A comparison of eastern North American seismic strain‐rates to glacial rebound strain‐rates

James, Thomas S.; Bent, Allison L.

doi:10.1029/94gl01854

Cited by 55 publications

(36 citation statements)

References 12 publications

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“…Ice sheets are known to have an impact on isostasy both through the loading of the ice sheet itself (James & Bent 1994;Klemann & Wolf 1998;Davis et al 1999;James et al 2000;Stewart et al 2000) and the changes to groundwater conditions affecting compaction of sediment (Boulton & Dobbie 1993;Saettem et al 1996;Piotrowski & Kraus 1997;O'Regan et al 2010O'Regan et al , 2016. The effects of changes to groundwater drainage under a significant ice load can result in strongly differential compaction.…”

Section: Onset Of the Quaternarymentioning

confidence: 99%

“…Isostatic loading from an ice sheet is equally complex, with vertical and horizontal stresses placed on the strata even well beyond the extent of the ice sheet. Although modern postglacial rebound models, constrained by field-based investigations, have improved greatly over the years they are reliant on knowing the extent and thickness of the ice sheet in question (James & Bent 1994;Klemann & Wolf 1998;Davis et al 1999;James et al 2000;Stewart et al 2000), for which the data are truly available only in the North Sea for the last glacial maximum (Huuse & Lykke-Andersen 2000;Graham et al 2011). Additionally, modern rebound models may not fully account for the cumulative effect of repeated glaciations, which the North Sea is known to be subject to (Klemann & Wolf 1998;Stewart et al 2000).…”

Section: Onset Of the Quaternarymentioning

confidence: 99%

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The early Quaternary North Sea Basin

Lamb

Harding

Huuse

et al. 2017

JGS

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The onset of the Quaternary (2.58 Ma) corresponds to significant paleo-environmental events, such as the intensification and southward extension of Northern Hemisphere glaciation. In the North Sea Basin a significant late Cenozoic succession has been identified as a high-resolution archive of paleo-environmental changes during the Pliocene and Pleistocene. However, the identification of the base of the Quaternary has been a long-standing issue owing to lack of stratigraphic calibration. This study incorporates continuous, regional 3D seismic data with high-quality chronostratigraphic markers to map the base-Quaternary surface at high resolution across the entire North Sea. Depth conversion, backstripping, seismic geomorphology and sedimentation rate calculations are integrated to analyse the paleogeographical evolution of the North Sea Basin and its infill of c. 83 × 10 3 km 3 of northward prograding marine to deltaic sediments. The basin is 600 km long from SSE to NNW and largely localized above residual topography of the Mesozoic graben system. During the earliest Quaternary (2.58 -2.35 Ma) paleo-water depths were c. 300 ± 50 m and solid sedimentation rates (calculated from 0% porosity) c. 32 km 3 ka −1 . The base-Quaternary provides an important marker for further studies of the changing environment of the Quaternary of NW Europe as well as resource and shallow geohazard analysis.Supplementary material: A base Quaternary two-way travel time structure map is available at https://doi.org/10.6084/m9. figshare.c.3900343

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Section: Onset Of the Quaternarymentioning

confidence: 99%

Section: Onset Of the Quaternarymentioning

confidence: 99%

The early Quaternary North Sea Basin

Lamb

Harding

Huuse

et al. 2017

JGS

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“…Numerical models and direct GPS measurements indicate that PGR elastic strain rates can reach 1-10 Â 10 À9 yr À1 in central and eastern Canada, mainly due to the slow response of the cold lithosphere and asthenosphere [e.g., James and Bent, 1994;Calais et al, 2006]. The GPS strain rate measured for the zone Alberta Plains (ALB) may partly or fully represent aseismic PGR deformation, thus accounting for the large difference between GPS and catalog moment rates in this zone.…”

Section: Gps Strain Rate and Aseismic Deformationmentioning

confidence: 99%

“…There, as in several other continental intraplate regions (e.g., northern Europe), viscoelastic postglacial rebound strain rates exceed seismic strain rates by a factor of 10 or more [e.g., James and Bent, 1994] and represent the primary deformation measured by GPS. Thus, for those intraplate regions, GPS strain rate data provide a maximum, unrealistically high estimate of the potential seismic moment rate, and are of limited value for PSHA analysis.…”

