TY - JOUR

T1 - Structure of the upper crust beneath the klyuchevskoy group of volcanoes revealed from ambient noise tomography

AU - Egorushkin, I. I.

AU - Koulakov, I. Yu

AU - Shapiro, N. M.

AU - Gordeev, E. I.

AU - Yakovlev, A. V.

AU - Abkadyrov, I. F.

N1 - Funding Information: This study was supported by the Russian Science Foundation, grant No. 20-17-00075, and the Ministry of Education and Science of the Russian Federation, grant No. 14. W03.31.0033. We express our gratitude to N.L. Dobretsov, R.G. Green, A. Mordret, and two anonymous reviewers. Their help and constructive comments allowed us to significantly improve this manuscript. Publisher Copyright: © 2021, V.S. Sobolev IGM, Siberian Branch of the RAS. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2021

Y1 - 2021

N2 - The Klyuchevskoy group of volcanoes (KGV) located in the central part of Kamchatka is a unique complex that demonstrates exceptional variety and intensity of volcanic manifestations. These features of the eruptive activity of the KGV are determined by a complex system of magmatic sources in the crust and mantle. While the structure of deep anomalies is quite reliably determined by tomography techniques based on body waves, the structure of the upper crust can only be determined using ambient noise tomography. We present the results of processing data from the KISS temporary network. This network consisted of more than 100 seismic stations that were installed from 2015 to 2016 over a large area covering the Klyuchevskoy group of volcanoes and its surroundings. To retrieve Rayleigh surface waves, cross-correlation of continuous seismic noise records from pairs of stations was used. We obtained the dispersion curves of the group velocities of these Rayleigh surface waves using frequency–time analysis (FTAN) of the calculated correlograms. These curves served as input data for performing ambient noise tomography. Tomography was performed in two stages: (1) computation of two-dimensional group velocity maps for different frequencies and (2) calculation of a three-dimensional model of the shear wave velocity to a depth of about 8 km based on the inversion of local dispersion curves obtained from these maps. The resulting models revealed the structural features of individual volcanic systems of the KGV. High velocities were observed at shallow depths beneath the large basaltic edifices of the Ushkovsky and Tolbachik volcanoes. At greater depths, while the velocity structure beneath Ushkovsky remained unchanged, we detected low velocities beneath Tolbachik. This fact illustrates the difference between dormant and active magmatic systems. Velocity anomalies of a complex shape are observed beneath the Klyuchevskoy, Kamen, and Bezymianny volcanoes, varying both laterally and with depth. Absolute velocities in vertical sections show that the edifices of these volcanoes are relatively low-velocity bodies located on a horizontal high-velocity basement. A low-velocity anomaly was discovered under the Bezymianny Volcano at a depth of 6 km, which is presumably associated with a shallow magma reservoir. An intense low-velocity anomaly was found beneath the Udina Volcano. It was interpreted as an image of a magma reservoir experiencing strong seismic unrest that began in December 2017 and continues to this day.

AB - The Klyuchevskoy group of volcanoes (KGV) located in the central part of Kamchatka is a unique complex that demonstrates exceptional variety and intensity of volcanic manifestations. These features of the eruptive activity of the KGV are determined by a complex system of magmatic sources in the crust and mantle. While the structure of deep anomalies is quite reliably determined by tomography techniques based on body waves, the structure of the upper crust can only be determined using ambient noise tomography. We present the results of processing data from the KISS temporary network. This network consisted of more than 100 seismic stations that were installed from 2015 to 2016 over a large area covering the Klyuchevskoy group of volcanoes and its surroundings. To retrieve Rayleigh surface waves, cross-correlation of continuous seismic noise records from pairs of stations was used. We obtained the dispersion curves of the group velocities of these Rayleigh surface waves using frequency–time analysis (FTAN) of the calculated correlograms. These curves served as input data for performing ambient noise tomography. Tomography was performed in two stages: (1) computation of two-dimensional group velocity maps for different frequencies and (2) calculation of a three-dimensional model of the shear wave velocity to a depth of about 8 km based on the inversion of local dispersion curves obtained from these maps. The resulting models revealed the structural features of individual volcanic systems of the KGV. High velocities were observed at shallow depths beneath the large basaltic edifices of the Ushkovsky and Tolbachik volcanoes. At greater depths, while the velocity structure beneath Ushkovsky remained unchanged, we detected low velocities beneath Tolbachik. This fact illustrates the difference between dormant and active magmatic systems. Velocity anomalies of a complex shape are observed beneath the Klyuchevskoy, Kamen, and Bezymianny volcanoes, varying both laterally and with depth. Absolute velocities in vertical sections show that the edifices of these volcanoes are relatively low-velocity bodies located on a horizontal high-velocity basement. A low-velocity anomaly was discovered under the Bezymianny Volcano at a depth of 6 km, which is presumably associated with a shallow magma reservoir. An intense low-velocity anomaly was found beneath the Udina Volcano. It was interpreted as an image of a magma reservoir experiencing strong seismic unrest that began in December 2017 and continues to this day.

KW - Ambient noise tomography

KW - Kamchatka

KW - KISS network

KW - Klyuchevskoy group of volcanoes

KW - Magma reservoir

KW - Seismology

KW - Surface wave

KW - Upper crust

KW - Velocity anomaly

KW - Volcanology

UR - http://www.scopus.com/inward/record.url?scp=85106281215&partnerID=8YFLogxK

UR - https://www.elibrary.ru/item.asp?id=46101706

U2 - 10.2113/RGG20204238

DO - 10.2113/RGG20204238

M3 - Article

AN - SCOPUS:85106281215

VL - 62

SP - 68

EP - 82

JO - Russian Geology and Geophysics

JF - Russian Geology and Geophysics

SN - 1068-7971

IS - 1

M1 - 5

ER -