Imaging the seismic LAB and deeper asthenospheric low-velocity layers in the Ibero-Maghrebian region

Abstract

We present a new lithosphere-asthenosphere boundary (LAB) depth map of Iberia and adjacent areas built using 34500 Sp receiver functions from 998 broadband seismic stations, alongside an updated Ps-derived crustal thickness map of Iberia. We found an overall shallow LAB, with a minimum depth of 70-80 km in areas of Cenozoic extension such as the eastern coast of Iberia and the Gibraltar-Alboran subduction back-arc, as well as in the Massif Central and the tectonically stable northwest of Iberia. LAB depths from 90 km to 110 km were only found within the areas of thickened crust in north-central Iberia and bordering the Gulf of Cádiz. The much deeper (150-180 km) oceanic LAB of the Gibraltar-Alboran slab was also imaged in the western Gibraltar Arc. Sublithospheric negative-velocity gradients (NVG) in the 110-140 km depth range are widespread in the back-arc of the Gibraltar-Alboran subduction system and in north-central Iberia, picturing a layered asthenospheric structure. In the Gibraltar Arc, the detachment of the slab through the subduction-transform edge propagator fault in the eastern Betics seems linked to the formation of the NVG, which are limited to the north by this structure.

Keywords

Receiver functions / Lithosphere-asthenosphere boundary / Asthenosphere / Iberia / Maghreb / Western Mediterranean

CRediT authorship contribution statement

J. Díaz: Investigation, Writing - review & editing. J.A. Parera-Portell: Formal analysis, Investigation, Writing - original draft. F.d.L. Mancilla: Conceptualization, Investigation, Writing - review & editing. J. Morales: Investigation, Writing - review & editing. X. Yuan: Investigation, Writing - review & editing. B. Heit: Investigation, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work has been funded by the grant PID2019-109608GB-I00 from Spanish Research Agency MCIN/AEI/10.13039/501100011033, and the FPI grant PRE2020-092556 from Spanish Research Agency MCIN/AEI/10.13039/501100011033 and the European Social Fund. We thank the ORFEUS EIDA (http://www.orfeus-eu.org/data/eida/) and FDSN (https://www.fdsn.org/services/) data services, as well as the Principal Investigators of the restricted seismic networks for granting us access to their dataset. We also thank the teams behind all the seismic networks used in this study (2 M, 3D, 3 J, 8A, 9C, 9H, Andalusian Seismic Network, CA, ES, FR, GE, IB, CAL, WM, X7, XB, YR, YS, ZC, ZI and ZU). Thank you to the Editor and the three anonimous reviewers, as well as to Bernhard Steinberger and Imma Palomeras for sharing their lithospheric thickness maps. This work has benefitted from the infrastructure of the GEO3BCN-CSIC LabSis laboratory (http://labsis.geo3bcn.csic.es). We acknowledge use of the software SAC ( Goldstein and Snoke, 2005 ), ObsPy ( Krischer et al., 2015 ) and GMT ( Wessel et al., 2019 ).

Appendix A. Supplementary data

Supplementary data associated with this article can be found, in the online version, at https://doi.org/10.1016/j.gsf.2025.102210.

References

[1] Amaru, M., 2007. Global Travel Time Tomography With 3-D Reference Models. PhD. thesis. University of Utrecht.

[2] Andrés, J., Draganov, D., Schimmel, M., Ayarza, P., Palomeras, I., Ruiz, M., Carbonell, R., 2019. Lithospheric image of the Central Iberian Zone (Iberian Massif) using global-phase seismic interferometry. Solid Earth 10, 1937-1950. https://doi.org/10.5194/se-10-1937-2019.

[3] Artemieva, I.M., Meissner, R., 2012. Crustal thickness controlled by plate tectonics: a review of crust-mantle interaction processes illustrated by European examples. Tectonophysics 530-531, 18-49. https://doi.org/10.1016/j.tecto.2011.12.037.

[4] Ayarza, P., Martínez Catalán, J.R., Martínez García, A., Alcalde, J., Andrés, J., Simancas, J.F., Palomeras, I., Martí D., DeFelipe, I., Juhlin, C., Carbonell, R., 2021. Evolution of the Iberian Massif as deduced from its crustal thickness and geometry of a mid-crustal (Conrad) discontinuity. Solid Earth 12, 1515-1547. https://doi.org/10.5194/se-12-1515-2021.

