Report of the review panel on the December 14, 1872 earthquake

The review panel on the December 14, 1872, earthquake in the Pacific Northwest concluded that the necessary seismographic data to determine the focal mechanism for the 1872 earthquake is lacking but available data on the nature of the effects of the ground shaking on people, the land, and structures suggests a predominance of low-frequency, rather than high-frequency, ground motion. This is what one would expect if the earthquake were 40 or more kilometers deep, for then even the epicentral area would experience far-field conditions, marked by relatively low accelerations, large displacements, and long duration of shaking. Such conditions are favorable to the excitation of landslides, such as those that occurred in the 1872 earthquake. The data indicate the epicenter lies in a region of central Washington that includes Lake Chelan and Entiat and the area north of it. The felt area is estimated to be approximately 13,000,000 square kilometers (500,000 square miles) as estimated from available reports of effects on people, vegetation, and geologic features that appeared in newspapers, books, ledgers, and other documents.