Abstract
The Padul-Nigüelas Fault Zone (PNFZ) is situated at the south-western mountain front of the Sierra Nevada (southern Spain) in the Internal Zone of the Betic Cordilleras and belongs to a NW-SE trending system of normal faults dipping SW. The PNFZ constitutes a major tectonic and lithological boundary in the Betics, and separates the metamorphic units of the Alpujárride Complex from Upper Tertiary to Quaternary deposits. Due to recent seismicity and several morphological and geological indicators, such as preserved fault scarps, triangular facets, deeply incised valleys and faults in the colluvial wedges, the PNFZ is suspected to be a tectonically active feature of the south-eastern Granada Basin. We performed morphotectonic GIS analyses based on digital elevation models (DEM, cell size: 10 m) to obtain tectonic activity classes for each outcropping segment of the PNFZ. We have determined the following geomorphic indices: mountain front sinuosity, stream-length gradient index, concavity index and valley floor width to height ratio. The results show a differentiation in the states of activity along the fault zone strike. The western and eastern segments of the PNFZ indicate a higher tectonic activity compared to the center of the fault zone. We discuss and critically examine the comparability and reproducibility of geomorphic analyses, concluding that careful interpretation is necessary, if no ground-truthing can be performed.
Highlights
The Padul-Nigüelas Fault Zone (PNFZ) is located at the southwestern border of the Sierra Nevada in southern Spain (Figure 1) and comprises a strongly segmented northwest-southeast trending system of normal faults that dip to the southwest
Since the PNFZ does not consist of one particular fault, but comprises a fault zone consisting of three segments, we are interested in the tectonic activity of each segment and if there is a differentiation between each segment
In the Padul segment, only five channels comply with the requirement of crossing the fault zone and, only these are selected for analyzing the concavity index
Summary
The Padul-Nigüelas Fault Zone (PNFZ) is located at the southwestern border of the Sierra Nevada in southern Spain (Figure 1) and comprises a strongly segmented northwest-southeast trending system of normal faults that dip to the southwest. Several authors have already studied the tectonic and seismic activity of the PNFZ as a separated part of the Granada Basin [Riley and Moore 1993, Keller et al 1996, Calvache et al 1997, Alfaro et al 2001, Ruiz et al 2003, 2007, El Hamdouni et al 2008]. Since the PNFZ does not consist of one particular fault, but comprises a fault zone consisting of three segments, we are interested in the tectonic activity of each segment and if there is a differentiation between each segment. This information is crucial for determining the seismic potential of the fault zone
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