Kinds Of Seismic Waves Research Articles

Analytic formula for the group velocity and its derivatives with respect to elastic moduli for a general anisotropic medium

Studying the anisotropy of seismic wave velocity can provide a theoretical basis for understanding the characteristics of seismic wave propagation in anisotropic media, such as forward modeling of seismic wavefield and simultaneous inversion of anisotropic parameters. It is an important work to calculate the group velocities of three kinds of seismic waves (qP, qS1, and qS2) and the analytical expressions of the partial derivatives of the group velocities with respect to 21 elastic parameters in general anisotropic media. Therefore, a new relationship between the phase and group velocity in the general anisotropic medium is introduced first, and then the analytical expressions of the group velocity of three kinds of waves are deduced. Then, the analytical formulas of partial derivatives of the group (or phase) velocity with respect to 21 elastic parameters are derived. Finally, the distribution of partial derivatives of group slowness with respect to 21 elastic parameters with varied ray angles is analyzed and discussed. The final analytical expressions of group velocity and its partial derivatives are relatively concise and can deal with the singular points and multivalued problems of qS waves. By drawing comparison to the numerical solution of the eigenvector method, the accuracy of the analytical formula of group velocity and its partial derivatives with respect to elastic parameters are verified. The numerical simulation results indicate that the algorithm can accurately obtain the partial derivatives of group slowness with respect to 21 elastic parameters and would provide a theoretical basis for seismic ray tracing and traveltime inversion in general anisotropic media.

Analysis and optimization of seismic performance of high-rise residential building

In order to improve the seismic performance of high-rise buildings, a friction damper installation scheme was proposed in the paper. Through numerical simulation and experimental testing, the vibration reduction effect was compared and verified. Herringbone structure was applied to install friction damper in the bearing wall. Based on this vibration reduction scheme, the finite element model of high-rise building was established, and the influence of damper on the modal characteristics of building frame was analyzed. It can be known that the damper has little influence on the natural frequency, but has a great influence on the amplitude range of the excitation response. In the finite element model, two kinds of seismic waves were applied, the strength and dynamic response was simulated and calculated, and the maximum deformation and stress results were obtained. Compared with the initial model, it can be known that the more intense the vibration is, the more obvious the damping effect of the damper is. A seismic excitation simulation system based on acceleration sensor detection is designed and applied to the wall vibration test. The results show that the maximum vibration acceleration of the measured point is reduced by 26.3 % by the damper, and the stable seismic effect can still be maintained during the impact of extension. Compared with the traditional hardness and volume reinforcement scheme, the friction damper can reduce the production cost and improve the adaptability to seismic wave excitation, which provides an important basis for seismic research in other fields.

INFLUENCE OF THE NEUTRAL SHADOWING FORCE ON THE PAIR CORRELATION FUNCTION OF THE DUSTY PLASMA UNDER CRYOGENIC CONDITIONS

In the course of recent years, progresses in sensor innovation has lead to increments in the interest for automated strategies for investigating seismological signals. Fundamental to the comprehension of the components creating seismic signals is the information on the phases of seismic waves. Having the option to indicate the kind of wave prompts better performing seismic forecasting frameworks. In this article, we propose another strategy for the characterization of seismic waves quantification from a three-channel seismograms. The seismograms are isolated into covering time windows, where each time-window is mapped to a lot of multi-scale three-dimensional unitary vectors that portray the direction of the seismic wave present in the window at a few physical scales. The issue of arranging seismic waves gets one of ordering focuses on a few two-dimensional unit circles. We take care of this issue by utilizing kernel based machine learning that are remarkably adjusted to the geometry of the circle. The grouping of the seismic wave depends on our capacity to gain proficiency with the limits between sets of focuses on the circles related with the various kinds of seismic waves. At each signal scale, we characterize a thought of vulnerability connected to the order that considers the geometry of the dissemination of tests on the circle. At long last, we join the grouping results acquired at each scale into a unique label.

