基于背景噪声面波成像法研究土耳其中部岩石圈速度结构

The eastern part of Turkey is the compression deformation area caused by collision，while the western part is the extension deformation area of the Aegean Sea caused by subduction. As the transition between the two，the central part of Turkey has a very complex geological situation，volcanism，long-term subduction，continental collision and other tectonic history. Therefore，obtaining the reliable velocity structure of the lithosphere in this region is very important for understanding the plate state at the end of subduction，magmatism and other phenomena. In order to better understand the lithospheric velocity structure of this area，we study this region using ambient noise tomography based on the continuous noise data of 172 stations in the area （31°E−38.8°E，34.5°N−42.0°N）. After obtaining the empirical Green’s function through the cross-correlation，the fundamental Rayleigh wave dispersion curves in the period range of 5−80 s is obtained by using the frequency-Bessel transform method，and the dispersion curve of overtones is obtained in some subarray. Subsequently，3-D shear velocity structure from surface to 124 km is obtained by quasi-Newton iterative version based on Broyden-Fletcher-Goldfarb-Shanno correction. These results show that the lateral velocity in central Turkey changes sharply （the maximum variation can reach 400 m/s），which is closely related to the geological boundary and suture. The velocity in the Central Anatolian volcanic province （CAVP） and some Eastern Taurus mountains （ETM） is less than 4.3 km/s at 0−110 km，so we speculate that there are no lithospheric mantle in this area. The African oceanic lithosphere，which began to subduct from the Cyprus trench，subducted beneath the Central Taurus mountains （CTM） at a near vertical angle，showing obvious high-velocity characteristics. For low velocity zones related to upwelling asthenosphere materials widely exist in this area from 70 km to 100 km，the lithospheric wave velocity in most of the study areas is less than the global average shear wave velocity，and the lithosphere is thin and variable in thickness. In particular，we also find that there is an obvious low velocity zone at a depth of 13−23 km in the CTM and ETM，which may be related to the partial melting of strata caused by block fracture.