K. I. Konstantinou

National Central University | NCU · Department of Earth Sciences

The Santorini-Amorgos zone is an area rich in microseismicity at the center of the Hellenic volcanic arc. The microseismicity of the zone is distributed along the Santorini-Amorgos ridge and Kolumbo submarine volcano. In this study, we utilized crustal events that were recorded by temporary networks during September 2002 to July 2004 and October 20...

Despite their usefulness for volcano monitoring, emergent seismic signals such as volcanic tremor, or signals generated by lahars, are difficult to identify with confidence in a timely fashion. Machine learning algorithms offer an objective alternative to traditional methods of identifying such volcanoseismic signals, since they are able to handle...

Changes in seismicity parameters is often utilized as a tool for forecasting eruptive activity at volcanoes world-wide. One of these parameters is the slope of the Gutenberg-Richter law, known as the b-value, whose temporal variation is studied here as an indicator of volcanic activity. Four Alaskan volcanoes (Makushin, Martin, Redoubt, Spurr) were...

Permutation entropy (PE) is a complexity metric that encodes a time series into sequences of symbols and can be used to decipher between deterministic and stochastic behavior. This study investigates PE variations in seismic noise during three eruption cycles in 2011, 2017, and 2018 at Shinmoedake volcano, Japan. The volcano is monitored by a dedic...

Large magnitude (Mw ∼ ≥6) earthquakes in extensional settings are often associated with simultaneous rupture of multiple normal faults as a result of static and/or dynamic stress transfer. Here, we report details of the coseismic breaching of a previously unrecognized large‐scale fault relay zone in central Greece, through three successive normal f...

The accelerating growth of seismic unrest before eruptions has been observed at many volcanoes and utilized for eruption forecasts. However, there are still many eruptions for which no precursory unrest has been identified, even at well-monitored volcanoes. The recent eruptions of Shinmoe-dake, Japan, had been another negative example of this kind....

Merapi volcano is located in central Java and is the most active volcano in Indonesia. Many thousands live on the volcano's flanks which itself is 28 km (17 mi) north of Yogyakarta and its 2.4 million inhabitants. Given this population at risk, and a history of 73 recorded eruptions in the past 500 years, the hazards posed by Merapi are worthy of s...

The Santorini-Amorgos zone is located in the central part of the Hellenic volcanic arc and is hosting eight large faults as well as Kolumbo and Santorini volcanic centers. The largest earthquake (Mw ~ 7.1) in the southern Aegean during the 20th century also occurred in this area on 9 July 1956. A total of 1868 crustal events were recorded by tempor...

In this study, we measured shear wave splitting (fast direction and delay time) from 5193 crustal earthquakes that occurred in the south Aegean that were recorded by 65 stations of the EGELADOS, GEOFON, and MedNet networks between November 2005–January 2007. We utilized the Multiple Filter Automatic splitting Technique (MFAST) that allows quick pro...

We applied sensitivity kernels based on perturbation theory to map the crustal intrinsic and scattering attenuation of S‐wave envelopes in the southern Aegean. The southern Aegean crust is under extension due to the rollback of the Nubian plate, which is subducting beneath the Aegean plate. The waveforms of 104531 crustal events (< 40 km) were used...

Kolumbo submarine volcano lies 7 km NE of Santorini caldera and its last eruption which occurred in 1650 AD, caused damage and casualties to the nearby islands. Here a simple model of a chamber, containing silicic magma underlain by a smaller quantity of mafic magma, is utilised in order to understand the chamber behaviour during the 1650 AD erupti...

Improving the ability to detect and characterize long-duration volcanic tremor is crucial to understand the long-term dynamics and unrest of volcanic systems. We have applied data reduction methods (permutation entropy and polarization degree, among others) to characterize the seismic wave field near Copahue volcano (Southern Andes) between June 20...

Mayon Volcano on eastern Luzon Island is the most active volcano in the Philippines. The high level of vulnerability to volcanic hazards is apparent since Mayon is surrounded by eight cities and municipalities with a total population of approximately one million inhabitants. Thus there is an urgent need to develop and expand reliable and affordable...

The existence of active faults near large cities poses significant risk to the life and property of its inhabitants as well as to its public infrastructure. Here, we investigate the interplay between seismicity, active faulting, and interseismic strain accumulation within a radius of ∼50 km from the metropolitan area of Athens, the capital of Greec...

This study performs a reanalysis of the seismicity recorded during the 1996 Gjálp eruption that occurred at NW Vatnajökull, Iceland. The seismicity was recorded by the temporary HOTSPOT network consisting of 30 three-component broadband stations. In total 301 events were identified between 29 September and 12 October and their phases were manually...

