Humboldt State University, Humboldt County research shows promise for measuring tsunami currents

Joint acoustic research by Humboldt State University scientists and Humboldt County shows solid promise for measuring the velocity of tsunami currents like those triggered along the California coast last March by the Japan earthquake, HSU said Friday.

A device called an acoustic profiler, deployed under a pilot project from a dock at Humboldt Bay's Fairhaven Terminal on the North Spit, captured the velocity signals of both the March 11 Japan and the Feb. 27, 2010, Chile tsunamis, an HSU press release said.

?That was really exciting and confirmed to us that this pilot project succeeded in measuring tsunami currents,? Humboldt State graduate researcher Amanda Admire said in the release. ?We also now have the velocity data posted online in near real-time.?

The link can be found at http://nrs-isa.humboldt.

edu/tsunami/content/data_

adcp_realtime.php.

The research supports tsunami science and local mitigation efforts along the earthquake- and tsunami-prone North Coast. One of the objectives is to determine the response of Humboldt Bay to tsunami-produced currents and to compare the measured currents to those predicted by numerical models.

?If we can gain a deeper understanding of the currents that are generated, then over the long term we can engineer the infrastructure of harbors and marinas to withstand the impact better,? said HSU's Department of Geology professor Lori Dengler, an internationally

recognized expert in earthquake and tsunami hazard mitigation.

Dengler conducted a 10-day reconnaissance of Japan disaster sites in May and found water heights topped five stories in some cities. Sea walls were overrun and obliterated. In other locations, water heights exceeded 30 feet and leveled whole blocks.

?There is a lot of discussion in Japan about rebuilding sea walls and other abatement structures,? Dengler said, ?but the question is whether you rebuild for a more common 100-year event or a 1,000-year catastrophe like the one on March 11. I don't think 60-foot sea walls are economically or structurally viable, and a lot of other factors will have to be considered, not just in Japan but here in Humboldt and all up and down our Pacific Coast. You have to take into account coastal configurations, population distribution and land use, as well as tsunami hazard zones and evacuation routes. Gauging the velocity of tsunami currents in Humboldt Bay is the kind of site information we need to underpin tsunami mitigation and infrastructure planning.?

The prototype measuring device is a Nortek Aquadopp 600 kHz acoustic two-dimensional current profiler. The Fairhaven dock in Humboldt Bay was chosen for the pilot project because of its proximity to the National Oceanic and Atmospheric Administration's tide gauge site, which continuously records water levels. The dock also affords easy access to HSU scientists who fine-tune the instrument.

Pacific Gas & Electric Co. provided $30,000 to purchase and install the instrument in Humboldt Bay. The Humboldt Bay Harbor Recreation and Conservation District has provided logistical support. Additional operating expenses have been financed with donations from private individuals.

Source: http://www.times-standard.com/localnews/ci_18305740?source=rss

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