Arabian Journal of Geosciences

, Volume 6, Issue 6, pp 1717–1730 | Cite as

Seismic anisotropy structure beneath the southeastern Mediterranean from shear-wave splitting

  • Mohamed K. Salah
Original Paper


Analysis of seismic anisotropy in the crust and the uppermost mantle gives lots of information about the ambient mantle flow, stress state, and the dynamic processes inside the Earth. Thus, seismic anisotropy and its main distinctive features beneath the southeastern Mediterranean region are studied through the analysis of teleseismic shear-wave splitting observed at six broadband seismic stations belonging to the GEOFON and the MedNet. Although the number of the recording stations is small; a total of 495 splitting parameters are obtained, which revealed significant variations in the observed fast polarization directions beneath the study area. The stations in northern Egypt and Cyprus show fast velocity directions oriented roughly N–S to NNE–SSW, coincident with many previous results. A slightly different splitting pattern comprising NE–SW fast polarization directions is observed in the stations located along the Dead Sea fault in the southeastern Mediterranean; which are consistent with the current strike-slip motion between Africa and Arabia. In addition, NW–SE fast polarization directions are recognized in the latter group. The observed delay times vary greatly but their averages lie between 0.35 and 1 s. Although large-scale mechanisms, such as the absolute plate motion of Africa and Arabia towards Eurasia and the differential motion between Arabia and Africa can be invoked to predominantly explain the origin of anisotropic features, we suggest that density-driven flow in the asthenosphere is a possible additional cause of the wide range of the splitting pattern observed beneath some stations.


Shear-wave splitting Seismic anisotropy Mantle flow Southeastern Mediterranean Middle East 



The waveform data analyzed in this study are retrieved from the websites of the Observatories and Research Facilities for European Seismology (, and the Incorporated Research Institutions of Seismology (IRIS; Fruitful comments of two anonymous reviewers greatly improved the manuscript. Most figures in this paper are made using GMT (Generic Mapping Tools) software written by Wessel and Smith (1998).


