{"id":1342,"date":"2023-01-23T12:15:53","date_gmt":"2023-01-23T11:15:53","guid":{"rendered":"https:\/\/www.sismoelettrica.it\/services\/electromagnetic-surveys\/"},"modified":"2025-02-13T07:50:39","modified_gmt":"2025-02-13T06:50:39","slug":"electromagnetic-surveys","status":"publish","type":"page","link":"https:\/\/www.sismoelettrica.it\/en\/services\/electromagnetic-surveys\/","title":{"rendered":"Electromagnetic surveys"},"content":{"rendered":"\t\t
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Electromagnetic surveys\u200b VLF and TDEM<\/h1>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Electromagnetic surveys<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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The Very Low Frequency method is based on the principle of electromagnetic induction and is particularly suitable for the investigation of rapidly submerging (pseudo-vertical) electrically conductive and elongated bodies. The primary field, in this case, is induced by military broadcasting stations positioned at strategic points around the planet, which were used to transmit with submarines. These signals, being transmitted from far away from the survey points, can be considered to have a predominantly horizontal component and, permeating the subsoil, induce electric currents inside the buried conductive bodies which in turn generate vertical secondary electromagnetic fields. So the principle is the same as for induced electromagnetic methods, only that in this case, the instrument used is only a receiver, can be used kilometers away from the transmitter (therefore the greater depth of investigation), and operates at lower frequencies.<\/p>\n

At buried pseudo-vertical conductive bodies the resulting electromagnetic field (primary + secondary) will have a positive peak before the body, will be zero at the body and will have a negative peak immediately after.<\/p>\n

The resistivity values that are obtained vary according to the type of material examined, the presence of soil or rock, the presence of cavities, the thickness and type of debris cover and the humidity conditions.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Services<\/h2>

- Planimetric layouts with measurement of apparent resistivity contrasts
\n- Punctual high-frequency mapping of anomalies up to a maximum depth of 12 m from the sensor
\n- Area mapping of large areas of the presence of aquifers by induction of a secondary low-frequency electromagnetic field.\n<\/p><\/div><\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Applications<\/h2>

Detection of:
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\n- Conductive materials such as metal, pipes, barrels, cables, concrete reinforcements, drains
\nLocation of faults and karstic or highly fractured areas (location of aquifers)
\n- Mapping of buried structures and presence of bedrock
\n- Mapping of aquifers
\n- Archaeology
\n- Cavity
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Equipments<\/h2>

- EMFAD\u00ae electromagnetic sensor system \u2013 UG12 DS\/WL. It works in passive reception mode of external Radio Stations and in active mode through two electromagnetic wave transmitters

\nFrequency range:
\n- External frequencies: 0-160kHz
\n- TRX2 and TRX3: 5, 7, 9, 19, 24, 33, 70, 90 and 124 kHz\n<\/p><\/div><\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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\"Inverse_Model_01\"<\/div>
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\"Immagine1\"<\/div>
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Electromagnetic surveys\u200b TDEM<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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The time domain electromagnetic method (TDEM) was developed starting from the 1970s simultaneously by the Russian, Canadian and Australian technical-scientific communities for the search for mineral deposits. It is around the 1980s that the method found a wider application in the hydrogeological and environmental fields (stratigraphic reconstruction of the subsoil, mapping of the percolate in the aquifer, etc.). TDEM measurements can be acquired on the ground or from a helicopter. This methodology is based on transmitting a time domain, square-wave signal into a large ungrounded loop. At some point in time, the loop current is interrupted as fast as possible thereby causing a rapid change in the magnetic field generated by the transmitter. The rapidly changing magnetic field induces eddy-currents to flow in nearby conductors producing small secondary magnetic fields that are generally measured by observing induced voltages in receiver loops. Induced currents in poor conductors (moderate resistivity) decay quickly, currents in good conductors (very low resistivity) decay slowly, and very poor conductors, will not sustain any measurable induced currents.<\/p>

Smooth-model inversion is a robust method for converting TEM measurements to profiles of resistivity versus depth. The result of the TEM smooth-model inversion is a set of estimated resistivities which vary smoothly with depth.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Services<\/h2>

- Performance of 1D surveys which allow to obtain a one-dimensional (1D) model of the subsoil, identifying \u201celectro-layers\u201d, i.e. units characterized by a well-defined electrical resistivity (expressed in ohm*m);
- 2D resistivity profiles from multiple 1D electromagnetic surveys for detailed mapping of complex geological structures.<\/p><\/div><\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Applications<\/h2>

1. Water research: Identification of aquifers.
2. Mineralogy: Mapping of mineral deposits.
3. Environmental monitoring: Assessment of soil contamination.
4. Geothermal energy: Study of geothermal resources.\n<\/p><\/div><\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Instrumentation<\/h2>

20 Ampere sTEM system as a fixed coil system and as an ultra-portable sTEMprofiler with a portable rig \u2013 TEMcompany \u2013 Loop profiler \u2013 20 m*20 m \u2013 40 m*40 m \u2013 80 m*80 m.
WalkTem2 20 Ampere Advanced System \u2013 ABEM - Loop \u2013 20 m*20 m \u2013 40 m*40 m \u2013 100 m*100 m.
Investigation depth 200 \u2013 600 m\n<\/p><\/div><\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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Electromagnetic surveys\u200b VLF and TDEM Electromagnetic surveys The Very Low Frequency method is based on the principle of electromagnetic induction and is particularly suitable for the investigation of rapidly submerging (pseudo-vertical) electrically conductive and elongated bodies. The primary field, in this case, is induced by military broadcasting stations positioned at strategic points around the planet, […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1338,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"site-sidebar-layout":"no-sidebar","site-content-layout":"page-builder","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"disabled","ast-breadcrumbs-content":"","ast-featured-img":"disabled","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"class_list":["post-1342","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.sismoelettrica.it\/en\/wp-json\/wp\/v2\/pages\/1342","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.sismoelettrica.it\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.sismoelettrica.it\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.sismoelettrica.it\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.sismoelettrica.it\/en\/wp-json\/wp\/v2\/comments?post=1342"}],"version-history":[{"count":15,"href":"https:\/\/www.sismoelettrica.it\/en\/wp-json\/wp\/v2\/pages\/1342\/revisions"}],"predecessor-version":[{"id":1554,"href":"https:\/\/www.sismoelettrica.it\/en\/wp-json\/wp\/v2\/pages\/1342\/revisions\/1554"}],"up":[{"embeddable":true,"href":"https:\/\/www.sismoelettrica.it\/en\/wp-json\/wp\/v2\/pages\/1338"}],"wp:attachment":[{"href":"https:\/\/www.sismoelettrica.it\/en\/wp-json\/wp\/v2\/media?parent=1342"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}