Tomography studies of active volcanoes of Kamchatka I. Koulakov1, A. Jakovlev1, P. Kuznetsov1, K. Jaxybulatov1, E. Gordeev2, I. Abkadyrov2, V. Chebrov3, N. Shapiro4. 1. Institute of Petroleum Geology and Geophysics, SB RAS, Novosibirsk, Russia. 2. Institute of Volcanology and Seismology FEB RAS, Petropavlovsk-Kamchatsky, Russia. 3. Kamchatkan Branch of Geophysical Survey RAS, Petropavlovsk-Kamchatsky, Russia. 4. Institut de Physique du Globe de Paris, France 26th IUGG General Assembly, 30 of June, 2015, Prague, Czech Republic Volcanoes of Kamchatka Klyuchevskoy Bezymyanny Tolbachik Avachinsky Koryaksky Gorely depth 220 km Depth of the slab: ~150 km Regional tomography: Koulakov et al., Distance to the edge of slab ~ 100 км (2011, Russ. Geol. Geoph) Volcanoes of the Kluchevskoy group: Variety of compositions and eruption styles Are there any time changes related to eruption activity? Kluchevskoy: Ushkovsky: shield basalts, basalt- basalt volcano andesites Kamen: andesite-basalts, 1 — Kluchevskoy; pyroxene, 2 — Kamen; plagioclase, andesites 3 — Ushkovsky; Tolbachik: olivine- 4 — Krestovsky; pyroxene and plagioclase basalts, 5 — Sharp Tolbachik; Bezymyanny: andesite-basalts 6 — Flat Tolbachik; andesite extrusion 7 — Bezymyanny; 8 — Sharp Zimina; Zimina: 9 — Oval Zimina; andesites, 10 — Large Udina; dacites 11 — Small Udina; Udina: dominating 12 — Middle; andesites 13 —Zub Depth and time distribution of seismicity. Activity of the Kluchevskoy and Bezymyanny volcanoes Data distribution: Permanent stations (diamonds) and seismicity (blue dots). One model cannot satisfy all the data simultaneously!!! Red triangles denote volcanoes. 80,000 events, 500,000 rays 4D tomography: we obtained clear images of significant changes of seismic structure beneath the volcanoes of Kluchevskoy group Activity of the Kluchevskoy and Bezymyanny volcanoes is linked with seismic structure variations. Vp/Vs ratio is the indicator of fluid and melt content Enhanced seismic model beneath Bezymyanny (PIRE Project, 2009) Magma reservoirs Vp/Vs ratio in vertical and horizontal sections Seismic network on the Tolbachik volcano (August 2014 – July 2015) Eruption of Tolbachik in 2012-2013 KISS (August 2015-July 2016) Klychevskoy Investigation - Seismic Structure of an Extraordinary Volcanic System ~100 seismic stations IPGG Novosibirsk IPGP Paris GFZ Potsdam IVS Petropavlovsk KBGS Petropavlovsk Seismic investigations of the Avacha volcano group Avacha and Koryaksky are the home volcanoes of Petropavlovsk-Kamchatsky The main attractive site and pride of the city However, it represents a real danger Eruption of Avacha in 1945 Mud flows on Avacha during the eruption in 1991 Inversion of active seismic data, DSS profile across Avacha PROFIT code (Koulakov et al., 2010) The DSS profile was shot in 1982-1984 Ray path Cross correlation of ambient noise using the records of stations on the Avacha volcano 3D seismic model derived from ambient noise tomography S-wave velocity anomalies in 3 horizontal and one vertical sections Comparison of seismic models derived using different methods: A. Balesta et al. (1988): direct modeling of the DSS data В. Tomographic inversion of the profile active data С. S-velocity from ambient noise tomography Gorely is a shield volcano located 70 km from Petropavlovsk-Kamchatsky At the rim of the caldera formed ~30,000 years ago Seismic network on the Gorely volcano (08.2013 – 07.2014 ) High seismic activity (hundreds weak events per day) Very low average Vp/Vs ratio = 1.5 Vp/Vs ratio beneath Gorely in horizontal and vertical sections Main feature is extremely low Vp/Vs ratio indicating to high content of gases 11 000 tons of gases are ejected from the crater daily Gorely is a huge Steam Boiler «Safety valve»: A single fumarole in the crater ejects 11,000 tons of gases daily CONCLUSIONS: Seismic tomography is an excellent tool to study deep magmatic sources beneath volcanoes! Time-dependent tomography can help to identify VERY STRONG variations of seismic structure due to eruption activity Every volcano is unique! Klyuchevskoy, Bezymyanny – multi- level magmatic systems Gorely – low Vp/Vs – high gas content Avacha – traces of large caldera- forming eruptions The Art of Studying Volcanoes.