Pn -velocity structure beneath Arabia–Eurasia Zagros collision and Makran subduction zones

Abstract

We use Pn-tomography to map lithospheric mantle velocity and anisotropy at the Arabia–Eurasia plate boundary, namely Makran and Zagros. We use catalogue events recorded by Oman, UAE, Saudi Arabia and Iran networks, the International Seismological Centre and the National Earthquake Information Center. Events of 1.8–16 degree distances were used for this Pn-tomography. In this study we show that the northeastern Arabia plate is characterized by cold and stable lithospheric mantle. Contrastingly, Eurasia is underlain by hot unstable lithospheric mantle. The Arabia–Eurasia lithospheric suture follows the Zagros collision surface suture within c. 70 km lateral proximity. At the southernmost Zagros collision, the Arabia lithosphere is inferred to extend further NE beneath Lut Block. This may be indicative of extended subduction of Arabia beneath Eurasia in southernmost Zagros. We find that eastern Makran shows typical subduction characteristics, with inferred oceanic lithosphere underlying the eastern Oman Sea and hot unstable lithospheric mantle below overriding Helmand Block. Contrastingly, the western Makran subduction zone including Arabia and Eurasia continental sides is underlain by a low-Pn-velocity anomaly, indicative of hot unstable lithospheric mantle. Surface evidence show that western, southern and eastern boundaries of western Makran low-Pn-velocity anomaly may represent a Late Neogene reactivated Precambrian terrane boundary in north Oman.

Non‐linear stochastic inversion of gravity data via quantum‐behaved particle swarm optimisation: application to Eurasia–Arabia collision zone (Zagros, Iran)

“…Recent Pn‐tomography by Al‐Lazki et al . () suggested that the Arabian foreland is underlain by a cold and stable lithosphere, whereas the Eurasian plate has a hot and unstable lithosphere. Based on the calculation of vertical integral of the lithospheric strength by Motavalli‐Anbaran et al .…”

“…; Hafkenscheid, Wortel and Spakman ; Al‐Lazki et al . ). The Zagros is composed of three almost parallel tectonic settings in NW‐SE direction, namely Zagros Fold and Thrust Belt (ZFTB), Sanandaj‐Sirjan Zone (SSZ), and Urumieh–Dokhtar Magmatic Assemblage (UDMA) (Alavi ; Berberian ; and references therein), of which ZFTB is located on the Arabian part of the collision zone and the rest are on the Eurasian part.…”

Seismic Anisotropy and Its Geodynamic Implications in Iran, the Easternmost Part of the Tethyan Belt

“…Such a transition between different deformation regimes may give rise to deviation of the lithospheric splittings from the observable belt‐parallel trend and even cause the domination of plate motion‐parallel fast axis orientations originating from the asthenospheric flow filed in eastern Zagros. The variation of lithospheric anisotropy along the Zagros inferred from Pn anisotropy (Al‐Lazki et al, ; Lü et al, , ) provides an important clue to the predicted non‐belt‐parallel lithospheric anisotropy in the eastern Zagros.…”

Constraints from GPS measurements on the dynamics of the zone of convergence between Arabia and Eurasia

“…The presence of widespread volcanism across the Turkish‐Iranian Plateau suggests, however, that there may be significant lateral variation in the density of the mantle beneath the region, and evidence from seismic receiver functions and surface wave tomography also indicate that the elevation of the plateau is partly supported by relatively low‐density lithospheric mantle [ Al‐Lazki et al , , , ; Alinaghi et al , ; Amini et al , ; Innocenti et al , ; Kaviani et al , ; Maggi and Priestley , ; Mutlu and Karabulut , ; engör et al , ; Zor et al , ]. We therefore also estimate differences in GPE from differences in geoid height Δ N …”

“…In contrast, seismic wave speeds in the upper mantle are lower beneath the plateaux of central and northwestern Iran than beneath surrounding regions, suggesting that these regions are underlain by hot, weak uppermost mantle and may therefore be intrinsically weaker than their surroundings. Wave speeds below the Zagros Mountains are higher, suggesting that this region may have stronger upper mantle [e.g., Al‐Lazki et al , , , ; Alinaghi et al , ; Amini et al , ; Kaviani et al , ; Maggi and Priestley , ; Mutlu and Karabulut , ; Priestley et al , ].…”