Publication Date:
2016-04-07
Description:
Application of the ambient noise surface wave tomography method (ANT) for determination of the upper-mantle structure requires data on long-periodic noise ( T 〉 40 s). The ANT technique implies that noise sources are distributed almost uniformly over the surface. This is practically true for short-periodic noise, however, it is not so in the case of long periods. In this paper we show that the main contribution to noise at long periods is caused by signals from earthquakes. In some cases, they may strongly distort noise cross-correlation. This leads to an incorrect determination of surface wave velocity dispersion curves. To minimize such a distortion we propose two means: (1) to use records of noise for the periods when there is no clustering of earthquakes, such as aftershocks of strong events; (2) to stack cross-correlation functions for a period of at least three years in order to achieve sufficient uniformity of earthquake locations. Validity of this approach is demonstrated by ANT results for Europe. Tomographic reconstruction of Rayleigh wave group velocities for 10–100 s measured along interstation paths was carried out in a central part of Western Europe where resolving power of the data was the highest. Locally averaged dispersion curves were inverted to vertical S -wave velocity sections in this area. The results correspond closely to known features of the structure of the region, namely: strong difference of the crust and upper-mantle structure at the opposite sides from the Tornquist–Teisseyre Line down to ~ 250 km, penetration of high-velocity material of East European Platform lithosphere under Carpathians, as well as penetration of low-velocity asthenospheric layer from the Carpathian region towards the northeast.
Keywords:
Seismology
Print ISSN:
0956-540X
Electronic ISSN:
1365-246X
Topics:
Geosciences
Published by
Oxford University Press
on behalf of
The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
