2-D and 3-D velocity patterns in southeastern Europe, Asia Minor and the eastern Mediterranean from seismological data

Abstract

2-D group velocity and 3-D P-wave velocity patterns have been obtained from analyses of the group velocity dispersion of Rayleigh waves in south-eastern Europe and Asia Minor and of the P-wave travel-time residuals along ray-paths with a penetration depth of 100-300 km in southeastern Europe, Asia Minor and the eastern Mediterranean. The inversion procedure used is based on Backus-Gilbert formalism for linear inversion of travel-time data extended to 2-D and 3-D inhomogeneous media. Group velocity distributions have been obtained for periods T = 10,20, 30 s and are in a very good agreement with the well-known characteristics of the crust and upper mantle structure. They can be used for the construction of models of the crust in south-eastern Europe and Asia Minor. The P-wave velocity patterns obtained for the depth interval 50-300 km are discussed in terms of geophysical (regional isostatic anomaly, heat flow) data for the region. It is proposed that the correlation found to exist between the different mapped geophysical parameters can be explained by compositional changes in the low-velocity layer (the increase of the iron content in minerals).

Tomography and velocity structure of the crust and uppermost mantle in southeastern Europe obtained from surface wave analysis

“…At the same time, Yanovskaya and Nikolova (1984) and Gobarenko et al (1987) developed 2D and 3D tomography methods, based on the Backus-Gilbert theory and applied it to real data in the region of southeast Europe. At present, the method is widely used for the determination of the group and/or phase velocities distribution on a local, regional and global scale.…”

“…Several studies of the velocity structure of southeastern Europe using different methods for inversion of P-waves travel times have been carried out (Holvand and Husebye, 1982;Gobarenko et. al, 1987;Spakman, 1991;Piromallo and Morelli, 2003).…”

“…At present, the method is widely used for the determination of the group and/or phase velocities distribution on a local, regional and global scale. However the inversion of the regionalised data for the construction of shear-wave velocity model is either not performed (Gobarenko et al, 1987), is made along some profile (Yanovskaya et. al., 1998), for some areas in the investigated region (Karagianni et.…”

The structure of the Kerch peninsula and north-eastern part of the Black sea crust according to the results of local seismic tomography

“…Для определения скоростной структуры коры района исследований использовалась томографическая инверсия, базирующаяся на методе Бэйкуса-Гильберта для трехмерного случая [Гобаренко, Яновская, 1983;Gobarenko et al, 1987]. Метод предназначен для оценки сглаженных скоростных поправок к исходной скоростной модели по данным невязок времен пробега сейсмических волн, пересекающих изучаемую область.…”

“…Для оценки степени сглаживания в разных точках исследуемой области строи-лись сглаживающие функции Q(θ, r), R(ϕ, r), P(z, r) (где r -координаты выбранной точки), приближаемые к функции единичного скачка [Гобаренко, Яновская, 1983;Gobarenko et al, 1987]. Ширина области существенного отличия указанных функций от функции единичного скачка характеризует размеры области сгла-живания по отдельным координатам.…”