Melt in the mantle and seismic azimuthal anisotropy: evidence from Anatolia


VINNIK L., ORESHIN S., Erduran M.

GEOPHYSICAL JOURNAL INTERNATIONAL, cilt.205, ss.523-530, 2016 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 205 Konu: 1
  • Basım Tarihi: 2016
  • Doi Numarası: 10.1093/gji/ggw021
  • Dergi Adı: GEOPHYSICAL JOURNAL INTERNATIONAL
  • Sayfa Sayıları: ss.523-530

Özet

Observations of shear wave splitting in SKS seismic phase play a key role in the current efforts to understand kinematics and dynamics of mantle flow, but azimuthal anisotropy as a depth-localized phenomenon still is poorly known. Here we analyse stratification of seismic azimuthal anisotropy beneath central and northern Anatolia (a microplate within the Alpine belt) by inverting P-wave receiver functions jointly with shear wave splitting in SKS seismic phase. The analysis is based on recordings of stations of the North Anatolian Fault (NAF) passive seismic experiment. In the resulting model in a depth interval from 120 to 200 km fast direction of anisotropy is nearly parallel to the plate motion direction (similar to E-W), whilst a normal direction (close to S-N) is found in the low velocity zone (LVZ) between 60 and 90 km. Our preferred interpretation of these data suggests that the flow in upper mantle is nearly parallel to the Anatolian plate motion direction in the depth range from the LAB to 200 km, but in part of the LVZ fast direction of anisotropy is normal to the direction of shear in the mantle. This relation between anisotropy and shear is known from laboratory experiments with peridotite-type rock containing melt. A similar relation between anisotropy and flow in the LVZ is found in Fennoscandia. These findings may have far-reaching implications for interpreting mantle anisotropy elsewhere.