Seismology: Tectonic strain in plate interiors? (Reply)

Smalley, Robert; Ellis, Michael A.; Paul, J.; Arsdale, Roy B. Van

doi:10.1038/nature04429

Cited by 6 publications

(5 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This result is consistent with geodetic measurements in the New Madrid seismic zone and surrounding regions, which show that the current strain rates are very slow (0 ± 2 mm/yr) (Newman et al, 1999;Gan and Prescott, 2001), rather than 5-8 mm/yr reported earlier (Liu et al, 1992). More recent GPS data have confi rmed the low strain rate around the New Madrid seismic zone (Smalley et al, 2005a); whether or not higher strain rates within the fault zone can be detected from present GPS data is debatable (Calais et al, 2005;Smalley et al, 2005b).…”

Section: Discussionsupporting

confidence: 89%

Stress evolution and seismicity in the central-eastern United States: Insights from geodynamic modeling

Li¹,

Liu²,

Zhang³

et al. 2007

Continental Intraplate Earthquakes: Science, Hazard, and Policy Issues

View full text Add to dashboard Cite

Although the central and eastern United States is in the interior of the presumably stable North American plate, seismicity there is widespread, and its causes remain uncertain. Here, we explore the evolution of stress and strain energy in intraplate seismic zones and contrast it with that in interplate seismic zones using simple viscoelastic fi niteelement models. We fi nd that large intraplate earthquakes can signifi cantly increase Coulomb stress and strain energy in the surrounding crust. The inherited strain energy may dominate the local strain energy budget for thousands of years following main shocks, in contrast to interplate seismic zones, where strain energy is dominated by tectonic loading. We show that strain energy buildup from the 1811-1812 large events in the New Madrid seismic zone may explain some of the moderate-sized earthquakes in this region since 1812 and that the inherited strain energy is capable of producing some damaging earthquakes (M >6) today in southern Illinois and eastern Arkansas, even in the absence of local loading. Without local loading, however, the New Madrid seismic zone would have remained in a stress shadow where stress has not been fully restored from the 1811-1812 events. We also derived a Pn velocity map of the central and eastern United States using available seismic data, the results do not support the NMSZ being a zone of thermal weakening. We simulated the long-term Coulomb stress in the central and eastern United States. The predicted high Coulomb stress concentrates near the margins of the North American tectosphere, correlating spatially with most seismicity in the central and eastern United States.

show abstract

Section: Discussionsupporting

confidence: 89%

Stress evolution and seismicity in the central-eastern United States: Insights from geodynamic modeling

Li¹,

Liu²,

Zhang³

et al. 2007

Continental Intraplate Earthquakes: Science, Hazard, and Policy Issues

View full text Add to dashboard Cite

show abstract

“…Space‐geodetic measurements of surface strain [ Smalley et al , 2005a] have played an increasingly important role in evaluating the significance of seismic risk in the NMSZ. The recent geodetic inference of rapid strain rates [ Smalley et al , 2005a] has proved to be controversial and it has led to an ongoing debate [ Calais et al , 2005; Smalley et al , 2005b]. The utility of surface geodetic data in assessing seismic risk has been considered from the perspective of mechanical models [ Kenner and Segall , 2000] which indicate that measurements of low rates of strain should not be used to rule out the possibility of future damaging earthquakes.…”

Section: Introductionmentioning

confidence: 99%

Descent of the ancient Farallon slab drives localized mantle flow below the New Madrid seismic zone

Forte

Mitrovica

Moucha

et al. 2007

Geophysical Research Letters

View full text Add to dashboard Cite

The great earthquake sequence that occurred in the central Mississippi River Valley during the winter of 1811–1812 is unprecedented in the historical record of seismicity within stable continental plate interiors. We show, using viscous flow models based on high resolution seismic tomography, that the descent of the ancient Farallon slab into the deep mantle beneath central North America induces a highly localized flow directly below the New Madrid seismic zone (NMSZ). This localization arises because of structural variability in the Farallon slab and the low‐viscosity of the sub‐lithospheric upper mantle, and it represents a heretofore unrecognized and possibly significant driving mechanism for the enigmatic intraplate seismicity.

show abstract

“…The New Madrid region was struck by four earthquakes of magnitude 7 or greater in 1811–1812 (Johnston & Schweig, ; Hough et al., ) and is currently undergoing low‐level seismic activity, with earthquakes rarely exceeding magnitude 3 (CERI, ; Page & Hough, ). Although once debated (Calais et al., ; Smalley et al., ), the current rate of strain accumulation on faults within the NMSZ is undistinguishable from zero, with a 95% confidence upper bound of 0.2 mm/year over about 500 km (Boyd et al., ; Craig & Calais, ).…”

Section: Seismological and Geological Settingmentioning

confidence: 99%

A Parametric Analysis of Fault Reactivation in the New Madrid Seismic Zone: The Role of Pore Fluid Overpressure

Leclère

Calais

2019

JGR Solid Earth

View full text Add to dashboard Cite

Earthquakes in Stable Continental Regions (SCR), where localized present-day tectonic loadingis negligible, remain difficult to explain. The New Madrid Seismic Zone (NMSZ) is a type-locale for such events, with four M>7 events in 1811-1812 and a regional seismicity that continues to this day. Here, we seek to determine the most favorable conditions for fault reactivation in such a context using 33 earthquakes in the 2.1-4.7 magnitude range with well-determined focal mechanisms while accounting for the vertical gradient of differential stress with depth. To do so, we developed a Mohr-Coulomb-based parametric analysis of fault reactivation that allows us to vary the orientation of the principal stresses, the shape ratio of the stress tensor, the fault friction coefficient, the pore fluid overpressure, and the gradient of differential stress with depth. Doing so, we are able to determine the lowest stress perturbation conditions required for fault reactivation. Our results show that the reactivation of the faults studied here requires pore fluid overpressure, unless their friction coefficient is 0.4 or less. We argue that such weak faults are unlikely and favor a triggering mechanism via deep fluids, possibly upwelling from the upper mantle where a low-velocity seismic anomaly could indicate their presence. This mechanism, documented in other intraplate areas, does not require local tectonic stress or strain accumulation to explain seismicity in active intraplate regions, where elastic strain is drawn from a prestressed crust.

show abstract

Seismology: Tectonic strain in plate interiors? (Reply)

Cited by 6 publications

References 2 publications

Stress evolution and seismicity in the central-eastern United States: Insights from geodynamic modeling

Stress evolution and seismicity in the central-eastern United States: Insights from geodynamic modeling

Descent of the ancient Farallon slab drives localized mantle flow below the New Madrid seismic zone

A Parametric Analysis of Fault Reactivation in the New Madrid Seismic Zone: The Role of Pore Fluid Overpressure

Contact Info

Product

Resources

About