This paper reviews the recent progress in the studies of experimental rock mechanics and tectonophysics concerning seismology and physics of the Earths interior in China. The progress is presented in the following asp...This paper reviews the recent progress in the studies of experimental rock mechanics and tectonophysics concerning seismology and physics of the Earths interior in China. The progress is presented in the following aspects: a) A lot of results of experiment and numerical simulation enrich our knowledge of the brittle fracturing process under the condition with heterogeneity in material and structure; b) Some new results on frictional behavior of non-homogeneous faults reveal the complexity of faulting behavior; c) Some new results on the brittle-plastic transition and plastic flow are obtained; especially the important progress is obtained on rheological properties of rocks in the lower crust and the upper mantle; d) A lot of experimental results are obtained on rock physics at high temperature and pressure and have been used in study of material composition and state. These results provide useful information for understanding the physical properties and deformation mechanisms of material of the Earths interior and earthquake physics.展开更多
The spatio-temporal characteristics of acoustic emission (AE) during the deformation of rock samples with compressional and extensional en-echelon faults have been studied. The results show that the pre-existing struc...The spatio-temporal characteristics of acoustic emission (AE) during the deformation of rock samples with compressional and extensional en-echelon faults have been studied. The results show that the pre-existing structure can significantly influence the patterns of AE spatial distribution. With increasing of differential stress, AE events firstly cluster around the two ends of pre-existing faults inside the jog and then along the line joining the two ends. The biggish AE events often occur around one end repeatedly. The image of AE clusters indicates the direction and the area of the fracture propagation. The direction of the macroscopic fracture in extensional and compressional jogs is perpendicular and parallel to the direction of axial stress, respectively. The weakening process before the fracturing of jog area is remarkable, and one of the typical precursors for the instability is that the cumulative frequency of AE events increases exponentially. After the fracturing of the jog the frequency and releasing strain energy of AE events decrease gradually. During the friction period, there is no precursory increasing of AE activity before the big stick-slip events. The change of b value in jog shows a typical change of decreasing tendentiously returning quickly before the instability. The decrease of b value occurs in the process of stress increasing and sometime goes down to the weakening stage, and the quick increase b values appears in a short time just before the instability. The comparative analysis shows that the difference in b value due to the different structures is larger than b value variation caused by increase of the differential stress. For the same sample, the temporal sequence of AE is strongly affected by the mechanical state, and the high loading velocity corresponds to the high release rate of strain energy and low b value. Due to its lower failure strength, the broken area is sensitive to small changes in differential stress. Therefore, it offers a potential explanation for the phenomena of precursory window or sensitive point and separation of seismic source and precursors.展开更多
The Region-Time-Length Algorithm (RTL algorithm) is introduced and improved in the paper. Compared with the original definition, the influence of rupture length on RTL function is emphasized and the weights of epicent...The Region-Time-Length Algorithm (RTL algorithm) is introduced and improved in the paper. Compared with the original definition, the influence of rupture length on RTL function is emphasized and the weights of epicentral distance function, time function, and rupture length function are ensured to be equal. The retrospective examinations of RTL algorithm in North China have indicated that the anomalies obtained by the improved RTL algorithm show the short or intermediate-short term precursory features in most cases. There are two types of RTL anomalous patterns before the main shock. For the I-type, the variation pattern of the VRTL, numerical values of the VRTL(x, y, z, t) function, is complete and most of them have shown the changing pattern of rising from 0 turning dropping or dropping from 0 turning rising. For the II-type, the variation pattern of VRTL is not complete, which increases or decreases quickly from 0 and there is no evident turning, the main shock generally occurs in the short period around the peak VRTL. The rising of VRTL indicates an increase of seismic activity relative to the background level, which means the enhancement of seismic activity, while the dropping of VRTL indicates the decrease of seismic activity relative to the background level, which represents the seismic quiescence to a certain extent. According to statistical examination results of RTL algorithm in North China, the methods to distinguish the intermediate and short-term anomalies and to estimate the occurrence time of the coming main shock are given in the paper. For both I and II-type RTL anomalies, the R-value, i.e., the forecasting score, is about 0.6 and 0.3 for the 3 months forecasting period and about 0.7 and 0.4 for the 6 months forecasting period. The preliminary discussion is also made for the influences of characteristic time-span t0, characteristic distance r0, and threshold magnitude M0 on computation of VRTL, as well as some other significant problems in application.展开更多
