
 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.

/pdf/surface-wave-analysis-for-building-near-surface-velocity-39ze2co0if.pdf

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

https://iris.polito.it/bitstream/11583/2540891/1/PREPRINT%20CANDIA%20CVES.pdf

Waterborne and on-land electrical surveys to suggest the geological evolution of a glacial lake in NW Italy

https://iris.polito.it/bitstream/11583/2440877/1/Bergamo_2011_SDEE_postprint.pdf

Seismic characterization of shallow bedrock sites with multimodal Monte Carlo inversion of surface wave data

Monitoring transport of dissolved substances in soil deposits is particularly relevant where safety is concerned, as in the case of geo-environmental barriers. Geophysical methods are very appealing, since they cover a wide domain, localising possible preferential flow paths and providing reliable links between geophysical quantities and hydrological variables. This paper describes a 3D laboratory application of electrical resistivity tomography (ERT) used to monitor solute transport processes. Dissolution and transport tests on both homogeneous and heterogeneous samples were conducted in an instrumented oedometer cell. ERT was used to create maps of electrical conductivity of the monitored domain at different time intervals and to estimate concentration variations within the interstitial fluid. Comparisons with finite element simulations of the transport processes were performed to check the consistency of the results. Tests confirmed that the technique can monitor salt transport, infer the hydro-chemical behaviour of heterogeneous geomaterials and evaluate the performances of clay barriers.

/pdf/3d-electrical-resistivity-tomography-monitoring-of-salt-18hh6kb2y7.pdf

3D-electrical resistivity tomography monitoring of salt transport in homogeneous and layered soil samples

/pdf/time-average-velocity-estimation-through-surface-wave-4o4wruwloj.pdf

Time-average velocity estimation through surface-wave analysis: Part 2 — P-wave velocityDirect static estimation 2: P-wave

. The Los Humeros geothermal system is steam dominated and
currently under exploration with 65 wells (23 producing). Having
temperatures above 380  ∘ C, the system is characterized as a super
hot geothermal system (SHGS). The development of such systems is still
challenging due to the high temperatures and aggressive reservoir fluids
which lead to corrosion and scaling problems. The geothermal system in
Acoculco (Puebla, Mexico; so far only explored via two exploration wells) is
characterized by temperatures of approximately 300  ∘ C at a depth
of about 2 km. In both wells no geothermal fluids were found, even though a
well-developed fracture network exists. Therefore, it is planned to develop
an enhanced geothermal system (EGS). For better reservoir understanding and prospective modeling, extensive
geological, geochemical, geophysical and technical investigations are
performed within the scope of the GEMex project. Outcrop analogue studies
have been carried out in order to identify the main fracture pattern,
geometry and distribution of geological units in the area and to
characterize all key units from the basement to the cap rock regarding
petro- and thermo-physical rock properties and mineralogy. Ongoing
investigations aim to identify geological and structural heterogeneities on
different scales to enable a more reliable prediction of reservoir
properties. Beside geological investigations, physical properties of the
reservoir fluids are determined to improve the understanding of the
hydrochemical processes in the reservoir and the fluid-rock interactions,
which affect the reservoir rock properties.

/pdf/outcrop-analogue-study-to-determine-reservoir-properties-of-z29e1v4ihl.pdf

Cesare Comina

Papers

Waterborne and on-land electrical surveys to suggest the geological evolution of a glacial lake in NW Italy

Seismic characterization of shallow bedrock sites with multimodal Monte Carlo inversion of surface wave data

3D-electrical resistivity tomography monitoring of salt transport in homogeneous and layered soil samples

Time-average velocity estimation through surface-wave analysis: Part 2 — P-wave velocityDirect static estimation 2: P-wave

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