pure and applied geophysics

, Volume 158, Issue 7, pp 1121–1163 | Cite as

Tomographic Imaging of Lg and Sn Propagation in the Middle East

  • E. Sandvol
  • K. Al-Damegh
  • A. Calvert
  • D. Seber
  • M. Barazangi
  • R. Mohamad
  • R. Gök
  • N. Türkelli
  • C. Gürbüz

Abstract

 — Observations based on relatively limited data recorded by sparsely distributed stations have indicated that regional seismic phase propagation (Lg and Sn) is very complex in the Middle East. Accurate characterization of regional seismic wave propagation in this region necessitates the use of a large number of seismic stations. We have compiled a large data set of regional and local seismograms recorded in the Middle East. This data set comprises approximately four years of data from national short-period networks in Turkey and Syria, data from temporary broadband arrays in Saudi Arabia and the Caspian Sea region, and data from GSN, MEDNET, and GEOFON stations in the Middle East. We have used this data set to decipher the character and pattern of regional seismic wave propagation. We have mapped zones of blockage as well as inefficient and efficient propagation for Lg, Pg, and Sn throughout the Middle East. Two tomographic techniques have been developed in order to objectively determine regions of lithospheric attenuation in the Middle East.¶We observe evidence of major increase in Lg attenuation, relative to Pg, across the Bitlis suture and the Zagros fold and thrust belt, corresponding to the boundary between the Arabian and Eurasian plates. We also observe a zone of inefficient Sn propagation along the Dead Sea fault system which coincides with low Pn velocities along most of the Dead Sea fault system and with previous observations of poor Sn propagation in western Jordan. Our observations indicate that in the northern portion of the Arabian plate (south of the Bitlis suture) there is also a zone of inefficient Sn propagation that would not have been predicted from prior measurements of relatively low Pn velocities. Mapped high attenuation of Sn correlates well with regions of Cenozoic and Holocene basaltic volcanism. These regions of uppermost mantle shear-wave attenuation most probably have anomously hot and possibly thin lithosphere.

Key words: Lg, Sn, wave propagation, Middle East, tectonics. 

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Copyright information

© Birkhäuser Verlag Basel, 2001

Authors and Affiliations

  • E. Sandvol
    • 1
  • K. Al-Damegh
    • 1
  • A. Calvert
    • 1
  • D. Seber
    • 1
  • M. Barazangi
    • 1
  • R. Mohamad
    • 2
  • R. Gök
    • 3
  • N. Türkelli
    • 3
  • C. Gürbüz
    • 3
  1. 1.Institute for the Study of the Continents, Snee Hall, Cornell University, Ithaca, New York 14853, USA.US
  2. 2.Syrian National Seismological Center, General Establishment of Geology and Mineral Resources, Damascus, Syria.SY
  3. 3.Department of Geophysics, Kandilli Observatory and Earthquake Research Institute, Bogaziçi University, Istanbul, Turkey.TR

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