings.Based on comprehensive analysis of regional tect...In this paper,approaches are developed to delineate the potential seismic source regions of moderately strong earthquakes that do not have clear seismotectonic settings.Based on comprehensive analysis of regional tectonic backgrounds and seismicity,the data,such as isoseisrnals,spatial distribution of after shocks,regional tectonic stress field,and focal mechanisms,are employed for the delineation of the potential seismic source regions.The reliability of such potential seismic source regions is also discussed.展开更多
This paper analyzes the distribution characteristics of geomagnetic low-value displacement in Gansu and its adjacent areas from 1995 to 2003 on the basis of the data of the daily amplitude minimum value time of the ge...This paper analyzes the distribution characteristics of geomagnetic low-value displacement in Gansu and its adjacent areas from 1995 to 2003 on the basis of the data of the daily amplitude minimum value time of the geomagnetic vertical component. It is shown that in addition to the changing rules of geomagnetic low-value displacement itself, there is a better correlation between geomagnetic low-value displacement and the occurrence of moderately strong earthquakes. There appeared to be geomagnetic low-value displacement before the moderately strong earthquakes in Gansu in the 9 years from 1995 to 2003. This result indicates that geomagnetic low-value displacement is of instructive significance for earthquake prediction to some extents.展开更多
Using the focal mechanism solutions of 24 moderately strong earthquakes in the northern Tianshan area,we carried out system cluster and stress field inversion analysis.The result indicates that,the focal mechanism sol...Using the focal mechanism solutions of 24 moderately strong earthquakes in the northern Tianshan area,we carried out system cluster and stress field inversion analysis.The result indicates that,the focal mechanism solutions of moderately strong earthquakes are mainly dip-slip reverse faulting in the northern Tianshan area.The principal rupture planes of earthquakes are NW-oriented.It is basically consistent with the strike of earthquake structure in its adjacent area.The direction of the principal compression stress P axis is nearly NS,and its inclination angle is small;while the inclination angle of the principal extensional stress T axis is large.It shows that the regional stress field is mainly controlled by the near-NS horizontal compressive stress.The direction of the maximum principal stress shows a gradation process of NNE-NS-NW from east to west.展开更多
In the paper, source mechanisms of 33 small-moderate earthquakes occurred in Yunnan are determined by modeling of regional waveforms from Yunnan digital seismic network. The result shows that most earthquakes occurred...In the paper, source mechanisms of 33 small-moderate earthquakes occurred in Yunnan are determined by modeling of regional waveforms from Yunnan digital seismic network. The result shows that most earthquakes occurred within or near the Chuandian rhombic block have strike-slip mechanism. The orientations of maximum compressive stresses obtained from source mechanism are changed from NNW-SSN to NS in the areas from north to south of the block, and tensile stresses are mainly in ENE-WSW or NE-SE. In the eastern Tibetan Plateau, the orientations of maximum compressive stress radiate toward outside from the plateau, and the tensile stress orientations mostly parallel to arc structures. Near 28N the orientations of both maximum compressive stress and tensile stress changed greatly, and the boundary seems to correspond to the southwestern extended line of Longmenshan fault. Outside of the Chuandian rhombic block, the orientations of P and T axes are some different from those within the block. The comparison shows that the source mechanism of small-moderate events presented in the paper is consistence with that of moderate-strong earthquakes determined by Harvard University, which means the source mechanism of small-moderate events can be used to study the tectonic stress field in this region.展开更多
The relationships between Earth's rotation and the 1975 Haicheng, Liaoning MS7.3 earthquake, 2008 Wenchuan, Sichuan MS8.0 earthquake and the 2004 Sumatra MS9.0 earthquake, as well as moderate-small earthquakes occ...The relationships between Earth's rotation and the 1975 Haicheng, Liaoning MS7.3 earthquake, 2008 Wenchuan, Sichuan MS8.0 earthquake and the 2004 Sumatra MS9.0 earthquake, as well as moderate-small earthquakes occurring around the epicenter regions prior to them are investigated in this study. The obtained results could benefit the further understanding of the relationship between the Earth's rotation and earthquakes.展开更多
The moment tensor solutions of 51 small to moderate earthquakes occurred in the Capital Region in the year of 2004 are obtained by inverting the broadband waveform data. Accordingly, other source parameters, such as s...The moment tensor solutions of 51 small to moderate earthquakes occurred in the Capital Region in the year of 2004 are obtained by inverting the broadband waveform data. Accordingly, other source parameters, such as scalar seismic moments, moment magnitudes, double-couple (DC) components and compensated-linear-vector-dipole (CLVD) components, are determined as well as fault parameters and stress-axis parameters. The inverted results are evaluated by groups of numerical tests.展开更多
