Appendix B. USGS Terminology for Geologic Hazard Warnings

Response Plan for Volcano Hazards in the Long Valley Caldera and Mono Craters Region, California

| Summary | Introduction | Condition-Code Thresholds | Organization and Response | References |

Appendix A. History of Volcanism in the Long Valley Region
Appendix B. USGS Terminology for Geologic Hazard Warnings
Appendix C. Scientific Rationale for Activity Criteria Under Color Codes
Appendix D. Monitoring Networks and Instrumentation
Appendix E. Sample Messages Accompanying Change in Color Code
Appendix F. Memo Defining the Role of the Long Valley Observatory (pdf)

Current Hazard Warnings

The transition to condition ORANGE from either condition GREEN or YELLOW will be accompanied by a formal HAZARD WARNING issued by the Director of the U.S. Geological Survey (USGS). A formal USGS HAZARD WARNING is defined as follows in the October 11, 1983, issue of the Federal Register (v. 48, n. 197):

GEOLOGIC HAZARD WARNING—a formal statement by the Director of the USGS that discusses a specific geologic condition, process, or potential event that poses a significant threat to the public, and for which some timely response would be expected.

This issue of the Federal Register further states that "The term Hazard Warning (italics added) is reserved for those situations posing a risk greater than normal and warranting considerations of a timely response in order to provide for public safety. Information regarding hazardous conditions that do not meet the criteria for a Hazard Warning (italics added) may, however, also be sent to public officials as it becomes available. Transmittal of such information would not constitute a Hazard Warning." The criteria for a Geologic Hazard Warning are:

  1. A degree of risk greater than normal for the area or a hazardous condition that has recently developed or has only been recently recognized and
  2. A threat that warrants consideration of a nearterm public response.

Hazard Warnings Prior to 1983

Prior to October 1983, official statements by the USGS on geologic hazards were based on the threelevel system described in the April 12, 1977, issue of the Federal Register (v. 42. no. 70). The three levels (from lowest to highest) were defined as follows:

NOTICE OF POTENTIAL HAZARD-Information on the location and possible magnitude of a potentially hazardous geologic condition. However, available evidence is insufficient to suggest that a hazardous event is imminent or evidence has not been developed to determine the time of occurrence.

HAZARD WATCH-Information, as it develops from a monitoring program or from observed precursors, that a potentially catastrophic event of a generally predictable magnitude may occur within an indefinite time (possibly months to years).

HAZARD WARNING-Information (prediction) as to the time, location, and magnitude of a potentially disastrous geologic event.

Official statements by the USGS on geologic hazards in the Long Valley Caldera-Mono Craters region issued in May 1980 (HAZARD WATCH for potentially damaging earthquakes) and May 1982 (NOTICE OF POTENTIAL VOLCANIC HAZARD) were based on this three-level system.

Maintained by: Michael Diggles
Last modified: May 18, 2005