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22 - 1 GEOMAGNETIC HAZARDS Instructor Claire Samson PhBDB...

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ERTH2&0&/1& Geomagnetic ha6ards 1 GEOMAGNETIC HAZARDS Instructor: Claire [email protected] [email protected] PBEngB
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ERTH2&0&/1& Geomagnetic ha6ards 2 Lecture obFectives H To describe the characteristics of the Earth’s magnetic field H To describe solar activity H To understand the interaction between the solar wind and the Earth’s [email protected] and its conseNuences on technological systems
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ERTH2&0&/1& Geomagnetic ha6ards 3 Contents H Electricity and magnetism H The Earth’s magnetic field – The internal geomagnetic field – Solar activity and the external geomagnetic field H Space weather H ConseNuences on technological systems
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ERTH2&0&/1& Geomagnetic ha6ards & Electricity and magnetism
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ERTH2&0&/1& Geomagnetic ha6ards 5 Faraday’s law H In the laboratory: – Magnetic field variations induce an electrical current in a medium – The induced current creates its own magnetic field
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ERTH2&0&/1& Geomagnetic ha6ards U N S A Magnetic field variations induce an electric current Author: SB HeffordB Shown with permissionB
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ERTH2&0&/1& Geomagnetic ha6ards W Faraday’s law H In nature: – Xariations in the Earth’s magnetic field induce electrical (Z telluric Z) currents H In the ground H \n electrically conducting networks – Telegraph network – Telephone lines and seafloor cables – Pipelines – Power transmission lines
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ERTH2&0&/1& Geomagnetic ha6ards ^ Magnetotelluric sounding H Prospecting techniNue H Record for a few hours to a few days – Earth’s magnetic field – Telluric currents H Estimate the electrical conductivity in the subsurface – Metallic ore bodies are more conductive than the surrounding rocks
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ERTH2&0&/1& Geomagnetic ha6ards _ Photo: IB [email protected] UB of Manitoba Magnetic sensors
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ERTH2&0&/1& Geomagnetic ha6ards 10 Photo: MB [email protected] Carleton UB Photo: Narod Geophysics. Shown with permission.
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ERTH2&0&/1& Geomagnetic ha6ards 11 Electrodes Photos: MB [email protected] Carleton UB ! 15 cm Photo: Phoenix GeophysicsB Shown with permissionB
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ERTH2&0&/1& Geomagnetic ha6ards 12 Photo: MB [email protected] Carleton UB
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ERTH2&0&/1& Geomagnetic ha6ards 13 Photo: CB Samson
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ERTH2&0&/1& Geomagnetic ha6ards 1& Electromagnetic surveying H Prospecting techniNue – Groundabased or airborne H Controlled experiment – An artificial varying magnetic field induces currents in subsurface ore bodies – These currents generate a magnetic field recorded at the surface H Estimate the [email protected] shape and electrical conductivity of subsurface ore bodies
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ERTH2&0&/1& Geomagnetic ha6ards 15 130m 50m 125m Transmitter Receiver Ore Body Subsurface X Y Z Secondary Field Primary Field Eddy Currents Author: SB HeffordB Shown with permissionB
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ERTH2&0&/1& Geomagnetic ha6ards 1U Photo: Fugro Airborne SurveysB Shown with permissionB
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ERTH2&0&/1& Geomagnetic ha6ards 1W
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ERTH2&0&/1& Geomagnetic ha6ards 1^ The Earth’s magnetic field (synB geomagnetic field )
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ERTH2&0&/1& Geomagnetic ha6ards 1_ Geomagnetic ha6ards H Extreme variations of the Earth’s magnetic field can have a significant effect on technological systems H Geomagnetic effects observed for 150 years – Disturbances on the telegraph first stimulated investigations
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ERTH2&0&/1& Geomagnetic ha6ards 20 The internal geomagnetic field
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