Location

San Diego, California

Session Start Date

5-24-2010

Session End Date

5-29-2010

Abstract

This paper summarizes geological, geophysical and seismological studies in two accepted and one candidate seismic zones in the central United States. The area was shaken by as many as 2,000 felt earthquakes in 1811-12, including four events greater than Magnitudes 7.0. These occurred before the area west of the Mississippi River was settled, so the intensity of shaking was not recorded over much of the affected region. Earthquakes in the central United States are felt over a much broader area than similar magnitude earthquakes in the western United States because of the low attenuation associated with undeformed Paleozoic age strata underlying the region. The New Madrid Seismic Zone (NMSZ) is believed to have been the source of the 1811-12 quakes and is the most studied source area in the central U.S. Some of the important structural features identified within this zone are summarized in this article, including the Reelfoot Fault scarp, Lake County Uplift, Crowley’s Ridge, Blytheville Arch, Bootheel Lineament and the Crittenden County Fault Zone. In just the last few years a GPS measurement array has been established around the Reelfoot Fault, and a debate has emerged about the accuracy and implications of these measurements. In the Wabash Valley Seismic Zone (WVSZ) limited historical and instrument arrays suggests that although the recorded seismic activity is much lower than a plate boundary region, it is, nevertheless, anomalously high activity for an intraplate region. Recent paleoliquefaction studies in the WVSZ suggest that it has likely spawned large-magnitude earthquakes, though not with as great a magnitude or frequency as the NMSZ. The anomalous historic seismicity recorded in South Central Illinois is believed to be the reactivation of old basement faults or background noise, but paleoliquefaction studies indicate that large magnitude earthquakes may also emanate from this region. It has not been accepted as a credible seismic source zone, but may be at some time in the future, as more data is collected and synthesized.

Department(s)

Civil, Architectural and Environmental Engineering

Second Department

Geosciences and Geological and Petroleum Engineering

Appears In

International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics

Meeting Name

Fifth Conference

Publisher

Missouri University of Science and Technology

Publication Date

5-24-2010

Document Version

Final Version

Rights

© 2010 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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May 24th, 12:00 AM May 29th, 12:00 AM

Overview of the Seismic Threat in the Central United States

San Diego, California

This paper summarizes geological, geophysical and seismological studies in two accepted and one candidate seismic zones in the central United States. The area was shaken by as many as 2,000 felt earthquakes in 1811-12, including four events greater than Magnitudes 7.0. These occurred before the area west of the Mississippi River was settled, so the intensity of shaking was not recorded over much of the affected region. Earthquakes in the central United States are felt over a much broader area than similar magnitude earthquakes in the western United States because of the low attenuation associated with undeformed Paleozoic age strata underlying the region. The New Madrid Seismic Zone (NMSZ) is believed to have been the source of the 1811-12 quakes and is the most studied source area in the central U.S. Some of the important structural features identified within this zone are summarized in this article, including the Reelfoot Fault scarp, Lake County Uplift, Crowley’s Ridge, Blytheville Arch, Bootheel Lineament and the Crittenden County Fault Zone. In just the last few years a GPS measurement array has been established around the Reelfoot Fault, and a debate has emerged about the accuracy and implications of these measurements. In the Wabash Valley Seismic Zone (WVSZ) limited historical and instrument arrays suggests that although the recorded seismic activity is much lower than a plate boundary region, it is, nevertheless, anomalously high activity for an intraplate region. Recent paleoliquefaction studies in the WVSZ suggest that it has likely spawned large-magnitude earthquakes, though not with as great a magnitude or frequency as the NMSZ. The anomalous historic seismicity recorded in South Central Illinois is believed to be the reactivation of old basement faults or background noise, but paleoliquefaction studies indicate that large magnitude earthquakes may also emanate from this region. It has not been accepted as a credible seismic source zone, but may be at some time in the future, as more data is collected and synthesized.