Rayleigh Waves

In the formulation above , we assumed we can integrate over the whole frequency band from 0 to 00 , but in practice , using the 30-100 WWNSS seismogram, for example, we are able to ob serve a band-limited seismic signal only. At the low frequency end of the spectrum it i s possible to use auxi li ary instrumen ts such as strain seismometers , tiltmeters or the like to r ecord fundamental and hi gher modes of free-o sc illation . We will discuss this in a later chapter, and use Isabella strain dat a and Berke ley Pendulum seismome ter data to estimate the long period energy for Alaska earthquake. At the high frequ ency end of the spectrum the attenuation is severe and th e effect of the crust -scatt e ring and diffracting render it difficult to recover the signa l accurately. As we have just shown that J(w) -+ 00 as w -+ 00 the amoun t of ene r gy we neglect ' by using a band-limited instrument or measuring energy at distances such that the high frequency waves are already reduced to noise level , can be quite significant. In t h i s sense, we are at best only measuring the lowe r limit of the total elastic wave energy released during the earthquake . In order to make clear t he meaning of t he numbe rs -energy in ergs in this case -it is always des irable to specify the band over which we int eg rate. In some applications, for example , to relate magnitude to energy, it may be advis ab le to bypass t he frequency integration and l ook at, say, surface wave spectrum density ins tead. A perusal of the ~ ~-!\)

Japan Agency for Marine-Earth Science and Technology Northwestern part of Pacific plate is very old as the crustal age is over 100 Ma. Seafloor subsidence and heat flow change with age for such old ocean have been explained by cooling of a plate with constant thickness (e.g., Parsons & Sclater, 1977; Stein & Stein, 1992). Electrical conductivity of the upper oceanic mantle typically has resistive layer over a conductive zone reflecting the thermal structure. However, our recent results on the electrical conductivity of the upper mantle beneath northwestern Pacific suggest that a simple plate cooling model can not explain the observations. We have run marine electromagnetic observation in two areas (Areas A and B) of the northwestern Pacific since 2010. Areas A and B locate northwest and southeast of Shatsky Rise, respectively. Although a part of the observation is still going on, we analyzed the data collected by the last year to obtain magnetotelluric responses and one-dimensional (1-D) electrical conductivity structure beneath the observation areas. Here, we compare the results together with a model obtained for the mantle beneath the Pacific ocean off the Bonin Trench (Area C) by a past project. The mean lithospheric ages of Area A, B, and C are about 130, 140, and 147 Ma, respectively. Based on a plate cooling model, the age differences for the thermal structure among the areas are very small. However, the obtained electrical conductivity models show significant difference in the thickness of the resistive layer. The depth the mantle become more conductive than 0.01 S/m are about 80 km for Area A, about 110 km for Area B, and about 200 km for Area C. These differences can not be reconstructed from the age difference of a single plate cooling model. Our observations revealed that there is large scale lateral heterogeneity in electrical conductivity. We need to consider another factors rather than age difference of the thermal structure to explain such the lateral heterogeneity.

We report on unique measurements of multiple microsecond-duration arrest periods during the propagation of high speed (> 1 km s -1) cracks in micromachined single-crystal silicon specimens. These events were recorded electronically and in physical features remaining on the fracture plane. Using time-of-flight calculations, we have determined that these arrest patterns are due to the interference of boundary-reflected stress waves with the propagating crack tip. The specimen size, the measurement method, and the low acoustic attenuation in crystalline silicon facilitated the observation of these phenomena.

Foundation-soil interaction is studied using an analytical two-dimensional model, for circular foundations embedded in a homogeneous elastic half-space and for incident plane P-and SV-and for surface Rayleigh waves. The scattered waves are expanded in complete series of cylindrical wave functions. A detailed analysis is presented of the foundation response to unit amplitude incident waves as a function of the type of incident waves and angle of incidence, the depth of the embedment and the foundation mass per unit length. It is shown that free-field translations and point rotation approximate well the foundation input motion only for very long incident waves. For shorter incident waves, those in general overestimate the foundation input motion. Neglecting the rotation of the foundation input motion (which is usually done in practice) may eliminate a major contribution to the base excitation of buildings and may cause nonconservative estimates of the forces in these buildings. Incident waves appear as 'longer' to a shallow foundation than to a deeper foundation. Therefore, deeper foundations are more effective in reflecting and scattering the short incident waves.

We present IntU package for Mathematica computer algebra system. The presented package performs a symbolic integration of polynomial functions over the unitary group with respect to unique normalized Haar measure. We describe a number of special cases which can be used to optimize the calculation speed for some classes of integrals. We also provide some examples of usage of the presented package.

