Figure 1: Map showing the earthquakes and planned response cruise track line. R/V Wecoma is scheduled to depart Newport, Oregon on April 20, 2008 (click for full-size)

Bill Hanshumaker's
Logbook from Sea:
4/21/2008

After leaving port on Sunday, we steamed towards the swarm of undersea tremors recently detected on the Juan de Fuca plate. Since these weren't located where scientist normally expect earthquakes, a three-day "Swarm Event Response Cruise" was organized by PMEL (NOAA). The R/V Wecoma steamed at 12 knots and deployed a hydrophone about 90 miles east of the swarm center. We then continued westward and have been conducting CTD casts to analyze the water chemistry at different depths at numerous locations (see map right, red stars indicate proposed CTD sample sites). This CTD array consists of twelve bottles that can capture seawater at specific depths. "CTD" stands for Conductivity (measuring salinity), Temperature, and Density, which refers to the types real-time data that is electronically sent back up to the ship. Once back on board, samples from the 10 liter bottles are analyzed and preserved for future laboratory studies. Carbon dioxide, methane, trace metals and helium isotopes are some of the types of measurements scientists use to detect hydrothermal activity. When these samples are processed, the NOAA scientists hope to map the underwater plume that would be produced IF there has been an eruptive event.

If you are interested in learning more about this cruise, visit the HMSC auditorium in Newport, Oregon. A map of the response cruise and other information is available. I will be back at HMSC at the end of the cruise and available for additional questions at the HMSC Visitor's Center. --Bill

Address inquiries to:
Robert Dziak - Seismologist - Email me
Robert Embley - Geologist - Email me
William Chadwick - Geologist - Email me
Matt Fowler - Analyst - Email me