We relocated the seismicity in SE Aegean that was recorded by both permanent and temporary seismic networks during 2004–2018 in order to investigate its correlation with the active faults in this area. P and S-phase travel times of best quality events were used to estimate a minimum 1D velocity model with station delays by utilizing VELEST. This ve...

Shallow hydrothermal vents are of pivotal relevance for ocean biogeochemical cycles, including seawater dissolved heavy metals and trace elements as well as the carbonate system balance. The Kueishan Tao (KST) stratovolcano off Taiwan is associated with numerous hydrothermal vents emitting warm sulfur-rich fluids at so-called White Vents (WV) and Y...

Southern Aegean is characterized by an ongoing process of oceanic subduction. In this study, 1718 intermediate depth (> 35 km) events recorded by temporary and permanent seismic networks in southern Aegean are used to study the spatial distribution of random inhomogeneities using peak delay times of S-waves. Peak delay times (t p ) are measured as...

Erebus is an intraplate stratovolcano of phonolitic composition located at the southern end of Terror Rift within the West Antarctica Rift system. The volcanic edifice of Erebus exhibits a summit plateau that hosts the main crater and a smaller inner crater that contains a persistent lava lake. Volcano-seismic signals are recorded at Erebus by a pe...

A collaborative strong motion array comprised mainly of low cost sensors has been deployed in the Patras city, Greece. Currently, it combines: 4 standard accelerometric stations operated by the National Observatory of Athens, Institute of Geodynamics (NOA) and 15 P-Alert MEMS acceleration devices deployed in public sector buildings, schools and pri...

Southern Aegean is characterized by an ongoing process of oceanic subduction. In this study, 1718 intermediate depth (> 35 km) events recorded by temporary and permanent seismic networks in southern Aegean are used to study the spatial distribution of random inhomogeneities using peak delay times of S-waves. Peak delay times (t p) are measured as t...

Erebus is an intraplate stratovolcano of phonolitic composition located at the southern end of Terror Rift within the West Antarctica Rift system. The volcanic edifice of Erebus exhibits a summit plateau that hosts the main crater and a smaller inner crater that contains a persistent lava lake. Volcano-seismic signals are recorded at Erebus by a pe...

Demonstrating how methods used in fields like biomedical research for measuring the randomness of observable data can be used to predict when volcanoes are close to eruption. Developing better forecasting systems is an urgent priority for civil managers and researchers, but these new systems will need to be easily deployed to areas with minimal res...

This study relocates the seismicity in NE Aegean during the period 2011–2017 using data recorded by the Hellenic Unified Seismic Network (HUSN) in order to elucidate the relationship between seismicity and active faults in this area. P- and S-phase travel times of well-recorded events were first inverted in order to derive a minimum 1D velocity mod...

This study investigates the hazard posed by Volcanic Ballistic Projectiles (VBPs) in the area surrounding Mt Chihshin, Tatun Volcano Group, northern Taiwan. Based on the volcano’s current evolutionary stage, we consider two types of volcanic activity during which VBPs can be generated, namely hydrothermal and vulcanian eruptions. Hydrothermal erupt...

During 2017 significant seismic activity occurred between the Greek island of Lesvos and the Turkish mainland. This activity started in February 2017 with a series of four moderate (Mw ∼5.0-5.2) earthquakes and their af-tershocks at the Biga peninsula, north of Lesvos island. It was followed on 12 June 2017 by a large (Mw ∼6.3) earthquake to the so...

We perform a systematic comparison between local and moment magnitudes in Greece for the period 2008–2016 when both magnitudes have been determined using waveform data recorded by the Hellenic Unified Seismic Network (HUSN). Differences between the two magnitudes scales on average do not exceed ± 0.2 units as has been found in other regions worldwi...

Based on its numerous historical explosive eruptions and high potential hazards to nearby population of millions, Taal Volcano is one of the most dangerous “Decade Volcanoes” in the world. To provide better investigation on local seismicity and seismic structure beneath Taal Volcano, we deployed a temporary seismic network consisting of eight stati...

The tectonics of northern Aegean are affected by the westward push of Anatolia and the gravitational spreading of the Aegean lithosphere that promote transtensional deformation in the area. This regime is also responsible for the creation of a series of pull-apart basins, collectively known as the North Aegean Trough. This work accurately relocates...

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 dataset of 1614 focal mechanisms is used as input to a regional-scale damped s...

Ambient seismic noise is characterized by randomness incurred by the random position and strength of the noise sources as well as the heterogeneous properties of the medium through which it propagates. Here we use ambient noise data recorded prior to the 1996 Gjálp eruption in Iceland in order to show that a reduction of noise randomness can be a c...

On June 8, 2008, a Mw 6.4 earthquake occurred on a strike-slip fault in northwest Peloponnese, Greece, 35 km southwest of the city of Patras. We analysed part of the aftershock sequence of the 2008 earthquake, recorded by a portable network of six stations and a permanent station of the Hellenic Unified Seismological Network, in order to perform a...