Based on digital seismic waveform data from Inner Mongolia Digital Seismic Network,the source spectrum parameters of 182 small and moderate earthquakes from January,2009to September,2016 are derived,and the seismic mo...Based on digital seismic waveform data from Inner Mongolia Digital Seismic Network,the source spectrum parameters of 182 small and moderate earthquakes from January,2009to September,2016 are derived,and the seismic momentmoment magnitude MW of the earthquakes are calculated.Theand the relationship between stress drop and magnitude are obtained using the linear regression method.It is clear that incorporating the moment magnitude into the seismic quick report catalog and the official earthquake catalog can enrich earthquake observation report content,thus providing better service for earthquake emergency and earthquake scientific research.展开更多
The change laws of intensity of nearly 200 moderate-small earthquakes with Ms=2.0~5.5 occurring on the Chinese mainland since 1954 have been analyzed and are compared with that of moderately strong earthquakes(Ms≥5.0...The change laws of intensity of nearly 200 moderate-small earthquakes with Ms=2.0~5.5 occurring on the Chinese mainland since 1954 have been analyzed and are compared with that of moderately strong earthquakes(Ms≥5.0).The results show that there is quite obvious regionality in the statistical laws by both moderate-small earthquakes and moderately strong earthquakes:attenuation of intensity in Eastern China is slower than that in Western China and the ratio of the major axis to the minor axis of iso-seismal lines in Eastern China is smaller than that in Western China.The results also show that for a fixed magnitude the attenuation of intensity of moderate-small earthquakes is faster when intensity is higher than V+ and slower when intensity is lower than V-in comparison with that of moderately strong earthquakes.Furthermore,there also have been some differences in the aspects as intensity-magnitude relation between statistical laws of moderate-small earthquakes and moderately strong earthquakes.These展开更多
Source spectra for moderate and small earthquakes are obtained after removing the path effect,site effect,and instrument response,etc. in the observed S-wave spectra. Based on the Brune source model and by means of ge...Source spectra for moderate and small earthquakes are obtained after removing the path effect,site effect,and instrument response,etc. in the observed S-wave spectra. Based on the Brune source model and by means of genetic algorithm, the source parameters including seismic moment, stress drop, source dimension, etc. are determined, the radiated seismic energy for small-to-moderate earthquakes is measured with consideration of underestimation and compensation brought forth by limited bandwidth of the instrument,and the scaling relationships of static and dynamic parameters for earthquakes with M_L 2. 0 ~ 5. 3 in the Yunnan region are analyzed. The results show that the seismic moment is between 2. 1 × 10^(12) N·m and 1. 2 × 10^(16) N·m,and there is a linear relation of lgM_0 = 1. 01M_L + 10. 59 between the seismic moment and local magnitude. The source dimension varies from 86. 9m to 1220. 4m. The seismic moment and rupture radius remain a linear correlation of lgM_0 = 0. 003a + 12. 90. The stress drop is in the range of 0. 03 ~ 57. 55MPa,and increases with seismic moment for M_0 < 4 × 10^(14) N·m,but it doesn't vary with seismic moment for M_0 > 4 × 10^(14) N·m. The seismic moment shows dependency of corner frequency. Assuming a constant stress drop,we can obtain the relationship of lgf_c = - 1/3 lgM_0 + 5. 32 between the seismic moment and corner frequency using least squares fitting. The theoretical radiated seismic energy is between 3. 01 × 10~6 J and 2. 06 × 10^(12) J. The linear relationship between the radiated seismic energy and local magnitude is lgE_R = 1. 18M_L + 5. 69. The scaled energy increases with seismic moment for M_0 < 4 × 10^(14) N·m,however it doesn't seem to vary with seismic moment for M_0 > 4 × 10^(14) N·m. The apparent stress is in the range of 0. 02 ~ 31. 4 MPa,and also seems independent of seismic depth.展开更多
Using the latest results of seismic tomography, we studied the deep tectonic settings of the moderate and strong earthquakes in Anhui Province and its neighboring areas (28°~39°N, 112°~124°E). Th...Using the latest results of seismic tomography, we studied the deep tectonic settings of the moderate and strong earthquakes in Anhui Province and its neighboring areas (28°~39°N, 112°~124°E). The results are as follows: (1) There exists a certain correlation between the location of moderate-strong earthquake, the geologic structure of the surface and the partitioning of active tectonic elements with the upper-crust velocity structure. Most earthquakes recording M≥6.0 occur in high-velocity zones or in the transitional areas between high-velocity and low-velocity zones in the upper crust. Seismicity in the low-velocity zone has a lesser impact. Earthquakes occuring