The lateral heterogeneity and apparent anisotropy of the upper mantle are studied by measuring Rayleigh and Love wave phase velocities in the period range 100-250 s. Spherical harmonic descriptions of the lateral heterogeneity are obtained for order and degree up to 1 = m = 10. Slow regions are evident at the East Pacific Rise, northeast Africa, Tibet, Tasman Sea, southwestern North America, and triple junctions in the northern Atlantic and Indian oceans. Fast regions occur in Australia, western Pacific, and the southern Atlantic. These features are also found by a completely different analysis based on the Backus-Gilbert method. The Backus-Gilbert method also shows that the obtained phase velocities are averaged values within an area of about 2000-km radius and the errors are about 1 'Yo of the phase velocity in the zeroth-order spherically symmetric earth. Inversion for azimuthal dependence shows that for low angular order the fast phase velocity directions seem to correlate well with the plate motion vectors. However, resolution analysis by the Backus-Gilbert method shows that the current data do not have enough resolution for everywhere on the globe. Only a few regions currently have adequate azimuthal coverage. Thus confirmation of the above correlation requires a more complete data set.

A time-domain pure-state polarization analysis method is used to characterize surface waves traversing California parallel to the plate boundary. The method is applied to data recorded at four broadband stations in California from twenty-six large, shallow earthquakes which occurred since 1988, yielding polarization parameters such as the ellipticity, Euler angles, instantaneous periods, and wave incident azimuths. The earthquakes are located along the circum-Pacific margin and the ray paths cluster into two groups, with great-circle paths connecting stations MHC and PAS or CMB and GSC. The first path (MHC-PAS) is in the vicinity of the San Andreas Fault System (SAFS), and the second (CMB-GSC) traverses the Sierra Nevada Batholith parallel to and east of the SAFS. Both Rayleigh and Love wave data show refractions due to lateral velocity heterogeneities under the path, indicating that accurate phase velocity and attenuation analysis requires array measurements. The Rayleigh waves are strongly affected by low velocity anomalies beneath Central California, with ray paths bending eastward as waves travel toward the south, while Love waves are less affected, providing observables to constrain the depth extent of anomalies. Strong lateral gradients in the lithospheric structure between the continent and the ocean are the likely cause of the path deflections.

We determined the seismic model of the soil column within a residential project site in Istanbul, Turkey. Specifically, we conducted refraction seismic survey at 20 locations using a receiver spread with 48 4.5-Hz vertical geophones at 2-m intervals. We applied nonlinear tomography to first-arrival times to estimate the P-wave velocity-depth profiles and performed Rayleigh-wave inversion to estimate the S-wave velocity-depth profiles down to a depth of 30 m at each of the locations. We then combined the seismic velocities with the geotechnical borehole information regarding the lithology of the soil column and determined the site-specific geotechnical earthquake engineering parameters for the site. Specifically, we computed the maximum soil amplification ratio, maximum surface-bedrock acceleration ratio, depth interval of significant acceleration, maximum soil-rock response ratio, and design spectrum periods TA-TB. We conducted reflection seismic survey along five line traverses with lengths between 150-300 m and delineated landslide failure surfaces within the site. We recorded shot gathers at 2-m intervals along each of the the seismic line traverses using a receiver spread with 48 40-Hz vertical geophones at 2-m intervals. We applied nonlinear tomography to first-arrival times to estimate a P-wave velocity-depth model and analyzed the reflected waves to obtain a seismic image of the deep near-surface along each of the line traverses.

This book is published on the understanding that the authors are solely responsible for the statements made and opinions expressed in it and that its publication does not necessarily imply that such statements and/or opinions are or reflect the views or opinions of the publishers. While every effort has been made to ensure that the statements made and the opinions expressed in this publication provide a safe and accurate guide, no liability or responsibility can be accepted in this respect by the authors or publishers Typeset by Helius, Brighton Printed and bound in Great Britain by MPG Books, Bodmin Contents Preface xi Part 1. Generation and propagation of railway noise 1. Theory of generation of wheel/rail rolling noise D. J. Thompson

Thin films of CN x deposited by physical vapor deposition (PVD) with different contents of nitrogen have been studied. An RF-powered antenna was added to a classical magnetron sputtering system. The addition of an antenna plays an important role in mechanical and physicochemical properties. The films have been characterized using XPS, AFM, Brillouin light scattering, grazing angle FTIR, and wettability test. The results show in particular that the Rayleigh wave velocity determined by BLS increased when deposit is assisted by the antenna. Refractive index and surface tension are also enhanced with the use of an antenna. Moreover, high deposition rates are obtain with antenna without modification of N/C ratio.

