Based on the research of computer model on unified seismogenic process of grouped earthquakes in tectonic blockunder tectonodynamic force, some characteristics of seismic activity and some features of earthquake precu...Based on the research of computer model on unified seismogenic process of grouped earthquakes in tectonic blockunder tectonodynamic force, some characteristics of seismic activity and some features of earthquake precursoryfield have been studied, including activity of grouped earthquakes, the relationship between earthquake activityand earthquake precursors, the cause of earthquake precursors and so on. By comparing research between the results of theoretical model and practical earthquake cases, some physical explanation for seismogenic process,some characteristics of earthquake activity, and the features of earthquake precursory field have been given.展开更多
Mathematical models in seismo-geochemical monitoring offer powerful tools for the study and exploration of complex dynamics associated with discharge of radon as the indicator of change of intense-deformed conditions ...Mathematical models in seismo-geochemical monitoring offer powerful tools for the study and exploration of complex dynamics associated with discharge of radon as the indicator of change of intense-deformed conditions of seismogenic layers or blocks within the lithosphere. Seismic precursory model of radon gas emanation in the process of earthquake prediction research aims to find out the distinct anomaly variation necessary to correlate radon gas with processes of preparation and realization of tectonic earthquakes in long-term and short-term forecasts tectonic earthquakes. The study involves a radon gas volume analytic model to find the correlation of radon fluctuations to stress drop under compression and dilatation strain condition. Here, we present a mathematical inference by observing radon gas emanation prior to the occurrence of earthquake that may reduce the uncertainties in models and updating their probability distributions in a Bayesian deterministic model. Using Bayesian melding theorem, we implement an inferential framework to understand the process of preparation of tectonic earthquake and concurrent occurrence of radon discharge during a tectonic earthquake phenomena. Bayesian melding for deterministic simulation models was augmented to make use of prior knowledge on correlations between model inputs. The background porosity is used as a priori information for analyzing the block subjected to inelastic strain. It can be inferred that use of probabilistic framework involving exhalation of radon may provide a scenario of earthquake occurrences on recession of the curve that represents a qualitative pattern of radon activity concentration drop, indicating associated stress change within the causative seismogenic fault. Using evidence analysis, we propose a joint conditional probability framework model simulation to understand how a single fracture may be affected in response to an external load and radon anomaly change that can be used to detect the slip, a predictable nature of the causative fault in the subsurface rock.展开更多
The northern margin of the South China Sea, as a typical extensional continental margin, has relatively strong intraplate seismicity. Compared with the active zones of Nanao Island, Yangjiang, and Heyuan, seismicity i...The northern margin of the South China Sea, as a typical extensional continental margin, has relatively strong intraplate seismicity. Compared with the active zones of Nanao Island, Yangjiang, and Heyuan, seismicity in the Pearl River Estuary is relatively low. However, a ML4.0 earthquake in 2006 occurred near Dangan Island(DI) offshore Hong Kong, and this site was adjacent to the source of the historical M5.8 earthquake in 1874. To reveal the seismogenic mechanism of intraplate earthquakes in DI, we systematically analyzed the structural characteristics in the source area of the 2006 DI earthquake using integrated 24-channel seismic profiles, onshore–offshore wide-angle seismic tomography, and natural earthquake parameters. We ascertained the locations of NW-and NE-trending faults in the DI sea and found that the NE-trending DI fault mainly dipped southeast at a high angle and cut through the crust with an obvious low-velocity anomaly. The NW-trending fault dipped southwest with a similar high angle. The 2006 DI earthquake was adjacent to the intersection of the NE-and NW-trending faults, which suggested that the intersection of the two faults with different strikes could provide a favorable condition for the generation and triggering of intraplate earthquakes. Crustal velocity model showed that the high-velocity anomaly was imaged in the west of DI, but a distinct entity with low-velocity anomaly in the upper crust and high-velocity anomaly in the lower crust was found in the south of DI. Both the 1874 and 2006 DI earthquakes occurred along the edge of the distinct entity. Two vertical cross-sections nearly perpendicular to the strikes of the intersecting faults revealed good spatial correlations between the 2006 DI earthquake and the low to high speed transition in the distinct entity. This result indicated that the transitional zone might be a weakly structural body that can store strain energy and release it as a brittle failure, resulting in an earthquake-prone area.展开更多
In this paper, we discussed the seismotectonic environment of the deep-seated and shallowcrust and seismological and geological model caused the 1927 Gulang great earthquake, basedon the recent research concerning abo...In this paper, we discussed the seismotectonic environment of the deep-seated and shallowcrust and seismological and geological model caused the 1927 Gulang great earthquake, basedon the recent research concerning about the active fault, surface rupture, fault planesolution, seismic activity, as well as the deep geophysical exploration data analysis in theepicentral area.The result shows that the 1927 Gulang great earthquake was caused by NE-SW-strikingcompressional thrusting. It was a latest event occurred in the reverse fault-folding belt thatdeveloped along the intracrustal decollement.展开更多