in the high-velocity zone are distributed mainly in the velocity variation area. The boundary belts and the interior of the North China plain fault block are the main active sites of moderate-strong earthquakes. Beneath the fault basins in the western and northern sides of the block, the upper crust is characterized by a wide discontinuous distribution in the low-velocity zone, and in the transition zone from the low- to high velocities, the moderate strong seismicity shows a zonal distribution where active faults are developed. The NW-extension Zhoukou-Hefei-Xuancheng low-velocity zone separates the high-velocity zones of Dabieshan Mountains and west Shandong-Anhui, and moderate-strong earthquakes on its northern side bordering the high-velocity zones are relatively frequent. This low-velocity zone is probably an important and deeply structured boundary between the North China and the South China tectonic provinces. (2) The frequent moderate-strong earthquake recorded in the past and the recent small earthquake activities in the Huoshan-Lu’an area are the result of a low-velocity zone in the middle crust beneath the central part of Dabieshan and the two sets of deep faults that cut through the crust.(3) In terms of deep structures, the distribution of moderate-strong earthquake in Anhui Province has an obvious regional feature. Based on historical earthquake recurrence intervals and analogue principles of deep seismogenic tectonics, the potential earthquake risk zones recording M_S5.0 in Anhui Province are determined.展开更多
Based on the statistical results of the relationship between the large earthquakes surrounding Xinjiang and moderate earthquakes within Xinjiang since 1950,this article calculates the Coulomb failure stress change pro...Based on the statistical results of the relationship between the large earthquakes surrounding Xinjiang and moderate earthquakes within Xinjiang since 1950,this article calculates the Coulomb failure stress change produced by the three groups of large earthquakes surrounding Xinjiang during the large earthquake active period outside Xinjiang and the quiet period inside Xinjiang from 1976 to 2007,and analyzes Xinjiang's moderate earthquake activity features in the three years after the large earthquakes surrounding Xinjiang. It then discusses the influence of large earthquake activity surrounding Xinjiang on seismic activity within Xinjiang. The research results show that the large earthquake activity surrounding Xinjiang may to a certain extent slow down the preparation process of moderate earthquakes in Xinjiang.展开更多
The growing correlation length prior to the moderate-great earthquakes occurred in Gansu Province and its nearby area since 1986 has been studied using the method of single-link cluster analysis (SLC). According to di...The growing correlation length prior to the moderate-great earthquakes occurred in Gansu Province and its nearby area since 1986 has been studied using the method of single-link cluster analysis (SLC). According to different conditions in the source area, the circular spatial window centered in the epicenter and the parallelgrammic spatial window along the fault belt have been selected. The results show that the phenomena of growing correlation length have been observed before the earthquakes studied in the paper.展开更多
This paper deals with the distributive characteristics of the occurrence time of earthquakes with respect to the aftershock sequences of strong earthquakes. The distribution of lunar and solar local hour angles at the...This paper deals with the distributive characteristics of the occurrence time of earthquakes with respect to the aftershock sequences of strong earthquakes. The distribution of lunar and solar local hour angles at the time of commencement of moderate and strong aftershocks indicates that the time of commencement of moderate and strong aftershocks is modulated by the positions of the sun and moon and then the earthquake restrained time zones exists also. In this paper the differences of earthquake restrained time zones between the preshock sequences and the aftershock sequences are compared, and the possible mechanism is analyzed preliminarily. And the possible maximum scope of accuracy in predicting the occurrence time of an earthquake is determined as well.展开更多
文摘In this paper,characteristics of spatial and temporal variation of linear fitting goodness before some moderately strong earthquakes(Ms≥5.0)in the eastern part of China(east of longitude 180)are studied according to the famous Gutenberg-Richter’s relation expressed as lgN=a-bM,by using the moderate and small events that occurred in and around the source area.The results show that the linear goodness of fitting varies abnormally prior to these moderately strong earthquakes.In the early stage of the earthquake preparatory process,distribution of the energy released through small events in and around the source area is isostatic and the fitting goodness approximates 1,while the distribution of the energy turns to be isostatic before moderately strong earthquakes,leading to the obvious decrease of the linear goodness of fitting.This phenomenon could be a medium term anomaly and a medium term criterion for moderately strong earthquake prediction.
