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IAPETUS doctoral training partnership Micro-morphology of normal fault scarps Project reference IAP/14/50. Please quote this reference when applying. Durham University, Dept of Earth Sciences In partnership with University of Glasgow, Dept of Geographical & Earth Sciences Supervisory Team Key Words Active faults, Normal Faults, LiDAR, geomorphology, slip rate Prof Ken McCaffrey, Durham University Dr Seamus Coveney, Glasgow University Prof Gerald Roberts, Birkbeck, U. of London Dr Nicola De Paola, Durham University Overview Active normal faults produce surface offsets and scarp at the Earth’s surface through the mechanism of fault slip during earthquakes1. Fault scarps in the central Italian Apennines (Abbruzzo) exhibit striated fault planes, offset dated Holocene sediments and geomorphic surfaces, and are the surface expression of a network of active normal faults formed over the past 2-3 Myrs. Preliminary results have shown that scarp morphology may be correlated with fault slip rate and the aim for this study will be to fully explore this relationship. Terrestrial and Airborne Laser Scan (TLS & ALS) datasets provide a new approach to mapping the geomorphology of active normal faults3. TLS datasets provide an accurate digital representation of the real world topography. The student will use TLS and ALS datasets to quantify slip rates for faults in the central Appenines High resolution TLS scans of the scarps will enable him/her to quantify the mm to cm scale morphology on the fault scarps. The results will feed into our knowledge of the slip rate patterns and variations on Italian faults. The work in general impacts seismic hazard assessment in Italy because earthquake recurrence intervals reflect long and short term throw rates. In addition, the geomorphic expression of fault segments depends on slip rate and hence controls sediment input into basins and resulting stratigraphic patterns. Methodology Preservation of scarps depends on the interplay between fault slip rate (throw rate) and geomorphic processes that are able to alter surface offset and the scarp exposures. Recent studies have shown that fault slip rates can vary significantly from geodeticallydetermined regional extensional rates both in time and space depending on fault geometry2, and the ability to interact with neighbouring structures. Building on previous studies that have established a methodology and produced intial results, the student will perform a geomorphic analysis of TLS & ALS datasets from the central Apennines in Italy. The data take the form of a point cloud that includes all returns from the laser scan survey. These point clouds will be processed to remove all points which are not ground returns using established filtering and manual editing routines. The geometric relationship between these points in 3D space will also be determined to provide additional information to aid geomorphic interpretation. The ground return points will then be meshed to form a Triangulated irregular network (TIN) and displayed as a bare earth hillshade rasters. A geomorphic interpretation will then be made to study the effects of erosional, depositional processes on the preserved scarps using a combination of manual and semi-automated methods. Slip rates can be determined using semi-automatic cross-sectional tools and maps compiled to show spatial variations. Subtle changes in slope can be used to identify important geomorphic features4. Such features include bowl-shaped rotational slips, colluvial wedges, alluvial fan deposits as well as footwall bedrock gullies and hangingwall erosional channels. Thus, reliable long term 105 yr slip rate determinations will be made at the best preserved portions of scarps along the entire traces of the normal faults. Roughness parameters will be calculated for point cloud strips scarps aligned along the slip direction for individual faults. For a number of the faults in the study area, these morphology parameters will be correlated with short term slip rates (<103 yrs) based on modelled results from 36Cl cosmogenic dating being generated in related NERC-funded research by the supervisors. of use to other geoscientists working in active tectonic fields and earthquake science. The results will be used to make an assessment of the feasibility of using morphology measures as a proxy for slip rate. The work will also provide new insights on scarp creation, preservation and degradation processes in carbonate-hosted normal faults. Any systematic natural variation of fault scarp morphology with tectonic or geomorphological processes will be Further Information Timeline Q1 Q2 Induction, training, lit review Fieldwork Data Analysis Results interpretation Paper preparation Thesis chapter writing Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Training & Skills Geomatic methods including Terrestrial laser scan Lidar) applications 3D geospatial analysis of structures Geomorphology, Earthquake Science and Paleoseismology References & Further Reading [1] Roberts, G.P., Michetti, A.M., 2004. Spatial and temporal variations in growth rates along active normal fault systems: an example from the Lazio-Abruzzo Apennines, central Italy. Journal of Structural Geology 26, 339–376. [2] Faure Walker J., Roberts G.P., Cowie P.A., Papanikolaou I., Michetti A.M., Sammonds P. and Phillips R., Horizontal strain-rates and throw-rates across breached relay-zones, central Italy: implications for the preservation of throw deficits at points of normal fault linkage, Journal of Structural Geology, 31, 386 11451160. [3] Wilkinson et al. 2014. Slip rate analysis of the Campo Felice fault from Terrestrial laser scan datasets. Geomorphology. [4] Bubeck et al 2014. The tectonic geomorphology of bedrock scarps on active normal faults in the Italian Apennines mapped using combined ground penetrating radar and terrestrial laser scanning. Geomorphology. Email: Ken McCaffrey - [email protected]