A method for inversion of layered shear wavespeed azimuthal anisotropy from Rayleigh wave dispersion using the Neighborhood Algorithm

Seismic anisotropy provides important constraints on deformation patterns of Earth＇s material. Rayleigh wave dispersion data with azimuthal anisotropy can be used to invert for depth-dependent shear wavespeed azimuthal anisotropy, therefore reflecting depth-varying deformation patterns in the crust and upper mantle. In this study, we propose a two-step method that uses the Neighborhood Algorithm （NA） for the point-wise inversion of depth-dependent shear wavespeeds and azimuthal anisotropy from Rayleigh wave azimuthally anisotropic dispersion data. The first step employs the NA to estimate depth- dependent Vsv （or the elastic parameter L） as well as their uncertainties from the isotropic part Rayleigh wave dispersion data. In the second step, we first adopt a difference scheme to compute approximate Rayleigh-wave phase velocity sensitivity kernels to azimuthally anisotropic parameters with respect to the velocity model obtained in the first step. Then we perform the NA to estimate the azimuthally anisotropic parameters Gc/L and Gs/L at depths separately from the corresponding cosine and sine terms of the azimuthally anisotropic dispersion data. Finally, we compute the depth-dependent magnitude and fast polariza- tion azimuth of shear wavespeed azimuthal anisotropy. The use of the global search NA and Bayesian analysis allows for more reliable estimates of depth-dependent shear wavespeeds and azimuthal anisotropy as well as their uncertainties.We illustrate the inversion method using the azimuthally anisotropic dispersion data in SE Tibet, where we find apparent changes of fast axes of shear wavespeed azimuthal anisotropy between the crust and uppermost mantle.

Airway function throughout the lifespan: Pediatric origins of adult respiratory disease

Chronic obstructive pulmonary disease(COPD)is a leading cause of disability and death of adults in the USA and worldwide.While environmental factors such as smoking and air pollution are major contributors to COPD,pediatric respiratory disease and more specifically early childhood wheezing are frequent predisposing factors.It is therefore possible that aggressive prevention and treatment of childhood respiratory illness may modify adult COPD risk.This article reviews some of the physiological factors that may explain the pediatric origins of childhood lung disease.One such factor is the"tracking"of normal lung function which occurs with growth.The maximal expiratory flow volume(MEFV)curve is an ideally suited tool to monitor tracking of airway function over the lifespan,as its relative effort independence makes it highly reliable.Study of the MEFV curve has demonstrated that individuals with similar lung volumes can have large differences in maximal flows,reflecting a disconnection between airway and lung growth("dysanapsis").Less than average airway size due to dysanaptic airway growth or airway remodeling may be independent risk factors for the development of COPD and the asthma/COPD overlap syndrome in adult life.There are intriguing early data suggesting that perhaps at least some of this risk is modifiable by improving asthma control with inhaled corticosteroids and minimizing asthma exacerbations.