OVERVIEW

The teaching unit introduces the principles and applications of the main near-surface geophysical methods for subsurface characterization and monitoring in natural and environmental hazard contexts. The teaching unit focuses on the integrated use of electrical, electromagnetic, gravimetric, magnetic and radar methods to address problems such as soil and groundwater contamination, landfills, slope instability, subsidence, seepage in earth structures, volcanic and hydrothermal systems, saltwater intrusion and coastal hazards.

Particular attention will be devoted to the link between subsurface physical properties and geophysical observables, survey design, data quality control, the principles of inversion and interpretation, and the development of conceptual models useful for hazard assessment and risk mitigation. The teaching unit adopts an applied and multidisciplinary approach, integrating geophysical, geological, hydrogeological and environmental aspects.

AIMS AND CONTENT

LEARNING OUTCOMES

The objective of the teaching unit is to provide students with the fundamental knowledge required to apply the main near-surface geophysical methods to subsurface characterization and monitoring, with specific reference to the assessment of natural and environmental hazards.

The teaching unit will cover the physical principles underlying electrical, electromagnetic, gravimetric and magnetic methods, together with criteria for survey design, quality control, data inversion and interpretation. Particular attention will be devoted to the integrated use of geophysical techniques in contexts such as soil and groundwater contamination, landfills, landslides, subsidence, volcanic and hydrothermal systems, and coastal hazards.

By the end of the teaching unit, students will be able to select the most appropriate methodologies for a given applied problem, evaluate their limitations and potential, and interpret the results in support of hazard assessment and risk mitigation.

AIMS AND LEARNING OUTCOMES

The objective of the teaching unit is to provide students with the fundamental knowledge required to apply the main near-surface geophysical methods to subsurface characterization and monitoring, with specific reference to the assessment of natural and environmental hazards.

By the end of the teaching unit, students will have acquired knowledge of:

• physical properties of the subsurface relevant to near-surface geophysical prospecting, such as electrical resistivity, polarizability, density, magnetic susceptibility and dielectric permittivity;
• relationships between petrophysical properties, hydrogeological conditions and geophysical observables;
• physical principles, potential and limitations of the main electrical, low-frequency electromagnetic, gravimetric, magnetic and ground-penetrating radar (GPR) methods;
• criteria for designing geophysical surveys according to the applied problem, observation scale, logistical conditions and geological-environmental setting;
• elements of quality control, processing, inversion and interpretation of geophysical data;
• integrated use of multiple geophysical techniques in applications related to natural, environmental and infrastructural hazards.

In terms of applied skills, by the end of the teaching unit students will be able to:

• select the most appropriate geophysical methods for specific subsurface characterization and monitoring problems;
• critically evaluate the limitations, ambiguities and uncertainties of geophysical results;
• interpret geophysical models in relation to geological, hydrogeological, geotechnical and environmental data;
• set up simple survey and monitoring strategies, including time-lapse configurations;
• communicate the results of a geophysical survey in technical form, highlighting implications for hazard assessment and risk mitigation.

PREREQUISITES

None

TEACHING METHODS

The teaching unit is delivered through lectures, discussion of case studies, guided exercises and critical analysis of real or realistic examples of near-surface geophysical investigations. Theoretical lectures will be integrated with applied activities aimed at linking the physical principles of geophysical methods to survey design, data interpretation and hazard assessment. Open-source software for data processing and modelling will be presented.

Teaching activities will specifically include:

• analysis of acquisition schemes and method-selection criteria;
• reading and interpretation of geophysical sections and maps;
• discussion of case studies related to contamination, landslides, landfills, coastal systems, earth structures and volcanic-hydrothermal environments;
• exercises on quality control, interpretative limitations, non-uniqueness and multi-method integration;
• use of demonstration datasets, teaching software or examples of inversion/interpretation.

The teaching unit is designed to develop not only methodological knowledge, but also technical reasoning skills in the selection, evaluation and communication of the results of an applied geophysical survey.

SYLLABUS/CONTENT

Part A - Methods

A1. Physical properties and near-surface rock physics

Physical properties of the subsurface and geophysical observables: electrical resistivity, chargeability/induced polarization, density, magnetic susceptibility and dielectric permittivity. Effects of porosity, saturation, clay content, salinity and temperature. Petrophysical constraints and calibration data: boreholes, samples, piezometers and direct geological information.

A2. Survey design, quality control and principles of interpretation

Definition of survey objectives, method selection, acquisition geometry and observation scale. Noise sources, instrumental coupling, cultural noise, topographic and logistical constraints. Principles of 2D and 3D inversion, non-uniqueness of the solution, regularization, resolution and uncertainty. Introduction to time-lapse/4D monitoring.

A3. Electrical and electromagnetic methods for hazard assessment

Electrical Resistivity Tomography (ERT) for stratigraphic imaging, moisture distribution, seepage and alteration zones. Induced Polarization (IP) for the characterization of clays, contamination, leachate and reactive materials. Frequency-domain and time-domain electromagnetic methods (FDEM/TDEM) for rapid screening, salinity, conductive plumes and lateral mapping. Self-Potential (SP) method for groundwater flow and hydrothermal circulation.