In this study, short-period noise characteristics at BURAR station were investigated by applying both power spectral density estimation (PSD) and frequency-wavenumber (f-k) array technique. Regular recording of noise spectra for 60 seconds time window sampled at every six hours has been performed over one-year period. F-k analysis estimates were calculated for 9 frequency bandwidths between 0.1 and 16 Hz. The

In this paper we present a seismological test of the 'thermal rejuvenation' model for the formation of the Hawaiian Swell, the archetype of a midplate hotspot swell. Twostation measurements of Rayleigh-wave group and phase velocities between Midway Atoll and O'ahu provide the basis for the test: comparison of the observed dispersion curves with age-dependent, regionalized dispersion curves suggests that the swell has the seismic velocity structure of 50-110 Myr old lithosphere rather than that of 20-50 Myr old lithosphere as suggested by the rejuvenation model. Joint inversion of the group-and phase-velocity curves for isotropic velocity models yields an estimate of -100 km for the seismic lithosphere's thickness along the swell. This value is difficult to reconcile with the 40-50 km thickness demanded by the rejuvenation model. Preliminary measurements of the coefficients of anelastic attenuation are also presented. Although the accuracy of these values is difficult to assess, they too appear to be consistent with thick lithosphere.

Simulated annealing was used to invert fundamental and higher-mode Rayleigh wave dispersion curves simultaneously for an S-wave velocity profile. The inversion was applied to near-surface seismic data (with a maximum depth of investigation of around 10 m) obtained over a thick lacustrine clay sequence. The geology was described either in terms of discrete layers or by a superposition of Chebyshev polynomials in the inversion and the contrasting results compared. Simulated annealing allows for considerable flexibility in model definition and parametrization and seeks a global rather than a local minimum in a misfit function. It has the added advantage in that it can be used to determine uncertainties in inversion parameters, thereby highlighting features in an inverted profile that should be interpreted with caution. Results show that simulated annealing works well for the inversion of multimodal near-surface Rayleigh wave dispersion curves relative to the same inversion that employs only the fundamental mode.

Brief literature reviews of laser ultrasonics modeling are presented in [2,3]. Much work has focused on representing the laser source by an equivalent mechanical loading and then using elasticity theory to predict the resulting waveforms. The problem has also been formulated in terms of fully coupled thermoelasticity. Generalized theories of thermoelasticity have been formulated to model problems where very short duration and high heat fluxes are present [e.g. 41. These formulations differ from those of classical thermoelasticity by introducing one or more relaxation time constants to account for thermal difision into the material. Semi-analytical approaches have been used to calculate waveforms where various transforms are applied to the equations involved and then the WTR\BWM %% ~~~~~~~? 1% ~~~~,~ DISCLAIMER

Direct seismic measurements of the thickening of oceanic lithosphere away from the spreading axis are rare due to the remoteness of mid ocean ridges. On the East Pacific Rise, at 17°S, there were two long-term broadband ocean bottom seismometer deployments, the MELT and GLIMPSE experiments. These arrays spanned young Pacific plate seafloor ranging in age from 0 to 8 Ma. Combining these two data sets, we describe the increase in Rayleigh wave phase velocities for 16-100 s period as function of distance from the ridge with two parameterizations: an arbitrary function of seafloor age and a simple polynomial function of age on the Pacific and Nazca plates. Although resolution analysis shows that 10 to 15 independent pieces of information about the age variation of phase velocity on the Pacific plate can be resolved at periods of ≤50 s, the three parameter polynomial model fits the data almost as well, indicating a simple pattern of the evolution of structure with age. To compare our observations to the predictions for the conductive cooling of the lithosphere, we convert a thermal half-space cooling model to shear velocity using anharmonic and anelastic contributions. The patterns in the velocities are not consistent with simple conductive cooling. The conductive cooling model under predicts the changes in phase velocity with age observed in the 20 to 78 s period range. We observe significant changes in shear velocity in the asthenosphere at depths greater than conductive cooling should extend. The asthenospheric low velocity zone is asymmetric, dipping to the west with the lowest velocities beneath the Pacific plate west of the spreading center. The conductive cooling model also over predicts the shear velocities in the lithosphere by ~0.2 km/s. These anomalies indicate that more complicated mantle flow and significant mantle heterogeneities such as melt are required.

