The conventional method of seismic data acquisition geometry design is based on the assumption of horizontal subsurface reflectors, which often is not suitable for complex structure. We start from a controlled illumin...The conventional method of seismic data acquisition geometry design is based on the assumption of horizontal subsurface reflectors, which often is not suitable for complex structure. We start from a controlled illumination analysis and put forward a method of seismic survey geometry design for target-oriented imaging. The method needs a velocity model obtained by a preliminary seismic interpretation. The one-way Fourier finite-difference wave propagator is used to extrapolate plane wave sources on the target layer to the surface. By analyzing the wave energy distribution at the surface extrapolated from the target layer, the shot or receiver locations needed for target layer imaging can be determined. Numerical tests using the SEG-EAGE salt model suggest that this method is useful for confirming the special seismic acquisition geometry layout for target-oriented imaging.展开更多
Based on the compressive sensing,a novel algorithm is proposed to solve reconstruction problem under sparsity assumptions.Instead of estimating the reconstructed data through minimizing the objective function,the auth...Based on the compressive sensing,a novel algorithm is proposed to solve reconstruction problem under sparsity assumptions.Instead of estimating the reconstructed data through minimizing the objective function,the authors parameterize the problem as a linear combination of few elementary thresholding functions,which can be solved by calculating the linear weighting coefficients.It is to update the thresholding functions during the process of iteration.The advantage of this method is that the optimization problem only needs to be solved by calculating linear coefficients for each time.With the elementary thresholding functions satisfying certain constraints,a global convergence of the iterative algorithm is guaranteed.The synthetic and the field data results prove the effectiveness of the proposed algorithm.展开更多
Determining an epicenter reference place name (herein after to be referred as "DERPN") is a basic task,but is very important for standardizing the compilation of earthquake catalogues.However,there has been ...Determining an epicenter reference place name (herein after to be referred as "DERPN") is a basic task,but is very important for standardizing the compilation of earthquake catalogues.However,there has been little studies on DERPN.This paper summarizes the development and issues surrounding DERPN and puts forward principles and methods of DERPN.展开更多
This paper presents an analytical foundation for probability-based formats for seismic design and assessment of structures. These formats are designed to be suitable for code and guideline implementation. The framewor...This paper presents an analytical foundation for probability-based formats for seismic design and assessment of structures. These formats are designed to be suitable for code and guideline implementation. The framework rests on non-linear, static seismic analysis. The formats can be used to ensure that the structural seismic design can be expected to satisfy specified probabilistic performance objectives, and perhaps （more novel） that it does so with a desired, guaranteed degree of confidence. Performance objectives are presumed to be expressed as the annual probability of exceeding a structural performance level. Structural performance levels are in turn defined as specified structural parameters （e.g., ductility, strength, maximum drift ratio, etc.） reaching a structural limit state （e.g. onset of yield, collapse, etc.）. The degree of confidence in meeting the specified performance objective may be quantified through the upper confidence bound on the （uncertain） probability. In order to make such statements, aleatory （random） uncertainty and epistemic （knowledge limited） uncertainty must be distinguished. The single seismic design foundation can be formatted into the alternative conventional design methods such as LRFD design and fragility-hazard design. Versions of the new developments reported here are already in place in recently completed seismic guidelines.展开更多
The Changjiang fault zone,also known as the Mufushan-Jiaoshan fault,is a famous fault located at the southern bank of the Changjiang River,near the Nanjing downtown area.Based on multidisciplinary data from shallow ar...The Changjiang fault zone,also known as the Mufushan-Jiaoshan fault,is a famous fault located at the southern bank of the Changjiang River,near the Nanjing downtown area.Based on multidisciplinary data from shallow artificial seismic explorations in the target detecting area(Nanjing city and the nearby areas),trenching and drilling explorations,classification of Quaternary strata and chronology dating data,this paper provides the most up-to-date results regarding activities of the Changjiang fault zone,including the most recent active time,activity nature,related active parameters,and their relation to seismic activity.展开更多
