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- Manaman, Navid Shad, et al.
(författare)
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Upper mantle S-velocity structure and Moho depth variations across Zagros belt, Arabian-Eurasian plate boundary
- 2010
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Ingår i: Physics of the Earth and Planetary Interiors. - : Elsevier BV. - 0031-9201 .- 1872-7395. ; 180:1-2, s. 92-103
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Tidskriftsartikel (refereegranskat)abstract
- The collision of the Arabian and Eurasian plates in the early Miocene, after the subduction of Neo-Tethys ocean beneath Eurasia, formed the Zagros belt, a seismically active continental-continental plate boundary in southwest Iran. The Zagros suture zone is an important seismotectonic boundary indicating an abrupt cutoff between the intense seismicity of the Zagros and the almost aseismic Central Iran plateau. Compared with other more evolved plate boundaries, little is known about the deep lithospheric structure of the Zagros belt, such as the fate of subducted Neo-Tethys plate and ambiguity in the presence of intermediate and deep earthquakes under the Zagros suture zone. In this study, we use the partitioned waveform inversion (PWI) method to image the upper mantle S-velocity structure and Moho depth variations across Zagros collisional zone. The resulting Moho depth along the profile shows the average Moho depth value of order of 40-45 km for most parts of the profile with abrupt crustal thickening in the middle of the profile up to about 65 km. As expected, the derived models show that the relatively old and cold Arabian plate has higher velocity at depth than the younger lithosphere farther north in Central Iran. A sharp and steep subcrustal boundary is found roughly coincident with the surficial expression of the Main Zagros Thrust (MZT), separating two different mantle domains. A high-velocity anomaly, possibly representing a fragment of subducted lithosphere, has been imaged beneath Central Iran at a depth between 350 and 600 km, which is quite similar to the case of Indo-Asian collision in Qinghai-Tibetan plateau. These observations as well as the sudden changes of shallow velocities along the cross-section with a sharp boundary under the Zagros suture zone support the idea that subducted oceanic lithosphere has broken-off under the region of maximum Moho depth. A relatively low velocity region beneath the Arabian plate is also imaged in our high resolution tomography model which is interpreted as an indication of lithospheric delamination within the Arabian lithosphere.
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| 2. |
- Shad Manaman, Navid, et al.
(författare)
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New constraints on upper-mantle S-velocity structure and crustal thickness of the Iranian plateau using partitioned waveform inversion
- 2011
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Ingår i: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 184:1, s. 247-267
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Tidskriftsartikel (refereegranskat)abstract
- The continental collision between the African and Eurasian plates resulted in a tectonically young and complex deformation in the Iranian plateau. The present-day Iranian plateau is characterized by diverse tectonic domains including the continental collisions (e.g. Zagros and Alborz) and the oceanic plate subduction (e.g. Makran). Partitioned waveform inversion method is used here to image the S-velocity structure of the upper-mantle and Moho-depth variations in the Iranian plateau. Of nearly 3000 waveforms originally selected for the analysis, we have fitted 974 waveforms from 101 events and 39 stations which result in 11 688 linear constraints on the upper-mantle S-velocity structure and Moho depth for the region.Our new seismic images show seismically faster upper mantle beneath the Zagros and the Arabian Plate compared to the Central Iran and Alborz. This high-velocity anomaly has descended beneath the Central Iran along the Main Zagros Thrust. Across the Zagros collision zone, the tomographic images show a slab stagnation in the transition zone (at about 410 km depth) in the form of a horizontal high-velocity zone which does not penetrate the deeper parts of the mantle. The lowest S-velocities are concentrated beneath the Central Iran and Alborz. According to our velocity models, a strong high-velocity anomaly is resolved beneath the trapped South Caspian Basin with clear indication of westward underthrusting beneath the Talesh and western Alborz. In Makran, southeast Iran, there is a clear evidence of subduction of oceanic crust of the Arabian plate beneath the Makran belt which is correlated with seismicity pattern across the Makran zone. Also, the inverted Moho map using a priori information of crustal thickness constraints shows the large crustal thickness beneath the Zagros suture zone (in some places to a maximum depth of 65 km) which indicates the influence of crustal thickening and shortening beneath Arabian-Eurasian Plate boundary. A significantly crustal thinning is observable across the South Caspian Basin compared to its margins.
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