Paleoseismic Evidence for Multiple
            <i>M</i>
            <sub>w</sub>
            ≥6 Earthquakes in the Eastern Tennessee Seismic Zone during the Late Quaternary

Warrell, Kathleen F.; Cox, Randel Tom; Hatcher, Robert D.; Vaughn, James D.; Counts, Ronald C.

doi:10.1785/0120160161

Cited by 10 publications

(5 citation statements)

References 30 publications

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“…Even though our strain rate model has an ~100‐km resolution in about all of the conterminous United States within intraplate North America, few coherent strain rate features of that (or larger) size are resolved beyond 2σ uncertainty. We resolve no strain accumulation at most of the notable areas of localized (instrumental and/or historic) seismicity such as the NMSZ (Johnston & Schweig, ; Kelson et al, ; Page & Hough, ; Tuttle et al, ), the Eastern Tennessee Seismic Zone (Powell et al, ; Warrell et al, ), and the Charleston, South Carolina area (Obermeier et al, ; Talwani & Cox, ). The only exception may be the Meers fault in Oklahoma.…”

Section: Discussionmentioning

confidence: 99%

A Robust Estimation of the 3‐D Intraplate Deformation of the North American Plate From GPS

2018

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Glacial isostatic adjustment (GIA) is the main cause of deformation in intraplate North America.Here we use up to 3,271 Global Positioning System station velocities to image this 3-D deformation across the entire plate. We apply a new robust strain rate estimation algorithm (median estimation of local deformation), which does not require the assumption that part of the plate is unaffected by GIA, an assumption we show to be false. Our results show extension in the area underneath the Laurentide ice sheet, contrasted with a semiannular belt of horizontal contraction of up to~4 × 10 À9 yr À1 around the former ice sheet. This contractional belt is kinematically linked to an~1-2 mm yr À1 far-field horizontal motion directed toward the ice sheet. Our results, together with a new robustly imaged vertical velocity field, are consistent with GIA as the main cause of deformation, although the contractional strain rates around the former ice sheet and the far-field horizontal velocities are significantly higher than those predicted by the ICE6G_C(VM5a) model. This finding suggests that our results, including the location of reversal in sign of horizontal motion relative to the ice sheet, will be useful to reevaluate the mantle viscosity structure used by GIA models. Besides the GIA-attributed deformation, we find almost no other region with significant strain accumulation. A plate-scale spatial correlation between strain rate and seismicity is absent, suggesting that GIA is a limited driver of contemporary seismogenesis and that intraplate seismicity must be attributable to factors other than secular strain accumulation.Plain Language Summary The theory of plate tectonics says that tectonic plates move as rigid blocks along the Earth's surface and that the Earth's crust should only deform at the boundary between plates. However, the recent explosion in the number of high-precision Global Positioning System stations allowed us to capture some subtle deformation patterns inside the North American plate that only became apparent by a very careful analysis of the relative motions between thousands of stations. We found that most of the plate is moving at 1-2 mm/year towards central Canada. Consequently, around most of Canada there is a zone where the crust is contracting. Within Canada, the crust is extending outward and is moving upward rapidly. These patterns can be explained by the process of the crust and mantle still rebounding from a time when it was covered by a thick ice sheet about 16,000 years ago. The fact that this causes the land to move towards the former ice sheet is an unexpected result that will be useful in understanding the relaxation properties of the underlying mantle. Moreover, we found that earthquakes inside the North American plate do not occur where we see the crust deform, which leaves these events still enigmatic.

