Microseismic activity in the Hellenic Volcanic Arc, Greece, with emphasis on the seismotectonic setting of the Santorini–Amorgos zone

Bohnhoff, Marco; Rische, M.; Meier, Thomas; Becker, Dirk; Stavrakakis, G.; Harjes, Hans-Peter

doi:10.1016/j.tecto.2006.03.024

Cited by 114 publications

(119 citation statements)

References 49 publications

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“…Earthquake activity at and around the Santorini volcanic complex is manifested with small magnitude earthquakes and low seismicity rates. The majority of earthquake foci are concentrated around the Columbos volcano, with fairly low activity observed at the rest of the complex (Bohnhoff et al, 2006;Dimitriadis et al, 2009). At present, it is not clear which part(s) of this activity is of tectonic or of volcanic origin.…”

Section: Introductionmentioning

confidence: 99%

Evidence of non-extensivity in the seismicity observed during the 2011–2012 unrest at the Santorini volcanic complex, Greece

Vallianatos

Michas

Papadakis

et al. 2013

Nat. Hazards Earth Syst. Sci.

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Abstract. During the period of October 2011-January 2012, an increase of earthquake activity has been observed in the volcanic complex of Santorini Island, Greece. Herein, the magnitude distribution of earthquakes as well as the temporal distribution of seismicity are studied. The statistics of both parameters exhibit complexity that is evident in the frequency-magnitude distribution and the inter-event time distribution, respectively. Because of this, we have used the analysis framework of non-extensive statistical physics (NESP), which seems suitable for studying complex systems. The observed inter-event time distribution for the swarm-like earthquake events, as well as the energy and the inter-event earthquake energy distributions for the observed seismicity can be successfully described with NESP, indicating the inherent complexity of the Santorini volcanic seismicity along with the applicability of the NESP concept to volcanic earthquake activity, where complex correlations exist.

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Section: Introductionmentioning

confidence: 99%

Evidence of non-extensivity in the seismicity observed during the 2011–2012 unrest at the Santorini volcanic complex, Greece

Vallianatos

Michas

Papadakis

et al. 2013

Nat. Hazards Earth Syst. Sci.

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“…The seismic moment of the first event is estimated to be 4.2-7.02×10 19 Nm corresponding to a mean moment magnitude of 7.1, a mean slip on the fault of about 1 m and a mean rupture area of about 900 km 2 . Although the Santorini-Amorgos graben is currently characterized by spatially and temporarily varying clusters of microseismic activity confined to the upper crust that are very likely related to fluid flow and the volcanic activity along the fault zone (Dimitriadis et al, 2005;Bohnhoff et al, 2006;Kolaitis et al, 2007;Dimitriadis et al, 2009;Hensch, 2009;Brüstle, 2012;Newman et al, 2012;Chouliaras et al, 2012;Vallianatos et al, 2013), the first of the Amorgos twin earthquakes shows the disquieting evidence for the extreme seismic hazard in this area.…”

Section: Discussionmentioning

confidence: 99%

“…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%

“…Local seismicity occurs at depths of 3-9 km within a 3 km wide vertical column beneath the northeastern flank of the submarine volcano as a result of magmatic intrusions (Dimitriadis et al, 2005;Bohnhoff et al, 2006;Kolaitis et al, 2007;Dimitriadis et al, 2009;Hensch, 2009). Focal mechanisms of these earthquakes also tend to show NE-SW striking normal faulting mechanisms implying a strong connection to the Kameni-Coloumbo fracture, the southern extension of the western Santorini-Amorgos fault zone.…”

Section: Introductionmentioning

confidence: 99%

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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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“…The last recorded volcanic activity at Kolumbo took place in 1650 AD and produced ash plumes that perforated the water surface, ash falls and tsunami on the coasts of the neighboring islands, and around 70 fatalities by volcanic gases in Santorini (Fouqué, 1879;Dominey-Howes et al, 2000;Nomikou et al, 2012b). The choice of Kolumbo is motivated by evidences of seismicity beneath the volcano (Bohnhoff et al, 2006;Dimitriadis et al, 2009), the existence of an active crustal magma chamber (Dimitriadis et al, 2010), intense CO 2 degassing from a hydrothermal field (Sigurdsson et al, 2006;Nomikou et al, 2013a;Kilias et al, 2013), and accumulation of acidic water in the crater ).…”

Section: Introductionmentioning

confidence: 99%

Numerical simulations of tsunamis generated by underwater volcanic explosions at Karymskoye lake (Kamchatka, Russia) and Kolumbo volcano (Aegean Sea, Greece)

Ulvrová

Paris

Kelfoun

et al. 2014

Nat. Hazards Earth Syst. Sci.

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Abstract. Increasing human activities along the coasts of the world provoke the necessity to assess tsunami hazard from different sources (earthquakes, landslides, volcanic activity). In this paper, we simulate tsunamis generated by underwater volcanic explosions from (1) a submerged vent in a shallow water lake (Karymskoye Lake, Kamchatka), and (2) from Kolumbo submarine volcano (7 km NE of Santorini, Aegean Sea, Greece). The 1996 tsunami in Karymskoye lake is a well-documented example and thus serves as a case study for validating the calculations. The numerical model reproduces realistically the tsunami run-ups measured onshore. Systematic numerical study of tsunamis generated by explosions of the Kolumbo volcano is then conducted for a wide range of energies. Results show that in case of reawakening, the Kolumbo volcano might represent a significant tsunami hazard for the northern, eastern and southern coasts of Santorini, even for small-power explosions.

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Microseismic activity in the Hellenic Volcanic Arc, Greece, with emphasis on the seismotectonic setting of the Santorini–Amorgos zone

Cited by 114 publications

References 49 publications

Evidence of non-extensivity in the seismicity observed during the 2011–2012 unrest at the Santorini volcanic complex, Greece

Evidence of non-extensivity in the seismicity observed during the 2011–2012 unrest at the Santorini volcanic complex, Greece

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

Numerical simulations of tsunamis generated by underwater volcanic explosions at Karymskoye lake (Kamchatka, Russia) and Kolumbo volcano (Aegean Sea, Greece)

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