[5] Babuška, V., Plomerová J., Vecsey, L., Granet, M., Achauer, U., 2002. Seismic anisotropy of the French Massif Central and predisposition of Cenozoic rifting and volcanism by Variscan suture hidden in the mantle lithosphere. Tectonics 21(4), 1029. https://doi.org/10.1029/2001tc901035.

[6] Badal, J., Corchete, V., Payo, G., Pujades, L., Canas, J.A., 1996. Imaging of shear-wave velocity structure beneath Iberia. Geophys. J. Int. 124, 591-611. https://doi.org/10.1111/j.1365-246x.1996.tb07039.x.

[7] Bezada, M., Humphreys, E., Toomey, D., Harnafi, M., Dávila, J., Gallart, J., 2013. Evidence for slab rollback in westernmost Mediterranean from improved upper mantle imaging. Earth Planet. Sci. Lett. 368, 51-60. https://doi.org/10.1016/j.epsl.2013.02.024.

[8] Bezada, M.J., Humphreys, E.D., Davila, J., Carbonell, R., Harnafi, M., Palomeras, I., Levander, A., 2014. Piecewise delamination of Moroccan lithosphere from beneath the Atlas Mountains. Geochem. Geophys. Geosyst. 15, 975-985. https://doi.org/10.1002/2013gc005059.

[9] Bonatto, L., Schimmel, M., Gallart, J., Morales, J., 2015. The upper-mantle transition zone beneath the Ibero-Maghrebian region as seen by teleseismic Pds phases. Tectonophysics 663, 212-224. https://doi.org/10.1016/j.tecto.2015.02.002.

[10] Booth-Rea, G., Ranero, C.R., Martínez-Martínez, J.M., Grevemeyer, I., 2007. Crustal types and Tertiary tectonic evolution of the Alborán sea, western Mediterranean. Geochem. Geophys. Geosyst. 8 (10), Q10005. https://doi.org/10.1029/2007gc001639.

[11] Carminati, E., Lustrino, M., Doglioni, C., 2012. Geodynamic evolution of the central and western Mediterranean: Tectonics vs. igneous petrology constraints. Tectonophysics 579, 173-192. https://doi.org/10.1016/j.tecto.2012.01.026.

[12] Chevrot, S., Sylvander, M., Diaz, J., Martin, R., Mouthereau, F., Manatschal, G., Masini, E., Calassou, S., Grimaud, F., Pauchet, H., Ruiz, M., 2018. The non-cylindrical crustal architecture of the Pyrenees. Sci. Rep. 8, 9591. https://doi.org/10.1038/s41598-018-27889-x.

[13] Civiero, C., Custódio, S., Duarte, J.C., Mendes, V.B., Faccenna, C., 2020. Dynamics of the Gibraltar Arc System: A complex interaction between plate convergence, slab pull, and mantle flow. J. Geophys. Res. Solid Earth 125 (7), e2019JB018873. https://doi.org/10.1029/2019jb018873.

[14] Civiero, C., Custódio, S., Rawlinson, N., Strak, V., Silveira, G., Arroucau, P., Corela, C., 2019. Thermal nature of mantle upwellings below the Ibero-Western Maghreb Region inferred from teleseismic tomography. J. Geophys. Res. Solid Earth 124, 1781-1801. https://doi.org/10.1029/2018jb016531.

[15] Diaz, J., Torne, M., Vergés, J., Jiménez-Munt, I., Martí J., Carbonell, R., Schimmel, M., Geyer, A., Ruiz, M., García-Castellanos, D., Alvarez-Marrón, J., Brown, D., Villaseñor, A., Ayala, C., Palomeras, I., Fernandez, M., Gallart, J., 2021. Four decades of geophysical research on Iberia and adjacent margins. Earth Sci. Rev. 222, 103841. https://doi.org/10.1016/j.earscirev.2021.103841.

[16] Diaz, J., Vergés, J., Chevrot, S., Antonio-Vigil, A., Ruiz, M., Sylvander, M., Gallart, J., 2018. Mapping the crustal structure beneath the eastern Pyrenees. Tectonophysics 744, 296-309. https://doi.org/10.1016/j.tecto.2018.07.011.

