Dogan Seber

Geodynamic evolution of the lithosphere and upper mantle beneath the Alboran region of the western Mediterranean: Constraints from travel time tomography

An edited version of this paper was published by the American Geophysical Union. Copyright 2000, AGU. See also: http://www.agu.org/pubs/crossref/2000/2000JB900024.shtml; http://atlas.geo.cornell.edu/morocco/publications/calvert2000.htm

The crustal structure of the East Anatolian plateau (Turkey) from receiver functions

An edited version of this paper was published by the American Geophysical Union (AGU). Copyright 2003, AGU. See also: http://www.agu.org/pubs/crossref/2003.../2003GL018192.shtml; http://atlas.geo.cornell.edu/turkey/publications/Zor-et-al_2003.htm

Grid search modeling of receiver functions: Implications for crustal structure in the Middle East and North Africa

An edited version of this paper was published by the American Geophysical Union (AGU). Copyright 1998, AGU. See also: http://www.agu.org/pubs/crossref/1996/95JB03112.shtml; http://atlas.geo.cornell.edu/MiddleEastNorthAfrica/publications/Sandvol1998.htm

Tomographic Pn velocity and anisotropy structure beneath the Anatolian plateau (eastern Turkey) and the surrounding regions

An edited version of this paper was published by the American Geophysical Union (AGU). Copyright 2003, AGU. See also: http://www.agu.org/pubs/crossref/2003.../2003GL017391.shtml; http://atlas.geo.cornell.edu/turkey/publications/Al-Lazki-et-al_2003.htm

Sn attenuation in the Anatolian and Iranian plateau and surrounding regions

An edited version of this paper was published in Geophysical Research Letters by the American Geophysical Union (AGU). Copyright 2003, AGU. See also: http://www.agu.org/pubs/crossref/2003/2003GL018020.shtml; http://atlas.geo.cornell.edu/turkey/publications/Gok-et-al_2003.htm

Three-dimensional upper mantle structure beneath the intraplate Atlas and interplate Rif mountains of Morocco

We integrate observations based on teleseismic P wave travel times and available geologic data to infer that the lithosphere beneath the intraplate Atlas mountains is thin and/or it is characterized by lower P wave velocities, while beneath the interplate Rif mountains and the adjacent Alboran Sea a previously thickened lithosphere has been delaminated into the upper mantle. Using surface geology and geochronology data, previous studies have proposed that lithospheric delamination took place in this region. In this study we show through analysis of teleseismic P wave residuals the existence of a high-velocity (>3%) upper mantle body, which is interpreted to be the delaminated, rigid lithosphere. This high-velocity layer is overlain by a very low velocity uppermost mantle material (Pn velocities of about 7.6–7.7 km s−1) interpreted to be asthenospheric material replacing the delaminated lithosphere. Teleseismic P waves recorded by a recently installed digital seismic network and an older analog network in Morocco provide the residuals database. A total of 734 P wave residuals from 92 selected teleseismic earthquakes are used to document the spatial pattern of upper mantle velocity structure beneath northern Morocco and the Alboran Sea. Subsequent use of these residuals in a tomographic inversion scheme produced a three-dimensional velocity image of the upper mantle. We infer from the P residuals that strong upper mantle velocity anomalies exist beneath both the Rif and Atlas regions. The Rif stations show negative residuals (∼1–1.5 s) for ray paths from the east and northeast and show positive residuals (∼1–1.5 s) for ray paths from the northwest and southwest. Tomographic results indicate the existence of a high-velocity body (∼3% higher velocities) in the upper mantle beneath the eastern Rif and Alboran Sea, extending approximately from subcrustal depths down to a depth of at least 350 km. In the western Rif, however, 1–2% lower velocity material is imaged in the upper mantle. The residuals of the Atlas stations also show azimuthal variations. In general, most of the P waves that travel beneath the High and Middle Atlas have about 0.5–1.0 s delays. In contrast, the rays that travel beneath the northwestern margin of the Atlas mountains and the adjacent Moroccan Meseta area show negative residuals (∼1 s), suggesting that higher velocity material exists beneath the platform area adjacent to the Atlas mountains. Tomographic results indicate that beneath most of the Atlas system the uppermost mantle has about 1% lower velocities. Beneath the Alboran Sea region, however, reported low uppermost mantle Pn velocities contrast strongly with higher velocity upper mantle velocities obtained by our analysis. Low-velocity uppermost mantle beneath the Alboran Sea underlain by a high-velocity upper mantle material is used to support earlier interpretations of lithospheric delamination beneath the Rif and Alboran Sea regions. The enigmatic occurrence of subcrustal earthquakes in these regions is also consistent with this active delamination mechanism.

Tomographic imaging of Lg and Sn propagation in the Middle east

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.

Lithospheric seismic velocity discontinuities beneath the Arabian Shield

We determined crustal and lithospheric mantle velocity structure beneath the Arabian Shield through the modeling of receiver function stacks obtained from teleseismic P waves recorded by the 9 station temporary broadband array in western Saudi Arabia. The receiver function deconvolution technique was used to isolate the receiver-side PS mode conversions. A grid search method, which should yield an unbiased global minimum, was used to solve for a shear wave velocity model that is optimal and has the minimum number of layers needed to fit the receiver function waveform. Results from this analysis show that the crustal thickness in the shield area varies from 35 to 40 km in the west, adjacent to the Red Sea, to 45 km in central Arabia. Stability tests of each solution indicate that the models are relatively well constrained. We have also observed evidence for a large positive velocity contrast at sub-Moho depths at four stations at depths of 80 to 100 km. This discontinuity may represent a change in rheology in the lower part of the lithosphere or remnant structure from the formation of the Arabian Shield.

Regional wave propagation in Turkey and surrounding regions

This paper was published by the American Geophysical Union (AGU). Copyright 2000, AGU. See also: http://www.agu.org/journals/gl/gl0003/1999GL008375/pdf/1999GL008375.pdf; http://atlas.geo.cornell.edu/turkey/publications/Gok-et-al_2000.htm

Shear wave splitting in a young continent‐continent collision: An example from Eastern Turkey

An edited version of this paper was published by the American Geophysical Union (AGU). Copyright 2003, AGU. See also: http://www.agu.org/pubs/crossref/2003.../2003GL017390.shtml; http://atlas.geo.cornell.edu/turkey/publications/Sandvol-et-al_2003b.htm