Ambient Seismic Noise Image of the Structurally Controlled Heat and Fluid Feeder Pathway at Campi Flegrei Caldera. Issue 13 (5th July 2018)

• Record Type: Journal Article
• Authors: De Siena, L.; Sammarco, C.; Cornwell, D. G.; La Rocca, M.; Bianco, F.; Zaccarelli, L.; Nakahara, H.
• Is Part Of: Geophysical research letters. Volume 45:Issue 13(2018)
• Page Start: 6428
• Page End: 6436
• Publication Date: 2018-07-05
• Subjects: ambient noise imaging -- volcano imaging -- fluid propagation -- seismicity -- volcano dynamics -- seismic scattering; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2018GL078817
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Earthquakes at Campi Flegrei have been low magnitude and sparse since 1985, denying onshore monitoring observations of their usual source for structural constraint: seismic tomography. Here we used continuous seismic records from 2011–2013 to reconstruct period‐dependent Rayleigh wave group velocity maps of the volcano. The Neapolitan Yellow Tuff rim faults bound high‐velocity intracrater products of historical eruptions, which act as a barrier for deep fluid migration. The anomaly with lowest group velocity is aseismic and corresponds to the portion of a fluid storage zone that was fractured during the 1984 volcanic unrest under Pozzuoli town. Earthquake locations show that fluids migrate from this area toward the Solfatara and Pisciarelli fumaroles along shallower low‐velocity fractures. The aseismic anomaly is likely fed by a deep‐seated offshore magmatic source. Its spatial relation with regional dynamics and observations from historical unrests mark the area as the most likely feeder pathway for fluid and magmatic inputs from depth. Plain Language Summary: We used the seismic noise produced by the seashore at Campi Flegrei volcano to detect magma and hot fluids under its surface. The area where likely magmatic fluids are entering the volcano was part of a reservoir, broken during the 1980s and intersected by strong earthquakes that forced the population to move outside of Pozzuoli town. This area is a feeder pathway as it connects deeper sources of magma, likely active since the 1980s, to the upper part of the volcano and feeds hot fluids to the hydrothermal systems. The injections of either magma or fluids that fractured the reservoir in the 1980s have changed Campi Flegrei characteristics, but the feeder pathway is still the most probable pathway for deeper magma and fluids to enter the volcano subsurface. Hazardous fluids migrate from the feeder pathway to fumaroles at Solfatara and Pisciarelli, west of the Napoli city center, following fractures and faults mapped at surface. Key Points: Rayleigh wave tomography of Campi Flegrei caldera used continuous ambient noise data recorded during the 2011–2013 volcanic unrest Low velocities map the aseismic pathway opened during the 1984 volcanic unrest, feeding heat and fluids to the shallow hydrothermal systems High‐velocity intracrater domes and structural faults control the feeder extension and fluid migration to fumaroles