The three largest earthquakes in northern California since 1849 were preceded by increased decadal activity for moderate-size shocks along surrounding nearby faults. Increased seismicity, double-difference precise loc...The three largest earthquakes in northern California since 1849 were preceded by increased decadal activity for moderate-size shocks along surrounding nearby faults. Increased seismicity, double-difference precise locations of earthquakes since 1968, geodetic data and fault offsets for the 1906 great shock are used to re-examine the timing and locations of possible future large earthquakes. The physical mechanisms of regional faults like the Calaveras, Hayward and Sargent, which exhibit creep, differ from those of the northern San Andreas, which is currently locked and is not creeping. Much decadal forerunning activity occurred on creeping faults. Moderate-size earthquakes along those faults became more frequent as stresses in the region increased in the latter part of the cycle of stress restoration for major and great earthquakes along the San Andreas. They may be useful for decadal forecasts. Yearly to decadal forecasts, however, are based on only a few major to great events. Activity along closer faults like that in the two years prior to the 1989 Loma Prieta shock needs to be examined for possible yearly forerunning changes to large plate boundary earthquakes. Geodetic observations are needed to focus on identifying creeping faults close to the San Andreas. The distribution of moderate-size earthquakes increased significantly since 1990 along the Hayward fault but not adjacent to the San Andreas fault to the south of San Francisco compared to what took place in the decades prior to the three major historic earthquakes in the region. It is now clear from a re-examination of the 1989 mainshock that the increased level of moderate-size shocks in the one to two preceding decades occurred on nearby East Bay faults. Double-difference locations of small earthquakes provide structural information about faults in the region, especially their depths. The northern San Andreas fault is divided into several strongly coupled segments based on differences in seismicity.展开更多
Various geologic signatures of fault creep along most of the active faults in the continental area of China can be recognized, although no surface deformation caused by creep slip event has been observed. These ...Various geologic signatures of fault creep along most of the active faults in the continental area of China can be recognized, although no surface deformation caused by creep slip event has been observed. These signatures include ordered regional taphrogeny, linear deformation zones distributed along the fault, and seismic slip rate much lower than the geologic slip rate, etc. The recognition and identification of this important fault behavior are of great theoretical and practical significance.展开更多
The correlation between the creep rupture behaviour and the stacking fault energy of matrices of γ′strengthened superalloys has been studied dur- ing constant load creep.At high temperature and intermediate stress,t...The correlation between the creep rupture behaviour and the stacking fault energy of matrices of γ′strengthened superalloys has been studied dur- ing constant load creep.At high temperature and intermediate stress,the creep rupture time and strain strongly depend on the stacking fault energy of matrices rather than the creep friction stress,but at higher stress,the role of grain boundary carbides becomes more obvious. However,in the considerably extensive stress range investigated here,the mean creep rate is a power function of the stacking fault energy of matrices and the power index decreases with in- creasing initial applied stress.Particularly,at inter- mediate stresses the product of this index and the initial applied stress compensated by the shear modulus is same for two series of superalloys. Hence,this product may be a criterion predicting that the matrix deformation controls high tempera- ture creep rupture.展开更多
Through the collection of oriented samples,consolidation of undisturbed samples,and systematic microscopy of thin sections,the deformation products from the Daqingshan piedmont active fault zone have been studied.The ...Through the collection of oriented samples,consolidation of undisturbed samples,and systematic microscopy of thin sections,the deformation products from the Daqingshan piedmont active fault zone have been studied.The obtained results have been analyzed in combination with those of rock fracture experiments and macroscopic surveys.Based on the above,the present article summarizes the microscopic indicators of stick-slip and creep-slip,which reflect the characteristics of fault movement,and has given some suggestion on relevant problems.展开更多
Abundant data have been gathered through measurements of radon gas emission in the soil on several major active faults,such as San Andreas and Calaveras,in California,U.S.A..They show radon emissions and their spatial...Abundant data have been gathered through measurements of radon gas emission in the soil on several major active faults,such as San Andreas and Calaveras,in California,U.S.A..They show radon emissions and their spatial variations at the unlocked,locked,and creeping sections of faults with different tectonic movements.The characteristics of these variations and the role of fault gases in the research on earthquake prediction are discussed in this paper.展开更多
Based on fault geometric features,composite pattern,faulting land-forms and seismic data,this paper discussed the activity behavior along the northern segment of the Anninghe fault(from Xichang to Shimian)since the La...Based on fault geometric features,composite pattern,faulting land-forms and seismic data,this paper discussed the activity behavior along the northern segment of the Anninghe fault(from Xichang to Shimian)since the Late Pleistocene.The fault can be divided into three active segments by discrepancies of their activity:the segment from Xichang to Mianning,the segment from Mianning to Zimakua,and the segment from Zimakua to Tianwan.The southern segment has the background of occurrence of great earthquakes,but the middle and the northern segments can generate strong and moderate events respectively.According to the features of quartz from fault gouges by scanning electron microscopy(SEM),this paper discussed the movement features along the fault and indicated the stick-slipping feature on the segment from Xichang to Zimakua,the creeping feature on the segment from Jiziping to Tianwan and the transitional feature on the segment in between.展开更多
