The Magnitude of the Problem

Abstract

“On Monday morning last, about a quarter past two, St. Louis and the surrounding country, was visited by one of the most violent shocks of earthquake that has been recorded since the discovery of our country.” (Louisiana Gazette, 21 December 1811 ) This is where the story begins, in the wee hours of the morning on 16 December 1811. Many early Americans, in particular in the sparsely populated midcontinent, were awakened that night by seismic waves from the powerful mainshock and kept awake by a robust aftershock sequence. Of those who experienced the shaking, only a small percentage documented their experiences in written accounts that have been handed down to us. The collection of known archival accounts numbers only in the hundreds. Some of the accounts appeared to defy credulity: waterfalls appearing on the Mississippi River, the course of the river itself temporarily reversed, riverbanks and even entire islands collapsing. Other accounts reveal remarkable insight, even prescience; for example, medical doctor Daniel Drake, who observed that shaking was stronger in the Ohio River Valley than in the adjacent uplands and went on to ascribe the difference to the fact that strata in the river valley are “loose.” Samuel Mitchill, a representative in the U.S. Congress with training in geology, set out to collect accounts in the hope that they would lead him to “something like a tolerable theory of earthquakes.” Along the way he came to appreciate the challenge of the task he set himself. “The phenomena,” he wrote in 1815, “were described in the most fearful and alarming strains by several writers. Much exaggeration was interwoven with some of the narratives. Some, indeed, were tinctured with fable and burlesque.” (Many of the accounts that likely impressed Mitchill as fable and burlesque have in fact found support in modern science: …