[17] Eaton, D.W., Darbyshire, F., Evans, R.L., Grütter, H., Jones, A.G., Yuan, X., 2009. The elusive lithosphere-asthenosphere boundary (LAB) beneath cratons. Lithos 109, 1-22. https://doi.org/10.1016/j.lithos.2008.05.009.

[18] El-Sharkawy, A., Hansteen, T.H., Clemente-Gomez, C., Fullea, J., Lebedev, S., Meier, T., 2024. Cenozoic volcanic provinces and shallow asthenospheric volumes in the Circum-Mediterranean: Evidence from magmatic geochemistry, seismic tomography, and integrated geophysical-petrological thermochemical inversion. Geochem. Geophys. Geosyst. 25 (9), e2023GC011017. https://doi.org/10.1029/2023gc011017.

[19] Faccenna, C., Piromallo, C., Crespo-Blanc, A., Jolivet, L., Rossetti, F., 2004. Lateral slab deformation and the origin of the western Mediterranean arcs. Tectonics 23 (1), TC1012. https://doi.org/10.1029/2002tc001488.

[20] Feng, L., Díaz, J., 2022. Azimuthal anisotropy of the westernmost Mediterranean: New constraints on lithospheric deformation and geodynamical evolution. Earth Planet. Sci. Lett. 593, 117689. https://doi.org/10.1016/j.epsl.2022.117689.

[21] Fischer, K.M., Ford, H.A., Abt, D.L., Rychert, C.A., 2010. The lithosphere-asthenosphere boundary. Annu. Rev. Earth Planet. Sci. 38, 551-575. https://doi.org/10.1146/annurev-earth-040809-152438.

[22] Frassetto, A., Zandt, G., Gilbert, H., Owens, T.J., Jones, C.H., 2010. Improved imaging with phase-weighted common conversion point stacks of receiver functions. Geophys. J. Int. 182 (1), 368-374. https://doi.org/10.1111/j.1365-246x.2010.04617.x.

[23] Fullea, J., Negredo, A., Charco, M., Palomeras, I., Afonso, J., Villaseñor, A., 2021. The topography of the Iberian Peninsula from integrated geophysical-petrological multi-data inversion. Phys. Earth Planet. Inter. 314, 106691. https://doi.org/10.1016/j.pepi.2021.106691.

[24] Funiciello, F., Horvàth, F., Jolivet, L., Piromallo, C., Royden, L., Rossetti, F., Faccenna, C., Becker, T.W., Auer, L., Billi, A., Boschi, L., Brun, J.P., Capitanio, F.A., Serpelloni, E., 2014. Mantle dynamics in the Mediterranean. Rev. Geophys. 52, 283-332. https://doi.org/10.1002/2013rg000444.

[25] Goldstein, P., Snoke, A., 2005. SAC availability for the IRIS community. In: Incorporated Research Institutions for Seismology Newsletter 7.

[26] Guimerà J., Mas, R., Alonso, A., 2004. Intraplate deformation in the NW Iberian Chain: Mesozoic extension and Tertiary contractional inversion. Journal of the Geological Society 161, 291-303. https://doi.org/10.1144/0016-764903-055.

[27] Heit, B., Mancilla, F.d.L., Yuan, X., Morales, J., Stich, D., Martín, R., Molina-Aguilera, A., 2017. Tearing of the mantle lithosphere along the intermediate-depth seismicity zone beneath the Gibraltar Arc: The onset of lithospheric delamination. Geophys. Res. Lett. 44, 4027-4035. https://doi.org/10.1002/2017gl073358.

[28] van Hinsbergen, D.J.J., Vissers, R.L.M., Spakman, W., 2014. Origin and consequences of western Mediterranean subduction, rollback, and slab segmentation. Tectonics 33, 393-419. https://doi.org/10.1002/2013tc003349.

[29] Hua, J., Fischer, K.M., Becker, T.W., Gazel, E., Hirth, G., 2023. Asthenospheric low-velocity zone consistent with globally prevalent partial melting. Nat. Geosci. 16, 175-181. https://doi.org/10.1038/s41561-022-01116-9.