A two-dimensional elastic Chebysbev spectral element method (SPEM) is used to model the seismic wavefield within a massive structure and in its vicinity. We consider 2-D models where a linear elastic structure, with quadrangular crosssection, resting on an elastic homogeneous half-space, is impinged upon by the waves generated by a surface impulse at some distance. The scattering of Rayleigh waves and the response of the structure are extensively analysed in a parametric way, varying size, mechanical parameters and shape of the load. Some of the models considered are representative of embankments and earth dams. The simulation shows that some models resonate, storing part of the incoming energy. With realistic parameters, the lowest resonance frequency is due to pure shear deformation and is controlled by the shear velocity and height of the load. Flexural modes are excited only at higher frequencies. The acceleration at the top of the structure may be five/seven times higher than at the base, depending on the mass of the structure. The gradual release of trapped energy produces a ground roll lasting several seconds after the wave front has passed. The ground-roll amp]Rude depends on the sturcture's mass and can be as large as 30% of the peak acceleration. Outside resonance conditions, the ground motion is almost unaffected by the presence of the artefact; the horizontal motion on top of it is nearly twice the motion at ground level. Similar results should be expected when the inciO~ent field is an upcoming shear wave. A qualitative discussion shows that the presence of anelastic attenuation in the embankment does not significantly alter the preceding conclusions, unless it is of very low values (e.g. Q < 15). Tim modelling results that we discuss indicate that the soil-structure interaction may substantially alter the 'free-field' ground motion. From a practical point of view, the main conclusions are: (1) careful analysis is necessary when interpreting seismic records collected in the vicinity of large artefacts; (2) seismic hazard at a site may depend on the presence of man-made structures such as embankments, dams, tall and massive buildings.

Synthetic seismograms from coupled free oscillations are calculated for a regionalized continentocean model of the upper mantle and a recently proposed spherical harmonic lateral structure model. Spectral correlation analysis of these synthetic records, containing Rayleigh waves with period T• 160 s, reveals the size of departures from the assumption that the waveform perturbation can be explained by just the structure under the great circle between source and receiver. Arrival azimuth deflections of up to 10 ø are observed on horizontal synthetics using a 2.3% variation in shear velocity between continents and oceans. Among the M84A synthetics, the great circle travel times R3-R I, R4-R 2, Rs-R 3 vary on average by 3--5 s for 3•<f •< 6 mHz surface wave motion. Comparison between synthetics, calculated to be sensitive to even-order structure or to both even-and odd-order structure, gives a 5-s average time delay attributable to odd-order structure. Significant Rayleigh wave packet amplitude anomalies are common in the synthetic records and are nearly as common in synthetics calculated for the even-order structure as in those sensitive to all structure, Examples suggest that model M84A does not consistently reproduce the amplitude anomalie s observed in International Deployment of Accelerometers (IDA) and Global Digital Seismographic Network (GDSN)data. Lastly, we demonstrate the effect of Coriolis coupling in the time domain. Visible precursors to Rayleigh wave packets are predicted in cases of favorable source-receiver geometry. These precursors are caused by the spheroidal component of the hybrid, predominantly tøroidal, low-frequency (f •< 4.2 mH z) LOve wave, whose arrival precedes that of the Rayleigh wave. We present examples of this anomalous waveform in IDA data from a large strike,slip earthquake in New Guinea, showing a qualitative fit to the coupled-mode prediction. 1. !NTRODUCTION AND METHODS Coupled-mode calculations, in principle, offer a more accurate method of determining the earth's response to seismic sources than techniques that rely on asymptotic or high.frequency forms of the equations of motion, e.g., surface wave tomography [Nakanishi and Anderson, 1983, 1984; Woodhouse and Dziewonski, 1984; Tanimoto and Anderson, 1985] or generalized ray techniques. For response at frequencies below a chosen cutoff frequency (Ocutoff, a seismogram can be represented as a finite sum of elastic-gravitational free oscillations. Nominally secondorder effects such as Coriolis coupling between spheroidal and toroidal modes are accounted for naturally by the coupled-mode formalism. There are additional, secondorder effects when seismic particle motion on an earth model with aspherical boundaries is expressed in terms of functions that satisfy spherical boundary conditions. These latter effects are not accounted for. In addition, approximations must always be made in order for the coupled-mode calculations to remain numerically tractable. The•errors induced by the second type of approximation are relatively easy to assess. One can test directly the effects of breaking a large coupling matrix into smaller blocks or else use theorems from numerical linear algebra to do so. In an asymptotic technique one. might need to construct a new theory to account for a breakdown of ini-

The observed secondary microseismic wave-field is composed by Rayleigh and Love waves. While the presence and amount of Rayleigh waves can be explained well, the generation of Love waves is still under debate. We investigate both internal multiple scattering of surface waves and interaction with strong seafloor topography as possible mechanisms that could be responsible for the generation of Love waves in the secondary microseism.

