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Spatial Distribution of Random Velocity Inhomogeneities in the Southern Aegean From Inversion of S Wave Peak Delay Times
Author(s) -
Ranjan P.,
Konstantinou K.I.,
Andinisari R.
Publication year - 2019
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2018jb017198
Subject(s) - geology , underplating , subduction , seismology , scattering , mantle (geology) , diapir , tectonics , geophysics , physics , optics
The southern Aegean is characterized by an ongoing process of oceanic subduction. In this study, 1,718 intermediate depth (>35 km) events recorded in the southern Aegean are used to calculate the peak delay times ( t p ). The t p are measured as the time difference between S wave onset and the peak of the S wave envelope in 2‐to 4‐, 4‐ to 8‐, 8‐ to 16‐, and 16‐ to 32‐Hz bands. The t p are also inverted to estimate the scattering parameters ( κ and ε param ) and power spectral density function (P ( m )) at large wave numbers ( m = 15 km −1 or m l ) of the medium modeled as von Kármán type. κ controls frequency dependence of scattering while P ( m l ) represents the scattering strength in high frequencies for ɑm l >> 1 ( ɑ = correlation length of inhomogeneities). High P ( m l ) with low κ across Peloponnese in 0‐ to 20‐km depth may result from intermixing of oceanic material with continental rocks at different levels with a possibility of fluid activity and salt diapirism in northwest Peloponnese. Moderate P ( m l ) in 0‐ to 60‐km depth across Crete is likely due to a combination of factors including past megathrust earthquakes, sediment underplating, and flow of metamorphosed material in a subduction channel. Cyclades shows low κ in 0‐ to 40‐km depth, indicative of inhomogeneities produced by metamorphic core complexes. Very low κ in 60‐ to 80‐km depth is consistent with the location of mantle magma reservoir in the back‐arc region. Our results suggest that a significant portion of total S wave attenuation ( Q s −1 ) in eastern Cyclades for 20‐ to 80‐km depth may be due to scattering losses.