Inversion of Oceanic Parameters Represented by CTD Utilizing Seismic Multi-Attributes Based on Convolutional Neural Network

In Recent years,seismic data have been widely used in seismic oceanography for the inversion of oceanic parameters represented by conductivity temperature depth(CTD).Using this technique,researchers can identify the water structure with high horizontal resolution,which compensates for the deficiencies of CTD data.However,conventional inversion methods are modeldriven,such as constrained sparse spike inversion(CSSI)and full waveform inversion(FWI),and typically require prior deterministic mapping operators.In this paper,we propose a novel inversion method based on a convolutional neural network(CNN),which is purely data-driven.To solve the problem of multiple solutions,we use stepwise regression to select the optimal attributes and their combination and take two-dimensional images of the selected attributes as input data.To prevent vanishing gradients,we use the rectified linear unit(ReLU)function as the activation function of the hidden layer.Moreover,the Adam and mini-batch algorithms are combined to improve stability and efficiency.The inversion results of field data indicate that the proposed method is a robust tool for accurately predicting oceanic parameters.

Assessing current faulting behaviors and seismic risk of the Anninghe-Zemuhe fault zone from seismicity parameters

Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segments of the Anninghe-Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for potential large earthquakes. The authors map the probable asperities from the abnormally low b-value distribution, develop and employ a method for identifying current faulting behaviors of individual fault segment from the combinations of multiple seismicity parameter values, and make an effort to estimate the average recurrence intervals of character-istic earthquakes by using the parameters of magnitude-frequency relationship of the asperity segment. The result suggests that the studied fault zone contains 5 segments of different current faulting behaviors. Among them, the Mianning-Xichang segment of the Anninghe fault has been locked under high stress, its central part is probably an asperity with a relatively large scale. The Xichang-Puge segment of the Zemuhe fault displays very low seismicity under low stress. Both the locked segment and the low-seismicity segment can be outlined on the across-profile of relocated hypocenter depths. The Mianning-Xichang segment is identified to be the one with potential large earth-quake risk, for which the average recurrence interval between the latest M = 6.7 earthquake in 1952 and the next characteristic event is estimated to be 55 to 67 years, and the magnitude of the potential earthquake between 7.0 and 7.5. Also, it has been preliminarily suggested that for a certain fault segment, its faulting behaviors may change and evolve with time gradually.

Assessing current faulting behaviors and seismic risk of the Anninghe-Zemuhe fault zone from seismicity parameters

Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segments of the Anninghe-Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for potential large earthquakes. The authors map the probable asperities from the abnormally low b-value distribution, develop and employ a method for identifying current faulting behaviors of individual fault segment from the combinations of multiple seismicity parameter values, and make an effort to estimate the average recurrence intervals of character-istic earthquakes by using the parameters of magnitude-frequency relationship of the asperity segment. The result suggests that the studied fault zone contains 5 segments of different current faulting behaviors. Among them, the Mianning-Xichang segment of the Anninghe fault has been locked under high stress, its central part is probably an asperity with a relatively large scale. The Xichang-Puge segment of the Zemuhe fault displays very low seismicity under low stress. Both the locked segment and the low-seismicity segment can be outlined on the across-profile of relocated hypocenter depths. The Mianning-Xichang segment is identified to be the one with potential large earth-quake risk, for which the average recurrence interval between the latest M = 6.7 earthquake in 1952 and the next characteristic event is estimated to be 55 to 67 years, and the magnitude of the potential earthquake between 7.0 and 7.5. Also, it has been preliminarily suggested that for a certain fault segment, its faulting behaviors may change and evolve with time gradually.

Robust H_∞ control for aseismic structures with uncertainties in model parameters

This paper presents a robust H∞ output feedback control approach for structural systems with uncertainties in model parameters by using available acceleration measurements and proposes conditions for the existence of such a robust output feedback controller. The uncertainties of structural stiffness, damping and mass parameters are assumed to be norm-bounded. The proposed control approach is formulated within the framework of linear matrix inequalities, for which existing convex optimization techniques, such as the LM1 toolbox in MATLAB, can be used effectively and conveniently. To illustrate the effectiveness of the proposed robust H∞ strategy, a six-story building was subjected both to the 1940 E1 Centro earthquake record and to a suddenly applied Kanai-Tajimi filtered white noise random excitation. The results show that the proposed robust H∞ controller provides satisfactory results with or without variation of the structural stiffness, damping and mass parameters.

