Quality Estimates of the Crust and Upper Mantle of the Northeast Caucasus Based on to Makhachkala Seismic Station Records

• Published in: Seismic instruments Vol. 56; no. 1; pp. 61 - 71
• Main Authors: Kirsanov, V. I., Pavlenko, O. V.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 2020; Springer Nature B.V
• Subjects: Earth and Environmental Science; Earth mantle; Earth Sciences; Earthquakes; Estimates; Geophysics/Geodesy; Q factors; Records; Seismic activity; Seismic propagation; Seismic waves; Stochastic models; Upper mantle; Wave propagation; Caucasus; Northeast Caucasus; Makhachkala seismic station; factor; earthquakes
• ISSN: 0747-9239; 1934-7871
• DOI: 10.3103/S0747923920010077

This article continues research of the seismic wave propagation parameters in the North Caucasus. The Q factors of the crust and upper mantle in the vicinity of Makhachkala are obtained, which are compared with the previously obtained Q factors in the vicinity of Sochi, Anapa, and Kislovodsk. According to records of regional (with epicentral distances up to ~300 km) earthquakes ( M W  ~ 3.9–5.6) acquired by the Makhachkala seismic station, estimates are obtained for the Q factor of the medium Q ( f ) in the form Q ( f ) ≈  f 0.98 (envelope method) and Q ( f ) ≈ 135 f 0.72 (by coda normalization method); the generalized estimate has the form Q  ( f ) ≈ 120 f 0.8 (at frequencies up to ~ 16 Hz). The obtained Q factors in the vicinity of Makhachkala at low frequencies are slightly higher than the estimates obtained for regions of the Northwest Caucasus: the environs of Sochi, Anapa, and Kislovodsk ( Q 0 ~ 55–90; n ~ 0.7–1.0). The obtained Q factor estimates are planned to be checked and, possibly, refined by stochastic modeling of local earthquake records.