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Effect of basal friction on surface and volumetric strain in models of convergent settings measured by laser scanner
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
2008 (English)In: Journal of Structural Geology, ISSN 0191-8141, Vol. 30, no 3, 366-379 p.Article in journal (Refereed) Published
Abstract [en]

This paper uses measurements by a high-accuracy laser scanner to investigate the role of basal friction on surface and volumetric strains in sandbox models simulating fold-thrust belts and accretionary wedges. We monitor progressive deformation, wedge growth, and strain distribution in three models with similar initial boundary conditions but with different basal frictions. Our analyses show that, in addition to influencing the kinematics and geometry of model wedges, basal friction also governs both the surface and volumetric strains of the wedge. After 16.3% bulk shortening, the volume decreased 5 +/- 0.5%, 9.5 +/- 0.5% and 12.5 +/- 0.5% in the models shortened above low, intermediate and high friction decollements, respectively. Applied to nature, our model results suggest that more compaction and penetrative strain is expected in convergent settings with a high-friction decollement than those shortened above a low-friction decollement or a weak basal bed (like the salt formation under parts of the Zagros fold-thrust belt). This volume decrease probably reduces the porosity in the deformed lithologies.

Place, publisher, year, edition, pages
2008. Vol. 30, no 3, 366-379 p.
Keyword [en]
analogue modeling, basal friction, fold-thrust belt, volumetric strain, laser scanning, Zagros
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:uu:diva-96015DOI: 10.1016/j.jsg.2007.09.013ISI: 000254368000008OAI: oai:DiVA.org:uu-96015DiVA: diva2:170420
Available from: 2007-05-07 Created: 2007-05-07 Last updated: 2011-11-30Bibliographically approved
In thesis
1. Ground Movements in the Zagros Fold-Thrust Belt of SW Iran Measured by GPS and InSAR Compared to Physical Models
Open this publication in new window or tab >>Ground Movements in the Zagros Fold-Thrust Belt of SW Iran Measured by GPS and InSAR Compared to Physical Models
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis uses geodetic satellite data to measure present-day crustal deformation in the Zagros fold-thrust belt (SW Iran). Geodetic-type measurements are also used in down-scaled models that simulate the surface deformations seen in convergent settings like the Zagros fold-thrust belt.

Global Positioning System (GPS) measurements of three surveys between 1998 and 2001 indicate 9 ± 3 mm/yr and 5 ± 3 mm/yr shortening across the SE and NW Zagros respectively. GPS results show that in addition to the different rates and directions of shortening on either side of the NS trending Kazerun fault, local along-belt extension occurs to the east.

Differential SAR interferograms of ERS1 & 2 images between 1992 and 1999 detect 8 ± 4 mm/yr uplift rate across a newly recognized fault in SW Qeshm Island. This can be attributed to a steep imbricate thrust that may still represent the local Zagros deformation front.

The salt diapirs in the Zagros rise from a source layer that acts as a low-frictional decollement that decouples the deformation of the cover sediments from their basement in the eastern Zagros whereas the cover to the west deforms above a high-friction decollement. Physical models were prepared to simulate cover deformation in the Zagros by shortening a sand pack above adjacent high- and low-frictional decollements (represented by a ductile layer). The strain distributions differed above the two types of decollements; it was more heterogeneous above the salt where local extension in the shortening direction was dominant. A separate work also investigated systematically the role of basal friction on cover deformation in convergent settings. Accurate height measurements of the model surface by laser-scanner indicated a deformation front more distal than usual, particularly in the low-basal frictional models. The volume reduction in our shortened sand models correlated directly with their basal friction.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 38 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 318
Keyword
Earth sciences, Zagros fold-thrust belt, deformation, GPS, InSAR, Physical modeling, tectonics, convergent settings, basal friction, Geovetenskap
Identifiers
urn:nbn:se:uu:diva-7928 (URN)978-91-554-6918-4 (ISBN)
Public defence
2007-06-01, Axel Hansrambergsalen, Geocentrum, Villavägen 16, SE75236, Uppsala, 10:00
Opponent
Supervisors
Available from: 2007-05-07 Created: 2007-05-07Bibliographically approved

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Nilforoushan, FaramarzKoyi, Hemin

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