  1. Akyuz HS, Altunel E, Karabacak V, Yalciner CC (2006) Historical earthquake activity of the northern part of the Dead Sea Fault Zone, southern Turkey. Tectonophysics 426:281–293CrossRefGoogle Scholar
  2. Al-Damegh K, Sandvol E, Al-Lazki A, Barazangi M (2004) Regional seismic wave propagation (Lg and Sn) and Pn attenuation in the Arabian plate and surrounding regions. Geophys J Int 157:775–795CrossRefGoogle Scholar
  3. Al-Lazki AI, Sandvol E, Seber D, Barazangi M, Turkelli N, Mohamad R (2004) Pn tomographic imaging of mantle lid velocity and anisotropy at the junction of the Arabian, Eurasian and African plates. Geophys J Int 158:1024–1040. doi: 10.1111/j.1365-246X.2004.02355x CrossRefGoogle Scholar
  4. Al-Tarazi E, Sandvol E, Gomez F (2006) The February 11, 2004 Dead Sea earthquake M L = 5.2 in Jordan and its tectonic implication. Tectonophysics 422:149–158CrossRefGoogle Scholar
  5. Badawy A (2001) Status of the crustal stress in Egypt as inferred from earthquake focal mechanisms and borehole breakouts. Tectonophysics 343:49–61CrossRefGoogle Scholar
  6. Badawy A (2005) Present-day seismicity, stress field and crustal deformation of Egypt. J Seismol 9:267–276CrossRefGoogle Scholar
  7. Badawy A, Horváth F (1999) Recent stress field of the Sinai sub-plate region. Tectonophysics 304:385–403CrossRefGoogle Scholar
  8. Baer G, Sandwell D, Williams S, Bock Y, 1999. Coseismic deformation associated with the November 1995, Mw = 7.1 Nuweiba earthquake, Gulf of Elat (Aqaba), detected by synthetic aperture radar interferometry. J Geophys Res 104 (25): 221–225Google Scholar
  9. Ben-Avraham Z, Ginzburg A, Makris J, Eppelbaum L (2002) Crustal structure of the Levant Basin, eastern Mediterranean. Tectonophysics 346:23–43CrossRefGoogle Scholar
  10. Ben-Menahem A (1979) Earthquake catalog for the Middle East (92BC–1980). Boll Geof Teor Appl 21:245–313Google Scholar
  11. Ben-Menahem A, Aboodi E (1981) Micro- and macroseismicity of the Dead Sea rift and off-coast eastern Mediterranean. In: R. Freund and Z. Garfunkel (Eds), The Dead Sea Rift. Tectonophysics 80:199–233CrossRefGoogle Scholar
  12. Cong L, Mitchell BJ (1998) Lg Coda Q and its relation to the geology and tectonics of the Middle East. Pure Appl Geophys 153:563–585CrossRefGoogle Scholar
  13. Crampin S (1977) Seismic anisotropy: a summary. J Geophys Z Geophys 43:499–501Google Scholar
  14. Dercourt J, Ricou LE, Vrielynck B (eds) (1993) Atlas Tethys Palaeoenvironmental Maps, pp 307, 14 maps, 1 pl. Gauthiers-Villars, ParisGoogle Scholar
  15. Eckstein Y, Simmons G (1978) Measurement and interpretation of terrestrial heat flow in Israel. Geothermics 6:117–142CrossRefGoogle Scholar
  16. Freund R (1970) The geometry of faulting in the Galilee. Isr J Earth Sci 19:117–140Google Scholar
  17. Fukao Y (1984) Evidence from core-reflected shear waves for anisotropy in the Earth’s mantle. Nature 309:695–698CrossRefGoogle Scholar
  18. Gashawbeza E, Klemperer S, Nyblade A, Walker K, Keranen K (2004) Shear-wave splitting in Ethiopia: Precambrian mantle anisotropy locally modified by Neogene rifting. Geophys Res Lett 31. doi: 10.1029/2004GL020471
  19. Gripp A, Gordon R (2002) Young tracks of hotspots and current plate velocities. Geophys J Int 150:321–361CrossRefGoogle Scholar
  20. Hadiouche O, Zürn W (1992) On the structure of the crust and upper mantle beneath the Afro-Arabian region from surface wave dispersion. In: C. J. Ebinger, H. K. Gupta and I. O. Nyambok (Eds.), Seismology and related sciences in Africa. Tectonophysics 209:179–196CrossRefGoogle Scholar
  21. Hansen SE, Schwartz SY, Al-Amri AMS, Rodgers AJ (2006) Combined plate-motion and density-driven flow in the asthenosphere beneath Saudi Arabia: evidence from shear-wave splitting and seismic anisotropy. Geology 34:869–872. doi: 10.1130/G22713.1 CrossRefGoogle Scholar