[30] Jammes, S., Manatschal, G., Lavier, L., Masini, E., 2009. Tectonosedimentary evolution related to extreme crustal thinning ahead of a propagating ocean: Example of the western Pyrenees. Tectonics 28 (4), TC4012. https://doi.org/10.1029/2008tc002406.

[31] Jammes, S., Tiberi, C., Manatschal, G., 2010. 3D architecture of a complex transcurrent rift system: The example of the Bay of Biscay-Western Pyrenees. Tectonophysics 489, 210-226. https://doi.org/10.1016/j.tecto.2010.04.023.

[32] Jolivet, L., de Lamotte, D.F., Mascle, A., Séranne, M., 1999. The Mediterranean Basins: Tertiary Extension within the Alpine Orogen — an introduction. Geological Society, London, Special Publications 156, 1-14. https://doi.org/10.1144/gsl.sp.1999.156.01.02.

[33] Jones, A.G., Plomerová J., Korja, T., Sodoudi, F., Spakman, W., 2010. Europe from the bottom up: A statistical examination of the central and northern European lithosphere-asthenosphere boundary from comparing seismological and electromagnetic observations. Lithos 120, 14-29. https://doi.org/10.1016/j.lithos.2010.07.013.

[34] Kennett, B.L.N., Engdahl, E.R., 1991. Traveltimes for global earthquake location and phase identification. Geophys. J. Int. 105, 429-465. https://doi.org/10.1111/j.1365-246x.1991.tb06724.x.

[35] Krischer, L., Megies, T., Barsch, R., Beyreuther, M., Lecocq, T., Caudron, C., Wassermann, J., 2015. ObsPy: a bridge for seismology into the scientific Python ecosystem. Computational Science & Discovery 8, 014003. https://doi.org/10.1088/1749-4699/8/1/014003.

[36] Langston, C.A., 1979. Structure under Mount Rainier, Washington, inferred from teleseismic body waves. J. Geophys. Res. 84, 4749. https://doi.org/10.1029/jb084ib09p04749.

[37] Lee, H., Bezada, M.J., Kim, Y., 2022. The origin of the low-velocity anomalies beneath the rootless Atlas Mountains: Insights gained from modeling of anisotropy developed by the travel of Canary Plume. J. Geophys. Res. Solid Earth 127 (11), e2022JB024622. https://doi.org/10.1029/2022jb024622.

[38] Ligorría, J., Ammon, C., 1999. Iterative deconvolution and receiver-function estimation. Bull. Seismol. Soc. Am. 89, 1395-1400.

[39] Lustrino, M., Duggen, S., Rosenberg, C.L., 2011. The Central-Western Mediterranean: Anomalous igneous activity in an anomalous collisional tectonic setting. Earth Sci. Rev. 104, 1-40. https://doi.org/10.1016/j.earscirev.2010.08.002.

[40] Mancilla, F.d.L., Diaz, J., 2015. High resolution Moho topography map beneath Iberia and Northern Morocco from receiver function analysis. Tectonophysics 663, 203-211. https://doi.org/10.1016/j.tecto.2015.06.017.

[41] Mancilla, F.d.L., Heit, B., Morales, J., Yuan, X., Stich, D., Molina-Aguilera, A., Azañón, J.M., Martín, R., 2018. A step fault in central betics, associated with lateral lithospheric tearing at the northern edge of the gibraltar arc subduction system. Earth Planet. Sci. Lett. 486, 32-40. https://doi.org/10.1016/j.epsl.2018.01.008.

[42] Mancilla, F.d.L., Stich, D., Morales, J., Martín, R., Diaz, J., Pazos, A., Córdoba, D., Pulgar, J.A., Ibarra, P., Harnafi, M., Gonzalez-Lodeiro, F., 2015. Crustal thickness and images of the lithospheric discontinuities in the Gibraltar Arc and surrounding areas. Geophys. J. Int. 203, 1804-1820. https://doi.org/10.1093/gji/ggv390.

[43] Martínez Catalán, J.R., Rubio Pascual, F.J., Montes, A.D., Fernández, R.D., Barreiro, J.G., Dias Da Silva, I., Clavijo, E.G., Ayarza, P., Alcock, J.E., 2014. The late Variscan HT/LP metamorphic event in NW and Central Iberia: relationships to crustal thickening, extension, orocline development and crustal evolution. Geological Society, London, Special Publications 405, 225-247. https://doi.org/10.1144/sp405.1.

