Carlo G. Lai

Bio: Carlo G. Lai is an academic researcher from University of Pavia. The author has contributed to research in topics: Seismic hazard & Liquefaction. The author has an hindex of 23, co-authored 105 publications receiving 1926 citations. Previous affiliations of Carlo G. Lai include Polytechnic University of Turin & Georgia Institute of Technology.

Surface Wave Methods for Near-Surface Site Characterization

Abstract: Overview of surface wave methods Seismic waves Test methodology Historical perspective Challenges of surface wave methods Typical applications Advantages and limitations Linear wave propagation in verticallyinhomogeneous continua Basic notions of wave propagation Rayleigh waves in homogeneous elastic half-spaces Existence of Love waves Surface waves in vertically inhomogeneouselastic continua Surface waves in vertically inhomogeneous, inelastic continua Measurement of surface waves Seismic data acquisition The wave field as a signal in time and space Acquisition of digital seismic signals Acquisition of surface waves Equipment Dispersion analysis Phase and group velocity Steady-state method Spectral analysis of surface waves Multi-offset phase analysis Spatial autocorrelation Transform-based methods Group velocity analysis Errors and uncertainties in dispersion analyses Attenuation analysis Attenuation of surface waves Univariate regression of amplitude versus offset data Transfer function technique and complex wavenumbers Multichannel multimode complex wavenumber estimation Other simplified approaches Uncertainty in the attenuation measurement Inversion Conceptual issues Forward modeling Surface wave inversion by empirical methods Surface wave inversion by analytical methods Uncertainty Case histories Comparison among processing techniques with active-source methods Comparison among inversion strategies Examples for determining Vs and Ds profiles Dealing with higher modes Surface wave inversion of seismic reflection data Advanced surface wave methods Love waves Offshore and nearshore surface wave testing Joint inversion with other geophysical data Passive seismic interferometry Multicomponent surface wave analysis, polarization studies, and horizontal-to-vertical spectral ratio References Index

Simultaneous Inversion of Rayleigh Phase Velocity and Attenuation for Near-Surface Site Characterization

Abstract: Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Georgia Institute of Technology Simultaneous Inversion of Rayleigh Phase Velocity and Attenuation for Near-Surface Site

In situ measurement of damping ratio using surface waves

Abstract: Measurements of surface wave attenuation provide a means to determine the in situ material damping ratio profile of near-surface soils. Frequency-dependent surface wave attenuation coefficients are determined from measurements of seismic wave amplitudes at various offsets from a swept-sine source. The accuracy of the measured attenuation coefficients is improved by properly accounting for the geometric attenuation of multimode Rayleigh waves. Once the frequency-dependent attenuation coefficients are determined, the shear damping ratio profile is calculated using a constrained inversion analysis. Application of the method is illustrated at the Treasure Island National Geotechnical Experimentation Site. Values of shear damping ratio, obtained using surface wave measurements, were less than those measured using cross hole tests, possibly because the higher frequencies used in cross hole tests result in more apparent attenuation due to scattering and because fluid losses contribute to damping at higher freque...

Propagation of Data Uncertainty in Surface Wave Inversion

Abstract: Although in recent years surface wave methods have undergone significant development that has greatly enhanced their capabilities, little effort has been spent to determine the uncertainty associated with surface wave measurements The objective of this study is to determine how the uncertainty of the experimental data is mapped into the uncertainty of the shear wave velocity profile via the inversion algorithm The methodology developed in this study for estimating the uncertainty of the shear wave velocity profile from surface wave measurements is based on the assumption that the experimental data are normally distributed The validity of this hypothesis was experimentally verified using data gathered at two sites in Italy where surface wave tests were performed using linear arrays of multiple receivers The experimental dispersion curve measured at the site was subsequently inverted to obtain the expected shear wave velocity profile together with an estimate of the associated standard deviation The final results show that uncorrelated noise has a very little influence on multistation surface wave tests, confirming their robustness for applications in noisy environments

Ground Motion Characteristics Estimated from Spectral Ratio between Horizontal and Verticcl Components of Mietremors.