The features of precursors of crustal deformation and gravity before some strong earthquakes in North China have been analyzed. The results show that, before strong earthquakes, a close tectonics-dependent dynamic pro...The features of precursors of crustal deformation and gravity before some strong earthquakes in North China have been analyzed. The results show that, before strong earthquakes, a close tectonics-dependent dynamic process should exist in large areas and the media in the epicentral area should change their state. With these results as a basis, an improved combination-hardening model has been put forward. When the adjusting element moves, the tectonic movements is intensified in large areas and the density of deep media on both sides of faults will be changed. In the stress concentration element, there will be a media hardening process due to the continuous accumulation of energy. It is such a mechanism that results in the various steps of precursors.展开更多
In seismic hazard analysis of nuclear power plant of China there is a need to identify both seismogenic structures and seismotectonic zones. In past practice,the identification of the seismogenic structures was often ...In seismic hazard analysis of nuclear power plant of China there is a need to identify both seismogenic structures and seismotectonic zones. In past practice,the identification of the seismogenic structures was often based on the surface active faults and characterization of linear seismic source. In a situation which shows quite strong non-random seismic activity and lacks surface active faults,it is difficult to evaluate the seismic hazard reasonably. Taking seismogenic structures in the Dayao-Yao'an area as a case study in this paper,we discuss the need and the possibility to apply the planar seismogenic structure to the seismotectonic method. We suggest that the planar seismogenic structure should be considered when applying the seismotectonic method to the seismic risk assessment of nuclear engineering in future.展开更多
Experiments were conducted repeatedly on Mannari granite under different temperature and confining pressure conditions. Systematic micro- and submicro-structural and mechanical analyses of granite samples deformed und...Experiments were conducted repeatedly on Mannari granite under different temperature and confining pressure conditions. Systematic micro- and submicro-structural and mechanical analyses of granite samples deformed under 1.5 GPa (confining pressure), at 25 ℃-650 ℃ temperatures and at 2×10-6s-1 strain rate show the brittle-ductile deformation microstructures and microstructural associations similar to those observed in naturally deformed crustal rocks and minerals. Brittle fracturing and crystalline plasticity co-exist and react with each other in the brittle-ductile transition domain of the continental lithosphere. The interaction between the different mechanisms in the transitional domain results in the variation of anomalous strength values, which may best explain the genesis of the continental seismogenic zone. A new fault zone model is proposed on the basis of detailed micromechanical and microstructural analyses.展开更多
文摘Based on the research of computer model on unified seismogenic process of grouped earthquakes in tectonic blockunder tectonodynamic force, some characteristics of seismic activity and some features of earthquake precursoryfield have been studied, including activity of grouped earthquakes, the relationship between earthquake activityand earthquake precursors, the cause of earthquake precursors and so on. By comparing research between the results of theoretical model and practical earthquake cases, some physical explanation for seismogenic process,some characteristics of earthquake activity, and the features of earthquake precursory field have been given.
文摘Mathematical models in seismo-geochemical monitoring offer powerful tools for the study and exploration of complex dynamics associated with discharge of radon as the indicator of change of intense-deformed conditions of seismogenic layers or blocks within the lithosphere. Seismic precursory model of radon gas emanation in the process of earthquake prediction research aims to find out the distinct anomaly variation necessary to correlate radon gas with processes of preparation and realization of tectonic earthquakes in long-term and short-term forecasts tectonic earthquakes. The study involves a radon gas volume analytic model to find the correlation of radon fluctuations to stress drop under compression and dilatation strain condition. Here, we present a mathematical inference by observing radon gas emanation prior to the occurrence of earthquake that may reduce the uncertainties in models and updating their probability distributions in a Bayesian deterministic model. Using Bayesian melding theorem, we implement an inferential framework to understand the process of preparation of tectonic earthquake and concurrent occurrence of radon discharge during a tectonic earthquake phenomena. Bayesian melding for deterministic simulation models was augmented to make use of prior knowledge on correlations between model inputs. The background porosity is used as a priori information for analyzing the block subjected to inelastic strain. It can be inferred that use of probabilistic framework involving exhalation of radon may provide a scenario of earthquake occurrences on recession of the curve that represents a qualitative pattern of radon activity concentration drop, indicating associated stress change within the causative seismogenic fault. Using evidence analysis, we propose a joint conditional probability framework model simulation to understand how a single fracture may be affected in response to an external load and radon anomaly change that can be used to detect the slip, a predictable nature of the causative fault in the subsurface rock.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDA13010101)the National Natural Science Foundation of China (Nos. 91328 206, 41576041, 41506046)+1 种基金 the Natural Science Foundation of Guangdong Province (No. 2017A030311015) Special Project of Guangdong Province
