Print Email Facebook Twitter Mapping and classifying large deformation from digital imagery Title Mapping and classifying large deformation from digital imagery: Application to analogue models of lithosphere deformation Author Broerse, D.B.T. (Universiteit Utrecht) Krstekanić, Nemanja (Universiteit Utrecht; University of Belgrade) Kasbergen, C. (TU Delft Pavement Engineering) Willingshofer, Ernst (Universiteit Utrecht) Date 2021 Abstract Particle image velocimetry (PIV), a method based on image cross-correlation, is widely used for obtaining velocity fields from time-series of images of deforming objects. Rather than instantaneous velocities, we are interested in reconstructing cumulative deformation, and use PIV-derived incremental displacements for this purpose. Our focus is on analogue models of tectonic processes, which can accumulate large deformation. Importantly, PIV provides incremental displacements during analogue model evolution in a spatial reference (Eulerian) frame, without the need for explicit markers in a model. We integrate the displacements in a material reference (Lagrangian) frame, such that displacements can be integrated to track the spatial accumulative deformation field as a function of time. To describe cumulative, finite deformation, various strain tensors have been developed, and we discuss what strain measure best describes large shape changes, as standard infinitesimal strain tensors no longer apply for large deformation. PIV or comparable techniques have become a common method to determine strain in analogue models. However, the qualitative interpretation of observed strain has remained problematic for complex settings. Hence, PIV-derived displacements have not been fully exploited before, as methods to qualitatively characterize cumulative, large strain have been lacking. Notably, in tectonic settings, different types of deformation-extension, shortening, strike-slip-can be superimposed. We demonstrate that when shape changes are described in terms of Hencky strains, a logarithmic strain measure, finite deformation can be qualitatively described based on the relative magnitude of the two principal Hencky strains. Thereby, our method introduces a physically meaningful classification of large 2-D strains. We show that our strain type classification method allows for accurate mapping of tectonic structures in analogue models of lithospheric deformation, and complements visual inspection of fault geometries. Our method can easily discern complex strike-slip shear zones, thrust faults and extensional structures and its evolution in time. Our newly developed software to compute deformation is freely available and can be used to post-process incremental displacements from PIV or similar autocorrelation methods. Subject and high strain deformation zonesand modellingContinental tectonics: compressionalContinental tectonics: extensionalContinental tectonics: strike-slip and transformfaultsFracturesKinematics of crustal and mantle deformationMechanicstheory To reference this document use: http://resolver.tudelft.nl/uuid:ffd44b49-7cf9-40ca-8104-9ebbbee47ae8 DOI https://doi.org/10.1093/gji/ggab120 ISSN 0956-540X Source Geophysical Journal International, 226 (2), 984-1017 Part of collection Institutional Repository Document type journal article Rights © 2021 D.B.T. Broerse, Nemanja Krstekanić, C. Kasbergen, Ernst Willingshofer Files PDF ggab120.pdf 18.18 MB Close viewer /islandora/object/uuid:ffd44b49-7cf9-40ca-8104-9ebbbee47ae8/datastream/OBJ/view