**Magma Fracking Beneath Active Volcanoes Based on Seismic Data and Hydrothermal Activity Observations**

#### **Alexey Kiryukhin \*, Evgenia Chernykh, Andrey Polyakov and Alexey Solomatin**

Institute of Volcanology & Seismology FEB RAS, Petropavlovsk-Kamchatsky 683006, Russia; jenia.chev@yandex.ru (E.C.); pol@kscnet.ru (A.P.); alf110111@gmail.com (A.S.) **\***Correspondence:avkiryukhin2@mail.ru

 Received: 28 November 2019; Accepted: 26 January 2020; Published: 29 January 2020

**Abstract:** Active volcanoes are associated with microearthquake (MEQ) hypocenters that form plane-oriented cluster distributions. These are faults delineating a magma injection system of dykes and sills. The Frac-Digger program was used to track fracking faults in the Kamchatka active volcanic belt and fore-arc region of Russia. In the case of magma laterally injected from volcanoes into adjacent structures, high-temperature hydrothermal systems arise, for example at Mutnovsky and Koryaksky volcanoes. Thermal features adjacent to these active volcanoes respond to magma injection events by degassing CO2 and by transient temperature changes. Geysers created by CO2-gaslift activity in silicic volcanism areas also flag magma and CO2 recharge and redistributions, for example at the Uzon-Geyserny, Kamchatka, Russia and Yellowstone, USA magma hydrothermal systems. Seismogenic faults in the Kamchatka fore-arc region are indicators of geofluid fracking; those faults can be traced down to 250 km depth, which is within the subduction slab below primary magma sources.

**Keywords:** magma; hydrothermal; fracking; volcanoes; Kamchatka
