| Passive- and active-source seismological studies of northern Scotland and the South Caspian Basin indicate: (1) pervasive and laterally heterogeneous velocity discontinuities within the upper mantle influenced by the localized tectonic and thermal history of northwest Scotland, and (2) growth fault-bend folds overriding a regional ductile detachment zone at a depth of about 13 to 16 km in response to a component of right-lateral simple shear of the underlying crust between the South Caspian Basin and the central and western Caucasus.; Teleseismic earthquakes recorded by a small array of portable broadband stations and permanent short-period stations are used to ascertain the lateral extent of velocity discontinuities within the continental mantle lithosphere beneath Scotland. Radial receiver functions contain distinct P-to-S ( Ps) converted phases at about 3.1–3.2 s and at 4.5–5.2 s after the direct P-wave. These observations suggest that the upper mantle Ps phase originates from a high velocity and/or anisotropic layer within the upper mantle. At two stations, ORE and BACA, located along the northern shoreline of Scotland, these upper mantle phases can be correlated with the W-reflector, a bright, regionally extensive seismic reflector previously observed on marine deep seismic reflection and wide-angle refraction-reflection profiles. However, the variability in physical characteristics suggests the possibility that there may be multiple layered reflectors in the upper mantle beneath northern Scotland and revives debates on the regional and global significance of upper mantle layering.; Deep seismic reflection profiles acquired in the deepwater of the South Caspian Sea, offshore Azerbaijan image a thick sequence of sediments (19–22 km thick) that structurally have been deformed into relatively symmetrical folds. These structures are interpreted as fault-bend growth folds overriding a regional ductile detachment zone at a depth of about 13 to 16 km. The analysis of the geophysical data in comparison with well documented earthquake focal mechanisms, centroid depths, and GPS velocity field measurements suggest the possibility that the present-day pattern of deformation of the overlying sedimentary cover within the South Caspian Basin is a response to right lateral shear between the underlying crust of the South Caspian Basin and the central and western Caucasus. |
