
 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

The use of Magneto Telluric (MT) data for geothermal resource assessment is widely documented in scientific literature. Full 3D inversions are however seldom performed since they are time consuming and provide, in most situations, smoothed models which are not suitable for accurate prospection of local anomalies. To overcome these limitations, an algorithm for the pseudo-3D interpretation of MT data based on a spatially constrained inversion is applied. An application to a real dataset is presented to show the potentialities of the selected approach. Data from an extensive MT survey carried out in the geothermal system of Travale (Tuscany, Italy) are presented. Geological constrains from a 3D seismic reflection survey, from geological data and from available stratigraphic logs were used as a-priori information for the inversion and for a correct tuning of the spatial constraints.

Pseudo-3D Characterization of a Geothermal Field through Magneto Telluric

Outcrop analogue study to determine reservoir properties ofthe Los Humeros and Acoculco geothermal fields, Mexico

Ultrasonic equipment aimed to detect grouting homogeneity in geothermal heat exchangers

Passive seismic monitoring data acquired at the potentially unstable granitic cliff of Madonna del Sasso (NW Italy) are presented in this work. The spectral content of seismic noise systematically highlighted clear energy peaks on the unstable sector, interpreted as resonant frequencies of the investigated volume. Ground motion at these frequencies was found to be controlled by the main fractures observed at the site and numerical modelling is currently under development for geomechanical and modal analysis of the site. Both spectral analysis and cross-correlation of seismic noise showed seasonal reversible variations related to temperature fluctuations. No irreversible changes, resulting from serious damage processes, were detected during the monitored period. Classification and location of microseismic events had also been attempted but resulted challenging due to the complex structural and morphological setting of the cliff.

https://iris.unito.it/bitstream/2318/1616409/1/ch199.pdf

Passive seismic monitoring of potentially unstable rock masses

Passive geophysical methods for geothermal exploration in the external crystalline argentera massif of the western italian alps: gravity and magnetotelluric

Cesare Comina

Papers

Pseudo-3D Characterization of a Geothermal Field through Magneto Telluric

Outcrop analogue study to determine reservoir properties ofthe Los Humeros and Acoculco geothermal fields, Mexico

Ultrasonic equipment aimed to detect grouting homogeneity in geothermal heat exchangers

Passive seismic monitoring of potentially unstable rock masses

Passive geophysical methods for geothermal exploration in the external crystalline argentera massif of the western italian alps: gravity and magnetotelluric