It is known that the seismic response of a structural system is highly influenced, in addition to the earthquake input, by the dynamic characteristics of the system itself. This paper presents an approach for the iden...It is known that the seismic response of a structural system is highly influenced, in addition to the earthquake input, by the dynamic characteristics of the system itself. This paper presents an approach for the identification of the characteristics of the structural system resisting to horizontal loads which enables to satisfy given seismic performance objectives. This is achieved by considering a total conceptual separation between the structural systems resisting to vertical and horizontal loads. The proposed approach is first briefly developed in general within a Performance-Based Seismic Design （PBSD） framework and then fully applied to the case study of a five-storey steel building structure. It is composed of three basic steps： （1） identification of the fundamental characteristics which should be possessed by the horizontal resisting system to satisfy a multiplicity of performance objectives, （2） development of a peculiar horizontal resisting system composed of ＂crescent shaped braces＂ which are specifically calibrated to satisfy given performance objectives, （3） verification, by means of appropriate time-history analyses, of the seismic performances achieved. In detail, the horizontal resisting system is calibrated to satisfy a multiplicity of performance objectives through the identification of an ＂objectives curve＂, in the Force-Displacement diagram, of the mechanical characteristics of the structure. The calibration is obtained by methods/tools borrowed either from Direct Displacement-Based Design （DDBD） or Force-Based Design （FBD）, depending on the specific performance objective to be imposed. The applicative example has been carried out with reference to three performance objectives and has led to the identification of a horizontal resisting system composed of special bracing elements capable of realizing a sort of properly-calibrated seismic isolation called crescent-shaped braces. The results obtained through non-linear dynamic analyses have shown that the proposed approach leads to the congruity between the imposed and the achieved seismic performances.展开更多
Experience from recent earthquakes such as Gilan, Zanjan, Bam and Lorestan earthquakes in Iran indicated that the constructed buildings are vulnerable against earthquake. Vulnerability of these structures is due to va...Experience from recent earthquakes such as Gilan, Zanjan, Bam and Lorestan earthquakes in Iran indicated that the constructed buildings are vulnerable against earthquake. Vulnerability of these structures is due to various reasons such as designing without considering seismic regulations, problems of regulations （design goals）, implementation problems, changing of the building occupancy class, increasing the weight of building stories, adding new stories to the building and changing in architecture of building without considering structural system. So the main objective of this research is to examine the features of building configuration and their effects as for the damages to buildings in past earthquakes. For this purpose, initially four occurred earthquakes in Iran are selected as case study. Then three types of buildings （steel structure, concrete structure and masonry buildings） are analyzed with details. Results showed that the most of damages are occurred in the old steel structures and masonry buildings which their ages are more than 25 years. The study showed that most of the buildings in the study area are steel structure and masonry buildings while concrete structures are infrequent which most of them had no or slight damages. Therefore, the importance and need to enhance the performance of available buildings against earthquake forces by rehabilitating methods would be more important than before. Also results indicated that the decisions related to architectural plan which have significant effect on seismic performance of buildings, can be divided into three categories： configuration of building, restrictive formal architectural plan and dangerous structural components, as these categories are not obstacle of each other, it is possible that each category has an influential effect on others. So organizing the design decisions in this way is very important so as to manage their effects and interdependencies.展开更多
文摘The conventional method of seismic data acquisition geometry design is based on the assumption of horizontal subsurface reflectors, which often is not suitable for complex structure. We start from a controlled illumination analysis and put forward a method of seismic survey geometry design for target-oriented imaging. The method needs a velocity model obtained by a preliminary seismic interpretation. The one-way Fourier finite-difference wave propagator is used to extrapolate plane wave sources on the target layer to the surface. By analyzing the wave energy distribution at the surface extrapolated from the target layer, the shot or receiver locations needed for target layer imaging can be determined. Numerical tests using the SEG-EAGE salt model suggest that this method is useful for confirming the special seismic acquisition geometry layout for target-oriented imaging.
文摘Based on the compressive sensing,a novel algorithm is proposed to solve reconstruction problem under sparsity assumptions.Instead of estimating the reconstructed data through minimizing the objective function,the authors parameterize the problem as a linear combination of few elementary thresholding functions,which can be solved by calculating the linear weighting coefficients.It is to update the thresholding functions during the process of iteration.The advantage of this method is that the optimization problem only needs to be solved by calculating linear coefficients for each time.With the elementary thresholding functions satisfying certain constraints,a global convergence of the iterative algorithm is guaranteed.The synthetic and the field data results prove the effectiveness of the proposed algorithm.
基金sponsored by the Special Earthquake Scientific Research Program(0270812),CEAthe Basic Scientific Funds for Institute(020904)
文摘Determining an epicenter reference place name (herein after to be referred as "DERPN") is a basic task,but is very important for standardizing the compilation of earthquake catalogues.However,there has been little studies on DERPN.This paper summarizes the development and issues surrounding DERPN and puts forward principles and methods of DERPN.