Numerical simulation of seismic waves in 3-D orthorhombic poroelastic medium with microseismic source implementation

SUMMARY We have carried out microseismic forward modelling in orthorhombic poroelastic medium. The seismic response to isotropic (ISO) source, double couple (DC) source and compensated linear vector dipole (CLVD) source was solved by finite-difference algorithm in time domain, respectively. We used analytical solution to test our numerical algorithm and find that the match between the analytical solutions and numerical solutions is sufficiently close. We then designed several different models to calculate the seismic response and analyse the effect of medium parameters and source mechanism on the propagation of seismic waves. We observed from the modelling results that ISO source excites two kinds of waves in isotropic medium, which are fast longitudinal wave and slow longitudinal wave, while the DC and CLVD sources excite three kinds of waves in isotropic medium, including a transverse wave in addition to the fast and slow longitudinal waves. All of these three kinds of sources generate four kinds of seismic waves in orthorhombic poroelastic medium. These are two separable transverse waves in addition to the fast and slow longitudinal waves. The fluid viscosity and medium tortuosity has an effect on the propagation of the slow longitudinal wave. The slow longitudinal wave appears in propagating mode under the effect of low fluid viscosity and appears at the source location in a static mode under the effect of high fluid viscosity. The wavefield snapshot of the slow longitudinal wave has a circular shape when the tortuosity is isotropic, whereas it has an oval shape when the tortuosity is anisotropic. As far as the anisotropic parameters are concerned, the anisotropy of the fast longitudinal wave is more sensitive to the value of $\varepsilon ( {{\varepsilon _1},{\varepsilon _2}} )$, while the value of ${\rm{\delta }}( {{{\rm{\delta }}_1},{{\rm{\delta }}_2},{{\rm{\delta }}_3}} )$ has more effect on the anisotropic behaviour of the two separable transverse waves.

Study of Shaking Table Test of Rigid-subrigid Pile Composite Foundation under Sandy Field Condition

To study the seismic response of rigid-subrigid pile composite foundation, shaking table test was conducted under sandy field condition. The experimental results show that the acceleration response strength of the pile top is greater than that of the pile bottom, and is smaller with the increase of buried depth; seismic wave types will have an impact on the acceleration amplification effect; from pile bottom to pile top, the peak value of Fourier spectrum increases gradually, and the frequency distribution of Fourier spectrum in frequency domain does not change. The frequency range of the peak value of Fourier spectrum under three kinds of seismic waves is different; with the peak acceleration of the input excitation increase, the strain peak of pile body changes more and more significantly along the length direction, and the strain peak of rigid pile appears abnormal, which is the weak part of seismic resistance.

Shaking table test of seismic response of immersed tunnels under effect of water

Seismic responses of immersed tube tunnel segments were obtained via a series of shaking table tests. The experiment took water effect into consideration in comparison with the existing researches published so far. Details focusing on test equipment, materials, similitude, experimental approach and cases are presented. Response data under 4 kinds of seismic waves whose peak accelerations were modified to 0.1 g, 0.2 g, 0.4 g at 4 water levels were acquired and analyzed. Results show that characteristics of seismic waves, wave amplitude and water all have effect on seismic response of immersed tube tunnel segments. Water has much greater influence on transverse responses than longitudinal ones.

Analysis on seismic dynamic response and liquefaction area of tailings dam

Taking a tailings dam in Hebei as the research object, the dynamic response of the dam under action of flood and earthquake is simulated by using a finite element software, and the seismic dynamic responses of the dam with respect to acceleration, stress, displacement, liquefaction area and stability are analysed. The results show that the vertical acceleration increases with the height of the dam, the horizontal acceleration is gradually increasing from outside to inside. A larger horizontal and vertical displacement occurs at the 3/4 height of tailings dam. After considering the relative density of the tailings dam and drainage condition, all the three kinds of seismic waves cause a small range of liquefaction area. The stability of the tailings dam is calculated with Sweden Arc Method, showing dynamic stability safety factor is 1.257 when considering drainage, which is larger than code value, indicating the tailings dam is stable in the case of earthquake.

