2-D Surface Wave Tomography in the Northwest Part of the Iranian Plateau

In this study, we obtained two-dimensional tomography maps of the Rayleigh wave group velocity for the northwest part of the Iranian Plateau in order to investigate the structure of the crust and the uppermost mantle of NW Iran. To do this, the local earthquake data during the period 2006-2013, recorded by the 10 broadband stations of the Iranian seismic network (INSN) were used. After the preliminary correction, Rayleigh wave group velocity dispersion curves for each source-station path using the time-frequency analysis (FTAN) were estimated. Then, using a 2D-linear inversion procedure, the lateral variations in the group velocity distribution at different periods were calculated. The results are consistent with the previous studies and show major structural units in this region. Our results for the lower periods show distinct velocity anomalies along the North Tabriz Fault (NTF) and beneath the Sahand and Sabalan Volcanoes. Also, along the boundary of the Urumieh-Dokhtar Magmatic Arc (UDMA) and the Sanandaj-Sirjan metamorphic Zone (SSZ), lateral velocity changes are observed. The results for the longest period (the uppermost mantle) show low-velocity anomalies for most parts of the study area.