New data on the deep structure of the Northern Vent of the Great Tolbachik Fissure Eruption (1975–1976)

Abstract

In order to restore the deep structure in the region of the Northern Vent (NV) of the Great Tol bachik Fissure Eruption (GTFE) (1975)(1976), low frequency microseismic sounding was applied. For this purpose accumulation of spectra of the microseismic field was performed in a wide frequency band in 29 points along a linear profile 14 km in length embedded transversely to the fissure eruption. A deep cross section of the Earth's crust was constructed up to 20 km, reflecting the distribution of relative velocities of transverse seismic waves. The revealed structural heterogeneities were interpreted with consideration of pre viously known results of complex studies of the eruption. The existence of an abnormal structure at the depths of 2-3 and 7-8 km under the NV GTFE was confirmed, which could be low depth magma chambers. Deep subvertical low velocity structures were revealed and spatially registered, which probably feed the conduits of the eruption. It was demonstrated that the ways of possible magma supply to the peripheral chamber at the depth of 2-3 km could be various. For the first time for the zone of areal volcanism, variation of the character of magmatic intrusions was demonstrated at the transition from a crystalline basement to the near surface depth: subvertical forms are replaced with a system of sills and interesting injections.

Magmatic plumbing systems of the monogenetic volcanic fields: A case study of Tolbachinsky Dol, Kamchatka

“…depth, going along the fault from the central to the southern part of TD (M2); large (~15-20 km along the fault zone and 9-10 in the transverse direction) trans-crust magma conduction zone under central part of TD, under the chain of the highest cinder cones (M3). More detailed research of the latter heterogeneity revealed alternate magma reservoirs and feeding conduits as well as regular patterns in their location and configuration (Kugaenko et al, 2011(Kugaenko et al, , 2013. Fig.…”