New Invention Advances Freshwater Seismology Research

For Ernie Aaron, Scripps Institution of Oceanography at University of California San Diego development technician, necessity was indeed the mother of invention. Aaron tackled a problem facing scientists in the lead-up to a research expedition to Lake Malawi in southeastern Africa, and created a patented invention in the process.

When Scripps technicians received a request to support an earthquake fault mapping study on the bottom of the freshwater lake that straddles Mozambique, Tanzania and Malawi, as part of the National Science Foundation-funded Ocean Bottom Seismograph Instrument Pool, they gladly accepted. And, then thought, how are we going to do this?

Seismic studies like this are fairly routine in the ocean. Until now few had been undertaken in freshwater largely due to the retrieval system that allows the instruments, and the data they contain, to be successfully recovered from thousands of feet below.

That’s because current ocean-bottom seismometers rely on seawater as an electrical conductor to erode a wire that releases a pin, and the instrument from its bottom tether. Without this highly ionic seawater environment to complete the electrical circuit, the scientists cannot remotely send the acoustic power signal necessary to set off the chain of events that prompts the instruments to float back to the surface.

Soon after receiving the request, the creative juices started flowing among the Scripps development technicians. Then, Aaron says he had somewhat of an epiphany.

“I needed a material that would go from a solid to a putty-like state,” said Aaron, who was already in the initial stages of developing a new release system.

After some research, Aaron found a plastic-like polymer that when heated would allow the release of the restraining pin. Unlike the traditional release, Aaron’s Multi Environment Low-power Trigger (MELT) can be reheated back to its original shape and used again.

Aaron conducted a series of tests and refinements on his new trigger device prior to the Malawi deployment to ensure it would work anywhere, most importantly in freshwater environments.

“The new system allows researchers to trigger the release of the instruments anywhere–in saltwater, freshwater, and in the air,” said Aaron.

During the Malawi experiment the researchers, aided by Aaron, were successful in recovering all but one of the 34 seismometers deployed, seven of which spent more than one year on the sediment-laden lake bottom. One instrument was lost for reasons unknown. Since the initial deployment, the device has been successfully tested as a back-up device on 26 instruments in the waters off Santorini, Greece.

Realizing he might have something of value to others, Aaron worked with UC San Diego’s Office of Innovation and Commercialization to file for patent protection on the release design, and market it to prospective companies. Recently, Aaron’s MELT device was licensed to EdgeTech, a leading developer of offshore engineering systems.

The release is currently on one of its longest and deepest tests to date–a yearlong deployment in over 5,000 meters (16,404 feet) of water off the coast of West Africa.

Aaron hopes that one day his system might be used with or as a replacement for the burn wire release system currently in use. The advantage of the new system is that it allows researchers to collect data anywhere with the added convenience of it being immediately reused for its next deployment.

The Incorporated Research Institutions for Seismology supported the research and production of MELT releases for the Lake Malawi expedition under their Cooperative Agreement (No. OCE-1112722) with the National Science Foundation.

-- Annie Reisewitz

Related Image Gallery: MELT release system