The complementarity of H/V and dispersion curves

Abstract

Noninvasive geophysical techniques based on the dispersion of surface waves in layered media are commonly used approaches for measuring shear-wave velocity profiles of the subsoil. Acquiring surface waves is a simple task, but the interpretation of their dispersion curves poses a number of challenges. In an increasing number of cases, shear-wave velocity profiles are derived from the inversion of dispersion curves of surface waves and single-station passive horizontal-to-vertical (H/V) spectral ratios, mostly using a blind joint fit of the two sets of curves. Here we emphasize the benefits of carrying out H/V surveys prior to any array acquisition. We propose to start by collecting at least two H/V recordings at a site to verify the 1D plane-parallel soil condition, as this is essential in dispersion curve inversion/modeling. Then, we look for the diagnostic features of velocity inversions in the H/V curves: when they occur, the interpretation of dispersion curves is made difficult by mode splitting/superposition and Love wave arrays will not be effective. Then we inspect the shape of the H/V curves: flat curves acquired on rock usually imply poor dispersion curves. Large receiver spacings are recommended in the arrays and Love wave arrays will not be efficient. Flat curves on soft material sites represent gently increasing [Formula: see text] gradients and Rayleigh wave arrays should be preferred. H/V curves with high frequency peaks indicate shallow impedance contrasts: this makes Love wave arrays efficient for the soft layer characterization, but provide little information at depth. H/V curves with low frequency peaks indicate deep bedrock and their inversion can provide approximate [Formula: see text] profiles down to greater depths than from an array. Equipped with the information coming from accurate H/V observations, practitioners could make better-informed decisions about array acquisition geometries, source/surface wave types, and inversion strategies.

Assessing subsoil void hazards along a road system using H/V measurements, ERTs and IPTs to support local decision makers

“…() and the reference therein, the dataset of the deepest impedance contrast depths and amplitudes was spatially interpolated in a GIS environment using the IDW geostatistical method to generate the thickness and peak amplitude maps. Among the possible alignments of the single‐station measures, those parallel to the ERTs/IPTs electrodes were selected to generate the vertical cross‐sections of the log(H/V) values (Castellaro ; Pazzi et al ). The H/V values acquired along these lines were converted as described in Castellaro (), moving from the frequency domain to the depth domain by means of the Ibs‐von Seht and Wohlenberg () simplified ‐depth relations.…”

“…The distribution of seismic noise single‐station measurements is shown in Figure b. Note that, (i) a trace recorded on a homogenous rock without a cover layer has a flat H/V curve, and no seismic wave amplification is expected; (ii) a trace recorded over a single‐layer stratigraphy (a sedimentary cover overlaying a seismic bedrock) gives an H/V curve with one peak; (iii) in a single‐layer stratigraphy, the H/V peak frequency could be related to the thickness h of the sedimentary layer and its shear velocity according to the well‐known equation ; (iv) the n‐peaks in the H/V curve are caused by n + 1 layers of different lithologies; (v) by constraining the shallow subsoil stratigraphy or the of the first layer, it is possible to model the profile by obtaining (with ) and (with ); and (vi) the high‐frequency peaks in the H/V curve are related to shallow depth interfaces, whereas the low‐frequency H/V peaks are related to the deep interfaces (Castellaro and reference within; Pazzi et al ).…”

Application of HVSR to estimating thickness of laterite weathering profiles in basalt

“…However, it has been employed to characterize site V s velocity profiles for engineering purposes, including amplification for ground shaking (Konno and Ohmachi, 1998;Del Monaco et al, 2013;Castellaro, 2016;Stanko et al, 2016Stanko et al, , 2017. However, it has been employed to characterize site V s velocity profiles for engineering purposes, including amplification for ground shaking (Konno and Ohmachi, 1998;Del Monaco et al, 2013;Castellaro, 2016;Stanko et al, 2016Stanko et al, , 2017.…”

Site characterisation in Kangra Valley (NW Himalaya, India) by inversion of H/V spectral ratio from ambient noise measurements and its validation by multichannel analysis of surface waves technique

“…The MSOR has proven to be an alternative of the MASW technique to derive one‐dimensional (1D) profiles along with HVSR curves at reduced time and cost of investigations in highly populated urban hilly terrains. The constraints for shallow depths were provided by the MSOR technique to model low frequency H/V peaks (Castellaro ), whereas active MASW measurement and its analysis were used for the validation of the profiles obtained by inversion modelling and compared with the lithologs obtained either from borehole information or from exposed litho‐sections.…”

“…The penetration depth will be less in comparison with the depth obtained using the MASW method. However, the DCs obtained from the MSOR method can be used to model H/V peaks using the initial velocity values, thus enabling the identification of the bedrock, which is of utmost importance for computing different parameters for engineering applications (Castellaro and Mulargia ; Castellaro ). This method is particularly useful for urban or hilly towns where space limitation is a big constraint.…”