Focal Mechanisms for Eastern Canadian Earthquakes, 1994-2000

Bent, Allison L.; Drysdale, J A; Perry, Heidi

doi:10.1785/gssrl.74.4.452

Cited by 20 publications

(11 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These higher strain rates in the northeastern United States and southern Québec (compared to the plate‐wide estimate reported above) are geographically consistent with the area of higher historical seismic moment release reported by Mazzotti and Adams [2005] in southeastern Canada. The NNW‐SSE to NW‐SE compression directions found here in the two triangles encompassing the St. Lawrence seismic zone are consistent with compressional earthquake focal mechanisms and their N‐S to NW‐SE P axis [ Bent et al , 2003]. In addition, we find strain rates in these triangles that are consistent with the lower end of the 1–4 × 10 −9 yr −1 rates reported by Mazzotti et al [2005] in the St. Lawrence region on the basis of denser GPS campaign measurements.…”

Section: Analysis Of the Velocity Fieldsupporting

confidence: 69%

Deformation of the North American plate interior from a decade of continuous GPS measurements

et al. 2006

View full text Add to dashboard Cite

A combination of two independent geodetic solutions using data from close to 300 continuous GPS stations covering the central and eastern United States shows that surface deformation in the North American plate interior is best fit by a model that includes rigid rotation of North America with respect to ITRF2000 and a component of strain qualitatively consistent with that expected from glacial isostatic adjustment (GIA). After correcting for the North American plate motion, residual horizontal velocities show a north‐to‐south deformation gradient of ∼1 mm yr−1, mostly localized between 1000 and 2200 km from the GIA center, corresponding to strain rates of about 10−9 yr−1. At distances farther than 2100 km from the GIA center, horizontal residual velocities are random with no evidence for regions of elevated strain rates. In particular, we find no detectable residual motion at the 95% confidence level in the New Madrid Seismic Zone, where the average weighted misfit of 0.7 mm yr−1 is the same as the weighted misfit of our rigid plate model. Vertical velocities show (1) a maximum uplift rate of 10 mm yr−1 at the assumed GIA center, (2) a hinge line located 1500 km from that center, and (3) a subsidence rate up to 1.4 mm yr−1 in the forebulge, with a maximum located about 2000 km from the GIA center. Our results have the potential to better constrain glacial isostatic adjustment models and contribute to a better definition of stable North America for tectonic and geodetic applications.

show abstract

Section: Analysis Of the Velocity Fieldsupporting

confidence: 69%

Deformation of the North American plate interior from a decade of continuous GPS measurements

et al. 2006

View full text Add to dashboard Cite

show abstract

“…Earthquake focal mechanisms. Solid, medium gray, and light gray symbols represent focal mechanisms derived from moment tensor solutions, well‐constrained first motion solutions, and less well constrained first motion solutions, respectively [ Bent , 1992, 1994, 1995, 1996a, 1996b, 2002; Bent et al , 2003; Haddon , 1995; Horner et al , 1978; Wetmiller et al , 1984]. …”

Section: Eastern Canadamentioning

confidence: 99%

Rates and uncertainties on seismic moment and deformation in eastern Canada

Mazzotti

Adams

2005

J. Geophys. Res.

View full text Add to dashboard Cite

[1] On the basis of earthquake statistics from the Canadian earthquake hazard model, we estimate the rates of seismic moment and deformation in seismic zones of eastern Canada. We use a logic tree approach to derive median values and 66% confidence intervals for models based on earthquake cluster distributions and geological and tectonic structures. Typical moment rates are low, (0.1-1) Â 10 17 N m yr À1 , equivalent to a magnitude M w = 7 earthquake every 350-3500 years in each seismic zone. In a few zones, such as Baffin Bay, moment rates reach (2-10) Â 10 17 N m yr À1 . Expressed in terms of relative velocity between zone boundaries, seismic deformation rates are typically 0.2-0.5 mm yr À1. For a few regions of high seismicity, such as Baffin Bay, Charlevoix, or Grand Banks, the relative velocities reach 1-2 mm yr À1 . Strain rates are typical of the intraplate environment (10 À13 -10 À10 yr À1 ), with values locally as high as 10 À8 yr À1 . These rates give some insight into geodynamic aspects of the northeastern North America plate. Assuming that the seismic deformation rates represent long-term deformation of the lithosphere, they provide some constraint to the amplitude and variability of intraplate strain. On a shorter timescale, seismic strain rates can be compared with postglacial rebound predictions and might help constrain some aspects of these models. Because they reflect the seismic energy released over the last few hundred years, our estimates, in combination with geodetic measurements, can also help constrain models of earthquake dynamics in eastern North America.Citation: Mazzotti, S., and J. Adams (2005), Rates and uncertainties on seismic moment and deformation in eastern Canada,

show abstract

“…Ma et al 2008), although the mechanisms along northeastern Baffin Bay are of normal and strike‐slip type (e.g. Hashizume 1973; Stein et al 1979; Talwani & Rajendran 1991; Bent 2002; Bent & Perry 2003). In order to explain localization of seismicity around certain zones, rather than in regions of maximum stress or uplift rate, Wu & Hasegawa (1996a,b) pointed out that rebound stress is likely to reactivate faults within pre‐weakened zones, but may not be large enough to rupture intact rocks lying outside these zones.…”

Section: Introductionmentioning

confidence: 99%

Moment tensors, state of stress and their relation to post-glacial rebound in northeastern Canada

Steffen

Eaton

2012

Geophysical Journal International

View full text Add to dashboard Cite

SUMMARY In the stable craton of northeastern Canada moderate seismicity as well as glacial isostatic adjustment (GIA) has been observed. We investigate five earthquakes with moment magnitudes between 3.6 and 4.1 that have occurred in northern Hudson Bay since 2007, which may be triggered by GIA. Focal mechanisms of the earthquakes are determined using a waveform‐fitting procedure for surface waves, in which the best double‐couple mechanism is obtained through a grid search over strike, dip, and rake. All events exhibit a thrust‐fault mechanism, in general agreement with mechanisms of previously analysed earthquakes in that area. Stress‐inversion results incorporating our new mechanisms as well as previously published results exhibit significant differences from previously calculated stresses from GIA models. For the first time, maximum horizontal stress direction SHmax is compared to the modelled stress values for northeastern Canada. We find that the maximum horizontal stress direction strikes roughly NNW–SSE, in contrast to previously inferred NE‐SW orientation of SHmax. Our results indicate that the local stress field in northern Hudson Bay deviates from regional stresses resulting from the existence of a roughly E–W oriented zone of faulting, which is not included in existing GIA models.

show abstract

Focal Mechanisms for Eastern Canadian Earthquakes, 1994-2000

Cited by 20 publications

References 47 publications

Deformation of the North American plate interior from a decade of continuous GPS measurements

Deformation of the North American plate interior from a decade of continuous GPS measurements

Rates and uncertainties on seismic moment and deformation in eastern Canada

Moment tensors, state of stress and their relation to post-glacial rebound in northeastern Canada

Contact Info

Product

Resources

About