Seismic tomography studies of volcanoes
IPGP - Îlot Cuvier
Séminaires de Sismologie
Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk, Russia
The talk includes an overview of recent tomography studies of different active volcanoes of the world. Most of the results are based on the analysis of travel time data from local earthquakes. Joint interpretation of P- and S-velocities, Vp/Vs ratio and source locations made possible revealing geodynamic scenarios for explaining the particularities of the volcanic activity in different sites. Based on the tomographic results, a series of stories on different volcanoes will be presented, such as: - “Lost eruption” in Mt.Spurr, Alaska in 2004-2005: there are two conduits, one of which is responsible for explosive activity (1992), and another brings volatiles without any explosions (2004-2005). - Changes inside the Redoubt volcano (Alaska) during the 2009 eruption: spectacular decrease of the S-velocity and almost unchanged P-velocity indicate to strong saturation of volcano subsurface part with fluids and melts. - Another “failed” eruption in Harrat Lunayyir (Saudi Arabia) in 2009: Tomography reveals a steady crustal reservoir which is episodically activated by incoming conduits. In 2009, a conduit did not hit to the center of the reservoir, part of volatiles was dispersed and thus the eruption did not occur. - Variations in the crust beneath the Klyuchevskoy volcano group (Kamchatka, Russia): 4D tomography model for 10 years of continuous observations reveal a single mantle source and variable structures of magma reservoirs in the crust. These variations are consistent with eruption activity of volcanoes. - Independent conduit beneath Bezymyanny (Kamchatka): More detailed tomography model based on data of a temporary network gives the evidence that the magma sources beneath Bezymyanny and Klyuchevskoy volcanoes are independent. - Trace of a relict caldera close to the Avacha volcano (Kamchatka). Active source profile and ambient noise tomography consistently reveal asymmetric structures around the Avachinsky volcano that can be interpreted by the presence of a relict caldera. - Detailed structure beneath the Toba caldera: An enhanced seismic model of Toba is obtained based on combination of various data and algorithms In addition, brief information about ongoing projects performed by IPGG on active volcanoes of Kamchatka will be presented.