  22. Hansen SE, Rodgers AJ, Schwartz SY, Al-Amri AMS (2007) Imaging ruptured lithosphere beneath the Red Sea and Arabian Peninsula. Earth Planet Sci Lett 259:256–265. doi: 10.1016/j.epsl.2007.04.035 CrossRefGoogle Scholar
  23. Heintz M, Vauchez A, Assumpção BG, Egydio-Silva M (2003) Shear-wave splitting in SE Brazil: an effect of active or fossil upper mantle flow, or both? Earth Planet Sci Lett 211:79–95. doi: 10.1016/S0012-821X(03)00163-8 CrossRefGoogle Scholar
  24. Hiramatsu Y, Ando M (1996) Seismic anisotropy near source region in subduction zones around Japan. Phys Earth Planet Inter 95:237–250CrossRefGoogle Scholar
  25. Hyndman RD, Peacock SM (2003) Serpentinization of the forearc mantle. Earth Planet Sci Lett 212:417–432CrossRefGoogle Scholar
  26. Joffe S, Garfunkel Z (1987) Plate kinematics of the circum Red Sea—a re-evaluation. Tectonophysics 141:5–22CrossRefGoogle Scholar
  27. Kearey P, Vine FJ (2004) Global tectonics, 2nd ed, pp. 19–28, ed. Blackwell: Oxford, UKGoogle Scholar
  28. Kennett BLN, Engdahl ER (1991) Travel times for global earthquake location and phase identification. Geophys J Int 105:429–465CrossRefGoogle Scholar
  29. Klinger Y, Avouac JP, Abou-Karaki N, Dorbath L, Bourles D, Reyss JL (2000) Slip rate on the Dead Sea transform fault in northern Araba Valley (Jordan). Geophys J Int 142:755–768CrossRefGoogle Scholar
  30. Koulakov I, Sobolev SV, Weber M, Oreshin S, Wylegalla K, Hofstetter R (2006) Teleseismic tomography reveals no signature of the Dead Sea Transform in the upper mantle structure. Earth Planet Sci Lett 252:189–200. doi: 10.1016/j.epsl.2006.09.039 CrossRefGoogle Scholar
  31. Le Pichon X, Bergerat F, Roulet MJ (1988) Plate kinematics and tectonics leading to the Albine belt formation: a new analysis. Spec Pap Geol Soc Am 218:111–131CrossRefGoogle Scholar
  32. Levin V, Park J (2000) Shear zones in the Proterozoic lithosphere of the Arabian Shield and the nature of the Hales discontinuity. Tectonophysics 323:131–148. doi: 10.1016/ S0040-1951(00)00105-0 CrossRefGoogle Scholar
  33. Levin V, Park J, Brandon MT, Menke W (2000) Thinning of the upper mantle during the late Paleozoic Appalachian orogenesis. Geology 28:239–242CrossRefGoogle Scholar
  34. Levin V, Henza A, Park J, Rodgers A (2006) Texture of mantle lithosphere along the Dead Sea Rift: recently imposed or inherited? Phys Earth Planet Inter 158:174–189. doi: 10.1016/j.pepi.2006.05.007 CrossRefGoogle Scholar
  35. Long MD, van der Hilst RD (2005) Upper mantle anisotropy beneath Japan from shear wave splitting. Phys Earth Planet Inter 151:206–222CrossRefGoogle Scholar
  36. Luccio FD, Pasyanos ME (2007) Crustal and upper mantle structure in the eastern Mediterranean from the analysis of surface wave dispersion curves. Geophys J Int 169:1139–1152. doi: 10.1111/j.1365-246X.2007.03332.x CrossRefGoogle Scholar
  37. Mainprice D, Silver P (1993) Interpretation of SKS-waves using samples from the subcontinental lithosphere. Phys Earth Planet Inter 78:257–280. doi: 10.1016/0031-9201(93)90160-B CrossRefGoogle Scholar
  38. McClusky S, Balassanian S, Barka A, Demir C, Ergintav S, Georgiev I, Gurkan O, Hamburger M, Hurst K, Kahle H, Kastens K, Kekelidze G, King R, Kotzev V, Lenk O, Mahmoud S, Mishin A, Nadariya M, Ouzounis A, Paradissis D, Peter Y, Prilepin M, Reilinger R, Sanli I, Seeger H, Tealeb A, Toksöz MN, Veis G (2000) Global positioning system constrains on plate kinematics and dynamics in the eastern Mediterranean and Caucasus. J Geophys Res 105:5695–5719Google Scholar
  39. McClusky S, Reilinger R, Mahmoud S, Ben Sari D, Tealeb A (2003) GPS constraints of Africa (Nubia) and Arabia plate motions. Geophys J Int 155:126–138CrossRefGoogle Scholar
  40. McKenzie DP (1970) Plate tectonics of the Mediterranean region. Nature 220:239–343CrossRefGoogle Scholar
