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Deep‐crustal magma plumbing at arc volcanoes controls the volume, frequency, and composition of magma being transported to and stored in the upper crust. However, the mid‐to‐lower crust remains a challenging region to image. We explore the mid‐to‐lower crustal velocity structure beneath the Christiana‐Santorini‐Kolumbo Volcanic Field (CSKVF) to better understand how an established stratovolcano and flanking volcano (Santorini and Kolumbo) are fed through the mid‐to‐lower crust. We use active‐source seismic data to obtain a P‐wave velocity model of the crust below the CSKVF. We invert direct and reflected P phases to cover the entire depth extent of the crust and solve for the Moho interface depth. Our model requires a curved Moho interface representative of crustal thickening via underplating. Results show a highVpanomaly in the lower crust under Santorini and a mid‐crustal lowVpanomaly offset from both Santorini and Kolumbo. We find that accumulation of magma is located under the local extensional basin in the upper mid‐crust (<10 km) but is offset at deeper depths. We find evidence for melt storage at 11–13 km depth feeding volcanism at the Kolumbo volcanic chain. This melt is also a plausible source for the 2025 seismic swarm and dike intrusion. Resolution is limited in the mid‐crust below the Santorini caldera, leaving Santorini's mid‐crustal magma plumbing unconstrained. We think it likely that Santorini and Kolumbo have entirely separate crustal plumbing systems and mantle sources, but allow the possibility of a connection in the mid or lower crust.
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This content will become publicly available on April 1, 2026
Seismic Structure of the Mid to Upper Crust at the Santorini‐Kolumbo Magma System From Joint Earthquake and Active Source V p ‐V s Tomography
Santorini volcano has a history of caldera‐forming eruptions, most recently in the Late Bronze Age, at 3.4 kya, and remains volcanically active. The Kolumbo submarine volcano, located 7 km to the northeast of Santorini, erupted in 1650 AD in a deadly phreatomagmatic eruption. Ongoing seismic activity and active hydrothermal venting at Kolumbo indicate this volcano is a significant hazard to the Santorini region. The magma source for Santorini and the Kolumbo edifice are considered separate in the shallow crust, though their deeper magma distribution is not yet constrained. In this study, we improve constraints on the mid‐crustal magma system of Santorini caldera and the nearby Kolumbo volcano using local earthquake tomography. We use 1515 P‐wave and 1435 S‐wave arrival times from 63 local earthquakes with magnitudes from 0.5 to 3.0 that occurred between 5 and 15 km depth together with an existing data set of active source Pg arrivals. The upper crustal magma system beneath Santorini is imaged to at least 6 km depth, and to 12 km depth beneath Kolumbo. We recover a high P‐wave velocity layer (∼6–8 km) under the Kolumbo magma reservoir that we infer is a rheologically strong seismogenic layer. We also recover a mid‐crustal magma body below 8 km depth located to the NE of Santorini and Kolumbo.
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- PAR ID:
- 10585689
- Publisher / Repository:
- AGU
- Date Published:
- Journal Name:
- Geochemistry, Geophysics, Geosystems
- Volume:
- 26
- Issue:
- 4
- ISSN:
- 1525-2027
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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