基金This project was sponsored by the Joint Earthquake Science Foundation (91013), China, contribution No. 96A0007, Institute of Geophysics, SSB, China
文摘The uncertainty of potential seismic regions for moderately strong earthquakes has a great effect on the results of seismic hazard analysis in weak seismicity regions,so it is the basement of seismic zoning and seismic hazard assessment for engineering sites by correctly dividing the potential seismic regions for moderately strong earthquakes.By taking Northeast and North China as examples,the authors compiled and systematically analyzed a large amount of basic data and then suggest the principles and methods of potential seismic regions for moderately strong earthquakes based on a great number of case studies.The practical division of potential seismic regions in the Changchun and Jilin areas shows that these principles and methods show better suitability.Moreover,the authors also discuss in this paper the progress obtained and put forward some problems that should be solved in the future.
文摘In this paper,approaches are developed to delineate the potential seismic source regions of moderately strong earthquakes that do not have clear seismotectonic settings.Based on comprehensive analysis of regional tectonic backgrounds and seismicity,the data,such as isoseisrnals,spatial distribution of after shocks,regional tectonic stress field,and focal mechanisms,are employed for the delineation of the potential seismic source regions.The reliability of such potential seismic source regions is also discussed.
基金sponsored by the Natural Science Foundation of Gansu Province (3ZS061-A25-008),China
文摘This paper analyzes the distribution characteristics of geomagnetic low-value displacement in Gansu and its adjacent areas from 1995 to 2003 on the basis of the data of the daily amplitude minimum value time of the geomagnetic vertical component. It is shown that in addition to the changing rules of geomagnetic low-value displacement itself, there is a better correlation between geomagnetic low-value displacement and the occurrence of moderately strong earthquakes. There appeared to be geomagnetic low-value displacement before the moderately strong earthquakes in Gansu in the 9 years from 1995 to 2003. This result indicates that geomagnetic low-value displacement is of instructive significance for earthquake prediction to some extents.
基金sponsored by the Subject of City ActiveFault Exploration Program of Urumqi and Joint Foundation of Earthquake Administration of Xinjiang Uygur Autonomous Region (200704),China
文摘Using the focal mechanism solutions of 24 moderately strong earthquakes in the northern Tianshan area,we carried out system cluster and stress field inversion analysis.The result indicates that,the focal mechanism solutions of moderately strong earthquakes are mainly dip-slip reverse faulting in the northern Tianshan area.The principal rupture planes of earthquakes are NW-oriented.It is basically consistent with the strike of earthquake structure in its adjacent area.The direction of the principal compression stress P axis is nearly NS,and its inclination angle is small;while the inclination angle of the principal extensional stress T axis is large.It shows that the regional stress field is mainly controlled by the near-NS horizontal compressive stress.The direction of the maximum principal stress shows a gradation process of NNE-NS-NW from east to west.
基金The National Key Basic Research Program under the Project "Mechanism and Prediction of Continental Strong Earthquake"(G1998040700) and Joint Seismological Science Foundation of China (100108).
文摘In the paper, source mechanisms of 33 small-moderate earthquakes occurred in Yunnan are determined by modeling of regional waveforms from Yunnan digital seismic network. The result shows that most earthquakes occurred within or near the Chuandian rhombic block have strike-slip mechanism. The orientations of maximum compressive stresses obtained from source mechanism are changed from NNW-SSN to NS in the areas from north to south of the block, and tensile stresses are mainly in ENE-WSW or NE-SE. In the eastern Tibetan Plateau, the orientations of maximum compressive stress radiate toward outside from the plateau, and the tensile stress orientations mostly parallel to arc structures. Near 28N the orientations of both maximum compressive stress and tensile stress changed greatly, and the boundary seems to correspond to the southwestern extended line of Longmenshan fault. Outside of the Chuandian rhombic block, the orientations of P and T axes are some different from those within the block. The comparison shows that the source mechanism of small-moderate events presented in the paper is consistence with that of moderate-strong earthquakes determined by Harvard University, which means the source mechanism of small-moderate events can be used to study the tectonic stress field in this region.
