Evidence for gas and magmatic sources beneath the Yellowstone volcanic field from seismic tomographic imaging

Seismic tomography of Central São Miguel, Azores

“…Low-velocity anomalies interpreted as partially molten volumes have been found at Toba Caldera [Masturyono et al, 2001], Yellowstone [Husen et al, 2004], and Rabaul [Finlayson et al, 2003]. Lowvelocity regions have also been associated with geothermal systems (e.g.…”

“…In spite of that, in volcanic environments high Vp/Vs values at shallow depths can be generally associated with saturated highly fractured materials (as in Vesuvio [Scarpa et al, 2002] and Kilauea [Hansen et al, 2004]). Deep, high Vp/Vs values are rather related to bodies of partial melt (as in Etna [Patané et al, 2006], Yellowstone [Husen et al, 2004] and Long Valley [Sanders et al, 1995]). Low ratios can be also found in geothermal systems near the water-steam transition as in Yellowstone [Chatterjee et al, 1985] and Onikobe volcanic area [Nakajima and Hasegawa, 2003].…”

Seismic velocity structure in and around the Naruko volcano, NE Japan, and its implications for volcanic and seismic activities

“…There are also low-V and low-Vp/Vs areas in the upper crust. A possible cause of the low Vp/Vs in the upper crust is the presence of H 2 O/CO 2 vapor released from cooled and solidified magma (Ito et al 1979;Julian et al 1998;Takei 2002;Husen et al 2004;Nakamichi et al 2007). Another reason could be the presence of water in the pores with small aspect ratio under equilibrium conditions (Watson and Brenan 1987;Takei 2002).…”

Hengill geothermal volcanic complex (Iceland) characterized by integrated geophysical observations

“…This builds on previous tomography studies carried out at Hengill volcano (e.g., Toomey and Foulger, 1989) that revealed the main structural features of the volcanic area and the triple junction. In particular, the V P /V S ratio and attenuation measurements are diagnostic of pore-fluid and temperature conditions when used in conjunction with V P (Evans et al, 1994;Gunasekera et al, 2003;Husen et al, 2004).…”