  41. McKenzie DP (1972) Active tectonics of the Mediterranean region. Geophys J R Astron Soc 30:109–185CrossRefGoogle Scholar
  42. McKenzie DP, Davies D, Molnar P (1970) Plate tectonics of the Red Sea and East Africa. Nature 26:243–248CrossRefGoogle Scholar
  43. Meade C, Silver PG, Kaneshima S (1995) Laboratory and seismological observations of lower mantle isotropy. Geophys Res Lett 22:1293–1296CrossRefGoogle Scholar
  44. Meijer PT, Wortel MJR (1999) Cenozoic dynamics of the African plate with emphasis on the Africa–Eurasia collision. J Geophys Res 104:7405–7418CrossRefGoogle Scholar
  45. Nakajima J, Hasegawa A (2004) Shear wave polarization anisotropy and subduction-induced flow in the mantle wedge of northern Japan. Earth Planet Sci Lett 225:365–377CrossRefGoogle Scholar
  46. Niu F, Perez AM (2004) Seismic anisotropy in the lower mantle: a comparison of waveform splitting of SKS and SKKS. Geophys Res Lett 31:L24612. doi: 10.1029/2004GL021196 CrossRefGoogle Scholar
  47. Okada T, Matsuzawa T, Hasegawa A (1995) Shear wave polarization anisotropy beneath the northeastern part of Honshu. Japan Geophys J Int 123:781–797CrossRefGoogle Scholar
  48. Papadimitriou EE, Karakostas VG (2006) Earthquake generation in Cyprus revealed by the evolving stress field. Tectonophysics 423:61–72. doi: 10.1016/j.tecto.2006.03.014 CrossRefGoogle Scholar
  49. Payo G (1969) Crustal structure of the Mediterranean Sea, part II: phase velocity and travel times. Bull Seismol Soc Am 59:23–42Google Scholar
  50. Pe’eri S, Wdowniski S, Shtibelman A, Bechor N, Bock Y, Nikolaidis R, van Domselaar M (2002) Current plate motion across the Dead Sea fault from three years of continuous GPS monitoring. Geophys Res Lett 29:1697. doi: 10.1029/2001GL013879 CrossRefGoogle Scholar
  51. Piromallo C, Morelli A (2003) P-wave tomography of the mantle under the Alpine–Mediterranean area. J Geophys Res 108:2065. doi: 10.1029/2002JB001757 CrossRefGoogle Scholar
  52. Reches Z, Hoexter DF (1981) Holocene seismic and tectonic activity in the Dead Sea area. Tectonophysics 80:235–254CrossRefGoogle Scholar
  53. Reilinger R, McClusky S, Oral M, King R, Toksoz M, Barka A, Kinik I, Lenk O, Sanli I (1997) Global positioning system measurements of present-day crustal movements in the Arabia–Africa–Eurasia plate collision zone. J Geophys Res 102:9983–10000CrossRefGoogle Scholar
  54. Reilinger et al (2006) GPS constraints on continental deformation in the Africa–Arabia–Eurasia continental collision zone and implications for the dynamics of plate interactions. J Geophys Res 111:B05411. doi: 10.1029/2005JB004051 CrossRefGoogle Scholar
  55. Robertson AHF (1998) Tectonic significance of the Eratosthenes Seamount: a continental fragment in the process of collision with subduction zone in the eastern Mediterranean (Ocean Drilling Program Leg 160). Tectonophysics 298:63–82CrossRefGoogle Scholar
  56. Rodgers AJ, Ni JF, Hearn TM (1997) Propagation characteristics of short-period Sn and Lg in the Middle East. Bull Seismol Soc Am 87:396–413Google Scholar
  57. Ron H, Freund R, Garfunkel Z, Nur A (1984) Block rotation by strike slip faulting: structural and paleomagnetic evidence. J Geophys Res 89:6256–6270CrossRefGoogle Scholar
  58. Ruempker G, Ryberg T, Bock G, the DESERT Seismology Group (2003) Boundary-layer mantle flow under the Dead Sea transform fault inferred from seismic anisotropy. Nature 425:497–501CrossRefGoogle Scholar
  59. Ryberg T, Rumpker G, Haberland C, Stromeyer D, Weber M (2005) Simultaneous inversion of shear-wave splitting observations from seismic arrays. J Geophys Res 110. doi: 10.1029/2004JB003303
  60. Salah MK, Seno T, Iidaka T (2008) Upper mantle anisotropy beneath central and southwest Japan: an insight into subduction-induced mantle flow. J Geodyn 46:21–37. doi: 10.1016/j.jog.2008.04.002 CrossRefGoogle Scholar