The objective of this study is to estimate the S-wave velocity structure of the Taichung basin in a near-fault region, which is needed for strong-motion evaluation for the 1999 Chi-Chi earthquake. We have conducted array measurements of microtremors with a total of 12 arrays at four sites and single-station measurements of microtremors at 48 sites in and around the Taichung basin. Based on the Rayleighwave inversion technique using phase velocities estimated from array records of microtremors, we find that a thick layer (the thickness of about 1000 to 1400 m) with an S-wave velocity of V S 1100 m/sec exists in the east-central part of the Taichung basin. We estimate the thicknesses of sedimentary layers above the pre-Tertiary bedrock at 48 sites to fit calculated peak and trough frequencies of horizontal-to-vertical spectral ratios of Rayleigh waves to observed peak and trough frequencies, assuming the same S-wave velocities estimated using array records. The pre-Tertiary bedrock depth was estimated to be about 5 to 6 km in this region. The estimated thickness of the layer with V S ‫ס‬ 1100 m/sec is largest in the east-central part of the basin and rapidly decreases to less than 400 m in the northeastern and western parts inside the basin. The estimated S-wave velocity structures reasonably explain arrival time of initial P and S waves of aftershock records observed by .

We map lateral variations of upper-mantle Q in eastern Eurasia using a new inversion procedure based on threedimensional partial-derivative (Fréchet) kernels. In our initial analysis, we utilize Rayleigh waves with periods longer than ~15 s, derived from regional and near-teleseismic earthquakes. We have collected and begun analysis on over 11000 vertical-component seismograms, derived from over 150 events with Mw > 6 that occurred within the eastern Eurasia region (10˚-60˚N, 70˚-140˚E) between 2000-2006. The data were recorded on 71 broadband seismic stations within eastern Eurasia (10˚-60˚N, 80˚-140˚E). The data are evaluated for signal-to-noise within the band of interest by comparing the records to complete normal-mode synthetic seismograms for radially symmetric and transversely anisotropic reference models. We then make mutually consistent measurements of frequency-dependent traveltime and amplitude anomalies for surface waves by cross-correlation between records and synthetics. We use coupled normal-mode summation to compute the three-dimensional Fréchet kernels of these traveltime and amplitude anomalies to both the elastic wave speeds and Q values. The initial model for Q is extracted from a recent global model of upper-mantle attenuation. The frequency-dependent traveltime and amplitude anomalies will be jointly inverted for three-dimensional models of both elastic (v s ) and anelastic structures. This coupled inversion will allow us to account for the effects on amplitudes from elastic heterogeneities such as scattering, focusing and defocusing, as well as the effects of anelastic dispersion on the traveltimes. The regional models will provide lateral resolution of upper-mantle Q that will be as high as the data permit. The models will be compared to other models of upper-mantle Q derived from higher-frequency Pn and Sn observations, as well as crustal Q models of Pg and Lg, providing a means to assess the process controlling seismic attenuation at different frequencies.

This study combines migration and forward source modeling techniques to examine the existence and location of persistent seismic noise near southern Italy. Our results demonstrate that noise source modeling is both feasible and recommended in validating the ''ambient source'' assumption prior to noise-based velocity analyses. Persistent noise sources near the Gargano promontory and the Tyrrhenian Sea coast are strongly suggested by the observed cross-correlations. The presence of a single point source or a cluster of point sources could both produce coherent Rayleigh wave energy in southern Italy. While the nature of the noise sources is still uncertain, baroclinic estimates and dynamic topography models favor an explanation that encompasses atmosphere-ocean coupling and heightened wave interaction off the Adriatic coast. Our records indicate that these noise sources can maintain their average location for up to 7 months despite seasonal and, possibly, daily variations.

