Frequency-dependent shear wave attenuation across the Central Anatolia region, Türkiye

Abstract

The Central Anatolian Plateau with its volcanic provinces represents a broad transition zone between the compressional deformation in the east and the extensional regime in the west. The Central Anatolian Fault Zone separates the Kırşehir Block in the north and the Anatolide–Tauride Block in the south within the plateau. A proper understanding of physical properties such as seismic attenuation in the crustal volume of this region can provide hints toward the possible source for the geodynamic events in the past and present that likely lead to the observed deformation. In order to model intrinsic and scattering attenuation separately, we perform a nonempirical coda-wave modeling approach in which a fitting process between observed and synthetic coda-wave envelopes is performed for each earthquake in multiple frequency bands. Here, the acoustic radiative transfer theory, assuming multiple isotropic scattering, was utilized for the forward modeling of the synthetic coda-wave envelopes of local earthquakes. Our findings generally highlight the prominent nature of intrinsic attenuation over scattering attenuation, implying the presence of thick volcanic rocks with relatively high attenuation values beneath Central Anatolia. Overall, the spatial distribution of the attenuation at varying frequencies marks the Kırşehir Massif distinctively with its considerable high-attenuating character. Our findings, combined with early seismological and geo-electrical models, suggest a possible partial melt beneath most of the Central Anatolian Volcanic Province, and the resultant zones of elevated fluid-rich content exhibit high and dominant intrinsic attenuation. To the southeast, a gradual decrease in the observed attenuation coincides with the Central Taurus Mountains where high altitude is considered to be evolved following the slab break-off and resulting mantle upwelling.