3D S-velocity model of the lithosphere-asthenosphere system beneath the Bering Sea

The 3D S-velocity structure for the Bering Sea region is determined from dispersion analysis (Rayleigh waves), from which the most conspicuous features of the crust and upper mantle (from 0 to 400 km depth) will be revealed. In the depth range from 0 to 5 km, this model shows the distribution of the sedimentary basins present in the study area, in terms of S-velocity. For the Bering Shelf, the S-velocity values decrease southward, indicating the presence of deep sedimentary basins in the southern Bering Shelf. In the depth range from 5 to 30 km, the S-velocity model shows clearly the division of the Bering Sea basin in three sub-basins: the Aleutian Basin, the Bowers Basin and the Komandorsky Basin, produced by the Bowers Ridge and the Shirshov Ridge. In this model, the low S-velocity pattern determined for the Bering Shelf confirms that its crust is similar to a continental-type crust, no an oceanic crust. The Moho map determined in the present study, from the 3D S-velocity model, is the first Moho map calculated for the Bering Sea region. In this map, the crust beneath the Bering Shelf shows thicker thickness than a typical oceanic crust, from which is concluded that this crust must be considered as a transitional crustal structure. In the depth range from 30 to 100 km, the Aleutian Basin shows a pattern of high S-velocity that can be correlated with the origin of this basin, because this basin is considered as formed by the entrapment of a piece of Pacific plate. In the depth range from 45 to 60 km, the low S-velocity pattern shown for the eastern Aleutian arc is associated to the active arc volcanoes present in this region. From the S-velocity model, the asthenosphere beneath the study area is firstly determined from similar to 100 to similar to 180 km depth. For the depth range from 80 to 400 km, the high S-velocity pattern determined for the eastern Aleutian arc, allows the modeling (imaging) of the subducting Pacific slab, in terms of S-velocity. This pattern of high S-velocity is not visible beneath the western Aleutian arc, because the Pacific plate is not subducting beneath the Bering Sea in the western Aleutian arc.