Geometry and kinematics of the Baza Fault (central Betic Cordillera, South Spain): insights into its seismic potential

Abstract

The geometry and kinematics of active faults have a significant impact on their seismic potential. In this work, a structural characterization of the active Baza Fault (central Betic Cordillera, southern Spain) combining surface and subsurface data is presented. Two sectors are defined based on their surface geometry: a northern sector striking N–S to NNW–SSE with a narrow damage zone and a southern sector striking NW–SE with a wide damage zone. A kinematic analysis shows pure normal fault kinematics along most of the fault. Geometric differences between the northern and southern sectors are caused by i) a heterogeneous basement controlling the fault geometry at depth and in the cover; ii) different orientations of the Baza Fault in the basement with respect to the regional extension direction and iii) interaction with other active faults. We use this structural characterization to analyse the segmentation of the Baza Fault. According to segmentation criteria, the entire Baza Fault should be considered a single fault seismogenic segment. Consequently, the seismic potential of the fault is defined for a complete rupture. Magnitude for the Mmax event is calculated using several scale relationships, obtaining values ranging between Mw 6.6 and Mw 7.1. Recurrence times range between approximately 2,000 and 2,200 years for Mmax events and between 5,300 and 5,400 years for palaeo-events. A geodetic scenario modelled for an Mmax event of Mw 6.7 shows permanent vertical displacements of more than 0.40m and an overall WSW–ENE extension during entire ruptures of the Baza Fault.

Geodetic fault slip rates on active faults in the Baza sub-Basin (SE Spain): Insights for seismic hazard assessment

“…Two major active faults have been described in the BsB: the normal Baza Fault and the strike-slip Galera Fault (Alfaro et al, 2008;García Tortosa et al, 2011;Medina-Cascales et al, 2020) Fig. 2).…”

Insights of Active Extension Within a Collisional Orogen From GNSS (Central Betic Cordillera, S Spain)

“…This convergence produces NNW‒SSE shortening, which is responsible for the main topographic features observed today (Sanz de Galdeano & Alfaro, 2004). After that geodynamic change, only the Central Betic Cordillera underwent extension, accommodated by NNW‒SSE to WNW‒ESE high‐angle normal faults (Alfaro et al., 2008; Azañón et al., 2004; Castro et al., 2018; García‐Tortosa et al., 2008; Medina‐Cascales et al., 2020; Sanz de Galdeano et al., 2012). These normal faults produced half‐grabens in their hanging walls filled by Upper Miocene to Quaternary sediments and, hence, led to the development of Neogene‐Quaternary sedimentary basins, including the Granada and Guadix‐Baza Basins (Figure 2).…”

“…Nevertheless, in this convergence setting of the Eurasian‐Nubia plates, the Central Sector of the Betic Cordillera is characterized by active NE‒SW extension (Figure 1). Studies on active tectonics describe NW‒SE active normal faults in the Granada and Guadix‐Baza Basins (Alfaro et al., 2001, 2008, 2021; Castro et al., 2018; Galindo‐Zaldívar et al., 1999; Gil et al., 2002; Medina‐Cascales et al., 2020, 2021; Rodriguez‐Fernandez & Sanz de Galdeano, 2006; Ruiz et al., 2003; Sanz de Galdeano & López‐Garrido, 1999; Sanz de Galdeano et al., 2012, 2020; and many others) (Figure 2). This extension is further confirmed by seismic studies, as seismic moment tensors are compatible with NE‒SW regional extension (Galindo‐Zaldívar et al., 1999; Herráiz et al., 2000; Palano et al., 2015; Stich et al., 2006, 2007) (Figure 1).…”

“…The Baza Fault (Figure 2) is another of these high‐angle normal faults (Alfaro et al., 2008; Castro et al., 2018; Fernández‐Ibáñez et al., 2010; García‐Tortosa et al., 2008; Medina‐Cascales et al., 2020; Sanz de Galdeano et al., 2012); this active structure is responsible for the development of the eastern sector of the Guadix‐Baza Basin. Other normal faults in the Central Betic Cordillera are the Solana del Zamborino Fault and the Graena Fault (Sanz de Galdeano et al., 2012) (Figure 2).…”

High‐ and Low‐Angle Normal Fault Activity in a Collisional Orogen: The Northeastern Granada Basin (Betic Cordillera)

“…At present, the most relevant set of active extensional faults are high angle, with NW‐SE orientation, and located mainly in Neogene‐Quaternary basins (Galindo‐Zaldívar et al., 2003; Figure 1). To the north, the Baza Fault dips northeastward (Alfaro et al., 2008; Medina‐Cascales et al., 2020). However, in the southern part of the Cordillera, most faults dip to the SW, including the Almeria‐Tabernas (Marín‐Lechado et al., 2005; Sanz de Galdeano et al., 2010), Balanegra (Galindo‐Zaldívar et al., 2013; Marín‐Lechado et al., 2010), and Padul fault zones (Gil et al., 2017), the latter extending toward the Granada Basin (Granada Fault zone; Morales et al., 1990; Rodríguez‐Fernández & Sanz de Galdeano, 2006; Ruano et al., 2004).…”