By dealing with strain and acoustic emission (AE) data for two parallelling faultss instability and failure with the same slip direction including asperities, the temporal-spatial evolution of strain and AE field dist...By dealing with strain and acoustic emission (AE) data for two parallelling faultss instability and failure with the same slip direction including asperities, the temporal-spatial evolution of strain and AE field distribution on the asperity of parallelling faults is analyzed. Furthermore the failure process of asperities and interaction among the asperities, i.e., positive and negative seismicity are discussed. Results show that instability and failure for the parallelling faults is a kind of negative seismicity.展开更多
Interferometry Synthetic Aperture Radar (InSAR) is a kind of new earth observation technique and great development has been made in the recent ten years. In the paper, InSAR and Differential Interferometric Synthetic ...Interferometry Synthetic Aperture Radar (InSAR) is a kind of new earth observation technique and great development has been made in the recent ten years. In the paper, InSAR and Differential Interferometric Synthetic Aperture Radar (D-InSAR) are generally introduced; then the factors affecting the data accuracy are primarily discussed. The 1997 Mani earthquake was selected as an example to obtain the coseismic deformation field with the three-pass differential interferometric processing method. The results show that the coseismic deformation field is about 200 km in length and 115 km in width. The interferometric fringes spread in the area with the NEE-trending seismogenic fault the Margaichaka fault as the center and they are primarily parallel to the fault. Based on the analysis to the interferogram, the seismogenic fault can be divided into three segments. The whole fault is about 110 km and the length of each segment from the west to the east is about 23 km, 60 km and 26 km. The maximum uplifting displacement in the side-looking direction near the seismic center is about 162.4 cm, the maximum subsiding displacement in the side-looking direction in the western part of the fault is about 103.6 cm, and the maximum horizontal surface dislocation near the seismic center is about 7.96 m.展开更多
The primary pattern of the late Cenozoic to the present tectonic deformation of China is characterized by relative movements and interactions of tectonic blocks. Active tectonic blocks are geological units that have b...The primary pattern of the late Cenozoic to the present tectonic deformation of China is characterized by relative movements and interactions of tectonic blocks. Active tectonic blocks are geological units that have been separated from each other by active tectonic zones. Boundaries between blocks are the highest gradient of differential movement. Most of tectonic activity occurs on boundaries of the blocks. Earthquakes are results of abrupt releases of accumulated strain energy that reaches the threshold of strength of the earth's crust. Boundaries of tectonic blocks are the locations of most discontinuous deformation and highest gradient of stress accumulation, thus are the most likely places for strain energy accumulation and releases, and in turn, devastating earthquakes. Almost all earthquakes of magnitude greater than 8 and 80%-90% of earthquakes of magnitude over 7 occur along boundaries of active tectonic blocks. This fact indicates that differential movements and interactions of active tectonic blocks are the primary mechanism for the occurrences of devastating earthquakes.展开更多
We have carried out a systematic experimental study on semi-brittle and plastic deformation of fine-grained Panzhihua gabbro under dry condition with temperature range of 700–1100 °C, confining pressure of 450–...We have carried out a systematic experimental study on semi-brittle and plastic deformation of fine-grained Panzhihua gabbro under dry condition with temperature range of 700–1100 °C, confining pressure of 450–500 MPa, and strain rate of 1 × 10-4-3.1 × 10-6 s-1, using a triaxial testing system with a Griggs type solid medium pressure vessel. In terms of the parameters in the flow law and microstructure after deformation, the rate-dependent deformation can be categorized into three modes: (i) In temperature range of 700–800°C, the deformation is accommodated by semi-brittle flow, with activation energy Q = 612 ± 12 kJ/mol, and stress exponent n = 14.6. The deformation in microscopic scale corresponds to the dislocation glide accompanied with microfracturing. (ii) In temperature range of 90–950°C, the predominant deformation mechanisms in this phase are mechanical twinning and dislocation glide, with activation energy Q =720 ± 61 kJ/mol, and stress exponent n = 6.4. (iii) In temperature range of 1000–1150°C, the major deformation mechanisms are dislocation glide and dislocation climb with minor processes of partial melting, with activation energy Q = 699 ± 55 kJ/mol and stress exponent n = 4.1. The microstructure and deformation mechanism of our experiments are comparable to the results of clinopyroxene and diabase as observed in previous studies. The flow stress of a mafic lower crust is calculated based on the rheological parameters of dry fine-grained gabbro, which implies that a lower curst with mafic granulite may be brittle, and it is possible to fracture and produce frictional slips. This may be an important implication for earthquake nucleation in the lower crust.展开更多
