The Morphological Characteristics of Normal Fault Traces in the Apennines, Italy
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Durham E-Theses The morphological characteristics of normal fault traces in the Apennines, Italy ELLIOTT, ROBERT,GILES How to cite: ELLIOTT, ROBERT,GILES (2019) The morphological characteristics of normal fault traces in the Apennines, Italy , Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/13046/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk 2 Department of Earth Sciences, University of Durham The morphological characteristics of normal fault traces in the Apennines, Italy A thesis submitted to the University of Durham for the degree of Master of Science (by Research) Robert Giles Elliott 2018 Under the supervision of Prof Ken McCaffrey and Dr Jonny Imber Research conducted at: The Department of Earth Sciences, University of Durham, Science Laboratories, DH1 3LE 1 Abstract Fault trace ruptures at the Earth’s surface show sinuosity (departure from linear trace morphologies) at a variety of scales in map view, reflecting the growth of the fault, the mechanical stratigraphy of the surrounding geology, and interactions with neighbouring faults. This study uses a combination of new remotely sensed LiDAR and SRTM datasets, and novel techniques which seek to eliminate the distorting effects of topography upon the fault traces. The 2D morphological characteristics of fault traces are mapped and quantified. The relationships between those characteristics and scale of observation and other fault parameters are investigated, to see what insight those relationships afford into fault growth and interaction. By characterising controls of sinuosity at different scales, a better understanding of the effect of fault trace variations on seismic hazard evaluation in active tectonic regions may be obtained. At the whole fault scale, stress interactions between neighbouring faults and between en échelon segments within a fault appear to be the main controls on trace sinuosity. Linear correlations between sinuosity values and fault length and slip rate respectively are weak. However, sinuosity appears to be smoothed out with repeated slip, particularly in central parts of the fault traces. At smaller scale (<100 m), sinuosity is more variable and values spread over a wider range. Local features such as pre-existing fractures/weaknesses appear to be a principal control over deviation. Sinuosity is apparently not much influenced by the controlling factors at the whole fault scale. The current regional extensional stress regime sees normal faults striking broadly SE-NW. Deviation from that pattern may be a significant factor in controlling sinuosity at the whole fault level. Here, anticlockwise deviance from the regional strike appears to coincide with an increase in sinuosity values. The anticlockwise variance brings the faults closer to a previous extensional regime, which left inherited structures trending broadly SW-NE. Those minor structures could be reactivated as transfer faults or segments between en échelon faults or fault segments, particularly in left-stepping situations. 2 Table of Contents Abstract ............................................................................................................................................ 2 Table of Contents ............................................................................................................................. 3 List of Figures ................................................................................................................................... 7 List of Tables .................................................................................................................................. 14 Acknowledgements ........................................................................................................................ 14 Chapter 1 Introduction .................................................................................................................. 15 1.1 Background to this study ..................................................................................................... 15 1.2. Hypotheses and questions to be addressed ....................................................................... 19 1.2.1. Coulomb shear stress change at the whole fault scale ................................................ 19 1.2.2. Relationships between sinuosity and common factors at the whole fault scale ........ 19 1.2.3. Localised influences at smaller scale ........................................................................... 20 1.2.4. Sinuosity values dependent upon scale of observation .............................................. 20 Chapter 2 Literature Review .......................................................................................................... 21 2.1 History of deformation in the Apennine region, Central Italy ............................................. 21 2.2 Analyses of normal faulting in the Abruzzo and Umbria regions of the Apennines, Central Italy ............................................................................................................................................ 23 2.3 Pre-existing structures and fracture patterns in the Abruzzo and Umbria regions of the Apennines, Central Italy ............................................................................................................. 30 2.4 Surface rupture traces morphology ..................................................................................... 32 2.5 Alternative models of fault growth ...................................................................................... 36 2.6 Geometrical structures in fault growth models ................................................................... 38 Chapter 3 Methodology ................................................................................................................. 42 3.1 Google Earth Traces ............................................................................................................. 42 3.2 Sensitivity analysis of data for projection of Google Earth traces ....................................... 46 3.3 LiDAR image traces .............................................................................................................. 48 3.4 Comparison of results from projected traces with non-projected traces ........................... 49 3.5 Identification of fracture patterns ....................................................................................... 49 3.6 Identification of local topographical features at small scale ............................................... 50 3.7 Coulomb Stress modelling ................................................................................................... 51 Chapter 4 Results/Analysis – Google Earth and LiDAR .................................................................. 56 4.1 Google Earth Trace analysis ................................................................................................. 56 4.1.1 All projected traces ....................................................................................................... 56 4.1.2 Longer traces ................................................................................................................. 61 3 4.2 Sensitivity analysis for data used in projection of Google Earth traces ............................... 66 4.2.1 Comparison with Roberts and Michetti, 2004 throw rates .......................................... 66 4.2.2 Use of alternative fault attributes in projection of fault traces .................................... 67 4.3 LiDAR image traces .............................................................................................................. 69 4.3.1 Overall sinuosity values using LiDAR datasets .............................................................. 69 4.3.2 Campo Felice fault......................................................................................................... 70 4.3.3 Fiamignano fault ........................................................................................................... 71 4.3.4 Magnola fault ................................................................................................................ 72 4.3.5 Parasano fault ............................................................................................................... 73 4.4 Comparison of results from projected traces with non-projected traces ........................... 74 4.5 Identification of fracture patterns ....................................................................................... 76 4.5.1 Campo Felice fault......................................................................................................... 76 4.5.2 Fiamignano Fault ..........................................................................................................