Recent geodetic unrest at Santorini Caldera, Greece

Newman, A. V.; Stiros, Stathis C.; Feng, Lujia; Psimoulis, Panos; Moschas, Fanis; Saltogianni, Vasso; Jiang, Yan; Papazachos, C. B.; Panagiotopoulos, Dimitris; Karagianni, Eleni; Vamvakaris, D.

doi:10.1029/2012gl051286

Cited by 111 publications

(162 citation statements)

References 20 publications

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“…The increased seismicity was accompanied by up to 10 cm inflation of the islands measured by GPS networks and by radar interferometry, corresponding to a modelled volume increase of about 10-20 million m 3 at 3-6 km beneath the northern caldera basin (Newman et al, 2012;Parks et al, 2012;Papoutsis et al, 2013;Foumelis et al, 2013). Small increases in the fluxes of H2 and mantle-derived CO2 also occurred during the unrest (Parks et al, 2013;Tassi et al, 2013).…”

Section: The 2011-2012 Unrest Periodmentioning

confidence: 96%

“…The volume increase associated with deformation was attributed to intrusion of magma and associated fluids (Newman et al, 2012;Parks et al, 2012). Both volume and gas composition changes may also have been in part tectonic in origin due to stress accumulation on regional faults (Feullet, 2013) caused by flexuring of the caldera block and increasing rock permeability and hence gas emissions (Tassi et al, 2013).…”

Section: The 2011-2012 Unrest Periodmentioning

confidence: 99%

“…The number of small-magnitude (M < 3.6) volcanotectonic earthquakes greatly increased during the 15-month-long unrest period at depths of 1-6 km on a near-vertical 6 km-long plane along the Kameni line (Newman et al, 2012). The increased seismicity was accompanied by up to 10 cm inflation of the islands measured by GPS networks and by radar interferometry, corresponding to a modelled volume increase of about 10-20 million m 3 at 3-6 km beneath the northern caldera basin (Newman et al, 2012;Parks et al, 2012;Papoutsis et al, 2013;Foumelis et al, 2013).…”

Section: The 2011-2012 Unrest Periodmentioning

confidence: 99%

“…The ISMOSAV monitoring network recorded changes in the monitored parameters (seismicity, topographic changes, thermal state, chemistry of the hot fluids and soil gases; Tassi et al, 2013), and campaign measurements also detected changes in soil gas fluxes and compositions (Parks et al, 2013;Rizzo et al, 2015). In addition, GPS networks (Newman et al, 2012) and satellite radar observations detected ground uplift at rates approaching 1 cm/month on parts of the Kameni islands (Parks et al, 2012Foumelis et al, 2013;Lagios et al, 2013), with higher (but unmeasured) uplift rates possibly occurring under water. All of these changes exceeded the limits defining the background state of the Kamenis volcanic center, based on the monitoring network data for the last 20 years.…”

Section: Introductionmentioning

confidence: 99%

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Volcanic Hazard Assessment at Santorini Volcano: A Review and a Synthesis in the Light of the 2011-2012 Santorini Unrest

et al. 2017

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Section: The 2011-2012 Unrest Periodmentioning

confidence: 96%

Section: The 2011-2012 Unrest Periodmentioning

confidence: 99%

Section: The 2011-2012 Unrest Periodmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Volcanic Hazard Assessment at Santorini Volcano: A Review and a Synthesis in the Light of the 2011-2012 Santorini Unrest

et al. 2017

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“…During the last 60 yr the Santorini volcano exhibited only weak background seismicity (Dimitriadis et al, 2005(Dimitriadis et al, , 2009Bohnhoff et al, 2006;Hensch, 2009), except for a period of unusually high seismicity lasting from January 2011 to January 2012, with local magnitudes up to 3.2 accompanied by surface deformations within the Caldera as a result of magma upwelling (Newman et al, 2012;Chouliaras et al, 2012;Vallianatos et al, 2013). In contrast, the submarine Coloumbo volcano is characterized Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Focal mechanism and depth of the 1956 Amorgos twin earthquakes from waveform matching of analogue seismograms