The GPS data in and around the Ordos block area indicate that the left-lateral slip rate along the northern or southern margin of the Ordos block is about twice or three times as fast as the right-lateral slip rate al...The GPS data in and around the Ordos block area indicate that the left-lateral slip rate along the northern or southern margin of the Ordos block is about twice or three times as fast as the right-lateral slip rate along the eastern or western margin of the block. However, many researchers stressed the dextral-slip of the eastern or western boundaries of the Ordos block, and suggested that the block as a whole rotated counterclockwise based on the available geological data. Focusing on the inconsistency, we reexamine the late Cenozoic deformation pattern in the Ordos region based on seismicity data and geodesy data (GPS and leveling) around it. The results indicate that the rigid block-like motion appears to be the basic characteristic of the kinematics of the Ordos region, and this motion is absorbed by the displacement of the faults around the block. When the faults along the northern and southern boundaries of the Ordos block are active, its eastern boundary is inactive. However, if the faults along the eastern boundary are active, the northern and southern are inactive. In recent years, the northern and southern boundaries of the Ordos block are in active. But in the long term, the Ordos block is moving southeastward relative to the Alxa and Yinshan blocks because of the strong pushing of the Tibetan Plateau on its southwestern side, and this deformation is accommodated by the counterclockwise rotation of the block itself.展开更多
The nucleation process of stick-slip instability was analyzed based on the experimental measurements of strain and fault slip on homogeneous and non-homogeneous faults. The results show that the nucleation process of ...The nucleation process of stick-slip instability was analyzed based on the experimental measurements of strain and fault slip on homogeneous and non-homogeneous faults. The results show that the nucleation process of stick-slip on the homogeneous fault is of weak slip-weakening behavior under constant loading point velocity. The existence of a short "weak segment" on the fault makes slip-weakening phenomenon in nucleation process more obvious, while the existence of a long "weak segment" on the fault makes the nucleation process changed. The nucleation is characterized by accelerating slip in a local region and rapid increase of shear stress along the fault in this case, which is more coincident with the rate and state friction law. During the period when fault is locked, increasing of shear stress causes lateral elastic dilation near the fault, and the rebound of the dilation at the time of instability causes an instantaneous increase of normal stress in the fault plane, which is an important factor making fault be rapidly locked and its strength recovered.展开更多
This study examines slip recurrence patterns in a two-block spring-slider model with rate- and state-dependent friction. Both weak and strong heterogeneities are considered with different settings of coupling stiffnes...This study examines slip recurrence patterns in a two-block spring-slider model with rate- and state-dependent friction. Both weak and strong heterogeneities are considered with different settings of coupling stiffness. The results show that the recurrence pattern of slips strongly depends on the degree of coupling between the two blocks. With strong coupling between the two blocks (e.g., kc/ki max >~1), the slip pattern of the system is simple and characterized by periodical stick-slips, with the two blocks slipping together. With strong heterogeneity in friction strength, period-2 motion is found for moderate coupling stiffness (kc/ki max=0.4) between the two blocks. More complicated patterns are found with weak coupling stiffness (kc/ki max=0.2) and strong heterogeneity. With strong heterogeneity, very weak coupling leads to chaotic slip patterns. With coupling stiffness kc=5 ki max and strong heterogeneity, chaotic slip patterns are not found, in contrast with the results by Huang and Turcotte who employed the classical static/kinetic friction law.展开更多
Synthetic Aperture Radar Interferometry (for short, InSAR) is a new kind of earth observation technology, which has obtained great development in recent ten years and has a great development potential and successful f...Synthetic Aperture Radar Interferometry (for short, InSAR) is a new kind of earth observation technology, which has obtained great development in recent ten years and has a great development potential and successful future. In this note, three typical regions with different physiognomies and terrains have been selected as study regions to extract their Digital Elevation Model (OEMs). Compared with the existing 1 : 250000 DEM and by analyzing their results, we have obtained its accuracy and applicable scopes. The results show that in the region (plains, mountains or highlands) with dry surface and sparse vegetation, because of the better correlatability of images, the DEM obtained by InSAR is evidently better than the existing 1 : 250000 DEM and the accuracy can reach 4-6m; in the thick-vegetation-covering region, correlatability between images descends and the accuracy of InSAR DEM can only reach about 30 m worse than its existing 1:250000 DEM; in the middle covering field, the accuracy of InSAR DEM展开更多
文摘This paper reviews the recent progress in the studies of experimental rock mechanics and tectonophysics concerning seismology and physics of the Earths interior in China. The progress is presented in the following aspects: a) A lot of results of experiment and numerical simulation enrich our knowledge of the brittle fracturing process under the condition with heterogeneity in material and structure; b) Some new results on frictional behavior of non-homogeneous faults reveal the complexity of faulting behavior; c) Some new results on the brittle-plastic transition and plastic flow are obtained; especially the important progress is obtained on rheological properties of rocks in the lower crust and the upper mantle; d) A lot of experimental results are obtained on rock physics at high temperature and pressure and have been used in study of material composition and state. These results provide useful information for understanding the physical properties and deformation mechanisms of material of the Earths interior and earthquake physics.
