
 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.

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

The Journal of the Acoustical Society of America

Cours d'economie politique

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.

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

With the advent of modern microstructural testing techniques and microstructure based constitutive models the microstructural characterisation of soils is gaining prominence. This paper reviews the history of microstructure investigation in unsaturated soils and discusses the engineering significance of this research to date. After a brief overview of the main microstructural techniques, the paper focuses on the evaluation of the current state of use and the development of two widely used techniques to study the microstructure of partially saturated soils, namely mercury intrusion porosimetry and the environmental scanning electron microscopy. The details of these techniques, their advantages and limitations, are first covered, followed by the presentation of selected test results. These results highlight the use of these techniques for understanding different hydro-mechanical behavioural features observed at macroscopic scale. Specifically, the paper shows the use of these techniques to explore the fundamental properties of water retention characteristics, water permeability, and micro and macrostructural interactions along different hydro-mechanical paths.

Microstructure Investigation in Unsaturated Soils: A Review with Special Attention to Contribution of Mercury Intrusion Porosimetry and Environmental Scanning Electron Microscopy

Elastic Full Waveform Inversion Tests for Shallow Targets Reconstruction from Surface Waves Analysis Based Initial Models

The ground thermal energy storage (GTES) is a useful application able to provide the H&C and DHW demand of commercial or residential buildings. Several examples in Canada and Northern Europe demonstrated the reliability and convenience of these systems in terms of both energy and economic savings, even though a remarkable initial investment is required. Owing to these conspicuous costs, an accurate preliminary study should be undertaken in order to correctly design the plant and achieve good efficiency of the system. Moreover, when the plant is operative, the monitoring of the thermal plume induced in the undisturbed ground should be a priority. The surrounding litho, hydro and biosphere are indeed influenced by the plant’s activity and a trustworthy supervision of the temperature field is advisable both for the environmental safety and for controlling the system’s efficiency. For these purposes, an integrated approach for design and monitoring GTES systems was tested first at laboratory scale and then applied to a field scale living lab, located nearby Torino (Northern Italy). The proposed methodology consists in lab analogical modeling of the heat propagation, geophysical measurements exploiting the existing relationship between temperature and electrical resistivity and numerical simulations of the studied phenomena with an open-source software (OpenGeoSys). The joint effort of temperature monitoring and numerical simulation at both lab and site scale, combined with direct measurements of the thermal properties, can be a useful tool for highlighting the best design solution for a GTES system. Moreover electrical resistivity surveys, calibrated at lab scale and then conducted at field scale, can be very useful in imaging the Thermal Affected Zone generated by the plant. The adopted approach showed a good potential towards reliable design and accurate monitoring activity.

The First Italian Experience of Ground Thermal Energy Storage: an Integrated Approach for Design and Monitoring, from Laboratory to Field Scale

Surface wave dispersion can be inverted for S-wave 1D velocity models that can be used for static computation. We here show a method that, without the need of inverting the data, provides a direct estimate of not only S- but also P-wave time average velocity required for static computation. The method is based on the relationship between investigation depth of Rayleigh waves and their wavelength. We prove that this relationship is robust for estimate a set of VS time average velocity models requiring only a set of dispersion curves and the knowledge of one VS model. We also show that this relationship is sensitive to Poisson’s ratio and can therefore be used to estimate VP. We successfully apply the method to a synthetic dataset.

P- and S-wave Direct Static Estimation from Surface Wave Dispersion Data

The Special Issue “Remote Sensing in Applied Geophysics” is focused on recent and upcoming advances in the combined application of remote sensing and applied geophysics techniques, sharing the advantages of being non-invasive research methods, suitable for surface and near-surface high-resolution investigations of even wide and remote areas [...]

Special Issue “Remote Sensing in Applied Geophysics”

This study deals with uncertainties associated to solution non-uniqueness in surface wave analysis, with special attention to the influence of maximum available wavelength in experimental data. Typically, it is assumed that the investigation depth is about half the maximum available wavelength in the experimental dispersion curve. In order to assess the validity of this assumption, three different datasets (one synthetic and two real world case histories) have been analyzed with a Monte Carlo approach. Low frequency experimental data have been progressively scalped to assess the consequences on the reliability of the solution. For the selected case histories, a reasonable estimate of average parameters is obtained with a limited amount of experimental information. Nevertheless, the risk of reaching a local minimum in the inversion process is associated to the availability of experimental data. The use of global search method has to be preferred as they can provide an estimate of the reliability of the solution

Cesare Comina

Papers

Elastic Full Waveform Inversion Tests for Shallow Targets Reconstruction from Surface Waves Analysis Based Initial Models

The First Italian Experience of Ground Thermal Energy Storage: an Integrated Approach for Design and Monitoring, from Laboratory to Field Scale

P- and S-wave Direct Static Estimation from Surface Wave Dispersion Data

Special Issue “Remote Sensing in Applied Geophysics”

Inversion Uncertainty in Surface Wave Analysis