Three different types of plumbing system beneath the neighboring active volcanoes of Tolbachik, Bezymianny, and Klyuchevskoy in Kamchatka

Abstract

The Klyuchevskoy group of volcanoes (KGV) in Kamchatka includes three presently active volcanoes (Klyuchevskoy, Bezymianny, and Tolbachik) located close together in an area of approximately 50 × 80 km. These three volcanoes have completely different compositions and eruption styles from each other. We have analyzed new data recorded by a temporary seismic network consisting of 22 seismic stations operated within the area of Tolbachik in 2014–2015 in conjunction with the data from the permanent network and the temporary PIRE network deployed at the Bezymianny volcano in 2009. The arrival times of the P and S waves were inverted using a local earthquake tomography algorithm to derive 3‐D seismic models of the crust beneath the KGV as well as accurate seismicity locations. High‐resolution structures beneath the Tolbachik volcanic complex were identified for the first time in this study. The tomography results reveal three different types of feeding system for the main KGV volcanoes. The basaltic lavas of the Klyuchevskoy volcano are supplied directly from a reservoir at a depth of 25–30 km through a nearly vertical pipe‐shaped conduit. The explosive Bezymianny volcano is fed through a dispersed system of crustal reservoirs where a lighter felsic material separates from the mafic component and ascends to the upper crust to form andesitic magma sources. For Tolbachik, low‐viscosity volatile‐saturated basalts ascend from two deep reservoirs following a system of fractures in the crust associated with the intersections of regional faults.

Fault‐Associated Magma Conduits Beneath Volcán de Colima Revealed by Seismic Velocity and Attenuation Tomography Studies

“…We propose that the prominent anomaly of a high Vp / Vs ratio to the southeast of CVC corresponds to the mantle diapir containing fluids and melts brought from the slab. Similar mantle reservoirs are observed beneath many volcanic systems, such as Toba (Koulakov et al, ) and Klyuchevskoy (Koulakov et al, ). The reason for accumulating a large amount of partially molten material at the base of the crust in these cases is the higher density of the mantle material, though hot, in respect to the continental crust.…”

“…In this case, it becomes clear that this anomaly might indicate the area of ascended magmas along a weakened fracture zone associated with a regional tectonic fault. Similar association of the volcano locations with tectonic faults is a rather common feature observed, for example, in the area of the Toba supervolcano (Koulakov et al, ) and Tolbachik in Kamchatka (Koulakov et al, ).…”

“…Importantly, within this anomaly, the P wave velocity is relatively high, whereas the S wave velocity is low. A similar combination of positive dVp and negative dVs is observed beneath many active volcanoes (e.g., Spurr in Alaska and Klyuchevskoy in Kamchatka, (Koulakov et al, , ). As the P waves are more sensitive to rock composition, and the S wave velocity is greatly affected by the presence of liquid phases, such a relationship is interpreted as indicating an intrusion of primitive composition magma that contains large amount of fluids and melts.…”

“…Different combinations of all these factors lead to a great variety in eruption regimes and composition of volcanoes in subduction zones. There are a number of case studies that propose feeding scenarios for different volcanoes worldwide (e.g., Ferrari et al, ; Koulakov et al, ; Stern, ). Many such studies are based on the results of seismic tomography, which can provide the geometry of the magma and fluid pathways as well as the locations of intermediate magma reservoirs (e.g., Koulakov et al, ; Schurr et al, ; Zhao, ).…”

“…There are a number of case studies that propose feeding scenarios for different volcanoes worldwide (e.g., Ferrari et al, ; Koulakov et al, ; Stern, ). Many such studies are based on the results of seismic tomography, which can provide the geometry of the magma and fluid pathways as well as the locations of intermediate magma reservoirs (e.g., Koulakov et al, ; Schurr et al, ; Zhao, ). Although the models that have been developed for some volcanoes improve our understanding how these plumbing systems work, this knowledge is not necessarily applicable to other volcanoes and cannot be easily extrapolated to them.…”