基金Project Study on the Short-term Forecasting Technique of Strong Earthquake (01-04-01) during the Tenth Five-Year Plan from Ministry of Science and Technology of China and Joint Seismological Science Foundation of China (102037).
文摘The spatio-temporal characteristics of acoustic emission (AE) during the deformation of rock samples with compressional and extensional en-echelon faults have been studied. The results show that the pre-existing structure can significantly influence the patterns of AE spatial distribution. With increasing of differential stress, AE events firstly cluster around the two ends of pre-existing faults inside the jog and then along the line joining the two ends. The biggish AE events often occur around one end repeatedly. The image of AE clusters indicates the direction and the area of the fracture propagation. The direction of the macroscopic fracture in extensional and compressional jogs is perpendicular and parallel to the direction of axial stress, respectively. The weakening process before the fracturing of jog area is remarkable, and one of the typical precursors for the instability is that the cumulative frequency of AE events increases exponentially. After the fracturing of the jog the frequency and releasing strain energy of AE events decrease gradually. During the friction period, there is no precursory increasing of AE activity before the big stick-slip events. The change of b value in jog shows a typical change of decreasing tendentiously returning quickly before the instability. The decrease of b value occurs in the process of stress increasing and sometime goes down to the weakening stage, and the quick increase b values appears in a short time just before the instability. The comparative analysis shows that the difference in b value due to the different structures is larger than b value variation caused by increase of the differential stress. For the same sample, the temporal sequence of AE is strongly affected by the mechanical state, and the high loading velocity corresponds to the high release rate of strain energy and low b value. Due to its lower failure strength, the broken area is sensitive to small changes in differential stress. Therefore, it offers a potential explanation for the phenomena of precursory window or sensitive point and separation of seismic source and precursors.
文摘The Region-Time-Length Algorithm (RTL algorithm) is introduced and improved in the paper. Compared with the original definition, the influence of rupture length on RTL function is emphasized and the weights of epicentral distance function, time function, and rupture length function are ensured to be equal. The retrospective examinations of RTL algorithm in North China have indicated that the anomalies obtained by the improved RTL algorithm show the short or intermediate-short term precursory features in most cases. There are two types of RTL anomalous patterns before the main shock. For the I-type, the variation pattern of the VRTL, numerical values of the VRTL(x, y, z, t) function, is complete and most of them have shown the changing pattern of rising from 0 turning dropping or dropping from 0 turning rising. For the II-type, the variation pattern of VRTL is not complete, which increases or decreases quickly from 0 and there is no evident turning, the main shock generally occurs in the short period around the peak VRTL. The rising of VRTL indicates an increase of seismic activity relative to the background level, which means the enhancement of seismic activity, while the dropping of VRTL indicates the decrease of seismic activity relative to the background level, which represents the seismic quiescence to a certain extent. According to statistical examination results of RTL algorithm in North China, the methods to distinguish the intermediate and short-term anomalies and to estimate the occurrence time of the coming main shock are given in the paper. For both I and II-type RTL anomalies, the R-value, i.e., the forecasting score, is about 0.6 and 0.3 for the 3 months forecasting period and about 0.7 and 0.4 for the 6 months forecasting period. The preliminary discussion is also made for the influences of characteristic time-span t0, characteristic distance r0, and threshold magnitude M0 on computation of VRTL, as well as some other significant problems in application.