Identification of Parameters in 2D-FEM of Valve Piping System within NPP Utilizing Seismic Response

Nuclear power plants(NPP)contain plenty of valve piping systems(VPS’s)which are categorized into high anti-seismic grades.Tasks such as seismic qualification,health monitoring and damage diagnosis of VPS’s in its design and operation processes all depend on finite element method.However,in engineering practice,there is always deviations between the theoretical and the measured responses due to the inaccurate value of the structural parameters in the model.The structure parameters identification of VPS within NPP is still an unexplored domain to a large extent.In this paper,the initial 2D-finite element model(FEM)for VPS with a DN80 gate valve was updated by utilizing seismic response.The objective function used in the model updating procedure is the vibration control equation error of the VPS.The experimental results show that the updated 2D-FEM can accurately predict the original dynamic characteristic of the VPS.It was also found the Rayleigh damping coefficients corresponding to the VPS vary slightly with the change in seismic excitation amplitude.The research displayed the complete procedure of updating the complex structured initial FEM by utilizing seismic response,and the results show that the parameters can be accurately identified even if the seismic response used for updating merely contained the fundamental frequency information of the structure.

Mathematical basis,correlativity and selection of seismicity parameters

Using the analytic expression of seismicity parameters, the dependency and correlativity between the statisticalparameters and seismic frequency or seismic intensity are discussed. The statistical parameters are divided into twokinds. One kind is the regional seismicity parameter, 17 parameters are analyzed in this paper. The other kind isthe seismicity distribution parameter. They are the distribution parameters of time, space and magnitude. The existent base and rationality of distribution parameters depend on the application of distribution model. We analyzeand draw an analogy between the natural probability, Poisson, Weibull distributions and multi-f racial analyticformula in time, space and magnitude. And some examples are given in this paper. The P value and H value of aftershock sequence attenuation, the U value and F value of eanhquake swarm sequence and the entropy of information are discussed preliminarily. Another method about analyzing relationships among time-series curves aregiven. The resemblance relativity degree R,.,, and the relativity degree G,.,, of relative change slope can be usedas the determining values. At last, some preliminary ideas about sifting and using for seismicity parameters are advanced in this paper.

Interrelation between seismicity parameters and delimiting potential seismic sources in a seismic statistical region and its influence on seismic risk estimation

In the paper, we have discovered the abnormal area distribution features of maximum variation values of ground motion parameter uncertainty with different probabilities of exceedance in 50 years within the range of 100°-120°E, 29°-42°N for the purpose to solve the problem that abnormal areas of maximum variation values of ground motion parameter uncertainties emerge in a certain cities and towns caused by seismicity parameter uncertainty in a seismic statistical region in an inhomogeneous distribution model that considers tempo-spatial nonuniformity of seismic activity. And we have also approached the interrelation between the risk estimation uncertainty of a site caused by seismicity parameter uncertainty in a seismic statistical region and the delimitation of potential sources, as well as the reasons for forming abnormal areas. The results from the research indicate that the seismicity parameter uncertainty has unequal influence on the uncertainty of risk estimation at each site in a statistical region in the inhomogeneous distribution model, which relates to the scheme for delimiting potential sources. Abnormal areas of maximum variation values of ground motion parameter uncertainty often emerge in the potential sources of Mu greater than or equal 8 (Mu is upper limit of a potential source) and their vicinity. However, this kind of influence is equal in the homogeneous distribution model. The uncertainty of risk estimation of each site depends on its seat. Generally speaking, the sites located in the middle part of a statistical region are only related to the seismicity parameter uncertainty of the region, while the sites situated in or near the juncture of two or three statistical regions might be subject to the synthetic influences of seismicity parameter uncertainties of several statistical regions.

