2002 Update

M&O Working Group Update
Reprinted from InterRidge News 11.1 (April 2002) by Chris Fox

Monitoring of low-level seismicity on the Mid-Atlantic Ridge (MAR) using autonomous underwater hydrophones will be continued and expanded in the coming years. The initial effort, consisting of six hydrophones moored in the region of 15o-35o N (see InterRidge News 8.1, March, 1999), was deployed in March 1999 by Debbie Smith (WHOI), Maya Tolstoy (LDEO) and Chris Fox (NOAA/PMEL) and funded by USRIDGE for two years of data collection. After extending this initial effort to a third year, US RIDGE recently agreed to fund four additional years of monitoring in a more operational mode, with routine posting of derived seismic source locations posted on the world wide web and raw hydrophone signals to be made available to the scientific community via FTP. PIs on the extended effort are Bob Dziak (OSU), Haru Matsumoto (OSU), Debbie Smith (WHOI), and Chris Fox (NOAA/PMEL). The existing array provides excellent coverage of the MAR from the equatorial region to the Azores, but bathymetric shadowing of the acoustic signals have not allowed monitoring of the MAR north of the Azores.

In May 2002, a French expedition (SIRENA) on the French research vessel Le Suroit will deploy a new array of six hydrophones around the MAR between the Azores and the Gibbs Fracture Zone. The PIs for this experiment are Jean Goslin (CNRS, Brest) and Chris Fox (NOAA/PMEL). The experiment is jointly funded by the French government and US NOAA. The array is only planned for a one-year deployment but every attempt will be made to maintain the array long-term, similar to the USRIDGE array to the south. Although the sensors will be located south of Gibbs, they should be able to routinely detect activity from the Reykjanes Ridge south of Iceland. This new data set, combined with data from the southern array, will provide excellent coverage of the Azores platform and can be combined with seismic sensors on the Azores for a more complete picture of the seismicity of the hotspot. The first data set will be recovered in summer 2003.

Planning is underway to deploy additional acoustic sensors at other locations in the Atlantic and other ocean areas by the Sound in the Sea project of NOAA's Ocean Exploration Programme (PI: C. Fox). One possible target area is along the equator in the Atlantic in conjunction with the existing PIRATA array of surface weather buoys. The acoustic data sets described, while being collected for ridge crest studies, provide valuable data to researchers studying the distribution of large marine mammals in the open ocean and the impact of manmade and natural noise on marine life. Further information on these experiments, access to seismic source information, and access to raw data (still under development) can be found at: http://www.pmel.noaa.gov/vents/acoustics.html . All of these topics will be discussed in detail at the upcoming MOMAR-II workshop June 15-17 in Horta, Azores.