The comparative study of the geologic and seismic dislocations often major active faults,such as the Aikin fault etc.,on China mainland,has shown that the ratio between the seismic slip rate(Vs)and geologic slip rate(...The comparative study of the geologic and seismic dislocations often major active faults,such as the Aikin fault etc.,on China mainland,has shown that the ratio between the seismic slip rate(Vs)and geologic slip rate(Vg),i.e.,Q=Vs/Vg,for most of the active faults ranges between 0.5-0.8,indicating that most of the active faults are characterized by stick slip movement.According to the magnitude of the Q value,the slip mode of the faults can further be classified into four types:strong stick-slip(Q≥0.75),mainly stick-slip(0.5≤Q【0.75),mainly creep-slip(0.5】0≥0.25),and strong creep-slip(Q【0.25).The authors have also analyzed the constraint of the determination of Q value,as well as the prospect of the application of Q value to the determination of slip mode of major active faults.展开更多
文摘The three largest earthquakes in northern California since 1849 were preceded by increased decadal activity for moderate-size shocks along surrounding nearby faults. Increased seismicity, double-difference precise locations of earthquakes since 1968, geodetic data and fault offsets for the 1906 great shock are used to re-examine the timing and locations of possible future large earthquakes. The physical mechanisms of regional faults like the Calaveras, Hayward and Sargent, which exhibit creep, differ from those of the northern San Andreas, which is currently locked and is not creeping. Much decadal forerunning activity occurred on creeping faults. Moderate-size earthquakes along those faults became more frequent as stresses in the region increased in the latter part of the cycle of stress restoration for major and great earthquakes along the San Andreas. They may be useful for decadal forecasts. Yearly to decadal forecasts, however, are based on only a few major to great events. Activity along closer faults like that in the two years prior to the 1989 Loma Prieta shock needs to be examined for possible yearly forerunning changes to large plate boundary earthquakes. Geodetic observations are needed to focus on identifying creeping faults close to the San Andreas. The distribution of moderate-size earthquakes increased significantly since 1990 along the Hayward fault but not adjacent to the San Andreas fault to the south of San Francisco compared to what took place in the decades prior to the three major historic earthquakes in the region. It is now clear from a re-examination of the 1989 mainshock that the increased level of moderate-size shocks in the one to two preceding decades occurred on nearby East Bay faults. Double-difference locations of small earthquakes provide structural information about faults in the region, especially their depths. The northern San Andreas fault is divided into several strongly coupled segments based on differences in seismicity.
文摘Various geologic signatures of fault creep along most of the active faults in the continental area of China can be recognized, although no surface deformation caused by creep slip event has been observed. These signatures include ordered regional taphrogeny, linear deformation zones distributed along the fault, and seismic slip rate much lower than the geologic slip rate, etc. The recognition and identification of this important fault behavior are of great theoretical and practical significance.
文摘The correlation between the creep rupture behaviour and the stacking fault energy of matrices of γ′strengthened superalloys has been studied dur- ing constant load creep.At high temperature and intermediate stress,the creep rupture time and strain strongly depend on the stacking fault energy of matrices rather than the creep friction stress,but at higher stress,the role of grain boundary carbides becomes more obvious. However,in the considerably extensive stress range investigated here,the mean creep rate is a power function of the stacking fault energy of matrices and the power index decreases with in- creasing initial applied stress.Particularly,at inter- mediate stresses the product of this index and the initial applied stress compensated by the shear modulus is same for two series of superalloys. Hence,this product may be a criterion predicting that the matrix deformation controls high tempera- ture creep rupture.
基金This project was sponsored by the Joint Earthquake Science Foundation (95133),China.
文摘Through the collection of oriented samples,consolidation of undisturbed samples,and systematic microscopy of thin sections,the deformation products from the Daqingshan piedmont active fault zone have been studied.The obtained results have been analyzed in combination with those of rock fracture experiments and macroscopic surveys.Based on the above,the present article summarizes the microscopic indicators of stick-slip and creep-slip,which reflect the characteristics of fault movement,and has given some suggestion on relevant problems.
文摘Abundant data have been gathered through measurements of radon gas emission in the soil on several major active faults,such as San Andreas and Calaveras,in California,U.S.A..They show radon emissions and their spatial variations at the unlocked,locked,and creeping sections of faults with different tectonic movements.The characteristics of these variations and the role of fault gases in the research on earthquake prediction are discussed in this paper.
文摘Based on fault geometric features,composite pattern,faulting land-forms and seismic data,this paper discussed the activity behavior along the northern segment of the Anninghe fault(from Xichang to Shimian)since the Late Pleistocene.The fault can be divided into three active segments by discrepancies of their activity:the segment from Xichang to Mianning,the segment from Mianning to Zimakua,and the segment from Zimakua to Tianwan.The southern segment has the background of occurrence of great earthquakes,but the middle and the northern segments can generate strong and moderate events respectively.According to the features of quartz from fault gouges by scanning electron microscopy(SEM),this paper discussed the movement features along the fault and indicated the stick-slipping feature on the segment from Xichang to Zimakua,the creeping feature on the segment from Jiziping to Tianwan and the transitional feature on the segment in between.
基金This pronject was sponsored by the Joint Earthquake Science Foundation,China.
文摘The comparative study of the geologic and seismic dislocations often major active faults,such as the Aikin fault etc.,on China mainland,has shown that the ratio between the seismic slip rate(Vs)and geologic slip rate(Vg),i.e.,Q=Vs/Vg,for most of the active faults ranges between 0.5-0.8,indicating that most of the active faults are characterized by stick slip movement.According to the magnitude of the Q value,the slip mode of the faults can further be classified into four types:strong stick-slip(Q≥0.75),mainly stick-slip(0.5≤Q【0.75),mainly creep-slip(0.5】0≥0.25),and strong creep-slip(Q【0.25).The authors have also analyzed the constraint of the determination of Q value,as well as the prospect of the application of Q value to the determination of slip mode of major active faults.
