Seismic attenuation tomography of the Sn phase beneath the Turkish-Iranian Plateau and the Zagros mountain belt

Abstract

The Turkish-Iranian Plateau and the Zagros highlands are among the most prominent physiographic features in the Middle East and were formed as a result of continental collision between the Arabian and Eurasian plates. To better understand the nature of the lithospheric mantle and the origin of the observed seismic anomalies in this region, we investigated seismic attenuation of the uppermost mantle by detailed measurements of the quality factor of the Sn seismic phase (Sn Q). To that end, we collected a large data set consisting of 30 years (1990–2020) of waveforms recorded by 1266 permanent and temporary seismic stations, applying both the two-station method (TSM) and reverse two-station method (RTM) to measure path-averaged Sn Q. Finally, we performed a tomographic inversion on the path-averaged Sn Q to map the lateral variations of the upper-mantle attenuation across the northern Middle East. Our Sn attenuation maps show moderately low Q (<250) values beneath the Turkish-Iranian Plateau and high Q values (>350) beneath the Zagros and northern edge of the Arabian plate. Furthermore, our Sn Q model is broadly consistent with seismic velocity models in the region suggesting that most of the seismic anomalies are the result of thermal rather than compositional effects.

Segmented Up‐Bending of the Arabian Continental Plate Revealed by Pn Attenuation Tomography

“…Some strong attenuation anomalies can be simultaneously observed in both the uppermost mantle and crust. For example, two anomalies with crustal low‐ Q Lg and uppermost mantle low‐ Q Pn values are revealed beneath the northwestern and southeastern UDMA (L1 and L2 in Figures 7c and 7d), suggesting upwellings from the uppermost mantle to the crust, which is consistent with previous velocity and attenuation tomographic images (e.g., Amini et al., 2012; Hearn, 2022; Kaviani et al., 2022; Pei et al., 2011). Additionally, the Lut magmatic belt with low‐ Q Lg and low‐ Q Pn values suggests magmatic accumulations in the crust and uppermost mantle (see Section 4.2 for detailed discussion).…”

“…Hearn's results are consistent with ours. Previous P-and S-wave attenuation images in the upper mantle also show a high-Q anomaly beneath the Zagros orogen and a low-Q anomaly north of the Main Zagros Thrust (Kaviani et al, 2022;Pasyanos et al, 2021). Seismic velocity tomography can reveal the temperature, melting distribution and rock composition of deep structures and has been widely applied in and around the Iranian Plateau (e.g., Alinaghi et al, 2007;Al-Lazki et al, 2004Amini et al, 2012;Lü et al, 2012Lü et al, , 2017Mahmoodabadi et al, 2019;Pei et al, 2011) (Al-Lazki et al, 2014;Amini et al, 2012;Lü et al, 2012Lü et al, , 2017Pei et al, 2011).…”

Segmented up-bending of the Arabian continental plate revealed by Pn attenuation tomography

“…Some strong attenuation anomalies can be simultaneously observed in both the uppermost mantle and crust. For example, two anomalies with crustal low-𝑄 and uppermost mantle low-𝑄 values are revealed beneath the northwestern and southeastern UDMA (L1 and L2 in Figures 2c and 2d), suggesting upwellings from the uppermost mantle to the crust, which is consistent with previous velocity and attenuation tomographic images (e.g., Amini et al, 2012;Hearn, 2022;Kaviani et al, 2022;Pei et al, 2011).…”

High‐Resolution Broadband Lg Attenuation Structure of the Anatolian Crust and Its Implications for Mantle Upwelling and Plateau Uplift

“…High conductivity zones obtained based on magnetotelluric data revealed the locally fluid‐rich EAP (Hacıoğlu et al., 2018; Türkoğlu et al., 2008). Additionally, low S‐wave velocities in the uppermost mantle (Gök et al., 2007), low Pn‐wave velocities (Lü et al., 2017; Mutlu & Karabulut, 2011), and strong Sn attenuation (Al‐Damegh et al., 2004; Gök et al., 2003; Kaviani et al., 2022) reflect an anomalously hot and partially molten uppermost mantle in the EAP. Upwelling of the sublithospheric mantle may have significantly reworked the EAP, causing thermal weakening and partial melting in the crust, thus strongly attenuating the wave propagation.…”