Reflection and attenuation of a Rayleigh surface acoustic wave from a small stripe of viscous fluid spreading across the acoustic path have been observed. As the stripe spreads across the acoustic path, with an accompanying decrease in stripe height to conserve volume, the reflected and attenuated acoustic signals show a distinct pattern of resonances. This paper reports experimental results for the spreading of highly viscous poly͑dimethyl͒siloxane oils ͑100 000 cS͒ in the propagation path of a 169 MHz Rayleigh wave operating in pulse mode and develops a model to explain the observed resonances of the transmission coefficient. Simultaneous optical observations enable the time evolution of the shape of the stripe to be converted into changes in geometric parameters ͑contact width, spherical radius, height, and contact angle͒. To model the acoustic attenuation, an approach treating the fluid as a viscoelastic fluid with a single relaxation time ͑Maxwell model͒ is developed. This approach is able to explain the structure of the observed transmitted signal. Resonances in the transmission coefficient occur cyclically and correspond to the stripe height matching n s /4, where n is odd and s is the shear wavelength in the fluid. ͓S0163-1829͑99͒08711-1͔

The study of surface and shallow sources has lately become of importance, especially in connection with nuclear-explosion seismology (Ben-Menahem & Vered 1975; Ben-Menahem 1975). An ad-hoc study of surface sources was deemed necessary in view of the observation that, in general, the radiation pattern of a surface source differs substantially from the radiation pattern of the same source buried in an infinite space (White 1960). Consequently, an exact generalized multipolar ray theory (GMRT) is developed for surface sources. This theory holds but approximately for buried sources. However, for shallow sources the approximation is quite acceptable, while making the tedious evaluation of surface reflections redundant. The same problem of computing theoretical seismograms for shallow sources was recently investigated, in an approximate way, by Langston & Helmberger (1975). Radiation patterns of surface sources may be derived in different ways: ab initio solution of a surface source problem (e.g. Miller & Pursey 1954; Cherry 1962) or finding the radiation field of a buried source and taking the limit as the burial depth tends to zero (e.g. Pekeris 1955). We use a version of the second technique. The direct and reflected displacement fields for buried multipolar sources were given in detail by . We form the total field by adding the direct and reflected fields. The resultant expression may be expanded in a Taylor series in a non-dimensional quantity which eventually may be shown to be kh where k is the wave number and h the burial depth of the source. Asymptotic ray expressions may be obtained by approximately evaluating the exact field entities using the stationary phase method and the initial motion approximation. The two main advantages of our method are that: (1) it applies equally easily to all multipolar sources, thus avoiding the need to re-evaluate the radiation pattern anew for every source, and (2) it may be straightforwardly applied to multilayered media. The first term in the above mentioned expansion yields the radiation pattern for surface sources. The second term in the series may be considered as a correction to be added to the first term, for small non-vanishing h, and so on. In this note we give (Table ) the results for h = 0 only, which apply either exactly to surface sources or approximately to shallow sources such that the wavelength

Sagaing City is one of the seismic prone regions since active Sagaing Fault passes through the urban center. The damage properties are commonly influenced by the seismic source properties and the site properties. Site condition associated with surface geological conditions is an important role of seismic hazard assessment. As the effects of earthquakes are commonly influenced by the seismic source properties and the site properties, geotechnical site investigation was carried out for an adequate evaluation of seismic hazard in Sagaing City. Totally (4) boreholes, two of them located in the east and west, and the other two in the north and south across the urban area of the city were carried out in Sagaing City. The collected soil samples from SPT test were sent for laboratory testing. The subsoil site classification will be made for seismic local size effect evaluation based on average shear wave velocity of 30m depth (V S 30 ) of sites by using Uniform Building Code (UBC) classification. Results were obtained from the geotechnical boreholes and it was shown that the results can be used for a rough estimation of sediment thickness. According to the values of shear wave velocity, the soil types found to be the very dense soil including soft rock and soil classes are S C and S D .

The square and triangular lattices are considered, where the uniform crack growth is accompanied by the wave radiation. The radiation energy and structure are studied. The energy radiated to the bulk of the lattice is found in a direct way. The radiation structure is described based on the crack problem solution and by means of the analysis of two dimensional dispersion relations for the intact lattice. The mode III problem for square lattice is discussed in detail, whereas, in the case of the plane problem for the triangular lattice, the only those results are derived which follow from the two dimensional dispersion relations. It is shown that there exists a finite crack speed dependent region of wavenumbers corresponding to the waves radiated to the bulk of the lattice. In the case of the triangular cell lattice, in addition, one or several lattice Rayleigh waves are radiated. For the square lattice a complete solution for the wave field is presented with the crack speed dependent far field asymptote. The latter is characterized by the wave amplitude asymptotically decreasing as the distance from the crack front in power-1/3. The asymptotically significant crack speed dependent direction of the radiation is determined. Such asymptotic results are also valid for the triangular lattice.