文摘The northern margin of the South China Sea, as a typical extensional continental margin, has relatively strong intraplate seismicity. Compared with the active zones of Nanao Island, Yangjiang, and Heyuan, seismicity in the Pearl River Estuary is relatively low. However, a ML4.0 earthquake in 2006 occurred near Dangan Island(DI) offshore Hong Kong, and this site was adjacent to the source of the historical M5.8 earthquake in 1874. To reveal the seismogenic mechanism of intraplate earthquakes in DI, we systematically analyzed the structural characteristics in the source area of the 2006 DI earthquake using integrated 24-channel seismic profiles, onshore–offshore wide-angle seismic tomography, and natural earthquake parameters. We ascertained the locations of NW-and NE-trending faults in the DI sea and found that the NE-trending DI fault mainly dipped southeast at a high angle and cut through the crust with an obvious low-velocity anomaly. The NW-trending fault dipped southwest with a similar high angle. The 2006 DI earthquake was adjacent to the intersection of the NE-and NW-trending faults, which suggested that the intersection of the two faults with different strikes could provide a favorable condition for the generation and triggering of intraplate earthquakes. Crustal velocity model showed that the high-velocity anomaly was imaged in the west of DI, but a distinct entity with low-velocity anomaly in the upper crust and high-velocity anomaly in the lower crust was found in the south of DI. Both the 1874 and 2006 DI earthquakes occurred along the edge of the distinct entity. Two vertical cross-sections nearly perpendicular to the strikes of the intersecting faults revealed good spatial correlations between the 2006 DI earthquake and the low to high speed transition in the distinct entity. This result indicated that the transitional zone might be a weakly structural body that can store strain energy and release it as a brittle failure, resulting in an earthquake-prone area.
基金This project was sponsored by the China SeismologicalBureau(85-04-10)
文摘In this paper, we discussed the seismotectonic environment of the deep-seated and shallowcrust and seismological and geological model caused the 1927 Gulang great earthquake, basedon the recent research concerning about the active fault, surface rupture, fault planesolution, seismic activity, as well as the deep geophysical exploration data analysis in theepicentral area.The result shows that the 1927 Gulang great earthquake was caused by NE-SW-strikingcompressional thrusting. It was a latest event occurred in the reverse fault-folding belt thatdeveloped along the intracrustal decollement.
基金This project is one of the research achievements of the "Ninth Five-Year Plan" under No. 95-04, CSB, China.
文摘The features of precursors of crustal deformation and gravity before some strong earthquakes in North China have been analyzed. The results show that, before strong earthquakes, a close tectonics-dependent dynamic process should exist in large areas and the media in the epicentral area should change their state. With these results as a basis, an improved combination-hardening model has been put forward. When the adjusting element moves, the tectonic movements is intensified in large areas and the density of deep media on both sides of faults will be changed. In the stress concentration element, there will be a media hardening process due to the continuous accumulation of energy. It is such a mechanism that results in the various steps of precursors.
基金jointly supported by the Special Fund for Major Large-scale Advanced PWR Nuclear Power Plant(2011ZX06002)the Special Fund for Basic Research and Operating Expenses of Institute of Geophysics,China Earthquake Administration(DQJB11C08)
文摘In seismic hazard analysis of nuclear power plant of China there is a need to identify both seismogenic structures and seismotectonic zones. In past practice,the identification of the seismogenic structures was often based on the surface active faults and characterization of linear seismic source. In a situation which shows quite strong non-random seismic activity and lacks surface active faults,it is difficult to evaluate the seismic hazard reasonably. Taking seismogenic structures in the Dayao-Yao'an area as a case study in this paper,we discuss the need and the possibility to apply the planar seismogenic structure to the seismotectonic method. We suggest that the planar seismogenic structure should be considered when applying the seismotectonic method to the seismic risk assessment of nuclear engineering in future.
文摘Experiments were conducted repeatedly on Mannari granite under different temperature and confining pressure conditions. Systematic micro- and submicro-structural and mechanical analyses of granite samples deformed under 1.5 GPa (confining pressure), at 25 ℃-650 ℃ temperatures and at 2×10-6s-1 strain rate show the brittle-ductile deformation microstructures and microstructural associations similar to those observed in naturally deformed crustal rocks and minerals. Brittle fracturing and crystalline plasticity co-exist and react with each other in the brittle-ductile transition domain of the continental lithosphere. The interaction between the different mechanisms in the transitional domain results in the variation of anomalous strength values, which may best explain the genesis of the continental seismogenic zone. A new fault zone model is proposed on the basis of detailed micromechanical and microstructural analyses.
