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New perspectives on ‘geological strain rates’ calculated from both naturally deformed and actively deforming rocks

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)100-110
Number of pages11
JournalJournal of Structural Geology
Volume125
Early online date9 Oct 2018
DOIs
DateAccepted/In press - 3 Oct 2018
DateE-pub ahead of print - 9 Oct 2018
DatePublished (current) - 1 Aug 2019

Abstract

A value of ~10-14 s−1 is commonly cited as an average geological strain rate. This value was first suggested for finite strain across an orogen, but based on more limited information than the combined geophysical, geological, and experimental data now available on active and ancient rock deformation. Thus, it is timely to review the data constraining strain rates in the continents, and to consider the quantifiable range of crustal strain rates. Here, where resolution allows, both spatial andtemporal strain rate variations are explored. This review supports that a strain rate of 10-14±1 s−1 arises from geological estimates of bulk finite strains. Microstructural arguments combining laboratory-derived piezometers and viscous flow laws, however, imply local rates that are orders of magnitude faster. Geodetic rates, in contrast, are typically 10-15 s−1 in actively deforming areas, about an order of magnitude slower than the bulk rates estimated from geological observations. This difference in estimated strain rates may arise from either low spatial resolution, or the fact that surface velocity fields can not capture strain localisation in the mid to lower crust. Integration of geological and geodetic rates also shows that strain rates can vary in both space and time, over both single and multiple earthquake cycles. Overall, time-averaged geological strain rates are likely slower than the strain rates in faults and shear zones that traverse the crust or lithosphere.

    Research areas

  • Faults, Geodesy, Rock deformation, Shear zones, Strain rate

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  • Full-text PDF (accepted author manuscript)

    Rights statement: This is the accepted author manuscript (AAM). The final published version (version of record) is available online via Elsevier at https://doi.org/10.1016/j.jsg.2018.10.004 . Please refer to any applicable terms of use of the publisher.

    Accepted author manuscript, 9 MB, PDF document

    Licence: CC BY-NC-ND

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