Brüstle¹,

Friederich

Meier

et al. 2014

Solid Earth

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Abstract. Historic analogue seismograms of the large 1956Amorgos twin earthquakes which occurred in the volcanic arc of the Hellenic subduction zone (HSZ) were collected, digitized and reanalyzed to obtain refined estimates of their depth and focal mechanism. In total, 80 records of the events from 29 European stations were collected and, if possible, digitized. In addition, bulletins were searched for instrument parameters required to calculate transfer functions for instrument correction. A grid search based on matching the digitized historic waveforms to complete synthetic seismograms was then carried out to infer optimal estimates for depth and focal mechanism. Owing to incomplete or unreliable information on instrument parameters and frequently occurring technical problems during recording, such as writing needles jumping off mechanical recording systems, much less seismograms than collected proved suitable for waveform matching.For the first earthquake, only seven seismograms from three different stations at Stuttgart (STU), Göttingen (GTT) and Copenhagen (COP) could be used. Nevertheless, the waveform matching grid search yields two stable misfit minima for source depths of 25 and 50 km. Compatible fault plane solutions are either of normal faulting or thrusting type. A separate analysis of 42 impulsive first-motion polarities taken from the International Seismological Summary (ISS bulletin) excludes the thrusting mechanism and clearly favors a normal faulting solution with at least one of the potential fault planes striking in SW-NE direction. This finding is consistent with the local structure and microseismic activity of the Santorini-Amorgos graben. Since crustal thickness in the Amorgos area is generally less than 30 km, a source depth of 25 km appears to be more realistic.The second earthquake exhibits a conspicuously high ratio of body wave to surface wave amplitudes suggesting an intermediate-depth event located in the Hellenic WadatiBenioff zone. This hypothesis is supported by a focal mechanism analysis based on first-motion polarities, which indicates a mechanism very different from that of the first event. A waveform matching grid search done to support the intermediate-depth hypothesis proved not to be fruitful because the body wave phases are overlain by strong surface wave coda of the first event inhibiting a waveform match. However, body to surface wave amplitude ratios of a modern intermediate-depth event with an epicenter close to the island of Milos observed at stations of the German Regional Seismic Network (GRSN) exhibit a pattern similar to the one observed for the second event with high values in a frequency band between 0.05 Hz and 0.3 Hz. In contrast, a shallow event with an epicenter in western Crete and nearly identical source mechanism and magnitude, shows very low ratios of body and surface wave amplitude up to 0.17 Hz and higher ratios only beyond that frequency. Based on this comparison with a modern event, we estimate the source depth of the second event to be greater than ...

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Sill intrusion as a source mechanism of unrest at volcanic calderas

et al. 2014

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The interpretation of dynamic processes that occur in volcanic calderas is not simple. The ground deformations and the local seismicity, which in other volcanic contexts are usually regarded as precursors to eruption, in caldera environment in many cases are not followed by any eruption. We formulate a general hypothesis that can explain these behaviors. Our hypothesis is that the intrusion of a sill can be responsible for the dynamics observed during unrest at calderas. In order to investigate the reliability of this hypothesis, we developed a dynamic model of sill intrusion in a shallow volcanic environment. In our model, the sill, fed by a deeper magma reservoir, intrudes below a horizontal elastic plate, representing the overlying rocks, and expands with axisymmetric geometry. The model is based on the numerical solution of the equation for the elastic plate, coupled with a Navier-Stokes equation for simulating the dynamics of the sill intrusion. We performed a number of simulations, with the objective of showing the main features of the model. In the experiments, when the feeding process stops, the vertical movement reverses its trend and the area of maximum uplift undergoes subsidence. Under certain conditions the subsidence can occur even during the intrusion of the sill. The stress field produced by the intrusion is mainly concentrated in a circular zone that follows the sill intrusion front. The features predicted by the model are consistent with many observations carried out on different calderas as reported in the scientific literature.

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Recent geodetic unrest at Santorini Caldera, Greece

Cited by 111 publications

References 20 publications

Volcanic Hazard Assessment at Santorini Volcano: A Review and a Synthesis in the Light of the 2011-2012 Santorini Unrest

Volcanic Hazard Assessment at Santorini Volcano: A Review and a Synthesis in the Light of the 2011-2012 Santorini Unrest

Focal mechanism and depth of the 1956 Amorgos twin earthquakes from waveform matching of analogue seismograms

Sill intrusion as a source mechanism of unrest at volcanic calderas

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