Toward a risk assessment of central Aegean volcanoes

Abstract

PAGES 401,407Active tectonic processes along the AfricanEurasian collision zone are associated with catastrophic events including earthquakes, major volcanic eruptions, and tsunamis. Understanding how these processes can affect the eastern Mediterranean is of increas ing scientific and public interest. The region includes a frequently crossed international sea traffic corridor and dense population centers. Furthermore, most of the small vol canic islands in the Aegean are major tourist attractions that contribute significantly to the wealth of this region.One of these Aegean islands is Santorini, which is a major explosive volcano and pos sibly one of the most dangerous volcanoes in Europe. During the past 150 million years, Santorini has had 12 major eruptions, and several of them ejected large columns of ash and debris high into the atmosphere. It is widely believed that the eruption of San torini about 3600 years before present (B.P) destroyed the Minoan civilization of Crete.In addition to the volcanic island, there are several submarine volcanic seamounts in the Aegean Sea. One of them, the Columbo seamount, is about eight kilometers northeast of Santorini, and recently has attracted atten tion due to the high earthquake activity of the Hellenic subduction zone [Bohnhoff et al,2006].This activity is concentrated in an area northeast of Santorini, within the socalled Santorini-Amorgos zone.The earthquakes occurred in the upper crust at a depth of 3-15 kilometers and are considered to be related to evolving volcanism and related magma or fluid migration. Whereas the potential risk of future erup tions of the Santorini volcano is well recog nized by scientists and by Santorini residents, the Columbo underwater volcano never has reached a level of public risk perception The newly completed first phase of the 'Inspecting Columbo' project consisted of an extensive marine geophysical survey that was carried out in order to map active tec tonic and volcanic features. More than 1500 kilometers of seismic and magnetic data, as well as 2500 kilometers of gravity data, were collected in June 2006 during a cruise onboard the research vessel (R/V) Poseidon. On the basis of onboard processing, optimized loca tions for deploying five ocean-bottom seis mometers and four newly developed oceanbottom tiltmeters were determined.The retrieval of these instruments, scheduled for spring 2007, will initiate the second phase of the program. Volcanic Complexes of the Santorini-Amorgos ZoneAccording to previous findings, the San torini-Amorgos zone (SAZ) marks a major structural boundary in a dextral transtensional regime that subdivides the Hellenic volcanic arc into a seismically and volcanically quiet western and an active eastern part. The highest earthquake activity has been observed beneath the submarine Columbo volcano and northeast of it along the Santorini-Amorgos Ridge [Perissoratis, 1995], which terminates south of the island of Amorgos (Figure 1).The activity close to the Columbo seamount is considered to be linked dire...

P and S velocity structures of the Santorini–Coloumbo volcanic system (Aegean Sea, Greece) obtained by non-linear inversion of travel times and its tectonic implications

“…This assumption is in very good agreement with recent independent geophysical (Huebscher et al, 2006, Hensch et al, 2008, seismological (Bohnhoff et al, 2006) and geothermal (Sigurdsson et al, 2006) results for the same area. The interpretation of the NE-SW cross-sections shown in Figures (12a) and (12b) should be considered with caution.…”

Post-eruptive flooding of Santorini caldera and implications for tsunami generation

“…56 and during the ‘ATLANTIS FOUND' project in 2015. The respective sources for the high-resolution seismic profiling system were a 45/105.…”

Active Tectonics in the Hellenic Volcanic Arc: The Kolumbo Submarine Volcanic Zone

“…Huebscher et al (2006) have been able to observe in seismic reflection profiles two cone-like volcaniclastic deposits, which indicate that the Kolumbo volcano evolved from at least two eruptions. Bohnhoff et al (2006) report that, the highest seismic activity in the area has been observed along the SW-NE striking Santorini-Amorgos zone.…”

“…The interpretation of this profile suggests that at least one older volcanic cone exists and is located underneath the present one, indicating that Kolumbo has been active at least once, prior to the 1650 eruption (see also Huebscher at al., 2006). Layered or massive lava flows form the lower part of the present Kolumbo cone and are displayed as stratified, high amplitude, subhorizontal reflectors on the profile.…”