Identification of expected seismic activity areas by forecasting complex seismic-mode parameters in Uzbekistan

In this paper, the author proposed a methodology to reveal expected seismic activation places for coming years by a complex of forecasting parameters of a seismic mode. Areas in Uzbekistan where currently observed anomalies in various parameters of a seismic mode has been revealed. By number of displayed abnormal signs the areas has been ranked based on probability of occurrence of strong earthquakes there. It has prepared schemes of the synoptic forecast of expected seismic activation places in case of occurrence of strong earthquakes in the Central-Asian region.

Seismic Acquisition Parameters Analysis for Deep Weak Reflectors in the South Yellow Sea

The Mesozoic-Paleozoic marine residual basin in the South Yellow Sea(SYS) is a significant deep potential hydrocarbon reservoir. However, the imaging of the deep prospecting target is quite challenging due to the specific seismic-geological conditions. In the Central and Wunansha Uplifts, the penetration of the seismic wavefield is limited by the shallow high-velocity layers(HVLs) and the weak reflections in the deep carbonate rocks. With the conventional marine seismic acquisition technique, the deep weak reflection is difficult to image and identify. In this paper, we could confirm through numerical simulation that the combination of multi-level air-gun array and extended cable used in the seismic acquisition is crucial for improving the imaging quality. Based on the velocity model derived from the geological interpretation, we performed two-dimensional finite difference forward modeling. The numerical simulation results show that the use of the multi-level air-gun array can enhance low-frequency energy and that the wide-angle reflection received at far offsets of the extended cable has a higher signal-to-noise ratio(SNR) and higher energy. Therefore, we have demonstrated that the unconventional wide-angle seismic acquisition technique mentioned above could overcome the difficulty in imaging the deep weak reflectors of the SYS, and it may be useful for the design of practical seismic acquisition schemes in this region.

Analysis of Seismic Activity in the Middle Part of the North-South Seismic Belt——Joint Study on Deep Seismic Sounding Profile and Seismicity Parameters

Using the rich deep seismic sounding data recorded in the middle part of the NorthSouth Seismic Belt in China,the horizontal and vertical profiles are constructed to obtain the seismic velocity structure,analyze the seismic distribution and calculate the seismic energy and the thickness of the seismogenic layer at the same time.On this basis,the seismicity parameters are calculated using the earthquake catalogue of the study area for the past 40 years,and the relationship between the b-value distribution and the velocity structure is analyzed.The results show an uneven b-value distribution in the study area and a segmented feature along the Longmenshan fault zone.Most of the earthquakes occur in the transition zone anomalies from the positive to the negative.In addition,the thickness of the crust drops from ~60 km to ~48 km from the Southeastern to the Northeastern Qinghai-Tibetan Plateau,but the thickness of the seismogenic layer increases gradually.It is speculated that the crustal composition of the Northeastern margin contains more felsic materials and has relatively stronger seismic activities than the Southeastern Qinghai-Tibetan Plateau,possibly associated with the subduction and compression of the Indian Ocean Plate.

Construction parameters of graded sand-gravel foundation on seismic response law of nuclear safety grade underground corridor

The treatment of soft soil foundation under nuclear safety grade corridors with graded sand and gravel materials has a good development prospect.It is of great engineering value to explore the influence of construction parameters of graded sand and gravel foundation on the seismic response of gallery structures.Taking the safety grade underground corridor of a nuclear power plant as the engineering background,the equivalent linear method is used to consider the nonlinear dynamic characteristics of graded sand and gravel.The energy transfer boundary is applied at the truncation boundary to simulate the dissipation effect of scattered wave fluctuation energy and the ground motion input.The thicknessless contact element is introduced to consider the contact effect between the corridor structure and the graded sand and gravel foundation,so as to establish the calculation model of the dynamic interaction between the graded sand and gravel foundation and the corridor structure.Furthermore,the influence of the relative compactness and the foundation treatment depth on the seismic response of the corridor structure is studied,and the calculation results of the acceleration response spectrum and relative displacement of the corridor structure are analyzed.The calculation results show that the two construction parameters have different degrees of influence on the seismic response of corridor structure.The research results can provide reference for the engineering design and construction of underground corridors,and provide technical support for the application of graded gravel materials in soft soil foundation treatment.

