Washington is well-known for snowclad mountains, white-water rivers, and thick rain forests. Some of the hazards of such an environment-avalanches, drowning, and fires-are obvious and the precautions necessary to deal with them well understood. The hazard from earthquakes in Washington is less well recognized, yet damage and loss of life during a large earthquake are certain. A 1975 study (U.S. Geological Survey, 1975) of six counties in the Puget Sound area, now considered by some to be too conservative, projects as many as 2,200 deaths and 8,700 injuries in the next magnitude 7.5 earthquake.

Each year more than 1,000 earthquakes are recorded in Washington. Fifteen to twenty of these earthquakes cause ground shaking strong enough to be felt. However, major destructive earthquakes occur much less often. The last earthquake to cause widespread damage in Washington occurred in 1965. Since that time the state's population has increased by nearly 50 percent. Washington residents have largely forgotten the 1965 earthquake, and this has contributed to a general lack of public awareness of the state's earthquake hazards. Some scientists suggest that even larger earthquakes have occurred every several hundred or thousand years in the Pacific Northwest and that the most recent such earthquake occurred about 300 years ago.

This publication contains answers to the most commonly asked questions about earthquakes in Washington: Why do we have earthquakes? Can we predict when and where the next big earthquake will occur? Where are the earthquake faults? What would happen if we had a large earthquake today? What can be done to prepare for an earthquake?

By understanding the causes and effects of Washington earthquakes, individuals can take appropriate actions to reduce loss of life and property. Many of the necessary actions are identified and described in this report. A glossary of technical terms (in bold print in the text) is included at the end of the text.