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Maria Helbig, TU Bergakademie Freiberg (Germany)
Michael Buchwitz, TU Bergakademie Freiberg (Germany)
Richard Gloaguen, TU Bergakademie Freiberg (Germany)
Amy Clifton, Háskóli Íslands (Iceland)
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Rift systems such as the Icelandic Rift and the northern Main Ethiopian Rift spread along a direction that is oblique to the rift axis trend and have fracture patterns that are controlled by the angle of obliquity. In addition, numerous studies have shown that magmatism also affects fault morphology, growth and linkage. In oblique spreading centers, crustal deformation is confined to tectono-magmatic segments with en-échelon fault zones separated by domains of minor faulting. However, until now, the development of tectonic segmentation is still discussed and therefore, there is a need to describe, quantify and localize deformation within the active rift zone.
This work combines remote sensing and geostatistics in order to quantify and qualify geomorphological features and deformation patterns in oblique rift zones. We examine the architecture and geomorphology of normal faults in the central part of Reykjanes Fissure Swarm in SW Iceland, where the spreading direction (103°) is highly oblique (approximately 30°) to the rift axis. A Kinematic GPS survey of the Háleyjabunga fault and Digital Elevation Models generated from aerial stereo pairs with a resolution of 1m allow a detailed geomorphological and structural analysis.
By applying gradient filtering and summation of vertical offset amounts it is possible to enhance the morphological effects of fault overlapping and linking and to detect zones where deformation is concentrated. We create plots of cumulative displacement against fault length from digital fault lines in order to recognize segmentation patterns.
We use geostatistical methods to analyze the spatial distribution of strike and vertical displacement, and find a "shear band"-like geometry in the Reykjanes fault population which is indicative of left-lateral transform motion along the plate boundary. We see faults striking approx. 044° bending into two main "bands" of faults striking approx. 085°, whereas the rift axis trends ca. 076°. We describe tectonic morphologies such as fault profiles with monoclinal bending and long, narrow grabens, radial-shaped collapse structures or large, tilted blocks along normal faults which may be evidence for dike-induced faulting.
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