The U.S. Geological Survey response plan for volcanic unrest in the Long Valley area is designed to improve communication about significant scientific information derived from monitoring measurements to local, state, and Federal civil authorities. The table shows a graded measure of the U.S. Geological Survey's concern about the possibility that a given level of unrest might threaten local communities with a volcanic eruption from within Long Valley caldera or along the Mono-Inyo Craters volcanic chain (it does not apply to regional earthquakes occurring in the tectonic regime outside the caldera or away from the Mono-Inyo Craters volcanic chain). This ranking offers civil authorities a framework they can use to gauge and coordinate their response to a developing seismic or volcanic crisis. Effective communication and coordination with emergency management officials are particularly important because the USGS has neither the authority nor the expertise to make decisions regarding the civil response to an evolving crisis.
The 4-level color-coded notification system below was developed in 1997 to replace a 5-level system devised in 1991 then modified in 2002 (see references below).
CONDITION | USGS RESPONSE1 | ACTIVITY LEVEL | RECURRENCE INTERVAL2 |
---|---|---|---|
GREENNo immediate risk |
Normal operations plus information calls to local and other authorities for weak through strong unrest as appropriate | Background or quiescence | Most of the time |
Weak Unrest | Days to weeks | ||
Minor Unrest | Weeks to months | ||
Moderate-to-Strong Unrest | Months to years | ||
YELLOW (WATCH) |
Full calldown and EVENT RESPONSE3 | Intense Unrest | Years to decades |
ORANGE (WARNING) |
Full and calldown and EVENT RESPONSE3 (if not already in place under YELLOW) | Accelerating intense unrest: eruption likely within hours to days | Decades to centuries |
RED (ERUPTION IN PROGRESS) |
Full and calldown and EVENT RESPONSE3
(if not already in place under YELLOW OR ORANGE)
Daily or more frequent updates on eruption levels |
LEVEL 1: Minor eruption | Centuries |
LEVEL 2: Moderate explosive eruption | Centuries | ||
LEVEL 3: Strong explosive eruption | Centuries | ||
LEVEL 4: Massive explosive eruption | Centuries to millennia |
1USGS response for a given condition will include the responses specified for all lower conditions.
2Estimated recurrence intervals for a given condition are based primarily on the recurrence of episodes of unrest in Long Valley Caldera since 1980, the record of M>4 earthquakes activity in the region since the 1930's, and the geologic record of volcanic eruptions in the region over the past 5,000 years.
3 Event Response involves staffing the USGS field office in Mammoth Lakes for enhanced, on-site monitoring as well as staffing a field office in Bridgeport. See full description in USGS Bulletin 2185.
CONDITION | EXPIRES AFTER* | SUBSEQUENT CONDITION |
---|---|---|
GREEN (No immediate risk) Weak Unrest Minor Unrest Moderate-to-Strong Unrest |
|
GREEN Background Weak Unrest Minor Unrest |
YELLOW (Watch) | 14 days |
GREEN (to appropriate Unrest level under green) |
ORANGE (Warning) | 7 days |
YELLOW |
RED (Alert: Eruption in progress) |
1 day |
ORANGE |
*Number of days after the activity level falls below the threshold for a given CONDITION
Hill, D.P., Johnston, M.J., Langbein, J.O., McNutt, S.R., Miller, C.D., Mortensen, C.E., Pitt, A.M., and Rojstaczer, S., 1991, Response Plans for Volcanic Hazards in the Long Valley Caldera and Mono Craters Area, California: U.S. Geological Survey Open-File Report 91-270, 64 p.