Coseismic deformation of the 2002 Denali Fault earthquake: Insights from GPS measurements

SUMMARY Models of postseismic deformation following the 2002 M 7.9 Denali Fault, Alaska earthquake provide insight into the rheologic structure of the Alaskan lithosphere and the physical processes activated following a large earthquake. We model coseismic GPS displacements and 4 yr of postseismic GPS position time‐series with a coupled model of afterslip on the fault in the lithosphere and distributed viscous flow in the asthenosphere. Afterslip is assumed to be governed by a simplified version of a laboratory‐derived rate‐strengthening friction law that is characterized with a single parameter, σ(a−b), where σ is the effective normal stress on the fault and a−b is a dimensionless empirical parameter. Afterslip is driven by coseismic stress changes on the fault generated by the main shock. The lithosphere is modelled as an elastic plate overlying a linear, Maxwell, viscoelastic asthenosphere. We devise a scheme to simultaneously estimate the distributions of coseismic slip and afterslip, friction parameters, lithosphere thickness and asthenosphere viscosity. The postseismic GPS time‐series are best reproduced with a 45–85 km thick elastic lithosphere overlying an asthenosphere of viscosity 0.6–1.5 × 1019 Pa s. The 45–85 km elastic lithosphere thickness is greater than or equal to the average crustal thickness in the region suggesting that distributed postseismic flow occurs largely within the mantle while postseismic deformation in the crust is confined largely to slip on a discrete fault penetrating the entire crust and perhaps into the uppermost mantle. For typical laboratory values of a−b of order 10−2 at temperatures corresponding to the inferred depth of afterslip, the estimated effective normal stress on the fault is ∼50 MPa, which is about an order of magnitude lower than effective normal stresses at hydrostatic pore pressure. Previous studies showed that models with linear Newtonian rheology cannot reproduce the observed GPS time‐series but that models incorporating non‐linear or biviscous flow of the mantle do fit the data. We show that a model with afterslip governed by a non‐linear fault zone rheology coupled to Newtonian mantle flow is sufficient to reproduce the GPS time‐series.

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“…Wright et al 2004;Hreinsdóttir et al 2006;Elliot et al 2007). The magnitude of right-lateral slip is shown on each patch.…”

Section: R E S U Lt Smentioning

confidence: 99%

Coupled afterslip and viscoelastic flow following the 2002 Denali Fault, Alaska earthquake

Johnson

Bürgmann

Freymueller

2009

Geophysical Journal International

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“… g Horizontal components corrected for Denali earthquake coseismic offset from the model of Hreinsdóttir et al [2006]. …”

Section: Gps Data Analysismentioning

confidence: 99%

“…The long‐term trends are disturbed by the 2002 M w 7.9 Denali fault earthquake [e.g., Eberhart‐Phillips et al , 2003], which resulted in significant coseismic and postseismic displacements over a large area [ Hreinsdóttir et al , 2003, 2006; Freed et al , 2006a]. Conversely, near‐field GPS data have been instrumental in constraining Denali earthquake fault slip models [ Freed et al , 2006a, 2006b; Hreinsdóttir et al , 2006] that we use to correct our data for the effects of the earthquake. GPS site motions in SW Yukon and part of the Alaskan Panhandle are also affected by post‐Little Ice Age glacioisostatic adjustment, which we correct for using the model of Larsen et al [2005].…”

Section: Introductionmentioning

confidence: 99%

Current deformation in the northern Canadian Cordillera inferred from GPS measurements

