11:45 AM - 12:00 PM
[SSS07-05] Magmatic and hydrothermal structure beneath Mutnovsky and Gorely volcanoes (Kamchatka) from ambient noise tomography
Keywords:seismic tomography, Kamchatka volcanoes, surface wave, ambient noise
Mutnovsky and Gorely volcanoes are located approximately 70 km from the city of Petropavlovsk-Kamchatsky in Kamchatka and approximately 15 km from each other. The Mutnovsky Geothermal Plant (MGP), located near Mutnovsky, supplies about 30% of the city's electricity. Mutnovsky is one of Kamchatka's most active volcanoes, known for its strong fumarolic activity. It has produced explosive phreatic eruptions in 2007 and 2013. Ash emissions, ash falls, and lahars from the volcano present significant risks to both human populations and infrastructure. The compositions of gases and hydrothermal solutions of Mutnovsky volcano have been studied since 1961, and a number of geochemical and geological studies have also been conducted. Gorely, a Holocene active volcano, has been studied for decades using geological, geochemical, and geophysical methods. In 2013, it experienced a significant gas eruption accompanied by seismic activity. During this activity phase, a local seismic network was installed, whose data were used to build a local-scale tomography model of the volcano and to analyse long-period seismicity. Another study based on a regional-scale temporary network has provided the mantle wedge structure beneath an area of Central Kamchatka including these two volcanoes. However, there was a gap related to insufficient studies of crustal structures below Mutnovsky and Gorely volcanoes, which is covered in this study owing to processing new experimental data.
In 2023-2024, a temporary seismic network with 65 seismic stations was deployed around Mutnovsky and Gorely. Continuous seismic data, combined with records of four permanent seismic stations of Kamchatka Branch of the Geophysical Survey (KB GS) of the Russian Academy of Sciences, were analyzed using the ambient noise surface wave tomography method to create a 3D shear wave velocity model of the volcanoes and surrounding areas. Vertical components of cross-correlations were computed. As a signal resembling volcanic tremor was identified in the cross-correlation functions, we analyzed the network response functions and the covariance matrix spectral width to determine the frequency range to exclude from the analysis. To enhance the signal-to-noise ratio, an SVD-based Wiener filter was applied. Rayleigh surface wave group velocity dispersion curves were extracted from the cross-correlations and used in two-step surface wave tomography to create the 3D Vsv velocity structure. A series of "Checkerboard" tests were performed to assess the robustness of structures in both horizontal and vertical directions.
The tomography results revealed a contrasting low-velocity anomaly around Gorely volcano, likely associated with thick sedimentary deposits within its caldera. A high-velocity anomaly below the central part of Mutnovsky is likely associated with a rigid core within the volcano edifice composed of consolidated igneous rocks. An isometric low-velocity anomaly beneath Mutnovsky's crater, at depths of 2-5 km below sea level may represent an active magmatic chamber. Below the MGP and nearby thermal springs, a large low-velocity anomaly was detected at depths of 2-5 km, linked to the surface by a narrow vertical anomaly. It can be assumed that this anomaly is caused by an intrusion that serves as a heat source for the Mutnovsky steam-hydrothermal field.
This study provides the first crustal-scale velocity model of the Mutnovsky and Gorely volcanoes and the surrounding area, including the MGP. The findings offer new insights into the structural characteristics of the magmatic and hydrothermal systems associated with these active volcanoes and the geothermal energy extraction process.
In 2023-2024, a temporary seismic network with 65 seismic stations was deployed around Mutnovsky and Gorely. Continuous seismic data, combined with records of four permanent seismic stations of Kamchatka Branch of the Geophysical Survey (KB GS) of the Russian Academy of Sciences, were analyzed using the ambient noise surface wave tomography method to create a 3D shear wave velocity model of the volcanoes and surrounding areas. Vertical components of cross-correlations were computed. As a signal resembling volcanic tremor was identified in the cross-correlation functions, we analyzed the network response functions and the covariance matrix spectral width to determine the frequency range to exclude from the analysis. To enhance the signal-to-noise ratio, an SVD-based Wiener filter was applied. Rayleigh surface wave group velocity dispersion curves were extracted from the cross-correlations and used in two-step surface wave tomography to create the 3D Vsv velocity structure. A series of "Checkerboard" tests were performed to assess the robustness of structures in both horizontal and vertical directions.
The tomography results revealed a contrasting low-velocity anomaly around Gorely volcano, likely associated with thick sedimentary deposits within its caldera. A high-velocity anomaly below the central part of Mutnovsky is likely associated with a rigid core within the volcano edifice composed of consolidated igneous rocks. An isometric low-velocity anomaly beneath Mutnovsky's crater, at depths of 2-5 km below sea level may represent an active magmatic chamber. Below the MGP and nearby thermal springs, a large low-velocity anomaly was detected at depths of 2-5 km, linked to the surface by a narrow vertical anomaly. It can be assumed that this anomaly is caused by an intrusion that serves as a heat source for the Mutnovsky steam-hydrothermal field.
This study provides the first crustal-scale velocity model of the Mutnovsky and Gorely volcanoes and the surrounding area, including the MGP. The findings offer new insights into the structural characteristics of the magmatic and hydrothermal systems associated with these active volcanoes and the geothermal energy extraction process.