  61. Sandvol E, Al-Damegh K, Calvert A, Seber D, Barazangi M, Mohamad R, Gök R, Türkelli N, Gürbüz C (2001) Tomographic imaging of Lg and Sn propagation in the Middle East. Pure Appl Geophys 158:1121–1163CrossRefGoogle Scholar
  62. Savage MK (1999) Seismic anisotropy and mantle deformation: what have we learned from shear-wave splitting? Rev Geophys 37:65–106CrossRefGoogle Scholar
  63. Schmid C, van der Lee S, Giardini D (2004) Delay times and shear-wave splitting in the Mediterranean region. Geophys J Int 159:275–290. doi: 10.1111/j.1365-246X.2004.02381.x CrossRefGoogle Scholar
  64. Schmid C, van der Lee S, VanDecar JC, Engdahl ER, Giardini D (2008) Three-dimensional S velocity of the mantle in the Africa-Eurasia plate boundary region from phase arrival times and regional waveforms. J Geophys Res 113:B03306. doi: 10.1029/2005JB004193 CrossRefGoogle Scholar
  65. Schwartz SY, Rodgers A (2003) Seismic anisotropy beneath the Red Sea Rift zone, IGPP-LLNL Technical Report, UCRP #03-GS-001Google Scholar
  66. Sella G, Dixon T, Mao A (2002) REVEL: a model for recent plate velocities from space geodesy. J Geophys Res 107. doi: 10.1029/2000JB000033
  67. Silver PG (1996) Seismic anisotropy beneath the continents: probing the depths of geology. Annu Rev Earth Planet Sci 24:385–432CrossRefGoogle Scholar
  68. Silver PG, Chan WW (1991) Shear wave splitting and subcontinental mantle deformation. J Geophys Res 96:16429–16454CrossRefGoogle Scholar
  69. Steckler MS, Feinstein S, Kohn BP, Lavier LL, Eyal M (1998) Pattern of mantle thinning from subsidence and heat flow measurements in the Gulf of Suez: evidence for the rotation of Sinai and along-strike flow from the Red Sea. Tectonics 17:903–920CrossRefGoogle Scholar
  70. van Eck T, Hofstetter A (1990) Fault geometry and spatial clustering of microearthquakes along the Dead Sea–Jordan rift fault zone. Tectonophysics 180:15–27CrossRefGoogle Scholar
  71. Vinnik L, Makeyeva L, Milev A, Usenko A (1992) Global patterns of azimuthal anisotropy and deformations in the continental mantle. Geophys J Int 111:433–447CrossRefGoogle Scholar
  72. Voggenreiter W, Hötzl H, Jado A (1988) Red Sea related history of extension and magmatism in the Jizan area (southwest Saudi Arabia): indication for simple shear during Red Sea rifting. Geol Rundsch 77:257–274. doi: 10.1007/BF01848688 CrossRefGoogle Scholar
  73. Walker K, Nyblade A, Klemperer S, Bokelmann G, Owens T (2004) On the relationship between extension and anisotropy: constraints from shear-wave splitting across the East African Plateau. J Geophys Res 109. doi: 10.1029/2003JB002866
  74. Wdowinski S, Ben-Avraham Z, Arvidsson R, Ekström G (2006) Seismotectonics of the Cyprian arc. Geophys J Int 164:176–181. doi: 10.1111/j.1365-246X.2005.02737.x CrossRefGoogle Scholar
  75. Wernicke B (1985) Uniform-sense normal simple shear of the continental lithosphere. Canad J Earth Sci 22:108–125CrossRefGoogle Scholar
  76. Wessel P, Smith WHF (1998) New improved version of Generic Mapping Tools released. EOS Trans Am Geophys Un 79:579CrossRefGoogle Scholar
  77. Wolfe C, Vernon F, Al-Amri AMS (1999) Shear-wave splitting across western Saudi Arabia: the pattern of upper mantle anisotropy at a Proterozoic shield. Geophys Res Lett 26:779–782CrossRefGoogle Scholar
  78. Woodside JM, Mascle J, Zitter TAC, Limonov AF, Ergun M, Volkonskaia A (2002) Shipboard scientists of the PRISMED II Expedition, The Florence Rise, the western bend of the Cyprus Arc. Mar Geol 185:177–194CrossRefGoogle Scholar

Copyright information

© Saudi Society for Geosciences 2011

Authors and Affiliations

  1. 1.Geology Department, Faculty of ScienceTanta UniversityTantaEgypt

Personalised recommendations