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Focal mechanisms in the northeast New Madrid seismic zone

Allison M. Shumway
Focal mechanisms in the northeast New Madrid seismic zone
Seismological Research Letters (May 2008) 79 (3): 469-477


On 23 January 1812, an estimated M7-M8 earthquake occurred in the New Madrid seismic zone. The New Madrid North fault (NMNF) has been proposed as the location of this rupture. Based on the estimated size of this earthquake, the rupture length of the fault plane would be expected to extend beyond the microseismicity that defines the NMNF. Seismicity data from this area show three alignments of earthquakes, running northeast from New Madrid, Missouri, into western Kentucky and southern Illinois that may represent an extension of the New Madrid seismic zone (NMSZ) and therefore alternative locations for the 23 January 1812 rupture. Earthquakes in the northeast NMSZ from June 1995 to June 2006 were relocated using a velocity model of the Mississippi embayment with appropriate depths to bedrock beneath seismic stations. Focal mechanisms were generated for events on the northeast trending alignments. The results show approximately half the focal mechanisms have a north-northeast-striking nodal plane and a right-lateral, strike-slip component consistent with earlier studies of the NMNF to the southwest. This shows that this part of the northeast NMSZ is influenced by the same fault pattern and stress regime as the NMNF, may be an extension of the NMSZ, and therefore alternate locations of the 23 January 1812 rupture.

ISSN: 0895-0695
EISSN: 1938-2057
Serial Title: Seismological Research Letters
Serial Volume: 79
Serial Issue: 3
Title: Focal mechanisms in the northeast New Madrid seismic zone
Author(s): Shumway, Allison M.
Affiliation: William Lettis & Associates, Golden, CO, United States
Pages: 469-477
Published: 200805
Text Language: English
Publisher: Seismological Society of America, El Cerrito, CA, United States
References: 36
Accession Number: 2008-096242
Categories: SeismologyEnvironmental geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch maps
N35°00'00" - N38°00'00", W91°00'00" - W88°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200832
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