基金State Key Basic Research Development and Programming Project Mechanism and Prediction of Continental Strong Earthquake (G19980407) and Foundation of Laboratory of Tectonophysics China Seismological Bureau and State Natural Science Foundation of China (
文摘By dealing with strain and acoustic emission (AE) data for two parallelling faultss instability and failure with the same slip direction including asperities, the temporal-spatial evolution of strain and AE field distribution on the asperity of parallelling faults is analyzed. Furthermore the failure process of asperities and interaction among the asperities, i.e., positive and negative seismicity are discussed. Results show that instability and failure for the parallelling faults is a kind of negative seismicity.
基金Joint Seismological Science Foundation of China (102096) and State Natural Scientific Foundation of China (40142031 49802027) and State Key Basic Research Development and Programming Project (G1998040703).
文摘Interferometry Synthetic Aperture Radar (InSAR) is a kind of new earth observation technique and great development has been made in the recent ten years. In the paper, InSAR and Differential Interferometric Synthetic Aperture Radar (D-InSAR) are generally introduced; then the factors affecting the data accuracy are primarily discussed. The 1997 Mani earthquake was selected as an example to obtain the coseismic deformation field with the three-pass differential interferometric processing method. The results show that the coseismic deformation field is about 200 km in length and 115 km in width. The interferometric fringes spread in the area with the NEE-trending seismogenic fault the Margaichaka fault as the center and they are primarily parallel to the fault. Based on the analysis to the interferogram, the seismogenic fault can be divided into three segments. The whole fault is about 110 km and the length of each segment from the west to the east is about 23 km, 60 km and 26 km. The maximum uplifting displacement in the side-looking direction near the seismic center is about 162.4 cm, the maximum subsiding displacement in the side-looking direction in the western part of the fault is about 103.6 cm, and the maximum horizontal surface dislocation near the seismic center is about 7.96 m.
文摘The primary pattern of the late Cenozoic to the present tectonic deformation of China is characterized by relative movements and interactions of tectonic blocks. Active tectonic blocks are geological units that have been separated from each other by active tectonic zones. Boundaries between blocks are the highest gradient of differential movement. Most of tectonic activity occurs on boundaries of the blocks. Earthquakes are results of abrupt releases of accumulated strain energy that reaches the threshold of strength of the earth's crust. Boundaries of tectonic blocks are the locations of most discontinuous deformation and highest gradient of stress accumulation, thus are the most likely places for strain energy accumulation and releases, and in turn, devastating earthquakes. Almost all earthquakes of magnitude greater than 8 and 80%-90% of earthquakes of magnitude over 7 occur along boundaries of active tectonic blocks. This fact indicates that differential movements and interactions of active tectonic blocks are the primary mechanism for the occurrences of devastating earthquakes.
基金State Key Basic Science Research Project(Grant No.G1998040704) a project of the Laboratory of Tectonophysics China Seismological Bueanu
文摘We have carried out a systematic experimental study on semi-brittle and plastic deformation of fine-grained Panzhihua gabbro under dry condition with temperature range of 700–1100 °C, confining pressure of 450–500 MPa, and strain rate of 1 × 10-4-3.1 × 10-6 s-1, using a triaxial testing system with a Griggs type solid medium pressure vessel. In terms of the parameters in the flow law and microstructure after deformation, the rate-dependent deformation can be categorized into three modes: (i) In temperature range of 700–800°C, the deformation is accommodated by semi-brittle flow, with activation energy Q = 612 ± 12 kJ/mol, and stress exponent n = 14.6. The deformation in microscopic scale corresponds to the dislocation glide accompanied with microfracturing. (ii) In temperature range of 90–950°C, the predominant deformation mechanisms in this phase are mechanical twinning and dislocation glide, with activation energy Q =720 ± 61 kJ/mol, and stress exponent n = 6.4. (iii) In temperature range of 1000–1150°C, the major deformation mechanisms are dislocation glide and dislocation climb with minor processes of partial melting, with activation energy Q = 699 ± 55 kJ/mol and stress exponent n = 4.1. The microstructure and deformation mechanism of our experiments are comparable to the results of clinopyroxene and diabase as observed in previous studies. The flow stress of a mafic lower crust is calculated based on the rheological parameters of dry fine-grained gabbro, which implies that a lower curst with mafic granulite may be brittle, and it is possible to fracture and produce frictional slips. This may be an important implication for earthquake nucleation in the lower crust.
