Crustal structure of Iraq from receiver functions and surface wave dispersion: implications for understanding the deformation history of the Arabian-Eurasian collision

Abstract

S U M M A R YWe report the crustal structure for two locations in Iraq estimated by joint inversion of P-wave receiver functions (RFs) and surface (Rayleigh) wave group velocity dispersion. RFs were computed from teleseismic recordings at two temporary broad-band seismic stations located in Mosul (MSL) in the Zagros Fold Belt and Baghdad (BHD) in the Mesopotamian Foredeep. Group velocity dispersion curves at the sites were derived from continental-scale tomography. The inversion results show that the crustal thicknesses are 39 km at MSL and 43 km at BHD. We observe a strong Ps Moho at BHD consistent with a sharp Moho discontinuity. However, at MSL we observe a weak Ps Moho suggesting a transitional Moho where crustal thickening is likely to be occurring in the deep crust. Both sites reveal low velocity surface layers consistent with sedimentary thickness of about 3 km at station MSL and 7 km at BHD and agreeing well with the previous reports. Ignoring the sediments, the crystalline crustal velocities and thicknesses are remarkably similar at both stations. The similarity of crustal structure suggests that the crust of the northeastern proto-Arabian Platform was uniform before subsidence and deposition of the sediments in the Cenozoic. If crystalline crustal structure is uniform across the northern Arabian Platform then crustal thickness variations in the Zagros Fold Belt and Thrust Zone should reveal the history of deformation and crustal shortening in the ArabianEurasian collision zone and not reflect pre-existing crustal thickness variations in the Arabian Plate.

Lithospheric mantle heterogeneities beneath the Zagros Mountains and the Iranian Plateau: a petrological-geophysical study

“…Our crustal model along transect A-A shows a crustal thickness of 42-43 km below the Arabian Foreland Basin, gradually increasing towards the Zagros Mountains. These values are similar to those proposed by Gök et al (2008) and Nasrabadi et al (2008). Maximum crustal thicknesses are obtained beneath the SSZ (55 km) and the Alborz Mountains (53 km) in good agreement with Paul et al (2010) and Nasrabadi et al (2008).…”

“…in the Alborz along A-A profile, in the UDMA and IZ along the B-B profile). In general, along both transects, our resulting Moho depth values are consistent with the results from Gök et al (2008), which found ∼42-45 km of crustal thickness in the Foreland Basin, from Gritto et al (2008), which calculated Moho depth values between 44 and 52 km in the NW Zagros, and from Radjaee et al (2010), which found ∼55 km below the Zagros Mountains and 53-58 km below the Alborz Mountains. Our values of Moho depth differ slightly from those proposed by Jimenez-Munt et al (2012), being 3-5 km higher along profile A-A (Fig.…”

“…A total of three heat flow sites were available in the study region located over 100 km far from the selected profiles and therefore, thus we are not considering surface heat flow as a constraint in our modelling. (Paul et al 2006(Paul et al , 2010Gök et al 2008;Gritto et al 2008;Nasrabadi et al 2008;Manaman et al 2011). A crustal root is identified below the Alborz (Nasrabadi et al 2008;Sodoudi et al 2009;Paul et al 2010;Radjaee et al 2010), with the crust-mantle boundary in a depth of 53-67 km.…”

“…During the last decade, many efforts have been devoted to unravelling the lithospheric structure and, particularly, in imaging the topography of the crust-mantle boundary (e.g. Paul et al 2006Paul et al , 2010Gök et al 2008;Gritto et al 2008;Sodoudi et al 2009;Manaman et al 2011; see also Jiménez-Munt et al 2012 for a thorough compilation on crustal thickness data).…”

Crustal structure beneath Kottamiya broadband station, northern Egypt, from analysis of teleseismic receiver functions

“…Amplitudes from phase conversions can be enhanced by deconvolving the vertical component, where P-waves dominate, from the radial component, where the SV-waves resulting from the conversions are prominent. Source and instrument effects are conveniently eliminated in the process (e.g., Gök et al, 2008). The deconvolution process is often performed by spectral division.…”