An Overview of Electromagnetic Methods in Subsurface Detection

Author(s):  
Kendall F. Casey ◽  
Brian A. Baertlein
2003 ◽  
Vol 16 (1) ◽  
pp. 1-23
Author(s):  
Konstanty Gawrylczyk

The article deals with progress in electromagnetic methods used for quality evaluation of conducting materials. The term "electromagnetic methods" covers the following areas: magneto-inductive methods, magnetic leakage flux probe method, magnetometer principle and eddy-current methods. For the aim of numerical cracks recognition the sensitivity analysis with finite elements was shown.


Geophysics ◽  
1986 ◽  
Vol 51 (7) ◽  
pp. 1462-1471 ◽  
Author(s):  
Brian R. Spies ◽  
Dwight E. Eggers

Problems and misunderstandings arise with the concept of apparent resistivity when the analogy between an apparent resistivity computed from geophysical observations and the true resistivity structure of the subsurface is drawn too tightly. Several definitions of apparent resistivity are available for use in electromagnetic methods; however, those most commonly used do not always exhibit the best behavior. Many of the features of the apparent resistivity curve which have been interpreted as physically significant with one definition disappear when alternative definitions are used. It is misleading to compare the detection or resolution capabilities of different field systems or configurations solely on the basis of the apparent resistivity curve. For the in‐loop transient electromagnetic (TEM) method, apparent resistivity computed from the magnetic field response displays much better behavior than that computed from the induced voltage response. A comparison of “exact” and “asymptotic” formulas for the TEM method reveals that automated schemes for distinguishing early‐time and late‐time branches are at best tenuous, and those schemes are doomed to failure for a certain class of resistivity structures (e.g., the loop size is large compared to the layer thickness). For the magnetotelluric (MT) method, apparent resistivity curves defined from the real part of the impedance exhibit much better behavior than curves based on the conventional definition that uses the magnitude of the impedance. Results of using this new definition have characteristics similar to apparent resistivity obtained from time‐domain processing.


2021 ◽  
Author(s):  
Luigi Capozzoli ◽  
Gregory De Martino ◽  
Giacomo Fornasari ◽  
Valeria Giampaolo ◽  
Enzo Rizzo

<p>Urban Resilience represents the capability of an urban system to preserve its features (in terms of public and private qualities and services) when shock events occur [1]. This topic is receiving an increasing interest for the climate change emergency which require innovative strategies for preserving the natural and anthropic resources present in the subsoil. In this framework, the Urban Geophysics could give a strong contribution to improving the knowledge of the critical issues affecting urban area [2].</p><p>One of the most interesting challenges is represented by the detection of ground collapse phenomena that can hardly reduce the safety and reliability of civil structures and infrastructures, as clearly demonstrated by the ground occurred in the Ospedale del Mare car park (Naples, Italy) [3] during the COVID-19 emergency that has brought the light on the weakness of the planning processes of the public authorities when fast decisions are required. Indeed, decision making in urban planning can be effectively supported by rational and reasoned use of the geophysical technologies able to reduce the risks imputable to the activities and decision required by the emergency planning in urban contexts.</p><p>This work focuses its attention on the capability of geophysical methodologies to detect, characterize and monitoring the presence of buried sinkholes, collapses, voids within the subsoil able to cause severe structural stability problems with rapid and non-invasive applications based on the use of Ground Penetrating Radar and Electrical Resistivity Tomographies. The studied cases showed how the cooperative use of the geoelectrical and electromagnetic methods can identify and monitor potential risks of collapses highlighting the pros and cons of the two techniques in terms of resolution and depth of study.</p><p> </p><p>REFERENCES</p><p>[1] Lapenna V. (2016) Resilient and sustainable cities of tomorrow: the role of applied geophysics. Bollettino di Geofisica Teorica ed Applicata 58(4):237–251. https ://doi.org/10.4430/bgta0204</p><p>[2] Capozzoli L., De Martino G., Polemio M. et E. Rizzo, Surveys in Geophysics 2019, Geophysicaltechniquesfor monitoring settlement phenomena occurring in reinforced concrete buildings, Surveys in Geophysics, DOI: 10.1007/s10712-019-09554-8;</p><p>[3] Borghese L.,  Mortensen A. and R. Picheta, https://edition.cnn.com/2021/01/08/europe/italy-hospital-sinkhole-scli-intl/index.html (latest access 01/20/2021, January 9, 2021</p>


Sign in / Sign up

Export Citation Format

Share Document