Daily Updates on Activity on the Gorda Ridge
Beginning at 0700 GMT on 28 February 1996, intense seismicity was detected in the northeast Pacific Ocean using the T-phase Monitoring System developed by NOAA/PMEL to access the U.S. Navy's SOund SUrveillance System (SOSUS) in the northeast Pacific. The current event is located on the northernmost segment of the Gorda Ridge near 42 40'N and 126 48'W. The nature of the seismicity is very similar to that observed in June 1993 at the CoAxial Segment of the Juan de Fuca Ridge, which was later documented to be a lateral magma injection with subsequent eruption.
DAILY UPDATES
THURSDAY (6/13/96) SUMMARY NOAA Ship Discoverer sailed from Seattle on Monday (6/10) to return to the Gorda Ridge eruption site. A neutrally buoyant RAFOS float that was planted in the plume in March resurfaced at 42 41.76'N, 126 57.72'W, just 9.2 km northwest of its launch point at 42 37.1'N, 126 55.2'W. Ed Baker reports that the plume is intact. Congratulations to John Lupton (NOAA/PMEL) and Toby Garfield (Naval Postgraduate School) for a successful experiment.
MONDAY (5/13/96) SUMMARY A comparison of Gorda event earthquake activity with CoAxial can be found under histogram. Colleagues interested in posting results on this page are encouraged to contact Chris Fox in Newport. It's been a little slow out there...
THURSDAY (4/18/96) SUMMARY A digital camera image of the contact between fresh and older lavas has been posted under Seafloor Geology Results. Some areas of the page have been moved to allow viewing on smaller workstations.
TUESDAY (4/16/96) SUMMARY The research vessel WECOMA has returned to Newport after a very successful expedition. (Regular daily updates will be discontinued at this time. Updates will be limited to posting of new scientific results - Chris Fox, NOAA/PMEL).
MONDAY (4/15/96) SUMMARY A new science report has been received from WECOMA, including a sketch-map of the distribution of features within the study site generated by shipboard GIS system. Morning report from WECOMA indicates 1000 arrival time tomorrow in Newport, gale-force winds.
FRIDAY (4/12/96) SUMMARY Morning report from WECOMA indicates that weather is improving and a CTD Tow-yo is planned for this morning. WECOMA is scheduled into Newport on Tuesday, 4/16, between 1000 and 1200. Epicenter map has been updated to show locations of lava flow and hot water plume.
THURSDAY (4/11/96) SUMMARY ***SEAFLOOR LAVA FLOW DISCOVERED*** The science party on WECOMA reports fresh lava and hot water from narrowgate area, see preliminary science report.
WEDNESDAY (4/10/96) SUMMARY Seismicity remains at background levels. R/V WECOMA has radio'ed in a morning report. Science Party has filed the first science report.
TUESDAY (4/9/96) SUMMARY Seismicity remains at background levels. R/V WECOMA has radio'ed in a morning report.
MONDAY (4/8/96) SUMMARY Seismicity remains at background levels. R/V WECOMA sailed on schedule from Newport at 10:00 AM PST on Saturday, 4/6 and is presumably on station. Any information from the ship will be posted here as it is received.
FRIDAY (3/29/96) through FRIDAY (4/5/96) SUMMARY Background seismicity only over the period. WECOMA is scheduled to depart from Newport on Saturday, 4/6. A copy of the cruise plan for WECOMA is available.
THURSDAY (3/28/96) 0900PST SUMMARY Background seismicity only. New particle chemistry results under Event Plume particle results
WEDNESDAY (3/27/96) 1400PST SUMMARY Background seismicity.
TUESDAY (3/26/96) 0900PST SUMMARY No detectable seismicity.
MONDAY (3/25/96) 0900PST SUMMARY No detectable seismicity over the weekend. Preliminary information on plume age from Gary Massoth under Event Plume Dissolved Chemistry Results. New particle imagery and analysis under Event Plume particle results
FRIDAY (3/22/96) 1400PST SUMMARY Seismicity has reduced to normal, background levels. WECOMA planning continues. New Event Plume Helium-3 results have been posted by John Lupton. Event Plume particle results have been posted by Dick Feely.