On April 2007, an earthquake swarm occurred in the vicinity of Trichonis Lake, western Greece. The seismic activity started on April 10th , 2007 after the occurrence of three moderate size earthquakes Mw 5.0-5.2. We performed shear wave splitting measurements on seismic events recorded during the first week of the seismic activity by a portable net...

On June 8, 2008, a Mw 6.4 earthquake occurred on a strike-slip fault in northwest Peloponnese, Greece, 35 km southwest of the city of Patras. We analysed part of the aftershock sequence of the 2008 earthquake, recorded by a portable network of six stations and a permanent station of the Hellenic Unified Seismological Network, in order to perform a...

On April 2007, an earthquake swarm occurred in the vicinity of Trichonis Lake, western Greece. The seismic activity started on April 10th, 2007 after the occurrence of three moderate size earthquakes Mw 5.0-5.2. We performed shear wave splitting measurements on seismic events recorded during the first week of the seismic activity by a portable netw...

The Hellenic region is the seismically most active area in Europe, having experienced numerous large magnitude catastrophic earthquakes and associated devastating tsunamis. A means of mitigating these potential hazards is by better understanding the patterns of spatial and temporal deformation of the crust across the Hellenic orogenic system, over...

Many different agencies and research groups routinely estimate moment magnitudes (Mw) in the Mediterranean area as a means of offering an unbiased quantitative assessment of earthquake size. In this work, a comprehensive comparison is undertaken of the moment magnitudes estimated for earthquakes in the Greek region by the Global Centroid Moment Ten...

Volcanic Ballistic Projectiles (VBPs) are rock/magma fragments of variable size that are ejected from active vents during explosive eruptions. VBPs follow almost parabolic trajectories that are influenced by gravity and drag forces before they reach their impact point on the Earth's surface. Owing to their high temperature and kinetic energies, VBP...

On 2010 January 18 and 22, two earthquakes of Mw 5.3 and 5.2, respectively, occurred near the town of Efpalio on the western Gulf of Corinth. We performed a shear wave splitting analysis using the cross-correlation method and calculated Vp/Vs ratios for events that occurred in the epicentral area of the Efpalio earthquakes, between 2009 January and...

A dataset of moment magnitudes and rupture areas is compiled for 53 earthquakes that occurred in the Mediterranean region during the period 1976–2013. Moment magnitudes of these events range from 4.45 to 7.56, and the rupture areas are mainly inferred from the dimensions of their aftershocks zone. Three magnitude–area relationships that have been d...

Taiwan is subjected to several natural hazards such as extreme weather, seis-mic activity or tsunamis excited by earthquakes occurring along the Pacific Ocean sub-duction zones. Fortunately, Taiwan has not experienced any volcanic activity in historical times, a fact which reinforced the belief that its volcanic centers are by now extinct. During t...

We analyze 25 episodes of volcanic tremor recorded from 22 November until 31 December 2009 at Mt Semeru volcano in order to investigate their spectral and dynamical properties. The overtone frequencies for most of the tremor events indicate a pattern of period-doubling, which is one possible route that can lead a system to chaotic behavior. Exponen...

Santorini caldera has experienced several explosive eruptions in the past, the most well-known of these being the Late Bronze Age (ca. 1628 BC) eruption that may have been responsible for the demise of the Minoan civilization. Since the early 1950's the volcano has been dormant without exhibiting any significant activity except from discharge of lo...

The Corinth Gulf is often referred to as a natural laboratory for the study of continental rift tectonics. It is a fast-spreading intra-continental rift, with the geodetically measured extension varying from ~5 mm/yr at the eastern part, to ~15 mm/yr at the western part. It is structured by a set of E-W striking, en-echelon active normal faults, pr...

On June 8, 2008, at 12:25 GMT, a Mw 6.4 earthquake, the Movri Mountain earthquake, occurred in the area of northwest Peloponnese, western Greece. The epicenter was located in the municipality of Movri, 35 km southwest of Patras. For this study, a crustal anisotropy analysis was performed in the epicentral area of the Movri Mountain earthquake. Spec...

The Tatun Volcano Group (TVG) is located in northern Taiwan near the capital Taipei. In this study we selected and analyzed almost four years (2004-2007) of its seismic activity. The seismic network established around TVG initially consisted of eight three-component seismic stations with this number increasing to twelve by 2007. Local seismicity ma...

The Tatun Volcano Group (TVG) is located in northern Taiwan near the capital Taipei. In this study we selected and analyzed almost four years (2004 - 2007) of its seismic activity. The seismic network established around TVG initially consisted of eight three component seismic stations with this number increasing to twelve by 2007. Local seismicity...