Section: Issues and Requirements For Gps-psha Integrationmentioning

confidence: 99%

Seismic hazard in western Canada from GPS strain rates versus earthquake catalog

et al. 2011

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[1] Probabilistic seismic hazard analyses (PSHA) are commonly based on frequencymagnitude statistics from 50-100 yearlong earthquake catalogs, assuming that these statistics are representative of the longer-term frequency of large earthquakes. We test an alternative PSHA approach in continental western Canada, including adjacent areas of northwestern U.S.A., using regional strain rates derived from 179 Global Positioning System (GPS) horizontal velocities. GPS strain rates are converted to earthquake statistics, seismic moment rates, and ground shaking probabilities in seismic source zones using a logic-tree method for uncertainty propagation. Median GPS-based moment rates and shaking estimates agree well with those derived from earthquake catalogs in only two zones (Puget Sound and mid-Vancouver Island). In most other zones, median GPS-based moment rates are 6-150 times larger than those derived from earthquake catalogs (shaking estimates 2-5 times larger), although the GPS-based and catalog estimates commonly agree within their 67% uncertainties. This discrepancy may represent an under-sampling of long-term moment rates and shaking by earthquake catalogs in some zones; however a systematic under-sampling is unlikely over our entire study area. Although not demonstrated with a high confidence level, long-term regional aseismic deformation may account for a significant part of the GPS/catalog discrepancy and, in some areas, represent as much as 90% of the total deformation budget. In order to integrate GPS strain rates in PSHA models, seismic versus aseismic partitioning of long-term deformation needs to be quantified and understood in terms of the underlying mechanical processes.

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“…Since our objective is not the accurate prediction of the isostatic stress eld but the identi cation of the parameters that in uence it, we may use simpli ed earth and load models. Beyond the scope of our study is also an assessment of the impact of our results on the question of the origin of the seismicity in Fennoscandia, which would require the superposition of the tectonic and isostatic stress elds and the analysis of the total stress eld in terms of a faulting criterion, such as Coulomb's criterion (Johnston,1989;Wu and Hasegawa, 1996a,b;Wu, 1997) or a criterion based on strain rates (James and Bent, 1994).…”

Section: Introductionmentioning

confidence: 99%

Modelling of stresses in the Fennoscandian lithosphere induced by Pleistocene glaciations

Klemann

Wolf

1998

Tectonophysics

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The seismicity observed in Fennoscandia is usually explained by tectonic stresses. The question of the contribution of stresses induced by glacial-isostatic adjustment to the seismicity has not nally been settled yet. In order to quantify the isostatic stress eld generated by the Fennoscandian glacial load, we consider layered Maxwell-viscoelastic half-spaces loaded by axisymmetric discs. In particular, we calculate the maximum shear-stress distribution induced by the load model and the associated stress regimes in the lithosphere. Emphasis is placed on a discussion of the sensitivity of the calculated isostatic stresses to variations in load cross-section, lithosphere thickness and asthenosphere viscosity. We also examine the e ects produced by the viscous relaxation of the lithosphere, whose viscosity is parameterized according to the strati cation expected for temperature-activated di usion creep.Our results show that the isostatic shear stresses typically reach 2 MPa near the surface at the present time but that their distribution may be modi ed strongly by the details of the earth and load models investigated. The viscous relaxation of the lithosphere becomes particularly important, if more than one glaciation is considered. Since the last ice age in Fennoscandia consisted of several glaciations, the model of a perfectly elastic lithosphere conventionally employed in models of glacialisostatic adjustment therefore may not be justi ed when calculating the isostatic stresses.

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A comparison of eastern North American seismic strain‐rates to glacial rebound strain‐rates

Cited by 55 publications

References 12 publications

The early Quaternary North Sea Basin

The early Quaternary North Sea Basin

Seismic hazard in western Canada from GPS strain rates versus earthquake catalog

Modelling of stresses in the Fennoscandian lithosphere induced by Pleistocene glaciations

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