[44] Missenard, Y., Cadoux, A., 2011. Can moroccan Atlas lithospheric thinning and volcanism be induced by edge-driven convection? Terra Nova 24, 27-33. https://doi.org/10.1111/j.1365-3121.2011.01033.x.

[45] Mitas, L., Mitasova, H., 1999. Spatial interpolation. In: Longley P., Goodchild M., Maguire D., Rhind D. (Eds.), Geographical Information Systems: Principles, Techniques, Management and Applications. Wiley, pp. 481-492.

[46] Molina-Aguilera, A., Mancilla, F.d.L., Morales, J., Stich, D., Yuan, X., Heit, B., 2019. Connection between the Jurassic oceanic lithosphere of the Gulf of Cádiz and the Alboran slab imaged by Sp receiver functions. Geology 47, 227-230. https://doi.org/10.1130/g45654.1.

[47] Mouthereau, F., Filleaudeau, P.Y., Vacherat, A., Pik, R., Lacombe, O., Fellin, M.G., Castelltort, S., Christophoul, F., Masini, E., 2014. Placing limits to shortening evolution in the Pyrenees: Role of margin architecture and implications for the Iberia/Europe convergence: Plate convergence in the Pyrenees. Tectonics 33, 2283-2314. https://doi.org/10.1002/2014tc003663.

[48] Muñoz, J.A., 1992. Evolution of a Continental Collision Belt: ECORS-Pyrenees Crustal Balanced Cross-section. Springer, Netherlands, pp. 235-246. https://doi.org/10.1007/978-94-011-3066-0_21.

[49] Palomeras, I., Villaseñor, A., Thurner, S., Levander, A., Gallart, J., Harnafi, M., 2017. Lithospheric structure of Iberia and Morocco using finite-frequency Rayleigh wave tomography from earthquakes and seismic ambient noise. Geochem. Geophys. Geosyst. 18, 1824-1840. https://doi.org/10.1002/2016gc006657.

[50] Parera-Portell, J., Mancilla, F.d.L., Morales, J., Díaz, J., 2024. High-resolution mapping of the mantle transition zone and its interaction with subducted slabs in the Ibero-Maghrebian region. Earth Planet. Sci. Lett. 640, 118798. https://doi.org/10.1016/j.epsl.2024.118798.

[51] Pedrera, A., García-Senz, J., Pueyo, E.L., López-Mir, B., Silva-Casal, R., Díaz-Alvarado, J., 2023. Inhomogeneous rift inversion and the evolution of the Pyrenees. Earth Sci. Rev. 245, 104555. https://doi.org/10.1016/j.earscirev.2023.104555.

[52] Plomerová J., Babuška, V., 2010. Long memory of mantle lithosphere fabric — European LAB constrained from seismic anisotropy. Lithos 120, 131-143. https://doi.org/10.1016/j.lithos.2010.01.008.

[53] Quesada, C., Oliveira, J.T., 2019. The Geology of Iberia:A Geodynamic Approach. Springer International Publishing. https://doi.org/10.1007/978-3-030-11190-8.

[54] Roure, F., Choukroune, P., Berastegui, X., Munoz, J.A., Villien, A., Matheron, P., Bareyt, M., Seguret, M., Camara, P., Deramond, J., 1989. Ecors deep seismic data and balanced cross sections: Geometric constraints on the evolution of the Pyrenees. Tectonics 8, 41-50. https://doi.org/10.1029/tc008i001p00041.

[55] Royden, L., Faccenna, C., 2018. Subduction orogeny and the Late Cenozoic evolution of the Mediterranean arcs. Annu. Rev. Earth Planet. Sci. 46, 261-289. https://doi.org/10.1146/annurev-earth-060115-012419.

[56] Rychert, C.A., Harmon, N., Constable, S., Wang, S., 2020. The nature of the lithosphere-asthenosphere boundary. J. Geophys. Res. Solid Earth 125 (10), e2018JB016463. https://doi.org/10.1029/2018jb016463.

[57] Rychert, C.A., Shearer, P.M., 2009. A global view of the lithosphere-asthenosphere boundary. Science 324, 495-498. https://doi.org/10.1126/science.1169754.

