A local earthquake of sufficient magnitude to seriously damage structures and disrupt transportation systems in the Crater Lake area probably does not occur more frequently than once every few thousand years. More frequent may be large, distant earthquakes on the Cascadia subduction zone for which shaking might be less violent but of much longer duration. Residents may wish to maintain supplies of food, water, clothing, flashlights, and first-aid materials (see Protecting Crater Lake National Park and surrounding communities from volcano hazards), such as recommended for people living in earthquake-prone areas elsewhere, and minimize the chances of large objects falling in their homes. Businesses and Crater Lake National Park should be aware of possible damage to structures, utilities, communication facilities, and transportation systems, in addition to the potential for rock falls and dangerous waves on Crater Lake described above. Communities should develop plans for responding to the effects of an earthquake. A relevant local example of moderate earthquake damage is provided by the M»6 “Klamath Falls” earthquakes of September 1993 (Wiley and others, 1993; Dewey, 1993).