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Topography of the Gibraltar Arc region and main geographic names. WAB, West Alboran Basin; EAB, East Alboran Basin; ABB, Algero-Balearic Basin. The shaded area indicates the positive velocity anomaly at 270 km depth found in the tomography study of Bezada et al. (2013) associated with the Gibraltar slab. Orange line denotes the Rif-Betic front (from Gutscher et al. (2012)) and purple line shows the position of the modelled cross-section in this work. The dashed portion of the profile is an extension of the model to prevent boundary effects. White arrows show the convergence direction of the Iberian and African (Nubia) plates. Blue dots indicates the regional intermediate seismicity (40 km < h < 150 km), from Instituto Andaluz de Geofisica Catalogue. The tomographic cross-section has been obtained from Hosseini et al. (2018) using the tomography model UU-P07 (Amaru, 2007).
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The origin and tectonic evolution of the Gibraltar Arc system is the result of a complex geodynamic evolution involving the convergence of the Eurasian and African plates and the dynamic impact of the Gibraltar slab. Although geologic and geophysical data collected in the last few years have increased our knowledge of the Gibraltar Arc region, it i...
Citations
... Ruiz-Constán et al. (2012) obtained N166°E (4 mechanisms) and N018°E (4 mechanisms) σ1 trends for the shallow seismicity, while for the intermediate earthquakes, they obtain a σ1 between N113°E-N126°E (29 mechanisms). The σ1 trend is located more towards the ESE-WSW concerning the surrounding areas, probably influenced by the remnant effect of the slab (Gea et al., 2023), more evident at depth (Ruiz-Constán et al., 2012). To test this effect, we inverted the 7 focal mechanisms corresponding to earthquakes with hypocentral depths of more than 20 km in this 740 zone (WBD), obtaining a σ1 of N114°E, more E-W than the shallow ones (Fig. 8 WB>20). ...
From the analysis of 542 moment tensor focal mechanisms in Iberia, active tectonic deformations and stresses were inferred by implementing different and complementary methodologies: FMC classification of the rupture type; composed focal mechanism based on the average seismic moment tensor; rotation angle between tensors estimates; Right Dihedra composed focal mechanisms; Slip Model analysis to determine the strain conditions and classical stress inversion methodology. By using the Slip Model results and considering the tectonic constraints of the Cenozoic deformation in Iberia, the study region was subdivided into a series of zones where the different methods were individually applied. The results indicate that thrust faulting stress regimes are active in the Gorringe-Horseshoe area and the easternmost Tell Atlas. In the south, most of the zones are transpressive, as well as in the southwestern corner of Iberia, south of Lisbon. The exception is the Granada Basin, which displays an almost radial normal faulting stress regime. Normal faulting stresses are dominant in the Pyrenees and in the Mediterranean rim, north of the Betics. In the central part of the Pyrenees, we find a maximum horizontal extension perpendicular to the range, indicating that local stresses related to post-orogenic collapse or isostatic rebound dominate over regional ones. The maximum horizontal compression along the Eurasia-Africa plate limit is very homogeneously close to N154° E, except in some parts of the Betics that are probably influenced by a remanent effect of the Alboran Slab. In the Central Ranges and offshore Atlantic, the maximum horizontal compression is slightly rotated anticlockwise to N140° E.
... Therefore, the GWB can be easily used to visualize tectonic and geodynamic settings for publications, teaching, and public outreach. The GWB has been used in several published studies to model global fault patterns, plumes, and plate dynamics (Gea et al., 2023;Sandiford & Craig, 2023;Saxena et al., 2023;and van der Wiel et al., 2024). Other tools to solve this problem have emerged at around the same time as the first GWB release (Fraters et al., 2019). ...
... The North of Morocco is considered as a complex tectonic region due to its geological and geodynamic complexity with several geological structures. The Betic-Rif Cordillera which the north Morocco is one part, is located in the Betic-Rif Cordillera vary significantly across the region [Pasquale et al., 1996;Custodio et al., 2019;Gea et al., 2023]. ...
Northern Morocco is known by its complex tectonic activity and has been the subject of various geophysical and geodynamic studies aimed to understand the physical properties and composition of the Earth’s crust and upper mantle. The waveforms of earthquakes recorded by the Topo – Iberia – Picasso seismic networks from 2008 to 2012 are analyzed to determine the decay properties of the coda wave and map the attenuation and absorption properties of the crust in this region. The coda quality factor Qc was estimated in five non‑overlapping frequency windows, ranging from 1.5 to 24 Hz, using recordings of local earthquakes. The measurements of Qc were then used to create maps of the absorption quality factor (Qi) using a linearized approximation. These maps were compared with the tectonic settings of the region to gain further insight into the crustal properties. Lateral and vertical variations of the coda quality factor (Qc) were investigated by creating a three‑dimensional tomographic image of the region. The results showed strong lateral variations of absorption in the northern part of Morocco, indicating high tectonic activity. Areas with high tectonic activity and high absorption were characterized by low values of Qc, while areas with low tectonic activity and low absorption had high values of Qc. The areas with thick cover sedimentary materials and shallow geothermal activity showed low‑frequency absorption. When compared to previous studies in northern Morocco, the study provides new information about the three‑dimensional attenuation model of the Earth’s crust.
... Finally, the significant decrease of V T with increasing T OP reported in Figure 6e demonstrates the strong impact of the OP thickness on trench retreat velocities. This result is in agreement with previous 3D and 2D models (Butterworth et al., 2012;Gea et al., 2023;Hertgen et al., 2020;Sharples et al., 2014;Yamato et al., 2009) finding that thin/weak OP favors faster trench velocities and rollback compared to a thick/strong OP. This result is enhanced by the fixed boundary condition of the OP at its trailing edge. ...
Slab width is a significant factor in controlling subduction zone dynamics, particularly the retreat velocities, which tend to decrease with wider slabs. However, observations of natural narrow subduction zones reveal no correlation between slab width and trench velocities. This suggests that other factors may exert a greater influence. In this study, we employ 3D numerical subduction models to systematically assess the impact of slab width, strength of slab coupling to the lateral plate (LP), and overriding plate (OP) thickness on trench kinematics and geometry. Our models focus on narrow slabs (400–1,200 km), and the results demonstrate that, in the case of narrow subduction zones, the slab width has little effect on trench migration rates and the viscous coupling at the lateral slab edge is only important for very narrow subduction zones (≤800 km). Conversely, the OP thickness emerges as a crucial factor, with increasing plate thickness leading to a strong decrease in trench velocities. These findings provide an explanation for the observed trench velocities in natural narrow subduction zones, where an inverse relationship with OP thickness is evident. Furthermore, our study reveals that not only slab width, but also the OP thickness and the slab coupling to the LP, significantly influence trench geometry. Strong lateral coupling promotes the formation of concave trench geometries, while thick overriding plates favor the development of “w”‐shaped geometries. Overall, a comprehensive understanding of subduction processes necessitates considering the interplay between slab width, OP thickness, and slab coupling to the LP.