[58] Santos-Bueno, N., Fernández-García, C., Stich, D., de Lis Mancilla, F., Martín, R., Molina-Aguilera, A., Morales, J., 2019. Focal mechanisms for subcrustal earthquakes beneath the gibraltar arc. Geophys. Res. Lett. 46, 2534-2543. https://doi.org/10.1029/2018gl081587.

[59] Schott, B., Schmeling, H., 1998. Delamination and detachment of a lithospheric root. Tectonophysics 296, 225-247. https://doi.org/10.1016/s0040-1951(98)00154-1.

[60] Sibson, R., 1981. A brief description of natural neighbor interpolation. In: Barnett V. (Ed.), Interpreting Multivariate Data. John Wiley & Sons, New York, pp. 21-36.

[61] Spakman, W., Wortel, R., 2004. A Tomographic View on Western Mediterranean Geodynamics. Springer, Berlin Heidelberg, pp. 31-52. https://doi.org/10.1007/978-3-642-18919-7_2.

[62] Spieker, K., Wölbern, I., Thomas, C., Harnafi, M., El Moudnib, L., 2014. Crustal and upper-mantle structure beneath the western Atlas Mountains in SW Morocco derived from receiver functions. Geophys. J. Int. 198, 1474-1485. https://doi.org/10.1093/gji/ggu216.

[63] Steinberger, B., Becker, T.W., 2018. A comparison of lithospheric thickness models. Tectonophysics 746, 325-338. https://doi.org/10.1016/j.tecto.2016.08.001.

[64] Stich, D., Serpelloni, E., Mancilla, F.d.L., Morales, J., 2006. Kinematics of the Iberia-Maghreb plate contact from seismic moment tensors and GPS observations. Tectonophysics 426, 295-317. https://doi.org/10.1016/j.tecto.2006.08.004.

[65] Sun, D., Miller, M.S., Holt, A.F., Becker, T.W., 2014. Hot upwelling conduit beneath the Atlas Mountains. Morocco. Geophys. Res. Lett. 41, 8037-8044. https://doi.org/10.1002/2014gl061884.

[66] Teixell, A., 1998. Crustal structure and orogenic material budget in the west central Pyrenees. Tectonics 17, 395-406. https://doi.org/10.1029/98tc00561.

[67] Teixell, A., Arboleya, M., Julivert, M., Charroud, M., 2003. Tectonic shortening and topography in the central High Atlas (Morocco). Tectonics 22 (5), 1051. https://doi.org/10.1029/2002tc001460.

[68] Torné M., Fernàndez, M., Vergés, J., Ayala, C., Salas, M.C., Jimenez-Munt, I., Buffett, G.G., Díaz, J., 2015. Crust and mantle lithospheric structure of the Iberian Peninsula deduced from potential field modeling and thermal analysis. Tectonophysics 663, 419-433. https://doi.org/10.1016/j.tecto.2015.06.003.

[69] Vergés, J., Fernàndez, M., 2006. Ranges and basins in the Iberian Peninsula: their contribution to the present topography. Geological Society, London, Memoirs 32, 223-234. https://doi.org/10.1144/gsl.mem.2006.032.01.13.

[70] Vinnik, L., 1977. Detection of waves converted from P to SV in the mantle. Phys. Earth Planet. Inter. 15, 39-45. https://doi.org/10.1016/0031-9201(77)90008-5.

[71] Wessel, P., Luis, J.F., Uieda, L., Scharroo, R., Wobbe, F., Smith, W.H.F., Tian, D., 2019. The generic mapping tools version 6. Geochem. Geophys. Geosyst. 20, 5556-5564. https://doi.org/10.1029/2019gc008515.

[72] Zhang, J.B., Liu, Y.S., Foley, S.F., Moynier, F., Zhao, L., Xu, R., Wang, C.Y., 2024. Widespread two-layered melt structure in the asthenosphere. Nat. Geosci. 17, 472-477. https://doi.org/10.1038/s41561-024-01433-1.

[73] Zhu, L., Kanamori, H., 2000. Moho depth variation in southern California from teleseismic receiver functions. J. Geophys. Res. Solid Earth 105, 2969-2980. https://doi.org/10.1029/1999jb900322.