November 2022 – Monthly Talk

November 2022 – Technical Talk

Speaker: Peter Kowalczyk, Chief Schientist Emeritus / Founder, Ocean Floor Geophysics

Title: Magnetic and Electric Fields around Subsea Cables – mapping and fault finding

Date: Wednesday, November 23, 2022

Time: 4:30pm to 5:30pm PST

Location: Room 111, 409 Granville Street, Vancouver, BC, V6C 1T2

Peter is a founder of Ocean Floor Geophysics. He has a background in mining geophysics and extensive experience in mineral exploration worldwide. Prior to starting OFG, he was chief geophysicist for Placer Dome, the second largest gold mining company in the world, at that time. Peter has a strong background in electrical, magnetic, and electromagnetic potential field methods used in mineral exploration and in the economic evaluation of mineral deposits.

Subsea cables can be divided into several classes – DC Power, AC Power, or communication with or without repeaters. Their magnetic signatures can be quite strong and they are distinct. There is considerable incentive to measure the depth of burial of AC power cables; they can overheat if buried too deeply, and are susceptible to damage if buried too shallowly. The magnetic signature measured when using a vector magnetometer is different from that seen using a total field magnetometer and extra information can be extracted using a vector magnetometer. The measurement of electric fields around subsea cables is not typical, but this can provide complementary and quite useful information, particularly when looking for faults. A brief discussion of theory and some example data collected during surveys is presented. Examples of data collected using an active seafloor following tow-fish (ROTV) and using an Autonomous Underwater Vehicle (AUV) are shown. An example illustrating how the depth of burial over an AC power cable can be readily measured using a high speed vector magnetometer is presented.

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