Analysis on seismic dynamic response and liquefaction area of tailings dam

Taking a tailings dam in Hebei as the research object, the dynamic response of the dam under action of flood and earthquake is simulated by using a finite element software, and the seismic dynamic responses of the dam with respect to acceleration, stress, displacement, liquefaction area and stability are analysed. The results show that the vertical acceleration increases with the height of the dam, the horizontal acceleration is gradually increasing from outside to inside. A larger horizontal and vertical displacement occurs at the 3/4 height of tailings dam. After considering the relative density of the tailings dam and drainage condition, all the three kinds of seismic waves cause a small range of liquefaction area. The stability of the tailings dam is calculated with Sweden Arc Method, showing dynamic stability safety factor is 1.257 when considering drainage, which is larger than code value, indicating the tailings dam is stable in the case of earthquake.

Shallow-Water-Equation Model for Simulation of Earthquake-Induced Water Waves

A shallow-water equation (SWE) is used to simulate earthquake-induced water waves in this study. A finite-difference method is used to calculate the SWE. The model is verified against the models of Sato and of Demirel and Aydin with three kinds of seismic waves, and the numerical results of earthquake-induced water waves calculated using the proposed model are reasonable. It is also demonstrated that the proposed model is reliable. Finally, an empirical equation for the maximum water elevation of earthquake-induced water waves is developed based on the results obtained using the model, which is an improvement on former models.

Dynamic Response of Railway Vehicles Running on Long-Span Cable-Stayed Bridge Under Uniform Seismic Excitations

In order to evaluate the dynamic response of the train running on long-span cable-stayed bridges under uniform seismic excitations, a time-domain framework of analysis for the train–bridge system is established. The rail irregularities are treated as internal excitation and seismic loads as external excitation considering the inertia forces induced by the 3D seismic waves. The vehicles are modeled as mass-spring-damper systems, and the cable-stayed railway bridge is simulated by finite elements. A comprehensive analysis of the train–bridge system subjected to earthquake is conducted, focused on the effect of seismic ground motions on the dynamic response of the running train. Four kinds of seismic waves, each with three components, are simulated, with their spectral characteristics taken into account. To consider the stochastic characteristic of actual seismic waves, the effect of the incident angle and occurrence time of earthquakes on the bridge and vehicles is analyzed. Moreover, the earthquakes with various occurrence probability levels are also studied and the safety of the train running under the seismic action is evaluated, which may be used as the operation reference for the railway authority. The results demonstrate that the seismic ground motions have significant effects on the dynamic response of railway vehicles running on the long-span cable-stayed bridge under various spectrum characteristics, incident angles, occurrence times, and occurrence probabilities.

Seismic Behavior of Steel Plate Shear Walls-Steel Frame

A model with the ratio of 1:4 of a six layers’ semi-rigid steel frame-steel plate shear wallssystem has been tested on the shaking table.The strain variation of the steel plate shear wallsand the system’s seismic behaviors to different kinds of seismic waves from four different siteclassification and with different peakaccelerationwere analyzed to provide theoretical and experimental evidence to the real projects.

A Study of the Earthquake-Resistance Performance of Frame Structures with Different Types of Stairs

This paper uses time-history analysis method to consider the effect of 3 kinds of seismic waves by means of finite element software Ansys, analyse earthquake response of 5 kinds of models, compares effect of structural performance of frame structures with different types of stairs. The results show that different types of stairs diversely affects period, stiffness, mode of vibration, mechanical performance, etc, after consideration of stairs in calculating. Although types of stairs different, it shows mainly that stairs make much larger contribution for stiffness parallelled to stairs, less contribution for stiffness perpendicular to stairs, each layer just affects stiffness this layer. It is not simple to consider different types of stairs as general supports.

