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 (see reference below).

Geologic behavior	Condition	USGS Response
Typical behavior since 1980 includes: Background: as many as 10 to 20 small earthquakes with magnitudes (M) less than 3 (M<3) per day and uplift of the resurgent dome at an average rate of about 1 inch per year. Weak unrest (likely to occur several times a year): For example increased number and (or) strength of small earthquakes or a single felt (magnitude M>3) earthquake. Minor unrest (likely to occur a few times a year): For example, a swarm with several M>3 earthquakes. Moderate unrest (likely to occur about once a year): For example a M>4 earthquake or more than 300 total earthquakes in a day.	GREEN No immediate risk	ROUTINE MONITORING plus Information Calls to USGS personnel, Town, County, and State (California OES, State Geologist) and local Federal agencies (USFS, BLM) regarding locally felt earthquakes and notable changes in other monitored parameters such as ground deformation, fumarole activity, and gas emissions.
Intense Unrest (may occur about once per decade): For example, a swarm with at least one magnitude 5 earthquake and (or) evidence of magma movement at depth as indicated by an increased rate in ground deformation.	YELLOW WATCH	INTENSIFIED MONITORING: Set up emergency field headquarters at Long Valley caldera. Initial WATCH message sent by USGS to California OES, which promptly informs local authorities. (Includes above information calls)
ERUPTION LIKELY within hours or days (may occur every few hundred years): Strong evidence of magma movement at shallow depth	ORANGE WARNING	GEOLOGIC HAZARD WARNING issued by USGS to Governors of California and Nevada and others who inform the public. (includes WATCH response)
ERUPTION UNDERWAY (may occur every few hundred years)	RED ALERT	SUSTAINED ON-SITE MONITORING AND COMMUNICATION. Maintain intensive monitoring and continuously keep civil authorities informed on progress of eruption and likely future developments.

Notes:

CONDITION
A given condition is keyed to successively more intense levels of geologic unrest detected by the monitoring networks. It is based on results from the geophysical monitoring networks operated in the region since 1980 and on premonitory activity observed before volcanic eruptions elsewhere in the world. They are derived from specific status tables for each monitoring network (see Open File Report 91-270).

USGS RESPONSE
The USGS response for a given condition includes the responses specified for all lower levels.

ESTIMATED RECURRENCE
Intervals for a given condition are based on the recurrence of unrest episodes in Long Valley caldera since 1980, the record of magnitude 4 or greater earthquakes in the region since the 1930's , and the geologic record of volcanic eruptions in the region over the last 50,000 years.

COLOR-CODE YELLOW CONDITION
During a color-code yellow condition, our response will involve establishing an on-site operations center and mobilizing USGS field crews for intensified, on-site monitoring.

EXPIRATION OF WATCH, WARNING, AND ALERT
The table below shows the length of time (in days) a given condition remains in effect AFTER the level of unrest drops below the threshold that initially triggered the condition.

CONDITION	EXPIRES AFTER	SUBSEQUENT CONDITION*
WATCH	14 days	GREEN (no immediate risk)
WARNING (eruption likely)	14 days	WATCH
ALERT (eruption in progress)	1 day	WARNING

*Determined by the level of unrest at the time the previously established condition expires. In the case of the end of an episode of eruptive activity (ALERT ), a WARNING will remain in effect for at least 14 days, depending on the level of ongoing unrest.