Seismic anisotropy in the rift of the Reykjanes Peninsula, SW Iceland, calculated using a new tomographic method

0545466 - GFÚ 2022 RIV CH eng J - Journal Article
Růžek, Bohuslav
Seismic anisotropy in the rift of the Reykjanes Peninsula, SW Iceland, calculated using a new tomographic method.
Pure and Applied Geophysics. Roč. 178, č. 8 (2021), s. 2871-2903. ISSN 0033-4553. E-ISSN 1420-9136
R&D Projects: GA ČR(CZ) GA18-05053S; GA MŠMT LM2010008
Institutional support: RVO:67985530
Keywords : seismic tomography * seismic anisotropy * crustal imaging * Iceland * Reykjanes Peninsula
OECD category: Volcanology
Impact factor: 2.641, year: 2021
Method of publishing: Limited access
https://link.springer.com/article/10.1007/s00024-021-02784-1

A new algorithm and computer code for seismic tomography in anisotropic inhomogeneous media was developed. The new tomographic approach is a generalization of classical isotropic seismic tomography which introduces spatially and directionally varying slowness. The velocity model was considered as a stack of homogeneous blocks in contact, with each block individually parameterized using background velocities of P- and S-waves and a set of 21 anisotropy parameters. The inverse problem was solved sequentially in five steps, using the velocity model from the previous step as the starting model for the subsequent step. These steps form a chain with increasing complexity: (1) isotropic homogeneous model, (2) isotropic velocity model with vertical velocity gradient, (3) 3-D inhomogeneous isotropic velocity model, (4) 3-D inhomogeneous model with uniform anisotropy, (5) 3-D inhomogeneous generally anisotropic model. The new algorithm was applied to real bulletin data of 18 seismic stations deployed in SW Iceland and operated favourably for the monitoring of local swarm-like seismicity. Next, the resolution, robustness and accuracy of the inversion were discussed using real and synthetic data. Real data inversion revealed a predominantly depth-dependent isotropic velocity background and additional general 3-D anisotropy. The parameterization of the medium was too flexible to allow for a reliable interpretation of the anisotropy inside the elementary blocks and a cluster analysis was applied to stabilize the inversion results. Three important clusters were identified as a result. The orientation of the anisotropy (fast and slow P-wave propagation directions) of two clusters coincided with the strike of the documented faults. The orientation of the anisotropy in the third cluster was interpreted as a consequence of the fluid dynamics around Kleifarvatn Lake. The P-wave anisotropy strength reached a value of ± 5–8%.
Permanent Link: http://hdl.handle.net/11104/0322159