Abstract: The spectral ratio between horizontal and vertical components (H/V ratio) of microtremors measured at the ground surface has been used to estimate fundamental periods and amplification factors of a site, although this technique lacks theoretical background. The aim of this article is to formulate the H/V technique in terms of the characteristics of Rayleigh and Love waves, and to contribute to improve the technique. The improvement includes use of not only peaks but also troughs in the H/V ratio for reliable estimation of the period and use of a newly proposed smoothing function for better estimation of the amplification factor. The formulation leads to a simple formula for the amplification factor expressed with the H/V ratio. With microtremor data measured at 546 junior high schools in 23 wards of Tokyo, the improved technique is applied to mapping site periods and amplification factors in the area.

Linear Differential Operators. By C. Lanczos. Pp. 580. 80s. 1961. (Van Nostrand, London)

Abstract: Preface Bibliography 1. Interpolation. Introduction The Taylor expansion The finite Taylor series with the remainder term Interpolation by polynomials The remainder of Lagrangian interpolation formula Equidistant interpolation Local and global interpolation Interpolation by central differences Interpolation around the midpoint of the range The Laguerre polynomials Binomial expansions The decisive integral transform Binomial expansions of the hypergeometric type Recurrence relations The Laplace transform The Stirling expansion Operations with the Stirling functions An integral transform of the Fourier type Recurrence relations associated with the Stirling series Interpolation of the Fourier transform The general integral transform associated with the Stirling series Interpolation of the Bessel functions 2. Harmonic Analysis. Introduction The Fourier series for differentiable functions The remainder of the finite Fourier expansion Functions of higher differentiability An alternative method of estimation The Gibbs oscillations of the finite Fourier series The method of the Green's function Non-differentiable functions Dirac's delta function Smoothing of the Gibbs oscillations by Fejer's method The remainder of the arithmetic mean method Differentiation of the Fourier series The method of the sigma factors Local smoothing by integration Smoothing of the Gibbs oscillations by the sigma method Expansion of the delta function The triangular pulse Extension of the class of expandable functions Asymptotic relations for the sigma factors The method of trigonometric interpolation Error bounds for the trigonometric interpolation method Relation between equidistant trigonometric and polynomial interpolations The Fourier series in the curve fitting 3. Matrix Calculus. Introduction Rectangular matrices The basic rules of matrix calculus Principal axis transformation of a symmetric matrix Decomposition of a symmetric matrix Self-adjoint systems Arbitrary n x m systems Solvability of the general n x m system The fundamental decomposition theorem The natural inverse of a matrix General analysis of linear systems Error analysis of linear systems Classification of linear systems Solution of incomplete systems Over-determined systems The method of orthogonalisation The use of over-determined systems The method of successive orthogonalisation The bilinear identity Minimum property of the smallest eigenvalue 4. The Function Space. Introduction The viewpoint of pure and applied mathematics The language of geometry Metrical spaces of infinitely many dimensions The function as a vector The differential operator as a matrix The length of a vector The scalar product of two vectors The closeness of the algebraic approximation The adjoint operator The bilinear identity The extended Green's identity The adjoint boundary conditions Incomplete systems Over-determined systems Compatibility under inhomogeneous boundary conditions Green's identity in the realm of partial differential operators The fundamental field operations of vector analysis Solution of incomplete systems 5. The Green's Function. Introduction The role of the adjoint equation The role of Green's identity The delta function -- The existence of the Green's function Inhomogeneous boundary conditions The Green's vector Self-adjoint systems The calculus of variations The canonical equations of Hamilton The Hamiltonisation of partial operators The reciprocity theorem Self-adjoint problems Symmetry of the Green's function Reciprocity of the Green's vector The superposition principle of linear operators The Green's function in the realm of ordinary differential operators The change of boundary conditions The remainder of the Taylor series The remainder of the Lagrangian interpolation formula

Surface-wave analysis for building near-surface velocity models — Established approaches and new perspectives

Abstract: Today, surface-wave analysis is widely adopted for building near-surface S-wave velocity models. The surface-wave method is under continuous and rapid evolution, also thanks to the lively scientific debate among different disciplines, and interest in the technique has increased significantly during the last decade. A comprehensive review of the literature in the main scientific journals provides historical perspective, methodological issues, applications, and most-promising recent approaches. Higher modes in the inversion and retrieval of lateral variations are dealt with in great detail, and the current scientific debate on these topics is reported. A best-practices guideline is also outlined.