基金sponsored by the Teacher's Scientific Research Fund of the China Earthquake Administration(20090103)
文摘The relationships between Earth's rotation and the 1975 Haicheng, Liaoning MS7.3 earthquake, 2008 Wenchuan, Sichuan MS8.0 earthquake and the 2004 Sumatra MS9.0 earthquake, as well as moderate-small earthquakes occurring around the epicenter regions prior to them are investigated in this study. The obtained results could benefit the further understanding of the relationship between the Earth's rotation and earthquakes.
基金The International 973 Programs (2001CB711005 and 2004DFA06000) the Special Program of China Earthquake Administration (2004BA601B)
文摘The moment tensor solutions of 51 small to moderate earthquakes occurred in the Capital Region in the year of 2004 are obtained by inverting the broadband waveform data. Accordingly, other source parameters, such as scalar seismic moments, moment magnitudes, double-couple (DC) components and compensated-linear-vector-dipole (CLVD) components, are determined as well as fault parameters and stress-axis parameters. The inverted results are evaluated by groups of numerical tests.
基金sponsored by the Major Science and Technology Projects in Inner Mongolia Autonomous Region “Research,Development,Popularization and Demonstration of Earthquake Prediction and Early Warning Technology in Key Areas”
文摘Based on digital seismic waveform data from Inner Mongolia Digital Seismic Network,the source spectrum parameters of 182 small and moderate earthquakes from January,2009to September,2016 are derived,and the seismic momentmoment magnitude MW of the earthquakes are calculated.Theand the relationship between stress drop and magnitude are obtained using the linear regression method.It is clear that incorporating the moment magnitude into the seismic quick report catalog and the official earthquake catalog can enrich earthquake observation report content,thus providing better service for earthquake emergency and earthquake scientific research.
文摘The change laws of intensity of nearly 200 moderate-small earthquakes with Ms=2.0~5.5 occurring on the Chinese mainland since 1954 have been analyzed and are compared with that of moderately strong earthquakes(Ms≥5.0).The results show that there is quite obvious regionality in the statistical laws by both moderate-small earthquakes and moderately strong earthquakes:attenuation of intensity in Eastern China is slower than that in Western China and the ratio of the major axis to the minor axis of iso-seismal lines in Eastern China is smaller than that in Western China.The results also show that for a fixed magnitude the attenuation of intensity of moderate-small earthquakes is faster when intensity is higher than V+ and slower when intensity is lower than V-in comparison with that of moderately strong earthquakes.Furthermore,there also have been some differences in the aspects as intensity-magnitude relation between statistical laws of moderate-small earthquakes and moderately strong earthquakes.These
基金funded jointly by the Key Applied and Fundamental Research Project of Yunnan Province (2010CC006)the Key Project of Yunnan Province (JCYB-20080601-4)the Joint Earthquake Science Foundation of China (C08065)
文摘Source spectra for moderate and small earthquakes are obtained after removing the path effect,site effect,and instrument response,etc. in the observed S-wave spectra. Based on the Brune source model and by means of genetic algorithm, the source parameters including seismic moment, stress drop, source dimension, etc. are determined, the radiated seismic energy for small-to-moderate earthquakes is measured with consideration of underestimation and compensation brought forth by limited bandwidth of the instrument,and the scaling relationships of static and dynamic parameters for earthquakes with M_L 2. 0 ~ 5. 3 in the Yunnan region are analyzed. The results show that the seismic moment is between 2. 1 × 10^(12) N·m and 1. 2 × 10^(16) N·m,and there is a linear relation of lgM_0 = 1. 01M_L + 10. 59 between the seismic moment and local magnitude. The source dimension varies from 86. 9m to 1220. 4m. The seismic moment and rupture radius remain a linear correlation of lgM_0 = 0. 003a + 12. 90. The stress drop is in the range of 0. 03 ~ 57. 55MPa,and increases with seismic moment for M_0 < 4 × 10^(14) N·m,but it doesn't vary with seismic moment for M_0 > 4 × 10^(14) N·m. The seismic moment shows dependency of corner frequency. Assuming a constant stress drop,we can obtain the relationship of lgf_c = - 1/3 lgM_0 + 5. 32 between the seismic moment and corner frequency using least squares fitting. The theoretical radiated seismic energy is between 3. 01 × 10~6 J and 2. 06 × 10^(12) J. The linear relationship between the radiated seismic energy and local magnitude is lgE_R = 1. 18M_L + 5. 69. The scaled energy increases with seismic moment for M_0 < 4 × 10^(14) N·m,however it doesn't seem to vary with seismic moment for M_0 > 4 × 10^(14) N·m. The apparent stress is in the range of 0. 02 ~ 31. 4 MPa,and also seems independent of seismic depth.
