Publication Date:
2021-12-24
Description:
This article has been accepted for publication in Geophysical Journal International ©: The Authors 2021. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
Description:
Ambient-noise records from the AlpArray network are used to measure Rayleigh wave
phase velocities between more than 150,000 station pairs. From these, azimuthally anisotropic
phase-velocity maps are obtained by applying the Eikonal tomography method. Several
synthetic tests are shown to study the bias in the Ψ2 anisotropy. There are two main
groups of bias, the first one caused by interference between refracted/reflected waves and
the appearance of secondary wavefronts that affect the phase travel-time measurements.
This bias can be reduced if the amplitude field can be estimated correctly. Another source
of error is related to the incomplete reconstruction of the travel-time field that is only
sparsely sampled due to the receiver locations. Both types of bias scale with the magnitude of the velocity heterogeneities. Most affected by the spurious Ψ2 anisotropy are areas
inside and at the border of low-velocity zones. In the isotropic velocity distribution, most
of the bias cancels out if the azimuthal coverage is good. Despite the lack of resolution
in many parts of the surveyed area, we identify a number of anisotropic structures that
are robust: in the central Alps, we find a layered anisotropic structure, arc-parallel at midcrustal depths and arc-perpendicular in the lower crust. In contrast, in the eastern Alps,
the pattern is more consistently E-W oriented which we relate to the eastward extrusion.
The northern Alpine forleand exhibits a preferential anisotropic orientation that is similar
to SKS observations in the lowermost crust and uppermost mantle.
Description:
German Science Foundation (SPP-2017, Project Ha 2403/21-1); Swiss National Science Foundation SINERGIA
Project CRSII2-154434/1 (Swiss-AlpArray); Progetto Pianeta Dinamico, finanziamento MUR-INGV, Task S2 – 2021
Description:
Published
Description:
151–170
Description:
1T. Struttura della Terra
Description:
JCR Journal
Keywords:
Seismic anisotropy
;
Seismic interferometry
;
Seismic tomography
;
Wave propagation
;
Continental tectonics: compressional
;
04.01. Earth Interior
;
04.06. Seismology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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