This thesis mainly focuses on thermal metamaterials, including thermal metadevices that can actively manipulate heat flux, and thermally responsive metamaterials that can deform in response to external heat stimuli in a controlled manner. We propose a method to design arbitrarily shaped 3D thermal cloaks with anisotropic and homogeneous material properties. Based on this approach, we study the steady-state and transient cloaking performance of multilayered cloaks. Then we propose a general road map to build thermal harvesting devices with microstructure design. The device is realized by naturally available materials. Both numerical and experimental results demonstrate good thermal harvesting performance. In addition to the above mentioned works on in-plane heat conduction control, we further propose a multilayered medium approach to flexibly manipulate out-of-plane thermal radiation. Based on this approach we realize functionalities like infrared camouflage, thermal coding and therm...

Mean separation of fades or flares. Example of the received power for the one-way case. Example of the received power for the monostatic case. 13c Example of the received power for the bistatic case. 13d Fxample of the combined power for identically distributed dual channels (summation algorithm). Example of the combined power for identically distributed dual channels (maximum 3lqorithm). 14 Fhase of the voltage for the one-way received power shown on Figure .

This paper describes the interaction of complex harmonic plane waves on a periodically corrugated surface. It is shown that the ability of complex harmonic plane waves to stimulate leaky Rayleigh waves on a corrugated surface is similar to the ability of harmonic inhomogeneous waves to stimulate leaky Rayleigh waves on a smooth interface. Because the experimental generation of harmonic inhomogeneous waves is more complicated and less flexible than the generation of complex harmonic waves, the combination of complex harmonic plane waves with a diffraction grating therefore offers an excellent alternative. The theoretical model developed here is based on the well-known and experimentally verified complex harmonic wave theory and the famous Rayleigh decomposition of the diffracted field. The numerical examples are given for combinations of frequency and corrugation dimensions that justify the use of the Rayleigh theory. A study of the influence of a complex frequency on the generation of Scholte-Stoneley surface waves is performed as well.

An overview of the S-wave velocity (Vs) structural model of the Caribbean is presented with a resolution of 2ºx2º. As a result of the frequency time analysis (FTAN) of more than 400 trajectories epicenter-stations in this region, new tomographic maps of Rayleigh waves group velocity dispersion at periods ranging from 10 s to 40 s have been determined. For each 2ºx2º cell, group velocity dispersion curves were determined and extended to 150 s adding data from a larger scale tomographic study . Using, as independent a priori information, the available geological and geophysical data of the region, each dispersion curve has been mapped, by non-linear inversion, into a set of Vs vs. depth models in the depth range from 0 km to 300 km. Due to the non-uniqueness of the solutions for each cell a Local Smoothness Optimization (LSO) has been applied to the whole region to identify a tridimensional model of Vs vs. depth in cells of 2ºx2º, thus satisfying the Occam razor concept. Through these models some main features of the lithosphere and asthenosphere are evidenced, such as: the west directed subduction zone of the eastern Caribbean region with a clear mantle wedge between the Caribbean lithosphere and the subducted slab; the complex and asymmetric behavior of the crustal and lithospheric thickness in the Cayman ridge; the diffused presence of oceanic crust in the region; the presence of continental type crust in the South America, Central America and North America plates, as well as the bottom of the upper asthenosphere that gets shallower going from west to east.

Regional seismic tomography provides valuable information on the structure of shields, thereby gaining insight to the formation and stabilization of old continents. Fennoscandia (known as the Baltic Shield for its exposed part) is a composite shield for which the last recorded tectonic event is the intrusion of the Rapakivi granitoids around 1.6 Ga. A seismic experiment carried out as part of the European project Svecofennian-Karelia-Lapland-Kola (SVEKALAPKO) was designed to study the upper mantle of the Finnish part of the Baltic Shield, especially the boundary between Archean and Proterozoic domains. We invert the fundamental mode Rayleigh waves to obtain a three-dimensional shear wave velocity model using a ray-based method accounting for the curvature of wave fronts. The experiment geometry allows an evaluation of lateral variations in velocities down to 150 km depth. The obtained model exhibits variations of up to ±3% in S wave velocities. As the thermal variations beneath Finland are very small, these lateral variations must be caused by different rock compositions. The lithospheres beneath the Archean and Proterozoic domains are not noticeably different in the S wave velocity maps. A classification of the velocity profiles with depth yields four main families and five intermediate regions that can be correlated with surface features. The comparison of these profiles with composition-based shear wave velocities implies both lateral and vertical variations of the mineralogy.