On June 8, 2008, at 15:25 local time (12:25 GMT) an Mw 6.4 earthquake occurred in the area of northwest Peloponnese, Western Greece. The epicenter was located in the municipality of Movri, about 35 km southwest of Patras. A crustal anisotropy analysis was performed in the epicentral area in relation to the occurrence of the earthquake. We used seis...

Coloumbo submarine volcano lies 6.5 km offshore the NE part of the Santorini island complex and exhibits high seismicity along with vigorous hydrothermal activity. This study models the local stress field around Coloumbo's magma chamber and investigates its influence on intrusion emplacement and geometry. The two components of the stress field, hoo...

On 9 July 1956 a large earthquake occurred near the island of Amorgos, southern Aegean, causing extensive damage while it was followed by a tsunami that inundated the coasts of nearby islands also reaching the Turkish coast. This chapter aims first at providing a thorough review of previous studies about this earthquake and then developing a seismo...

The Gulf of Gökova is located in the southeast Aegean along the coast of the southwest Anatolia. It is surrounded by the Bodrum Peninsula to the north, Datça Peninsula to the south and the island of Kos to the west. The Gulf is under a N-S regional extensional tectonic regime related to the westerly escape of the Anatolian plate, as a result of the...

We derive a three dimensional velocity model of seismic waves beneath Taal Volcano, Philippines, from about 2300 local earthquakes recorded by the Taal Volcano seismic network during the time period from March 2008 to March 2010. In the early data processing stage, with the cross-correlation functions of continuous record of station pairs, unexpect...

The southern Ryukyus represents an area where different tectonic stress regimes result in high seismicity and increased seismic hazard for nearby areas such as Taiwan. On 18 December 2001 at 04:03 (GMT) a strong earthquake (Mw 6.8) occurred in the forearc area of the southern Ryukyu subduction zone. Revised moment tensor solutions published by GCMT...

SKS splitting parameters are measured in the Aegean region using events recorded at a dense temporary network in the south Aegean and the operating permanent networks, especially focusing in the back-arc and the near-trench areas of the Hellenic arc. In general, fast anisotropy directions are trench perpendicular in the back-arc area and trench par...

Since its first use by Aki (1966), seismic moment has been recognized as the most physically meaningful measure of the strength of the seismic source. The subsequent development of the moment magnitude scale further increased its usefulness, giving seismologists the opportunity to measure even the magnitude of very large events without concern abou...

On 8 June 2008 a strong (Mw 6.4) earthquake occurred in the area of northwest Peloponnese, western Greece. The event originated in the lower crust and was caused by the rupture of a previously unknown fault probably inherited from past tectonic phases. In this study we perform a stress inversion of all available focal mechanisms in this area in ord...

The 9 July 1956 Amorgos earthquake (Mw 7.6) was the largest event that hit Greece during the last century followed by a tsunami that inundated the coastal areas of the southern Aegean. This study investigates the rheological properties of the 1956 rupture zone between Amorgos and Santorini islands, in an effort to place some constraints on the nucl...

The Tatun volcano group (TVG) is just located nearby the Taipei metropolis, where is the major economic and political center of Taiwan. To improve the understanding of the volcanic structures and their properties, we have deployed a dense seismic network at the TVG for monitoring the volcanic earthquakes since 2004. This network is composed of 18 s...

In this study we investigate the stress regime of the subducting slab beneath the Hellenic Arc aiming to answer two fundamental questions; a) How does the slab deformation vary horizontally and vertically along this large curvature arc? b) Which are the mechanisms inferred from global observations that can explain this deformation and have not been...

Online material: Solution quality classification criteria and moment tensor solution data.

In order to investigate seismicity and tectonic structure under Taal volcano, Philippines, a temporary seismic array consisting of 8 stations was deployed in this area since March 2008. As a pioneer seismic study in this area, our first goal is to build a robust 1-D velocity model using local earthquakes. In the mean time, we also apply ambient noi...

The 9 July 1956 Amorgos earthquake (Mw 7.6) was the largest event that hit Greece during the last century while it was also followed by a tsunami that inundated the coastal areas of the southern Aegean. This study investigates the rheological properties of the 1956 rupture zone between Amorgos and Santorini islands, in an effort to place some const...

On 8 June 2008 at 12: 25 (GMT) an M-w 6.4 strong earthquake occurred in the area of northwest Peloponnese, western Greece, causing the death of two people and extensive damage to the surrounding area. The main event and its aftershocks were recorded by one nationwide and three regional networks equipped with three-component broadband seismometers....

The Tatun Volcano Group (TVG) represents the main volcanic center in northern Taiwan and based on various observations it is considered a potentially active volcano. TVG has been monitored since 2003 by a seismic network that consists of eight stations equipped with three-component, short-period and broadband seismometers. In this study, we use wav...