Tsunami Potential of Moderate Earthquakes: The July 1, 2009 Earthquake (Mw 6.45) and its Associated Local Tsunami in the Hellenic Arc

Bocchini, Gian Maria; Novikova, Tatyana; Papadopoulos, Gerassimos A.; Agalos, Apostolos; Mouzakiotis, E.; Karastathis, V.; Voulgaris, Nicholas

doi:10.1007/s00024-019-02246-9

Cited by 11 publications

(9 citation statements)

References 48 publications

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“…The relative motion between the Aegean region and the subducting slab is accommodated by shallowly dipping fault planes with dip angles <20° along the interplate seismogenic zone as indicated by fault-plane solutions [ 41 , 42 , 43 , 44 , 45 ]. Higher-angle reverse faults (dip angles > 30°), likely splaying off from the plate interface, are observed at shallower depths with respect to the interplate earthquakes [ 45 , 46 ] and have been observed as playing a major role in the seismogenesis along the outer Hellenic fore-arc, e.g., [ 47 , 48 ]. The predominant compressive stress regime observed in the study area to the west and southwest of Peloponnese changes to strike-slip in the area to the NW of Zakynthos, Kefalonia and Lefkada Islands along the so-called Kefalonia Fault Zone, e.g., [ 49 ] ( Figure 1 a).…”

Section: Methodsmentioning

confidence: 99%

Short-Term Foreshocks as Key Information for Mainshock Timing and Rupture: The Mw6.8 25 October 2018 Zakynthos Earthquake, Hellenic Subduction Zone

Papadopoulos

Agalos

Minadakis

et al. 2020

Sensors

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Significant seismicity anomalies preceded the 25 October 2018 mainshock (Mw = 6.8), NW Hellenic Arc: a transient intermediate-term (~2 yrs) swarm and a short-term (last 6 months) cluster with typical time-size-space foreshock patterns: activity increase, b-value drop, foreshocks move towards mainshock epicenter. The anomalies were identified with both a standard earthquake catalogue and a catalogue relocated with the Non-Linear Location (NLLoc) algorithm. Teleseismic P-waveforms inversion showed oblique-slip rupture with strike 10°, dip 24°, length ~70 km, faulting depth ~24 km, velocity 3.2 km/s, duration 18 s, slip 1.8 m within the asperity, seismic moment 2.0 × 1026 dyne*cm. The two largest imminent foreshocks (Mw = 4.1, Mw = 4.8) occurred very close to the mainshock hypocenter. The asperity bounded up-dip by the foreshocks area and at the north by the foreshocks/swarm area. The accelerated foreshocks very likely promoted slip accumulation contributing to unlocking the asperity and breaking with the mainshock. The rupture initially propagated northwards, but after 6 s stopped at the north bound and turned southwards. Most early aftershocks concentrated in the foreshocks/swarm area. This distribution was controlled not only by stress transfer from the mainshock but also by pre-existing stress. In the frame of a program for regular monitoring and near real-time identification of seismicity anomalies, foreshock patterns would be detectable at least three months prior the mainshock, thus demonstrating the significant predictive value of foreshocks.

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Section: Methodsmentioning

confidence: 99%

Short-Term Foreshocks as Key Information for Mainshock Timing and Rupture: The Mw6.8 25 October 2018 Zakynthos Earthquake, Hellenic Subduction Zone

Papadopoulos

Agalos

Minadakis

et al. 2020

Sensors

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“…The NOA-04 tide-gauge station, located in the port of Ierapetra, recorded a peak-to-trough excursion exceeding 30 cm, with a positive peak amplitude of about 20 cm recorded 23 minutes after the earthquake origin time, with a wave period of ~3.5 minutes. Small tsunami waves (less than 10 cm peak-totrough) were also recorded at the NOA-03 tide-gauge, located in the Kasos Island, where the peak amplitude of 5 cm was recorded at 13:53 UTC, and the wave period was estimated to be 8 minutes by Papadopoulos et al (2020) and 4.5 minutes by Heidarzadeh and Gusman (2021). As in the Mw 6.4, July 1, 2009, event (Bocchini et al, 2020), the tsunami was also observed in the Chrysi islet (located offshore south of Ierapetra), where no tide-gauges are operating.…”

Section: Introductionmentioning

confidence: 96%

“…Small tsunami waves (less than 10 cm peak-totrough) were also recorded at the NOA-03 tide-gauge, located in the Kasos Island, where the peak amplitude of 5 cm was recorded at 13:53 UTC, and the wave period was estimated to be 8 minutes by Papadopoulos et al (2020) and 4.5 minutes by Heidarzadeh and Gusman (2021). As in the Mw 6.4, July 1, 2009, event (Bocchini et al, 2020), the tsunami was also observed in the Chrysi islet (located offshore south of Ierapetra), where no tide-gauges are operating. No casualties, injuries or damage were reported due to the tsunami.…”

Section: Introductionmentioning

confidence: 96%

“…Another large tsunamigenic earthquake (M ~ 7.0-7.5) occurred near southern Crete on July 1, 1494 (Yolsal-Çevikbilen and Taymaz, 2012). More recently, an earthquake of Mw 7.5 occurred on February 9, 1948, near the coast of Karpathos, on the Pliny Trench (Papadopoulos et al, 2007) and, on July 1, 2009 (UTC 09:30), a moderate earthquake (Mw 6.5) located in the southern offshore margin of Crete caused a local tsunami of about 0.3 m of wave height (Bocchini et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