A4. Gravity, magnetics and GPR in integrated near-surface imaging

Microgravity for mass changes, voids, cavities and subsurface heterogeneity. Magnetics for anthropogenic targets, support to landfill mapping, buried structures and lineaments. Ground Penetrating Radar (GPR) for shallow stratigraphy, fractures, discontinuities and utilities. Integration of results into subsurface conceptual models.

A5. Integrated workflows, monitoring and reporting

Multi-method strategies and joint interpretation. Integration with geological, hydrogeological, geotechnical and environmental data. Definition of technical deliverables for identifying priority interventions and monitoring plans.

Part B - Applications

B1. Contaminated sites and groundwater risk

Detection and monitoring of contaminant plumes using ERT, EM and IP. Coupling with hydrogeological data. Saltwater intrusion and salinization of coastal aquifers. Time-lapse monitoring of remediation effectiveness.

B2. Landfills and industrial sites

Characterization of the waste body, detection of leachate and possible migration pathways. Indirect indications of containment system integrity. Rapid screening strategies and detailed investigations. Production of criticality maps and support for monitoring planning.

B3. Landslides and slope instability

Imaging of landslide body geometry, identification of slip surfaces, saturated zones and hydrological controls. Contribution of geophysical imaging to the monitoring of temporal changes associated with rainfall, drainage and reactivation processes.

B4. Subsidence and ground deformation related to fluids and infrastructure

Processes related to groundwater withdrawal, sediment consolidation, and geothermal or industrial fluids. Role of geophysical methods in the characterization of predisposing conditions and in indirect monitoring.

B5. Dams, levees and critical earth structures

Detection of seepage, internal erosion and hydraulic anomalies using electrical methods, SP and thermal approaches. Design of long-term monitoring systems and support for infrastructural risk management.

B6. Volcanic and hydrothermal hazards

Multi-parameter applications in volcanic and hydrothermal systems. Use of resistivity, gravimetry and other observables to interpret fluid variations, alteration and mass changes.

B7. Coastal hazards and nearshore environments

Saltwater intrusion, coastal erosion, instability in littoral and transitional environments. Role of near-surface methods in characterizing the vulnerability of aquifers and coastal systems.

B8. Monitoring of geological CO2 storage and CCS

Framing of leakage risk and storage system integrity. Objectives and limitations of geophysical monitoring. Overview of the most relevant geophysical observables, with particular attention to electromagnetic and gravimetric methods.

RECOMMENDED READING/BIBLIOGRAPHY

• Teaching notes provided by the lecturer.

Additional references:

• Milsom, J., Eriksen, A. (2011). Field Geophysics. 4th Edition. Wiley. 283 pp.
• Reynolds, J. (2011). An Introduction to Applied and Environmental Geophysics. 2nd Edition. Wiley-Blackwell.

TEACHERS AND EXAM BOARD

LESSONS

LESSONS START

Lesson start

Students may refer to the following link: students-timetable

Class schedule

The timetable for this teaching unit is available at: EasyAcademy Portal

Class schedule

The timetable for this course is available here: Portale EasyAcademy

EXAMS

EXAM DESCRIPTION

The examination consists of an individual written test, including open-ended questions and the solution of applied problems. The test is designed to assess students’ understanding of the physical principles of the main near-surface geophysical methods, their ability to select the most appropriate techniques according to the applied problem, and their ability to critically interpret geophysical results and scenarios in natural and environmental hazard contexts.

The written test may include:

• theoretical questions on the principles of electrical, electromagnetic, gravimetric, magnetic and GPR methods;
• questions on geophysical survey design and data quality control;
• exercises or applied problems concerning method selection, evaluation of interpretative limitations and integration of multiple techniques;
• qualitative or semi-quantitative interpretation of diagrams, sections, maps or geophysical results;
• discussion of case studies related to contamination, landfills, landslides, subsidence, earth structures, coastal hazards and volcanic-hydrothermal systems.

ASSESSMENT METHODS

Learning will be assessed through evaluation of the written test. The test will verify the achievement of the expected learning outcomes, with particular reference to:

• knowledge of the physical principles and subsurface properties that control the geophysical response;
• understanding of the potential, limitations and interpretative ambiguities of the different near-surface methods;
• ability to design a survey strategy consistent with the objectives, scale of the problem, geological setting and logistical constraints;
• ability to apply geophysical methods to natural, environmental and infrastructural hazard problems;
• ability to interpret geophysical results and integrate them with geological, hydrogeological and environmental information;
• clarity, rigor and correctness in written presentation.

The assessment will take into account the correctness of the answers, the ability to connect theoretical and applied aspects, the quality of technical reasoning, awareness of the limitations of methods and interpretative models, appropriate use of technical language, and correct use of discipline-specific terminology. The degree of detail required for each topic will be provided during lessons.

FURTHER INFORMATION

The degree of detail required for each topic will be provided during lessons.