Mentawai, Indonesia earthquake (M w 7.8) ruptured the shallow portion of the subduction zone seaward of the Mentawai islands, offshore of Sumatra, generating 3 to 9 m tsunami run-up along southwestern coasts of the Pagai Islands that took at least 431 lives. Analyses of teleseismic P, SH and Rayleigh waves for finite-fault source rupture characteristics indicate ∼90 s rupture duration with a low rupture velocity of ∼1.5 km/s on the 10°dipping megathrust, with total slip of 2-4 m over an ∼100 km long source region. The seismic moment-scaled energy release is 1.4 × 10 −6 , lower than 2.4 × 10 −6 found for the 17 July 2006 Java tsunami earthquake (M w 7.8). The Mentawai event ruptured up-dip of the slip region of the 12 September 2007 Kepulauan earthquake (M w 7.9), and together with the 4 January 1907 (M 7.6) tsunami earthquake located seaward of Simeulue Island to the northwest along the arc, demonstrates the significant tsunami generation potential for shallow megathrust ruptures in regions up-dip of great underthrusting events in Indonesia and elsewhere.

Fractal modeling of the rugged crack geometry is considered for the stable and dynamic fracture mechanics characterizing the morphology of a fracture surface and the influence of its growth. It is shown that the fractal dimension has a strong influence on the rising of the R-curve in brittle materials. For the unstable Griffith-MottÕs approach or dynamical crack growth the fractal dimension has a strong influence on the velocity limit of the crack growth. It is also shown that the limit of crack velocity lowers with increasing surface ruggedness (higher fractal dimension D = 2 À H) explaining the intangibility of the Rayleigh wave velocity by the cracks.

In this paper we focus on the experimental observation of the broadband dispersion relation of wedge waves using laser ultrasound technique. The dispersion spectra are measured for an extremely large bandwidth which has not been investigated before. It is found that within a characterized small-wave-number regime, the dispersion behavior is predicted with reasonable accuracy by McKenna&#39;s thin-plate theory. Through a transition region towards large wave numbers, the dispersion spectra converge on the Rayleigh wave velocity of the wedge material.

Article Methods Geochemistry Sample preparation. Crystals were separated from crushed and sieved scoria, pumice or lava. Picked crystals from the size fractions 0.5-1 mm and 1-2 mm were mounted on glass slides within 2.5-cm-diameter aluminium rings, back-filled with epoxy resin and polished to expose the centre of the crystals. Crystals were imaged under transmitted light to locate the most suitable glassy inclusions before further polishing to expose the maximum number of melt inclusions. All epoxy mounts were gold-coated before SIMS analysis.

The lithospheric structure in Oman has been determined by analyzing teleseismic P-receiver functions recorded at broad-band and short-period seismic stations of the Oman Seismological Network. Lithospheric structure is obtained by jointly inverting receiver functions and Rayleigh wave group velocities derived from continental-scale surface wave tomography of Pasyanos. We observe relatively thick crust (40-48 km) within the ophiolite formed mountains in northern Oman. The crustal thickness is about 35 km within the passive continental margin of the southern Oman region. Uppermost (<5 km) crustal shear wave velocities are faster in the northern ophiolite regions compared to the southern Oman region, while shear velocities in the middle crust are faster in the Southern Oman region compared to the ophiolite region. This observation coincides well with cretaceous to Eocene marine platform sequences overlying Precambrian to Cambrian basement of the southern part. Joint inversion analysis shows that the Moho depth of Oman varies from 34 km in the southern region to 48 km in the northern part.

Rksumi. Nous avons engendrk et detect6 optiquement des ondes de Rayleigh sur une sphkre mktallique. La source est un laser YAG fonctionnant en r6gime pulse. Le deplacement mkcanique est mesurk, au point diamktralement opposk au point d'impact, par une sonde interf6romBtrique hetkrodyne. Les frkquences de dsonance d'une sphere en acier inoxydable de diamktre 20 rnm ont Bt6 d6duites directement du spectre du signal ainsi que les variations de la vitesse de groupe. Les rksultats exp6rimentaux sont en bon accord avec les valeurs prkvues par l'analyse. Abstract. Rayleigh waves have been optically generated and detected on a metallic sphere. The source was a pulsed YAG laser. The mechanical displacement was measured, at a point diametrically opposite to the laser impact, by an heterodyne interferometer. The resonance frequencies of stainless-steel sphere of diameter 20 mm was rapidly obtained from the fast Fourier transform of the probed signal. The variation of the group velocity was also deduced from the resonance spectrum. Experimental results agree with the analysis.