Time‐space modeling of the dynamics of Santorini volcano (Greece) during the 2011–2012 unrest

Saltogianni, Vasso; Stiros, Stathis C.; Newman, A. V.; Flanagan, Kelly; Moschas, Fanis

doi:10.1002/2014jb011409

Cited by 20 publications

(33 citation statements)

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“…The swarm occurred immediately after the cessation of unrest in Santorini caldera that had started a year earlier and was characterized by intense seismicity and vertical/radial deformation [see Konstantinou et al ., , and references therein]. The temporal proximity of the caldera unrest and the swarm suggests a possible triggering effect that was subsequently confirmed through Coulomb stress modeling [ Feuillet , ; Saltogianni et al ., ]. Despite the transient nature of the swarm in the Sea of Crete, its generation provided us with the opportunity to probe into the stress regime in this aseismic part of the southern Aegean.…”

Section: Description Of Stress Inversion Resultsmentioning

confidence: 99%

Present‐day crustal stress field in Greece inferred from regional‐scale damped inversion of earthquake focal mechanisms

et al. 2017

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In this study we utilize regional and teleseismic earthquake moment tensor solutions in order to infer the contemporary crustal stress in the Greek region. We focus on crustal earthquakes and select only solutions with good waveform fits and well‐resolved nodal planes. A data set of 1614 focal mechanisms is used as input to a regional‐scale damped stress inversion algorithm over a grid whose node spacing is 0.35°. Several resolution and sensitivity tests are performed in order to ascertain the robustness of our results. Our findings show that for most of the Greek region the largest principal stress σ1 is vertically oriented and that the minimum principal stress axis σ3 are subhorizontal with a predominant N‐S orientation. In the SW Peloponnese the orientation of σ3 axes rotates clockwise and in SE Aegean counterclockwise. These results are in agreement with the generally accepted model that slab rollback combined with gravitational spreading of the Aegean lithosphere are the main causes of the extension. Transitions between different faulting types in NW Greece or in the Aegean occur within narrow zones in the order of tens of kilometers. A visual comparison of the principal horizontal stress axes and the principal strain axes derived from GPS observations shows good agreement, suggesting that the crust in the Greek region behaves largely in an elastic manner.

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Section: Description Of Stress Inversion Resultsmentioning

confidence: 99%

Present‐day crustal stress field in Greece inferred from regional‐scale damped inversion of earthquake focal mechanisms

et al. 2017

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“…Most recently, Saltogianni et al . [] explored whether multiple pressure sources were required to explain the GPS times series and patterns of seismicity throughout the period of unrest.…”

Section: Santorini Volcanic Complexmentioning

confidence: 99%

From quiescence to unrest: 20 years of satellite geodetic measurements at Santorini volcano, Greece

et al. 2015

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Periods of unrest at caldera-forming volcanic systems characterized by increased rates of seismicity and deformation are well documented. Some can be linked to eventual eruptive activity, while others are followed by a return to quiescence. Here we use a 20 year record of interferometric synthetic aperture radar (InSAR) and GPS measurements from Santorini volcano to further our understanding of geodetic signals at a caldera-forming volcano during the periods of both quiescence and unrest, with measurements spanning a phase of quiescence and slow subsidence (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(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 indicate an average subsidence rate of~6 mm/yr over the southern half of the intracaldera island Nea Kameni. This subsidence can be accounted for by a combination of thermal contraction of the 1866-1870 lava flows and load-induced relaxation of the substrate. For the period of unrest, we use a joint inversion technique to convert InSAR measurements from three separate satellite tracks and GPS observations from 10 continuous sites into a time series of subsurface volume change. The optimal location of the inflating source is consistent with previous studies, 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) × 10 6 m 3 , and the second pulse has a ΔV of (9.73 ± 0.10) × 10 6 m 3 . 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. We find no evidence suggesting a change in source location between the two pulses. The decline in the rates of volume change at the end of both pulses and the observed lag of the deformation signal behind cumulative seismicity, suggest a viscoelastic response. We use a simple model to show that two separate pulses of magma intruding into a shallow magma chamber surrounded by a viscoelastic shell can account for the observed temporal variation in cumulative volume change and seismicity throughout the period of unrest. Given the similarities between the geodetic signals observed here and at other systems, this viscoelastic model has potential use for understanding behavior at other caldera systems.

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“…The details of this algorithm and its assessment using synthetic data are analyzed in Saltogianni and Stiros [, ] and in Saltogianni et al . [].…”

Section: Geodetic Data and Analysismentioning

confidence: 99%

Fault slip source models for the 2014M_w6.9 Samothraki‐Gökçeada earthquake (North Aegean Trough) combining geodetic and seismological observations

Saltogianni

Gianniou²,

Taymaz

et al. 2015

JGR Solid Earth

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The 24 May 2014, Mw 6.9, Samothraki‐Gökçeada shallow (depth: 11 km) earthquake along the North Aegean Trough (NAT), at the westward extension of the North Anatolian Fault Zone (NAFZ), is investigated using constraints from seismological and geodetic data. A point source solution based on teleseismic long‐period P and SH waveforms suggests an essentially strike‐slip faulting mechanism consisting of two subevents, while from a finite fault inversion of broadband data the rupture area and slip history were estimated. Analysis of data from 11 permanent GPS stations indicated significant coseismic horizontal displacement but no significant vertical or postseismic slip. Okada‐type inversion of horizontal slip vectors, using the new TOPological INVersion algorithm, allowed precise modeling of the fault rupture both as single and preferably as double strike‐slip faulting reaching the surface. Variable slip models were also computed. The independent seismological and geodetic fault rupture models are broadly consistent with each other and with structural and seismological data and indicate reactivation of two adjacent fault segments separated by a bend of the NAT. The 2014 earthquake was associated with remote clusters of low‐magnitude aftershocks, produced low accelerations, and filled a gap in seismicity along the NAT in the last 50 years; faulting in the NAT seems not directly related to the sequence of recent faulting farther east, along the NAFZ and the seismic gap in the Marmara Sea near Istanbul.

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Time‐space modeling of the dynamics of Santorini volcano (Greece) during the 2011–2012 unrest

Cited by 20 publications

References 46 publications

Present‐day crustal stress field in Greece inferred from regional‐scale damped inversion of earthquake focal mechanisms

Present‐day crustal stress field in Greece inferred from regional‐scale damped inversion of earthquake focal mechanisms

From quiescence to unrest: 20 years of satellite geodetic measurements at Santorini volcano, Greece

Fault slip source models for the 2014M_w6.9 Samothraki‐Gökçeada earthquake (North Aegean Trough) combining geodetic and seismological observations

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Time‐space modeling of the dynamics of Santorini volcano (Greece) during the 2011–2012 unrest

Cited by 20 publications

References 46 publications

Present‐day crustal stress field in Greece inferred from regional‐scale damped inversion of earthquake focal mechanisms

Present‐day crustal stress field in Greece inferred from regional‐scale damped inversion of earthquake focal mechanisms

From quiescence to unrest: 20 years of satellite geodetic measurements at Santorini volcano, Greece

Fault slip source models for the 2014Mw6.9 Samothraki‐Gökçeada earthquake (North Aegean Trough) combining geodetic and seismological observations

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Product

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Fault slip source models for the 2014M_w6.9 Samothraki‐Gökçeada earthquake (North Aegean Trough) combining geodetic and seismological observations