Qp structure of Mount Etna: Constraints for the physics of the plumbing system

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Abstract

[1] In this study we present the three-dimensional Qp structure of the Mount Etna volcano (Italy), obtained by using local earthquake data. The attenuation along ray paths (t*), computed from the high-frequency decay of velocity spectra, is used to reconstruct the deep structure of the volcano down to 15 km depth. The tomographic images reveal two broad low-Qp anomalies at 0 and 3 km depth, located to the south and southwest of the summit area and extending at depth to the west of a central high-Qp anomaly located between 6 and 15 km depth. The joint analysis of P wave attenuation and velocity allows us to better constrain the physics of the plumbing system. The shallow low-Qp anomalies are associated with high-Vp anomalies beneath the top of the volcano and normal low Vp toward its western borders. We interpret the regions of low Qp and normal-low Vp as shallow volumes where magmatic fluids are stored. Conversely, the low-Qp, high-Vp region may indicate intensely fractured rock volumes filled by fluids surrounding the magma branches. At depth, the low-Qp anomaly defines the path of the magma ascent to the west of an extremely high-Qp, high-Vp volume located beneath the southeastern side of the summit area. The high-Qp, high-Vp body is interpreted to be the compact, solidified, high-density intrusive body formed by nonerupted material during past volcano activity.

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