Geodetic evidence and modeling of a slow, small-scale inflation episode in the Thera (Santorini) volcano caldera, Aegean Sea

Abstract Analysis of a radial geodetic monitoring record indicated small-scale inflation of the NW part of the Thera (Santorini) caldera (up to 10 cm baseline length increase) between 1994 and 2000, corresponding to up to 2 * 10−5 strain, and subsequent stabilization especially after 2006, as GPS data indicate. The southern part of the caldera on the contrary remained practically stable. This partial caldera inflation was assigned to slow magma intrusion which was not associated with changes in the seismicity. Using a stochastic approach based on numerical analysis and the theory of graphs and sets, the Mogi source of this magmatic activity was identified between the Nea Kammeni and the Therasia islets, along a major tectonovolcanic lineament, at a depth of around 1 km, or possibly 5.5 km, it remained stable during the whole small-scale inflation period and was associated with small-scale pressure changes. Slow-deformation events have been observed in other volcanoes as well, but they were associated with abrupt seismicity changes.

[1]  Giuseppe Puglisi,et al.  New integrated geodetic monitoring system at Stromboli volcano (Italy) , 2005 .

[2]  A. Newman,et al.  Constraints on continued episodic inflation at Long Valley Caldera, based on seismic and geodetic observations , 2009 .

[3]  S. Stiros,et al.  GEODETIC MONITORING OF THE SANTORINI (THERA) VOLCANO , 2003 .

[4]  J. C. Savage,et al.  Precision of geodolite distance measurements for determining fault movements , 1973 .

[5]  T. Druitt,et al.  Caldera formation on Santorini and the physiography of the islands in the late Bronze Age , 1992 .

[6]  Fabrizio Innocenti,et al.  Tertiary to Quaternary evolution of volcanism in the Aegean region , 1984, Geological Society, London, Special Publications.

[7]  Stathis C. Stiros,et al.  Landslide monitoring based on geodetically derived distance changes , 2004 .

[8]  James Foster,et al.  Magmatically Triggered Slow Slip at Kilauea Volcano, Hawaii , 2008, Science.

[9]  Giuseppe De Natale,et al.  3-D Modelling of Campi Flegrei Ground Deformations: Role of Caldera Boundary Discontinuities , 2004 .

[10]  C. Roman,et al.  Marine investigations of Greece's Santorini Volcanic Field , 2006 .

[11]  John J. Dvorak,et al.  Volcano geodesy: The search for magma reservoirs and the formation of eruptive vents , 1997 .

[12]  Y. Okada.  Surface deformation due to shear and tensile faults in a half-space , 1985 .

[13]  D. Patanè,et al.  Fast deformation processes and eruptive activity at Mount Etna (Italy) , 1996 .

[14]  F. Sigmundsson,et al.  Multiple volcano deformation sources in a post-rifting period : 1989-2005 behaviour of Krafla, Iceland constrained by levelling, tilt and GPS observations , 2008 .

[15]  John J. Dvorak,et al.  Recent Ground Movement and Seismic Activity in Campi Flegrei , 1991 .

[16]  G. Nunnari,et al.  The global positioning system as a useful technique for measuring ground deformations in volcanic areas , 1994 .

[17]  R. Sparks,et al.  The Minoan eruption of Santorini, Greece , 1976, Journal of the Geological Society.

[18]  Paul Segall,et al.  Kilauea slow slip events: Identification, source inversions, and relation to seismicity , 2009 .

[19]  R. S. J. Sparks,et al.  Explosive volcanism on Santorini, Greece , 1989, Geological Magazine.

[20]  S. Stiros,et al.  Direct determination of tidal levels for engineering applications based on biological observations , 2008 .

[21]  G. Heiken,et al.  Caldera Development During the Minoan Eruption, Thira, Cyclades, Greece , 1984 .

[22]  G. Vougioukalakis,et al.  The south Aegean active volcanic arc : present knowledge and future perspectives , 2005 .

[23]  T. Meier,et al.  Microseismic activity in the Hellenic Volcanic Arc, Greece, with emphasis on the seismotectonic setting of the Santorini–Amorgos zone , 2006 .

[24]  T. Meier,et al.  Seismicity and active tectonics at Coloumbo Reef (Aegean Sea, Greece): Monitoring an active volcano at Santorini Volcanic Center using a temporary seismic network , 2009 .

[25]  John R. Elliott,et al.  Quantitative morphology, recent evolution, and future activity of the Kameni Islands volcano, Santorini, Greece , 2006 .

[26]  K. Mogi.  Relations between the Eruptions of Various Volcanoes and the Deformations of the Ground Surfaces around them , 1958 .

[27]  S. Stiros,et al.  Mean deformation tensor and mean deformation ellipse of an excavated tunnel section , 2009 .

[28]  Pierre Briole,et al.  Ground deformation at Nisyros volcano (Greece) detected by ERS-2 SAR differential interferometry , 2003 .

[29]  T. Meier,et al.  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 , 2010 .

[30]  R. Cattin,et al.  Effects of superficial layers on coseismic displacements for a dip-slip fault and geophysical implications , 1999 .

[31]  Kristy F. Tiampo,et al.  Spherical and ellipsoidal volcanic sources at Long Valley caldera, California, using a genetic algorithm inversion technique , 2000 .

[32]  J. C. Savage,et al.  Strain Accumulation Rates in the Western United States Between 1970 and 1978 (Paper 9B0527) , 1979 .

[33]  W. Prescott,et al.  Short-range distance measurements along the San Andreas fault system in central California, 1975 to 1979 , 1981 .

[34]  I. Stewart,et al.  The Archaeology of Geological Catastrophes , 2000 .

[35]  P. Burton,et al.  Seismicity in the Hellenic Volcanic Arc: relation between seismic parameters and the geophysical fields in the region , 1994 .

[36]  C. Papazachos,et al.  Recent seismic activity (1994-2002) of the Santorini volcano using data from local seismological network , 2005 .

[37]  Alastair H. F. Robertson,et al.  Introduction: aspects of the geological evolution of the Eastern Mediterranean , 1984, Geological Society, London, Special Publications.

[38]  J. Huijsmans,et al.  Post-caldera dacites from the Santorini volcanic complex, Aegean Sea, Greece: an example of the eruption of lavas of near-constant composition over a 2,200 year period , 1986 .

[39]  G. Heiken,et al.  Tsunami Generated by the Late Bronze Age Eruption of Thera (Santorini), Greece , 2000 .

[40]  Shinji Toda,et al.  Evidence from the ad 2000 Izu islands earthquake swarm that stressing rate governs seismicity , 2002, Nature.