Leonard¹,

Hyndman²,

Mazzotti³

et al. 2007

J. Geophys. Res.

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Continuous and campaign‐style Global Positioning System (GPS) measurements provide new constraints on the first‐order current deformation pattern of the northern Cordillera of NW Canada and eastern Alaska. The Yakutat block is currently colliding with North America in the corner of the Gulf of Alaska. Our data infer that relative Yakutat–North America motion is accommodated across the eastern boundary by right‐lateral motion (∼40 mm/a), mainly on the Fairweather fault, and minor shortening (∼6 mm/a). To the north, collision is taken up by shortening (∼31 mm/a) mainly on the Chugach–St. Elias fault system, with westward extrusion and possible counterclockwise rotation of the Yakutat block and Alaskan fore arc facilitated by ∼23 mm/a right‐lateral motion that is shared by several faults. The seismicity pattern indicates that plate boundary deformation is far reaching, producing strain throughout eastern Alaska, Yukon, and western Northwest Territories. Our GPS data confirm the transfer of strain from the Yakutat collision zone and enable the extent of plate boundary deformation to be mapped, thereby defining the western edge of “stable” North America. GPS sites in SW Yukon show motion of 3–10 mm/a to the NE, confirming that strain is transferred at least 400 km from the Yakutat collision. Continued transfer north toward the Mackenzie Delta and NE to the Mackenzie Mountains, indicated by current seismicity, is not yet well resolved by the campaign GPS data, which are hampered by coseismic and postseismic effects of the 2002 Mw 7.9 earthquake on the Denali fault in eastern Alaska.

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“…La Fig. 2 (Zumberge et al, 1997), que utiliza observables GPS no diferenciales, se ha convertido en una herramienta de gran utilidad para investigar procesos geofísicos a nivel sub-centimétrico (Larson et al, 2004;Smith et al, 2004;Kouba, 2005;Hreinsdóttir et al, 2006). Esta técnica ha sido utilizada en época reciente para estimar campos de velocidad en diversas regiones tectónicamente activas (Pérez et al, 2003;Teferle et al, 2007).…”

Section: Datos Cgpsunclassified

Velocidad cortical y campo de esfuerzos en el Archipiélago Balear utilizando series temporales GPS de la red XGAIB (2010-2013

Sánchez‐Alzola

Sánchez

Giménez³

et al. 2014

Fís. Tierra

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ResumenEn este artículo se presenta la velocidad cortical y el campo de esfuerzos en la zona del archipiélago Balear en base a observaciones GPS continuas de la red XGAIB en el período 2010-2013. La red XGAIB está compuesta por nueve estaciones GPS permanentes distribuidas de manera homogénea por el archipiélago y se encuentra activa desde el año 2010. En esta contribución se describe la red XGAIB y el proceso de cálculo con las estaciones GPS continuas (CGPS) realizado, presentando las velocidades absolutas y relativas para todas las estaciones. Además se ha estimado el campo de esfuerzos para obtener un modelo de deformación cortical realista del archipiélago. Los resultados muestran una variación gradual de los esfuerzos sobre las Islas Baleares, desde la extensión WNW-ESE presente en el suroeste (Islas Pitiusas) hasta la compresión NW-SE del nordeste (Isla de Menorca). Estos resultados constituyen un avance en el conocimiento de la tectónica en la región más occidental del Mediterráneo. Palabras clave: CGPS, posicionamiento puntual de precisión, deformación cortical, series temporales, Islas Baleares.Crustal velocity and strain rate fields in the Balearic Islands based on GPS time series from the XGAIB network (2010-2013) AbstractIn this paper, a first estimation of the crustal velocity and strain rate fields in the Balearic Islands is presented. This study is based on continuous GPS observations from the XGAIB network spanning the period 2010-2013. The XGAIB network consists of nine permanent, widely distributed stations that have operated continuously since 2010. We describe the network, the continuous GPS (CGPS) data processing and present our principle results in terms of absolute and residual velocities of all of the sites. In addition, strain tensors were estimated from the velocity field to obtain the first realistic crustal deformation model of the archipelago. The strains exhibit gradual variation across the Balearic Islands, from WNW-ESE extension in the southwest (Pitiusas Islands) to NW-SE compression in the northeast (Menorca Island). These results constitute an advance in the knowledge of the tectonics of the western Mediterranean region.

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Coseismic deformation of the 2002 Denali Fault earthquake: Insights from GPS measurements

Cited by 54 publications

References 40 publications

Coupled afterslip and viscoelastic flow following the 2002 Denali Fault, Alaska earthquake

Coupled afterslip and viscoelastic flow following the 2002 Denali Fault, Alaska earthquake

Current deformation in the northern Canadian Cordillera inferred from GPS measurements

Velocidad cortical y campo de esfuerzos en el Archipiélago Balear utilizando series temporales GPS de la red XGAIB (2010-2013

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