“…The 2020 Cretan Passage earthquake generated a local tsunami along the south-eastern coast of Crete, as reported by eyewitnesses and local authorities and documented by a series of pictures and video shootings taken by authorities, press, and amateurs at Arvi and Kastri villages (Papadopoulos et al, 2020). The NOA-04 tide-gauge station, located in the port of Ierapetra, recorded a peak-to-trough excursion exceeding 30 cm, with a positive peak amplitude of about 20 cm recorded 23 minutes after the earthquake origin time, with a wave period of ~3.5 minutes.…”

Section: Introductionmentioning

confidence: 99%

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Characterisation of fault plane and coseismic slip for the May 2, 2020, Mw 6.6 Cretan Passage earthquake from tide-gauge tsunami data and moment tensor solutions

Baglione

Lorito

Piatanesi

et al. 2021

Preprint

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Abstract. We present a source solution for the tsunami generated by the Mw 6.6 earthquake that occurred on May 2, 2020, about 807thinsp;km offshore south of Crete, in the Cretan Passage, on the shallow portion of the Hellenic Arc Subduction Zone (HASZ). The tide-gauges recorded this local tsunami on the southern coast of Crete island and Kasos island. We used these tsunami observations to constrain the geometry and orientation of the causative fault, the rupture mechanism and the slip amount. We first modelled an ensemble of synthetic tsunami waveforms at the tide-gauge locations, produced for a range of earthquake parameter values as constrained by some of the available moment tensor solutions. We allow for both a splay and a back-thrust fault, corresponding to the two nodal planes of the moment tensor solution. We then measured the misfit between the synthetic and the observed marigrams for each source parameter set. Our results identify the shallow steeply-dipping back-thrust fault as the one producing the lowest misfit to the tsunami data. However, a rupture on a lower angle fault, possibly a splay fault, with a sinistral component due to the oblique convergence on this segment of the HASZ, cannot be completely ruled out. This earthquake reminds us that the uncertainty regarding potential earthquake mechanisms at a specific location remains quite significant. In this case, for example, it is not possible to anticipate if the next event will be one occurring on the subduction interface, on a splay fault, or on a back-thrust which seems the most likely for the event under investigation. This circumstance bears important consequences because back-thrust and splay faults might enhance the tsunamigenic potential with respect to the subduction interface due to their steeper dip. Then, these results are relevant for tsunami forecasting both in the framework of the long-term hazard assessment and of the early warning systems.

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A Review of the Dynamics of Subduction Zone Initiation in the Aegean Region

Catlos

Çemen

2021

Preprint

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The Hellenic arc, where the African (Nubian) slab subducts beneath the Aegean and Anatolian microplates, has emerged as a type-locality for understanding subduction dynamics, including slab tear, slab fragments, drips, and transfer zones. Based on field evidence and geophysical, tectonics, and geochemical studies, it has been recognized that the subducting African slab is a primary driver for extension in the Aegean and Anatolian microplates and plays a significant role in accommodating present-day westward extrusion of the Anatolian microplate. Thus, understanding the Hellenic arc subduction zone initiation (SZI) age is critical in deciphering ancient mantle flow, how plate tectonics is maintained, and the mechanisms involved in triggering the onset of subduction. The SZI for the Hellenic arc has two disparate ages based on different lines of evidence. A Late Cenozoic (Eocene-Pliocene) SZI is proposed using the analysis of topography combined with estimates of slab age and depth, paleomagnetism, the timing of metamorphism, and volcanic activity, and timing of sedimentation within its accretionary wedge, the Mediterranean Ridge. This age follows an induced-transference SZI model, where a new subduction zone initiates following the jamming of an older subduction zone by buoyant crust due to regional compression, uplift, and underthrusting. A Late Cretaceous-Jurassic SZI age has also been proposed using reconstructions of images of subducted slabs seen using tomography and timing of obducted ophiolite fragments thought to be related to the system. In this case, the induced-transference SZI model fails, and a single subduction zone persists. As a result, continental lithospheric fragments and the ancient oceans between them become incorporated into the overall system without creating a new subduction zone. The presence of a long-lived subduction zone has implications for understanding Earth's mantle dynamics and how plate tectonics operates. This paper describes and summarizes the evidence for both models in the Aegean-Western Anatolia region.

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Tsunami Potential of Moderate Earthquakes: The July 1, 2009 Earthquake (Mw 6.45) and its Associated Local Tsunami in the Hellenic Arc

Cited by 11 publications

References 48 publications

Short-Term Foreshocks as Key Information for Mainshock Timing and Rupture: The Mw6.8 25 October 2018 Zakynthos Earthquake, Hellenic Subduction Zone

Short-Term Foreshocks as Key Information for Mainshock Timing and Rupture: The Mw6.8 25 October 2018 Zakynthos Earthquake, Hellenic Subduction Zone

Characterisation of fault plane and coseismic slip for the May 2, 2020, Mw 6.6 Cretan Passage earthquake from tide-gauge tsunami data and moment tensor solutions

A Review of the Dynamics of Subduction Zone Initiation in the Aegean Region

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