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Reverberations on the watery element: A significant tsunamigenic historical earthquake offshore the Carolina coast

Seismological Research Letters

By:
, , and
DOI: 10.1785/0220120152

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Abstract

We investigate an early nineteenth-century earthquake that has been previously cataloged but not previously investigated in detail or recognized as a significant event. The earthquake struck at approximately 4:30 a.m. LT on 8 January 1817 and was widely felt throughout the southeastern and mid-Atlantic United States. Around 11:00 a.m. the same day, an eyewitness described a 12-inch tide that rose abruptly and agitated boats on the Delaware River near Philadelphia. We show that the timing of this tide is consistent with the predicted travel time for a tsunami generated by an offshore earthquake 6–7 hours earlier. By combining constraints provided by the shaking intensity distribution and the tsunami observation, we conclude that the 1817 earthquake had a magnitude of low- to mid-M 7 and a location 800–1000 km offshore of South Carolina. Our results suggest that poorly understood offshore source zones might represent a previously unrecognized hazard to the southern and mid-Atlantic coast. Both observational and modeling results indicate that potential tsunami hazard within Delaware Bay merits consideration: the simple geometry of the bay appears to catch and focus tsunami waves. Our preferred location for the 1817 earthquake is along a diffuse northeast-trending zone defined by instrumentally recorded and historical earthquakes. The seismotectonic framework for this region remains enigmatic.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Reverberations on the watery element: A significant tsunamigenic historical earthquake offshore the Carolina coast
Series title:
Seismological Research Letters
DOI:
10.1785/0220120152
Volume
84
Issue:
5
Year Published:
2013
Language:
English
Publisher:
Seismological Research Letters
Contributing office(s):
Earthquake Science Center
Description:
8 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Seismological Research Letters
First page:
891
Last page:
898
Country:
United States
State:
South Carolina
Other Geospatial:
South Carolina Coast