Study on Uncertainties of Seismicity Parameters b and ν_4 in Seismic Statistical Zones

For several seismic statistical zones in North China, the key factors causing uncertainties in the important seismicity parameters b and v4 and the features of their uncertainties are discussed in this paper. The magnitude of uncertainty is also analyzed. It can be seen that the key influencing factors are statistical period, methods of processing statistical samples, lower limit magnitude and the annual average occurrence ratio of large earthquakes. The variation ranges of b and v4 in the Tancheng-Lujiang zone are as high as 0.2 and 1. 4 respectively, which are similar to those in the Fenwei zone. They are much smaller however in the Hebei zone because of its sufficient statistical samples.

The Relationship Among Bedrock Seismic Ground Motion Parameters with Different Exceedance Probabilities in the Panxi Area

Based on the calculation of the bedrock effective peak acceleration (EPA) zoning map in the Panxi area, the ratios of EPA with exceedance probabilities of 63%, 5%, 3%, 2% and 1% over 50 years to that of 10% in 50 years are 0.302, 1.30, 1.55, 1.76 and 2.14, respectively. The seismic effect will be conservative and safe if taking this zoning map as the earthquake resistant fortification level and following the relevant rules of the Code for Seismic Design of Buildings (GBJ11 89) to calculate the seismic effect. Furthermore, the main factors that influence the A10/A63 ratios have been found to be the attenuation relationship of seismic ground motion, the division of seismic potential source regions and the seismicity parameters. These achievements are helpful to the spreading and applying of the zoning map.

Evaluation of Uncertainty of Earthquake Parameters for the Purpose of Seismic Zoning of Iran

An efficient procedure is used for explicit description and evaluation of uncertainty of earthquake parameters in the uniform catalog of earthquakes in Iran and neighboring regions.An inadequate number of local and regional seismographic stations,poor station distribution,and Inadequacy of velocity models have resulted in conspicuous uncertainty in different parameters of recorded events.In a comprehensive seismic hazard analysis such uncertainties should be considered.Uncertainty of magnitude and location of events are evaluated for three different time periods,namely,historical,early instrumental,and modern instrumental time periods,for which existing seismological information differ widely in quantity,quality,and type.It is concluded that an uncertainty of 0.2-0.3 units of magnitude and 10-15 km in epicenter determinations should be considered in the most favorable conditions.None of the hypocenters of earthquakes in Iran can be considered as reliable,unless supported by other information such as

Analysis of acquisition parameters and geometry quality

High-quality seismic geometry is the key to obtain high-quality seismic data, and can affect the accuracy of data processing and imaging. Based on the analysis of the relationship between the quality of the geometry and the four acquisition parameters(the number of traces, shot line spacing, and the space and number of receiver lines), a quality evaluation method of the geometry based on comprehensive quality factor(CQF) is proposed, and the relationship between the geometry quality and the four parameters is given. We use field data collected in an oil field in Western China with complex geology: First we use a wide azimuth geometry. Then, we calculate the relationship curve between geometry and data quality by varying each parameter while keeping the rest fixed. and the analysis results are given by using the CQF evaluation method. The results show that the shot-line spacing has the greatest effect on the quality of the geometry, and the increase of the receiver line spacing can appropriately improve the quality of the geometry, and the increase of the number of receiving traces can improve the geometry quality. The different acquisition parameters have different effects on the imaging quality of shallow and deep events. The model forward and prestack depth migration are used to generate prestack depth migration profiles with different acquisition parameters. The imaging results are consistent with the above calculated results. According to the depth of the target layer, the quality factor evaluation method is applied to guide the design of the geometry and optimize the acquisition parameters to improve the imaging accuracy of seismic data.

