Santorini

Volcano number:212040
Region:Mediterranean and W. Asia
Country:Greece
Geodetic measurements?Yes
Deformation observation?Yes
Measurement method(s):InSAR, GPS - continuous, GPS - campaign
Duration of observation:
Inferred cause of deformation:
Characteristics of deformation:

Between 1950 and 2010, the volcano remained quiet, with no documented reports of seismic activity. Although reports of minor inflation were documented in the northern part of the caldera between 1994 and 2000, other studies have argued that the observations are not consistent with the inflation of a shallow magma chamber (Parks et al., 2015 and references therein). Multiple measurements of surface deformation between 1992 and 2010 have confirmed a slow subsidence signal in the southwest region of Nea Kameni. The location and velocity of this signal remained relatively stable throughout this period, with an observed average subsidence rate on the order of 5 to 6 mm/yr (Parks et al., 2015 and references therein).

Parks et al. (2015) use a 20 year record of InSAR and GPS measurements, with measurements spanning a phase of quiescence and slow subsidence (1993–2010), followed by a phase of unrest (January 2011 to April 2012) with caldera-wide inflation and seismicity.

Mean InSAR velocity maps from 1993–2010 from Parks et al. (2015) indicate an average subsidence rate of ~6 mm/yr over the southern half of the intracaldera island Nea Kameni. This subsidence is due to a combination of thermal contraction of the 1866–1870 lava flows and load-induced relaxation of the substrate.

For the period of unrest,  the location of the inflating source is situated north of Nea Kameni at a depth of ~4 km. However, the time series reveals two distinct pressure pulses. The first pulse corresponds to a volume change (ΔV) within the shallow magma chamber of (11.56 ± 0.14) × 106 m3, and the second pulse has a ΔV of (9.73 ± 0.10) × 106 m3. The relationship between the timing of these pulses and microseismicity observations suggests that these pulses may be driven by two separate batches of magma supplied to a shallow reservoir. 

Reference:Parks, M. M., Moore, J. D., Papanikolaou, X., Biggs, J., Mather, T. A., Pyle, D. M., ... & Nomikou, P. (2015). From quiescence to unrest: 20 years of satellite geodetic measurements at Santorini volcano, Greece. Journal of Geophysical Research: Solid Earth, 120(2), 1309-1328.
Reference:Smithsonian Institution Global Volcanism Program
http://www.volcano.si.edu/volcano.cfm?vn=212040
Location:25.396, 36.404

View of Santorini volcano. Source: Smithsonian Institution Global Volcanism Program

Source: Parks et al. (2015). Map of Santorini showing the location of recent seismic activity and continuous GPS (cGPS) sites. The black dots show the epicenters of earthquakes greater than local magnitude 2.0 occurring from October 2010 to September 2012.  NK and PK labels represent the islands of Nea Kameni and Palea Kameni, respectively. The cGPS sites are presented by the blue triangles. N.B. Open access journal article.