Earthquake crisis unveils the growth of an incipient continental fault system

Gràcia, Eulália; Grevemeyer, Ingo; Bartolomé, Rafael; Perea, Héctor; Martínez-Loriente, S.; Peña, L. Gómez de la; Villaseñor, Antonio; Klinger, Yann; Iacono, Claudio Lo; Díez, Susana García; Calahorrano, Alcinoe; Camafort, Miquel; Costa, Sergio; d’Acremont, Elia; Rabaute, Alain; Ranero, César R.

doi:10.1038/s41467-019-11064-5

Cited by 35 publications

(86 citation statements)

References 66 publications

(122 reference statements)

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“…NNE‐SSW sinistral faults (Al Idrissi fault zone) cross the central Alboran Sea and continue onshore through the Adra and Al Hoceima regions (Figure 1) (e.g. d'Acremont et al, 2014; Lafosse et al, 2016, 2018; Gràcia et al, 2019). At present, the Al Idrissi fault zone and the WNW‐ESE dextral Yusuf fault system (Figure 1) (Koulali et al, 2011) are consistent with a tectonic indentation of the African rigid plate toward the NW (Estrada et al, 2018).…”

Section: Geodynamic and Geological Settingmentioning

confidence: 99%

Polyphase Tectonic Evolution of Fore‐Arc Basin Related to STEP Fault as Revealed by Seismic Reflection Data From the Alboran Sea (W‐Mediterranean)

et al. 2020

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Since the Miocene, the thinned continental crust below the Alboran Sea and its overlying sedimentary cover have been undergoing deformation caused by both convergence of Eurasia and Africa and by deep processes related to the Tethyan slab retreat. Part of this deformation is recorded at the Xauen and Tofiño banks in the southern Alboran Sea. Using swath bathymetry and multichannel seismic reflection data, we identified different stages and styles of deformation. The South Alboran Basin is made up of Early Miocene to Pliocene sedimentary layers that correlate with the West Alboran Basin depocenter and are dominated by E-W trending folds and thrusts. The Xauen and Tofiño Banks first recorded the phase of extension and strike-slip movement during the slab retreat, followed by the phase of compressional inversion since the Tortonian and are now structured by tight folds, thrusts, and mud bodies. This study proposes that the Banks were located on the southern-inherited Subduction Tear Edge Propagator (STEP) fault related to the westward migration of the Alboran domain during the Miocene. The STEP fault zone, acting as a boundary between the African block and the Alboran block, was located along the onshore Jebha-Nekor fault and the offshore Alboran Ridge and the Yusuf fault zone. Thick-skinned and thin-skinned shortening occurred when slab retreat stopped, and inversion began. The present-day style of the deformation seems to be linked to a decollement level made of undercompacted shale on top of the Ghomaride complex.

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Section: Geodynamic and Geological Settingmentioning

confidence: 99%

Polyphase Tectonic Evolution of Fore‐Arc Basin Related to STEP Fault as Revealed by Seismic Reflection Data From the Alboran Sea (W‐Mediterranean)

et al. 2020

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“…Here, we analyze the kinematics of an intense earthquake sequence that occurred in 2016 in the southern Alboran Sea (Buforn et al, 2017;Medina and Cherkaoui, 2017;Galindo-Zaldivar et al, 2018;Kariche et al, 2018;Gràcia et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Slip Partitioning in the 2016 Alboran Sea Earthquake Sequence (Western Mediterranean)

et al. 2020

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A M W 5.1 earthquake on January 21st, 2016 marked the beginning of a significant seismic sequence in the southern Alboran Sea, culminating in a M W 6.3 earthquake on January 25th, and continuing with further moderate magnitude earthquakes until March. We use data from 35 seismic broadband stations in Spain, Morocco and Portugal to relocate the seismicity, estimate seismic moment tensors, and isolate regional apparent source time functions for the main earthquake. Relocation and regional moment tensor inversion consistently yield very shallow depths for the majority of events. We obtain 50 moment tensors for the sequence, showing a mixture of strike-slip faulting for the foreshock and the main event and reverse faulting for the major aftershocks. The leading role of reverse focal mechanisms among the aftershocks may be explained by the geometry of the fault network. The mainshock nucleates at a bend along the left-lateral Al-Idrisi fault, introducing local transpression within the transtensional Alboran Basin. The shallow depths of the 2016 Alboran Sea earthquakes may favor slip-partitioning on the involved faults. Apparent source durations for the main event suggest a ∼21 km long, asymmetric rupture that propagates primarily toward NE into the restraining fault segment, with fast rupture speed of ∼3.0 km/s. Consistently, the inversion for laterally variable fault displacement situates the main slip in the restraining segment. The partitioning into strikeslip rupture and dip-slip aftershocks confirms a non-optimal orientation of this segment, and suggests that the 2016 event settled a slip deficit from previous ruptures that could not propagate into the stronger restraining segment.

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“…We agree with the referee, the AIF appears to produce a very limited lateral displace-C3 ment (<10km). We argue that it is the consequence of its young age and that the overall regional deformation rates are low (Gràcia et al, 2019;Martínez-García et al, 2017).…”

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confidence: 82%

“…However, more recent plate tectonic models suggest that the direction of convergence is constant through time since 6Ma (DeMets et al 2015). Two recent publications (Galindo-Zaldivar et al, 2018;Gràcia et al, 2019) propose that the Al-Idrissi fault zone is a recent feature, and corresponds to the present-day Africa-Eurasia plate boundary. Therefore, the questions are how can we explain the change of local tectonic, and can we propose a model explaining the evolution of the Alboran tectonic and the inception of the Al Idrissi fault zone.…”

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confidence: 99%