Imaging Marine Gas Hydrate using Electromagnetic Methods
headshot of Steve Constable wearing glasses

Dr. Steve Constable
Professor, UCSD Scripps Institute of Oceanography – Institute of Geophysics and Planetary Physics

Wednesday, May 5th, 2021
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Methane hydrate, a solid mix of water and methane, is found on the continental shelves worldwide, and is an important part of the global carbon budget.  It is a potential hazard to people and infrastructure, having been implicated in seafloor landslides.   Hydrate may play a role in ocean acidification and even climate change.  Some countries consider hydrate a strategic source of natural gas.  Yet, we know very little about its distribution and abundance, largely as a result of its weak seismic signature, especially at lower concentrations.  Since pure methane hydrate is more electrically resistive than ice, geophysical surveying using electromagnetic methods is an ideal way to learn about the distribution of hydrate in the environment.  Active source EM techniques were developed over 40 years ago at Scripps, but more recently we have developed instrument systems which are optimized for hydrate targets, and have used these around the world.  To assist in the interpretation of field data, we have carried out laboratory measurements on various mixtures of methane hydrate, sand, silt, and salt, which have also provided information on electrical conduction mechanisms in methane hydrate.  As a coda to our work on methane hydrate, recent laboratory measurements on CO2 hydrate show it to have different conductivity and conduction mechanisms than methane hydrate, and suggest that marine EM methods may play a role in monitoring CO2 sequestration in seafloor sediments.