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Section: Discussionmentioning

confidence: 99%

A Robust Estimation of the 3‐D Intraplate Deformation of the North American Plate From GPS

2018

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“…The ETSZ is the only location along the extensive NY‐AL magnetic lineament that is currently seismogenic. Warrell et al () present paleoseismic evidence for multiple M w ≥ 6 earthquakes in the ETSZ during the late Quaternary. Difficulties (e.g., lack of suitable surface materials) in obtaining paleoseismic evidence will probably preclude a determination if other parts of the lineament were seismically active in the past.…”

Section: Major Intraplate Seismic Zonesmentioning

confidence: 99%

Necessary Conditions for Intraplate Seismic Zones in North America

Thomas

Powell

2017

Tectonics

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The cause of intraplate seismic zones persists as an important scientific and societal question. Most intraplate earthquakes are concentrated in specific seismic zones along or adjacent to large‐scale basement structures (e.g., rifts or sutures at ancient plate boundaries) within continental crust. The major intraplate seismic zones are limited to specific segments and are not distributed along the lengths of the ancient structures. We present a new hypothesis that major intraplate seismic zones are restricted to places where concentrated crustal deformation (CCD) is overprinted on large‐scale basement structures. Examples where CCD affects the stability of specific parts of large‐scale structures in response to present‐day stress conditions include the most active seismic zones in central and eastern North America: Charlevoix, Eastern Tennessee, and New Madrid. Our hypothesis has important implications for the assessment of seismic hazards.

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“…Despite being a passive margin since the Jurassic, eastern North America has not been tectonically quiet (Figure 1). Faults that show Cretaceous and Cenozoic displacement, some of which show evidence for movement at least as recently as the Pleistocene, are found throughout the SEUS (e.g., Hatcher et al, 2013;Powars et al, 2015;Prowell, 1988;Warrell et al, 2017; examples of such faults are shown in Figure S1 in the Supporting Information). Some of these faults are reactivated older structures, but many rupture through thick accumulations of Cretaceous and Cenozoic Coastal Plain sediments without any clear connection to older features.…”

Section: Geologic and Geodynamic Overviewmentioning

confidence: 99%

Insights Into Intraplate Stresses and Geomorphology in the Southeastern United States

Murphy

Liu

Egbert

2019

Geophysical Research Letters

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The stress field in the eastern United States is commonly considered to be broadly uniform and due to homogeneous far‐field forces; however, modern and geologic stress indicators in this region show substantial heterogeneity. Using CitcomS to model stresses based on simple input density, temperature, and viscosity fields, we show that local isostasy is key in explaining the intraplate stress field in the southeastern United States. Crustal thickness variations appear to be most important in reproducing observations, although we slightly better match the observed stress field by including variable crustal viscosity informed by magnetotelluric imaging. Our results demonstrate that local gravitational body forces can substantially reorient far‐field stresses and thereby influence patterns of intraplate seismicity. We also show that variable crustal viscosity encourages a steepening of isostatic topography in the southeastern United States; this observation suggests that a sharp boundary in crustal strength may be important in explaining the apparently long‐lived Appalachian topographic escarpment.

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Paleoseismic Evidence for Multiple M _w ≥6 Earthquakes in the Eastern Tennessee Seismic Zone during the Late Quaternary

Cited by 10 publications

References 30 publications

A Robust Estimation of the 3‐D Intraplate Deformation of the North American Plate From GPS

A Robust Estimation of the 3‐D Intraplate Deformation of the North American Plate From GPS

Necessary Conditions for Intraplate Seismic Zones in North America

Insights Into Intraplate Stresses and Geomorphology in the Southeastern United States

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Paleoseismic Evidence for Multiple M w ≥6 Earthquakes in the Eastern Tennessee Seismic Zone during the Late Quaternary

Cited by 10 publications

References 30 publications

A Robust Estimation of the 3‐D Intraplate Deformation of the North American Plate From GPS

A Robust Estimation of the 3‐D Intraplate Deformation of the North American Plate From GPS

Necessary Conditions for Intraplate Seismic Zones in North America

Insights Into Intraplate Stresses and Geomorphology in the Southeastern United States

Contact Info

Product

Resources

About

Paleoseismic Evidence for Multiple M _w ≥6 Earthquakes in the Eastern Tennessee Seismic Zone during the Late Quaternary