文摘The GPS data in and around the Ordos block area indicate that the left-lateral slip rate along the northern or southern margin of the Ordos block is about twice or three times as fast as the right-lateral slip rate along the eastern or western margin of the block. However, many researchers stressed the dextral-slip of the eastern or western boundaries of the Ordos block, and suggested that the block as a whole rotated counterclockwise based on the available geological data. Focusing on the inconsistency, we reexamine the late Cenozoic deformation pattern in the Ordos region based on seismicity data and geodesy data (GPS and leveling) around it. The results indicate that the rigid block-like motion appears to be the basic characteristic of the kinematics of the Ordos region, and this motion is absorbed by the displacement of the faults around the block. When the faults along the northern and southern boundaries of the Ordos block are active, its eastern boundary is inactive. However, if the faults along the eastern boundary are active, the northern and southern are inactive. In recent years, the northern and southern boundaries of the Ordos block are in active. But in the long term, the Ordos block is moving southeastward relative to the Alxa and Yinshan blocks because of the strong pushing of the Tibetan Plateau on its southwestern side, and this deformation is accommodated by the counterclockwise rotation of the block itself.
文摘The nucleation process of stick-slip instability was analyzed based on the experimental measurements of strain and fault slip on homogeneous and non-homogeneous faults. The results show that the nucleation process of stick-slip on the homogeneous fault is of weak slip-weakening behavior under constant loading point velocity. The existence of a short "weak segment" on the fault makes slip-weakening phenomenon in nucleation process more obvious, while the existence of a long "weak segment" on the fault makes the nucleation process changed. The nucleation is characterized by accelerating slip in a local region and rapid increase of shear stress along the fault in this case, which is more coincident with the rate and state friction law. During the period when fault is locked, increasing of shear stress causes lateral elastic dilation near the fault, and the rebound of the dilation at the time of instability causes an instantaneous increase of normal stress in the fault plane, which is an important factor making fault be rapidly locked and its strength recovered.
文摘This study examines slip recurrence patterns in a two-block spring-slider model with rate- and state-dependent friction. Both weak and strong heterogeneities are considered with different settings of coupling stiffness. The results show that the recurrence pattern of slips strongly depends on the degree of coupling between the two blocks. With strong coupling between the two blocks (e.g., kc/ki max >~1), the slip pattern of the system is simple and characterized by periodical stick-slips, with the two blocks slipping together. With strong heterogeneity in friction strength, period-2 motion is found for moderate coupling stiffness (kc/ki max=0.4) between the two blocks. More complicated patterns are found with weak coupling stiffness (kc/ki max=0.2) and strong heterogeneity. With strong heterogeneity, very weak coupling leads to chaotic slip patterns. With coupling stiffness kc=5 ki max and strong heterogeneity, chaotic slip patterns are not found, in contrast with the results by Huang and Turcotte who employed the classical static/kinetic friction law.
基金This work was supported by the Key Basic Research and Development Program of China (Grant No. G1998040703)the National Natural Science Foundation of China (Grant No.49802027).
文摘Synthetic Aperture Radar Interferometry (for short, InSAR) is a new kind of earth observation technology, which has obtained great development in recent ten years and has a great development potential and successful future. In this note, three typical regions with different physiognomies and terrains have been selected as study regions to extract their Digital Elevation Model (OEMs). Compared with the existing 1 : 250000 DEM and by analyzing their results, we have obtained its accuracy and applicable scopes. The results show that in the region (plains, mountains or highlands) with dry surface and sparse vegetation, because of the better correlatability of images, the DEM obtained by InSAR is evidently better than the existing 1 : 250000 DEM and the accuracy can reach 4-6m; in the thick-vegetation-covering region, correlatability between images descends and the accuracy of InSAR DEM can only reach about 30 m worse than its existing 1:250000 DEM; in the middle covering field, the accuracy of InSAR DEM
