January 8, 1817 Tsunami: Philadelphia, Pennsylvania, United States

Ashmead [reference #1722] reports, "On Jan 8, 1817, an earthquake occurred which tossed vessels about the river and raised the water one foot."

A earthquake in the Philadelphia area caused “the most important disturbance and was sort of a tidal wave, its effects being much more powerful on the water though the houses and churches of the city were rocked.” (Philadelphia Inquirer) “The river was much agitated by the earthquake on the southward, tossing about vessels, and raising the water one foot.” (Pennsylvania Department of Internal Affairs, 1944). validity 2. (reference #541) (see Comments in earthquake on validity of shaking in Philadelphia)

a Philadelphia newspaper [ref #13847] describes a so-called agitation on the Delaware River around 11 a.m. LT: “vessels at wharves were violently tossed about,” and the “tide swelled upwards of 12 inches” […] The [modeled] tsunami travel time from the 1817 epicenter to the upper Delaware Bay would thus have been six or seven hours […] Thus, given the predicted timing and size of the wave, it is plausible that a tsunami from an earthquake with the preferred source parameters could account for a sudden 12-inch tide observed farther up the bay […] In early January, sunrise is around 7:30 a.m. at the latitude of Charleston, South Carolina. A low-amplitude wave (<1 m) may have gone unnoticed along an open coastline in predawn hours. The wave would have arrived in Bermuda even earlier, around 5:30 a.m. (LT). (reference #10759)

Note: reference #10759 indicates It is not clear from the account exactly where the reporter witnessed the agitation, but likely he was somewhere between Wilmington and Philadelphia

We are informed, by a gentleman, who witnessed the phenomenon, that on the 8th of this month, about 11 o'clock, a sudden agitation of the river Delaware took place, to such a degree that vessels at he wharves were violently tossed about, and the tide swelled upwards of 12 inches. - The gentleman who made this remark, observes, that as an earthquake was experienced to the Southward on the same day, it is most probable the effect on the Delaware was the reverberation or concussion of the earth operating upon the watery element". (reference #13847)

Reference #12345 lists as validity 3 (probable tsunami) with a source region local to observation near Philadelphia, PA. (accessed August 2024)

Note: not listed as Oceanic Tsunami as the only observation is in Delaware River