Analysis of the Reinforced Masonry on Shear Capacity

The reinforced masonry structure system is turned up as a new group of high-rise building structure type. This paper mainly researched the shear of reinforced masonry structure under earthquake. The maximum shears of the structure are calculated in X and Y direction by numerical analysis method. The changing of the shear bearing capacity is presented under three kinds of seismic waves.

Analysis and Calculation of Seismic Performance for UHV Equipment of HGIS

In order to analyze and understand the seismic performance of UHV HGIS, and further improve it, the analysis of dynamic characteristics and seismic response spectra for 1100kV HGIS was carried out in four kinds of seismic waves, and then acquired structural frequencies and mode features. The situation that the natural frequency of UHV equipment and the main frequency of seismic wave were so similar that quasi resonance occurred was considered in the process of analysis. The calculation is conducted by the string of modulated wave that includes three sinusoidal-resonant waves and five sinusoidal-resonant modulated waves to analyze mechanical strength and seismic performance of integral structure. The results show that 1100kV HGIS under those seismic waves has certain safety margin, provide effective data for analysis of seismic performance of UHV equipment.

Elastic-plastic Seismic Response Analysis of Tank Considering Fluid-solid Coupling

It is less for seismic performance study of storage tank considering fluid-solid couple, based on basic theory of the storage tank under seismic action, this paper has built 2000 m3 finite element models of empty tank and tank with medium using ANSYS software. According to the specification, time-history analysis of the tank was carried out under general earthquake by exerting 3 kinds of seismic waves, and variation of displacement, acceleration response and equivalent stress for empty and full tank is gotten. On this basis, time-history analysis is further developed for tank with medium under rare earthquake, and destruction form and axial compressive stress time-history curves of tank are acquired. The results show that the elephant foot buckling and diamond buckling occur near the bottom of the tank wall, these can provide reference for seismic design of tanks in earthquake region.

Research on Vibration Characteristics and Seismic Response of Shell of LNG Tank

Liquefied Natural Gas (LNG) tank is the important equipment in storage LNG. There has been a lot of research results abroad, but lack of seismic studies for the LNG tank in China. Domestic structural designers also have an urgent need for internal force and deformation law of LNG tanks under a variety of dynamic loads. This study focused on vibration characteristics and seismic response of a shell of LNG tank. Using ANSYS creat finite element model, obtain natural frequency and vibration mode etc. According to requirements of Chinese "code of building seismic design", analyze this shell of LNG tank of unidirectional horizontal seismic response under the action of selected three kinds of seismic waves. Time-history curves of LNG tank’s displacement, acceleration, stress distribution law under the action of selected three kinds of seismic waves are obtained.

Seismic Behavior Analysis on the Steel Cold-Formed in Modular House

The cold-formed thin-walled steel has such advantages as light-weight , good seismic capability and is suitable for reconstruction in seismic disastrous area. Nonlinear analysis by software ANSYS on the performances of static and dynamic of a 2 -story building has been done. The analysis reveals that: (1) under the conditions of participation in the earthquake, the top lateral value of structural is large and the maximum is 9.985 mm, but all lateral displacement values standard requirement. (2) Based on the analysis under three kinds of seismic waves, the corner roofing of second independent room has much larger displacement values than others, torsion has been happened on structure. (3) Under the seismic wave, the maximum value is 2.47 which happened on the 400cm/s2 of Taft wave; structure has obviously response under Taft wave。

