Wednesday, December 14, 2016

Major Earthquake Rocks Idaho Panhandle and the Pacific Northwest [otd 12/14]

Late on the evening of Saturday, December 14, 1872, residents in North Idaho felt a major earthquake that swayed buildings, caused shelved objects to rattle around, and agitated animals. In its report of the incident, the Lewiston Signal said, “The violence of the first shock created considerable alarm among those who had never experienced such a thing before.”

The initial strong shock stopped clocks, and rattled crockery and glassware all around the region. Many Lewiston residents heeded the normal advice and ran out into the streets. Those who had gone to bed felt their berths rock and sway along with their home or hotel. Some thought a sudden, tremendous gust of wind had hit.
U. S. Geological Survey image, retouched to focus on 1872 event.

The Signal wrote that during the quake, “Frightened chickens flew about as though possessed of the devil. Dogs howled, cattle lowed, and all nature, animate and inanimate, was much disturbed.”

Elk City is located deep in the Idaho mountains, nearly ninety miles to the southeast of Lewiston. There, residents felt the quake “very plainly.” At that time, only scattered ranches occupied Paradise Valley, future location of Moscow. The Signal article said, “North of here, in the vicinity of Paradise valley, the shock was so severe as to make everything fairly dance.”

Most witnesses reported a short, sharp initial jolt: It lasted about eight seconds in Lewiston. However, at least one Idaho location along the Clearwater River reported that the shaking lasted around two minutes. Despite the relative severity of the quake, no one observed any soil or rock displacement, nor any serious structural damage.

Idahoans recorded at least three quick shocks and others apparently felt four. These were all within a few minutes of the first event. No one in Idaho reported any delayed aftershocks. However, several locations between the Idaho border and the Cascades – many in Washington and a couple in Oregon – recorded intermittent aftershocks into the early morning hours.

Contemporary accounts indicate that people felt the quake all over the Pacific Northwest, including parts of Montana and Canada. In Wallula, Washington, 20-25 miles west of Walla Walla, witnesses reported a heavy shaking that lasted almost a minute, followed by five lighter shocks accompanied by rumbles like “a heavy peal of thunder.” In Portland, people noticed swaying chandeliers and some stopped clocks, but no actual damage.

Reports were not without an element of humor: The Oregonian had a statement from Walla Walla that said, “The accounts that reach us seem to indicate that the further north, the greater the severity of the earthquake. There is a report that up in the Spokane country, the earth opened and swallowed up a number of Indians and their horses. This, doubtless, is an exaggeration ... ”

The quake hit much harder around Puget Sound and Vancouver Island. There, many buildings “swayed to and fro like small craft at sea.” As in Lewiston, residents ran into the street for fear the structures would collapse. A number of windows broke, and homes and restaurants found  “crockery tumbled from the shelves.”

Back then, of course, there was no seismograph network to provide objective measurements. However, analysis of various motion and damage reports provide an estimated magnitude of 6.8 to 7.4 – a strong to major event. Other assessments placed the epicenter in the foothills of the Cascades about 100 miles east of Seattle.
References: [Illust-North]
William H. Bakun, Ralph A. Haugerud, Margaret G. Hopper, Ruth S. Ludwin, "The December 1872 Washington state earthquake," Bulletin of the Seismological Society of America, Vol. 92, No. 8, pp. 3239-3258 (2002).

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