THURSDAY (3/21/96) 1100PST SUMMARY Seismicity continues at a very low level.
WEDNESDAY (3/20/96) 1000PST SUMMARY Seismicity continues at a very low level. The NSF RIDGE program has broadcast a message to the research community on the upcoming WECOMA Cruise.
TUESDAY (3/19/96) 0930PST SUMMARY Seismicity continues throughout the segment. There is still no indication of focussing of activity or high-frequency seismicity associated with extrusion. Ed Baker has provided an EVENT PLUME CROSS-SECTION based on casts collected from McArthur.
MONDAY (3/18/96) 1030PST SUMMARY Seismicity continued throughout the northern segment of the Gorda Ridge over the weekend. Preliminary locations for the new activity are are shown in red on the accompanying epicenter map . The histogram of hourly event counts has been updated
FRIDAY (3/15/96) 1400PST SUMMARY ***RENEWED ACTIVITY*** At 1625GMT on 3/15/96, seismic activity renewed on the Gorda Ridge, increasing from a few events per hour to over 25 events in the first hour. The nature of the seismicity still appears to be due to magma injection rather than eruption. Preliminary locations for the new activity are in the summit (narrowgate) area. The histogram of hourly event counts has been updated
THURSDAY (3/14/96) SUMMARY Seismicity continues at a low level (see histogram below). NOAA Ship McArthur is due in Seattle at 1330 PST today. Plans are proceeding to use the Oregon State University research vessel WECOMA for another expedition to the site in early April.
WEDNESDAY (3/13/96) SUMMARY Seismicity continues at a low level (<5 earthquakes/hour). McArthur is scheduled to return to Seattle on Thursday 3/14/96 at 1530 PST. Discussions are ongoing for an additional expedition on R/V WECOMA, emphasizing seafloor imaging to help localize the source of activity. NOAA Ship McArthur report 1600 PST, 3/12/96: Weather has worsened and two-day forecast shows no improvement. They have broken off operations and are enroute to Seattle. WELL DONE!
TUESDAY (3/12/96) SUMMARY Seismicity continues at a reduced level. McArthur reported at 1000PST that poor weather has prevented operations for the last 12 hours. Ship is scheduled to depart area early PM on 3/13/96, returning to Seattle midday on Friday 3/15/96.
MONDAY (3/11/96) SUMMARY ****FIELD CONFIRMATION**** Report from Ed Baker on McArthur at 1600PST (3/10) indicated the discovery of a large hydrothermal plume ("Megaplume") near 42 39'N, 126 47'W. Seismicity continues at a low level.
SUNDAY (3/10/96) SUMMARY Only minor seismic activity, mostly from the "narrow-gate" area near 42 45'N. Report from McArthur at 1000PST indicated that no plumes have been identified. The available CTD cable restricts depth to 2900m. They began casts at 42 26'N and are working north at 2-minute intervals. Will contact again at 1600PST.
SATURDAY (3/9/96) SUMMARY Seismicity has decreased to less than 10 events/hour. McArthur should be on station by noon local time today. We were unable to establish radio communications but broadcast information. Will repeat tomorrow.
FRIDAY (3/8/96) SUMMARY Seismicity continues throughout the southern half of the ridge segment. The activity seems to be showing some periodic behavior (see histogram below). There is still no clear indication of lava extrusion. NOAA SHIP McArthur is off the coast of Washington enroute to the site. Radio communications will be made between Newport and the ship each day at 1000 and 1600 PST.
THURSDAY (3/7/96) SUMMARY Seismicity continues throughout the southern half of the ridge segment from 42 25'N to 42 45'N. This may indicate the propagation of a dike to the south from the segment high, although direct evidence is not available. There is no clear indication of lava extrusion. NOAA SHIP McArthur departs Seattle 1500 PST today; should arrive at the study site late Saturday (3/9). Reports from Chief Scientist Ed Baker will be posted on this page as they are received.
WEDNESDAY (3/6/96) SUMMARY Seismicity continues at a reduced rate. Third SOSUS array is now operational allowing improved sensitivity and epicenter locations. Cruise planning for NOAA SHIP McArthur continues. The UNOLS vessel R/V Wecoma may be available in the area in early April.
Last Modified: March 9, 1998; 1400 PDT