Predicting Natural or Induced Fracture Azimuths From Shear-Wave Anisotropy

Summary Prediction of fracture orientation to determine depletion geometry is a key step in reservoir characterization and development optimization. Wireline crossed-dipole anisotropy logs measure shear-wave velocity anisotropy and provide a relatively inexpensive alternative to tiltmeter surveys and nine-component vertical seismic profiles (9C VSP's) for such predictions. A multiwell study in Cymric oil field, California, was conducted to map the variations in the predicted azimuth of induced fractures in a shallow Miocene siliceous shale reservoir (>500 millions of barrels of oil in place). Results from anisotropy data showed that the azimuths predicted by anisotropy logs and VSP's agreed. The agreement is significant because these two technologies measure very different kinds of seismic waves and have scales of investigation differing by two orders of magnitude. Within the productive zone, the predicted fracture azimuths from anisotropy data differed by about 60° from the regional stress in the NW portion of the Cymric development, while they were approximately aligned with the regional stress in the SE portion. Marked changes in azimuth also occurred as a function of depth across a regional Plio-Miocene (P-M) unconformity. Independent evidence, including observed steam breakthrough, natural fracture azimuths, and curvature analysis, supports the azimuths predicted from anisotropy data. Time-lapse temperature data from observation wells in a pilot steamflood showed anisotropy in horizontal permeability. Microresistivity borehole imaging logs allowed measurements of borehole breakouts and large, open natural fractures. The curvature analysis indicated a NW trending region of high curvature in the NW part of the Cymric structure. The large changes in azimuth with both depth and location in the development area show that regional stress maps are inadequate for planning oilfield development when stress patterns are complex, especially when deviated wells or induced fracturing are planned. Local stress configurations, therefore, must also be determined.

SEISMIC GROUND MOTION SYNTHETICS OF THE 1989 LOMA PRIETA EARTHQUAKE

A discrete wave number approach in conjunction with a propagator-based formalism is used to synthesize the Loma Prieta earthquake ground motion at both the near and the far field, taking into account all kinds of seismic waves (body and surface). A bilaterally propagating shear slip over a rectangular fault is used to describe the seismic source mechanism, while the earth model is based on geological profiles of the Santa Cruz mountain area and consists of three layers overlaying a half-space. The synthesized ground motion is first compared with actual records from the Loma Prieta earthquake and the agreement between the two is found to be satisfactory, as far as magnitude, duration and essential wave form characteristics are concerned. Then, ground motions are synthesized and plotted at a dense grid of observer locations over a large area around the epicenter, at different time instants. Using such plots, it is possible to study the generation ana propagation of different kinds of seismic waves, the spatial variability of ground motion, as well as the development of the permanent gound deformation.

1986年パームスプリングス地震の強震記録を用いた多重震源位置のインバージョン解析

upture propagation process of multiple events is identified from short-period strong motion seismograms. The North Palm Springs earthquake (ML=5.9), which occurred in southern California on July 8, 1986, provided many strong motion records in the near field. CDMG's digital records from the five close stations (Δ=10-42km) are used for inversion analysis of multiple events. Short-period records obtained in the near field are thought to be more informative for understanding the local rupture mechanism than long-period worldwide records. However, waveforms of short-period records are usually very complicated to identify rupture mechanism. In addition, near-field records tend to include many kinds of seismic waves (i. e., direct P-, S-, reflected, or surface waves) at the same moment, while in the far-field records most of these waves would be separately observed. These facts make it difficult to discern distinct phases from strong motion records. Therefore, we employ non-stationary spectra (multi filter) to identify feeble distinct phases. Then sveral phases are successfully distinguished from other noiselike signals on the specta. Especially, two distinct phases, which have consicuous peaks and similar predominant frequencies among the records, appear in the all spectra of transverse components of the five stations. We regard them as S-wave arrivals that have directly propagated from two sub-sources. Source locations and trigger times of these sub-events are inversely calculated from the arrival times. Numerical results show that these events occurred immediately after initial rupture of the mainshock, and they were located close to the fault plane and within several kilometers from the initial hypocenter. Considering a fault dimension of 16km×12km which was inferred from aftershock distribution, it can be concluded that the major ruptures causing short-period motions concentrated near the initial hypocenter and did not extend throughout the fault plane.