The focus parameters and their correlation from small earthquakes before and after the 1995 Douhe earthquake

Based on seismic source spectrum solution by multi-station and multi-event coda method, applying Brune seismic source model, we have got the source factors and spectra of 48 small earthquakes occurred before and after the Douhe earthquake of October 6 in 1995. The seismic moments, corner frequencies and stress drops are estimated from the Spectra, and their corrclation and variation with time before and after the Douhe ear-thquake are discussed. The results indicate that the source factors show good stability, their peak frequencies and variation with frequencyappear quite similar. Some events with higher stress drops occurred about one year before the Douhe ertquake.Taking into the account that the Stress drop is calculated from seismic moment and frequency, as well as the correlation betwen them, we emphasis that the higher stress drop mentioned here just implies the higher corner frequency than the normal value.

Connecting parameters optimization on unsymmetrical twin-tower structure linked by sky-bridge

Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were derived,by assuming the white noise as the earthquake excitation.The effects of connecting parameters,such as linking stiffness ratio and linking damping ratio,on the structural vibration responses were then studied,and the optimal connecting parameters were obtained to minimize the vibration energy of either the independent monomer tower or the integral structure.The influences of sky-bridge elevation position on the optimal connecting parameters were also discussed.Finally,the distribution characteristics of the top displacement PSD and the structural responses,excited by El Centro,Taft and artificial waves,were compared in both frequency and time domain.It is found that the connecting parameters at either end of connection interactively affect the responses of the towers.The optimal connecting parameters can greatly improve the damping connections on their seismic reduction effectiveness,but are unable to reduce the seismic responses of the towers to the best extent simultaneously.It is also indicated that the optimal connecting parameters derived from the simplified 3-DOF model are applicable for two multi-story structures linked by a sky-bridge with dampers.The seismic reduction effectiveness obtained varies from 0.3 to 1.0 with different sky-bridge mass ratio.The displacement responses of the example structures are reduced by approximately 22% with sky-bridge connections.

Parameter sensitivity analyses in seismic hazard

It is stressed in this paper that the seismic hazard analysis is a complex system with multi parameters and its parameter sensitivity should be studied as a whole. We have inspected the effects of parameters continuing variation on the result and the effects of exceeding probability and upper bound magnitude of potential source on the parameter sensitivity. Some useful cognitions were got. We have overall calculated the interactions among the parameters including spatial distribution function of earthquake and suggested the concept of relative interaction. The relative interaction is not great than 10% with annual exceeding probability 2×10 -3 . The relative interaction between upper bound magnitude and annual mean rate and the one between upper bound magnitude and space distribution function are 17% and 22% respectively for potantial sources higher upper bound magnitudes in annual exceeding probability 10 -4 . It is convenient to judge whether considering the interactions in actual application. The importance and necessity of calculating the result of the probabilistic distribution are indicated. The effect of the result distribution by different parameter level weights is analyzed. The whole picture of multi parameter sensitivity is revealed. It makes necessary preparation for the reasonable uncertainty correction.

Inversion of source parameters for moderate and small earthquakes in Beijing region

According to the geological structural features, Beijing and the adjacent areas can be divided into two regions of plain in the east and mountain in the west. Among the stations covered by the telemetered digital seismic station network of Earthquake Administration of Beijing Municipality, the stations in the plain area are all borehole ones and the stations in the western mountainous region are all located on the surface bedrock. In the paper, 511 wave- form data recorded by the network from Oct. 2001 to Oct. 2004 are used in the researches for the entire Beijing region, the western mountainous region and the eastern plain area, respectively. The Q values are calculated for each area by Atkinson′s method and compared with the existed data. The reliability of the Q values and the reasons for the difference in the Q values are also discussed. Then, the source parameters and site response are inverted by the Moya′s method, in which two models are used. The first model uses the Q values, earthquakes and stations in the sub-areas and the second model uses the Q values, earthquakes and stations in the entire Beijing region. The results indicate that the source parameters and site responses obtained by two models are basically consistent with each other. It also indicates that the source parameters obtained by these methods are not affected by the size of station network.