文摘This paper presents an analytical foundation for probability-based formats for seismic design and assessment of structures. These formats are designed to be suitable for code and guideline implementation. The framework rests on non-linear, static seismic analysis. The formats can be used to ensure that the structural seismic design can be expected to satisfy specified probabilistic performance objectives, and perhaps （more novel） that it does so with a desired, guaranteed degree of confidence. Performance objectives are presumed to be expressed as the annual probability of exceeding a structural performance level. Structural performance levels are in turn defined as specified structural parameters （e.g., ductility, strength, maximum drift ratio, etc.） reaching a structural limit state （e.g. onset of yield, collapse, etc.）. The degree of confidence in meeting the specified performance objective may be quantified through the upper confidence bound on the （uncertain） probability. In order to make such statements, aleatory （random） uncertainty and epistemic （knowledge limited） uncertainty must be distinguished. The single seismic design foundation can be formatted into the alternative conventional design methods such as LRFD design and fragility-hazard design. Versions of the new developments reported here are already in place in recently completed seismic guidelines.
基金sponsored by the Key Construction Programof the National Tenth"Five-year Plan"the Sub-project forthe Earthquake Active Fault Detecting Technology System(1-4-10)the Active Fault Detecting and Earthquake Risk Evaluation of Nanjing City
文摘The Changjiang fault zone,also known as the Mufushan-Jiaoshan fault,is a famous fault located at the southern bank of the Changjiang River,near the Nanjing downtown area.Based on multidisciplinary data from shallow artificial seismic explorations in the target detecting area(Nanjing city and the nearby areas),trenching and drilling explorations,classification of Quaternary strata and chronology dating data,this paper provides the most up-to-date results regarding activities of the Changjiang fault zone,including the most recent active time,activity nature,related active parameters,and their relation to seismic activity.
文摘It is known that the seismic response of a structural system is highly influenced, in addition to the earthquake input, by the dynamic characteristics of the system itself. This paper presents an approach for the identification of the characteristics of the structural system resisting to horizontal loads which enables to satisfy given seismic performance objectives. This is achieved by considering a total conceptual separation between the structural systems resisting to vertical and horizontal loads. The proposed approach is first briefly developed in general within a Performance-Based Seismic Design （PBSD） framework and then fully applied to the case study of a five-storey steel building structure. It is composed of three basic steps： （1） identification of the fundamental characteristics which should be possessed by the horizontal resisting system to satisfy a multiplicity of performance objectives, （2） development of a peculiar horizontal resisting system composed of ＂crescent shaped braces＂ which are specifically calibrated to satisfy given performance objectives, （3） verification, by means of appropriate time-history analyses, of the seismic performances achieved. In detail, the horizontal resisting system is calibrated to satisfy a multiplicity of performance objectives through the identification of an ＂objectives curve＂, in the Force-Displacement diagram, of the mechanical characteristics of the structure. The calibration is obtained by methods/tools borrowed either from Direct Displacement-Based Design （DDBD） or Force-Based Design （FBD）, depending on the specific performance objective to be imposed. The applicative example has been carried out with reference to three performance objectives and has led to the identification of a horizontal resisting system composed of special bracing elements capable of realizing a sort of properly-calibrated seismic isolation called crescent-shaped braces. The results obtained through non-linear dynamic analyses have shown that the proposed approach leads to the congruity between the imposed and the achieved seismic performances.
文摘Experience from recent earthquakes such as Gilan, Zanjan, Bam and Lorestan earthquakes in Iran indicated that the constructed buildings are vulnerable against earthquake. Vulnerability of these structures is due to various reasons such as designing without considering seismic regulations, problems of regulations （design goals）, implementation problems, changing of the building occupancy class, increasing the weight of building stories, adding new stories to the building and changing in architecture of building without considering structural system. So the main objective of this research is to examine the features of building configuration and their effects as for the damages to buildings in past earthquakes. For this purpose, initially four occurred earthquakes in Iran are selected as case study. Then three types of buildings （steel structure, concrete structure and masonry buildings） are analyzed with details. Results showed that the most of damages are occurred in the old steel structures and masonry buildings which their ages are more than 25 years. The study showed that most of the buildings in the study area are steel structure and masonry buildings while concrete structures are infrequent which most of them had no or slight damages. Therefore, the importance and need to enhance the performance of available buildings against earthquake forces by rehabilitating methods would be more important than before. Also results indicated that the decisions related to architectural plan which have significant effect on seismic performance of buildings, can be divided into three categories： configuration of building, restrictive formal architectural plan and dangerous structural components, as these categories are not obstacle of each other, it is possible that each category has an influential effect on others. So organizing the design decisions in this way is very important so as to manage their effects and interdependencies.
