Time-Critical Studies: Rapid response to Transient Dynamic Mid-Ocean Ridge Events

The Time-Critical Studies (TCS) Theme of Ridge 2000 focuses on observations of the immediate geochemical and geobiological consequences of magmatic and tectonic events along the global mid-ocean ridge system. To date funding has centered on the Juan de Fuca and Gorda Ridges which are within the range of the U.S. Navy's Northeast Pacific Sound Surveillance System (SOSUS). NOAA's T-Phase Monitoring Program has accessed SOSUS in real-time since 1993, providing the TCS community with detection of seismicity associated with eruptive or tectonic activity along these two ridges. This remote detection of earthquake swarms along the N.E. Pacific mid-ocean ridge coupled to NSF funding for pre-event staging of equipment and supplies has allowed directed and increasingly well-organized field responses to the event site. Major rapid and follow-up response cruises have been successfully mounted to 1993 CoAxial, 1996 and 2001 Gorda Ridge, the 1998 Axial Volcano, and 2001 Middle Valley magmatic episodes. The logistical approach required to study these events has been greatly facilitated by the RIDGE/Ridge 2000 programs and collaboration between university, NOAA and Canadian investigators. The U.S. Navy has recently fully restored the SOSUS hydrophone arrays to essentially fully operational status, assuring long-term remote real-time detection capabilities for the Juan de Fuca and Gorda Ridges. Recent seismic swarms on the West Valley, N. JFR (July, 2003), and on the Cobb Offset (May, 2004) were detected by SOSUS, but were not responded to because of their low intensity and short durations. However, the response team remains poised for the next significant event. Proposals to enhance the event detection and rapid shore-to-event response effort are welcome at any Ridge 2000 target date. The Ridge 2000 program recognizes that even the most rapid ship response will miss the earliest subsurface and water column expressions of magmatic events. Consequently, Ridge 2000 also seeks proposals to develop alternate ultra-rapid response methods including air-droppable monitoring devices and in situ sensors. Coordination with Integrated Study Sites and proposed cabled and moored Ocean Observatories at Ridge 2000 Integrated Study Sites is also encouraged.