基金The research was under the key science and technologyresearchfunds of the Earthquake Administration of Anhui Province ,China .
文摘Using the latest results of seismic tomography, we studied the deep tectonic settings of the moderate and strong earthquakes in Anhui Province and its neighboring areas (28°~39°N, 112°~124°E). The results are as follows: (1) There exists a certain correlation between the location of moderate-strong earthquake, the geologic structure of the surface and the partitioning of active tectonic elements with the upper-crust velocity structure. Most earthquakes recording M≥6.0 occur in high-velocity zones or in the transitional areas between high-velocity and low-velocity zones in the upper crust. Seismicity in the low-velocity zone has a lesser impact. Earthquakes occuring in the high-velocity zone are distributed mainly in the velocity variation area. The boundary belts and the interior of the North China plain fault block are the main active sites of moderate-strong earthquakes. Beneath the fault basins in the western and northern sides of the block, the upper crust is characterized by a wide discontinuous distribution in the low-velocity zone, and in the transition zone from the low- to high velocities, the moderate strong seismicity shows a zonal distribution where active faults are developed. The NW-extension Zhoukou-Hefei-Xuancheng low-velocity zone separates the high-velocity zones of Dabieshan Mountains and west Shandong-Anhui, and moderate-strong earthquakes on its northern side bordering the high-velocity zones are relatively frequent. This low-velocity zone is probably an important and deeply structured boundary between the North China and the South China tectonic provinces. (2) The frequent moderate-strong earthquake recorded in the past and the recent small earthquake activities in the Huoshan-Lu’an area are the result of a low-velocity zone in the middle crust beneath the central part of Dabieshan and the two sets of deep faults that cut through the crust.(3) In terms of deep structures, the distribution of moderate-strong earthquake in Anhui Province has an obvious regional feature. Based on historical earthquake recurrence intervals and analogue principles of deep seismogenic tectonics, the potential earthquake risk zones recording M_S5.0 in Anhui Province are determined.
基金sponsored the National Key TechnologyR&D Program (2006BAC 01B03-04-02),China
文摘Based on the statistical results of the relationship between the large earthquakes surrounding Xinjiang and moderate earthquakes within Xinjiang since 1950,this article calculates the Coulomb failure stress change produced by the three groups of large earthquakes surrounding Xinjiang during the large earthquake active period outside Xinjiang and the quiet period inside Xinjiang from 1976 to 2007,and analyzes Xinjiang's moderate earthquake activity features in the three years after the large earthquakes surrounding Xinjiang. It then discusses the influence of large earthquake activity surrounding Xinjiang on seismic activity within Xinjiang. The research results show that the large earthquake activity surrounding Xinjiang may to a certain extent slow down the preparation process of moderate earthquakes in Xinjiang.
基金Joint Seismological Science Foundation of China (95-07-436)
文摘The growing correlation length prior to the moderate-great earthquakes occurred in Gansu Province and its nearby area since 1986 has been studied using the method of single-link cluster analysis (SLC). According to different conditions in the source area, the circular spatial window centered in the epicenter and the parallelgrammic spatial window along the fault belt have been selected. The results show that the phenomena of growing correlation length have been observed before the earthquakes studied in the paper.
文摘This paper deals with the distributive characteristics of the occurrence time of earthquakes with respect to the aftershock sequences of strong earthquakes. The distribution of lunar and solar local hour angles at the time of commencement of moderate and strong aftershocks indicates that the time of commencement of moderate and strong aftershocks is modulated by the positions of the sun and moon and then the earthquake restrained time zones exists also. In this paper the differences of earthquake restrained time zones between the preshock sequences and the aftershock sequences are compared, and the possible mechanism is analyzed preliminarily. And the possible maximum scope of accuracy in predicting the occurrence time of an earthquake is determined as well.