Elena Papageorgiou

Aristotle University of Thessaloniki

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Michael Foumelis

Aristotle University of Thessaloniki

ΕΛ

Ε. Λάγιος

National and Kapodistrian University of Athens

Elisa Trasatti

Istituto Nazionale di Geofisica e Vulcanologia

Philippe Bally

European Space Research Institute

Aliki Konsolaki

National and Kapodistrian University of Athens

Patrick Bassal

The Ohio State University

Andreas Scharf

Sultan Qaboos University

Christos Evangelidis

National Observatory of Athens

KÖ

Kemal Önder Çetin

Middle East Technical University

GΚ

George Κaviris

National and Kapodistrian University of Athens

Cooperative Institutions

National and Kapodistrian University of Athens

Harokopio University of Athens

European Space Research Institute

European Space Agency

The Ohio State University

ORCID

Sultan Qaboos University

National Observatory of Athens

University of California, Berkeley

Terradue (Italy)

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Liquefaction ground deformations and cascading coastal flood hazard in the 2023 Kahramanmaraş earthquake sequence

Earthquake Spectra (2024)

Patrick Bassal Elena Papageorgiou Diane Moug Jonathan D. Bray Kemal Önder Çetin

The 2023 Kahramanmaraş earthquake sequence produced extensive liquefaction-induced ground deformations and ongoing flooding along the shoreline of the Mediterranean port city of İskenderun, Türkiye. This study compiles field observations and analyses from cross-disciplinary perspectives to investigate whether earthquake-induced liquefaction was a significant factor for increasing the flood hazard in İskenderun. Geotechnical reconnaissance observations following the earthquakes included seaward lateral spreading, settlement beneath buildings, and failures of coastal infrastructure. Three presented lateral spreading case histories indicate consistent ground deformation patterns with areas of reclaimed land. Persistent scatterer interferometry (PSI) measurements from synthetic aperture radar (SAR) imagery identify a noticeably greater rate of pre- and post-earthquake subsidence within the İskenderun coastal and urban areas relative to the surrounding regions. The PSI measurements also indicate subsidence rates accelerated following the earthquakes and were typically highest near the observed liquefaction manifestations. These evaluations suggest that while the liquefaction of coastal reclaimed fill caused significant ground deformations in the shoreline area, ongoing subsidence of İskenderun and other factors likely also exacerbated the flood hazard. Insights from this work suggest the importance of evaluating multi-hazard liquefaction and flood consequences for enhancing the resilience of coastal cities.

Settlement (finance)

Soil liquefaction

10.1177/87552930241247830

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Citations (5)

Multi-Sensor SAR Geodetic Imaging and Modelling of Santorini Volcano Post-Unrest Response

Remote Sensing (2019)

Elena Papageorgiou Michael Foumelis Elisa Trasatti Guido Ventura Daniel Raucoules

Volcanic history of Santorini over recent years records a seismo-volcanic unrest in 2011–12 with a non-eruptive behavior. The volcano deformation state following the unrest was investigated through multi-sensor Synthetic Aperture Radar Interferometry (InSAR) time series. We focused on the analysis of Copernicus Sentinel-1, Radarsat-2 and TerraSAR-X Multi-temporal SAR Interferometric (MT-InSAR) results, for the post-unrest period 2012–17. Data from multiple Sentinel-1 tracks and acquisition geometries were used to constrain the E-W and vertical components of the deformation field along with their evolution in time. The interpretation of the InSAR observations and modelling provided insights on the post-unrest deformation pattern of the volcano, allowing the further re-evaluation of the unrest event. The increase of subsidence rates on Nea Kameni, in accordance with the observed change of the spatial deformation pattern, compared to the pre-unrest period, suggests the superimposition of various deformation sources. Best-fitting inversion results indicate two deflation sources located at southwestern Nea Kameni at 1 km depth, and in the northern intra-caldera area at 2 km depth. A northern sill-like source interprets the post-unrest deflation attributed to the passive degassing of the magma intruded at 4 km during the unrest, while an isotropic source at Nea Kameni simulates a prevailing subsidence occurring since the pre-unrest period (1992–2010).

Unrest

Caldera

10.3390/rs11030259

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Citations (30)

Long-and Short-Term Deformation Monitoring of Santorini Volcano: Unrest Evidence by DInSAR Analysis

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (2012)

Elena Papageorgiou Michael Foumelis Issaak Parcharidis

Santorini Volcano is an active strato volcano, located at the central part of the Hellenic Volcanic Arc, developing ad retro of the Hellenic Arc and Trench. The explosive history of the volcano dates back to 1645 BC with the Minoan eruption, while it is documented to have produced at least ten eruptions until 1950 AD. The most recent volcanic unrest began in early 2011. Multi-reference Synthetic Aperture Radar (SAR) Interferometric techniques were applied to study the evolution of ground deformation during 1992-2011, with the use of ERS-1 and -2 and ENVISAT radar imagery. Datasets of common acquisition geometry were added into a single stack so as to obtain the linear deformation rates by means of phase averaging. However, to reveal the deformation history of the volcano, Singular Value Decomposition (SVD) method was implemented. This allowed retrieving ground deformation time-series on a pixel basis over regions with high temporal coherence levels. Results from independent tracks, agreeing with each other, suggest a deformation rate of approximately 5 mm/yr of subsidence at the southern part of Nea Kammeni Volcano, for the period 1992-2010. For the unrest period of 2011, intense uplift of 4.8 cm was observed throughout Nea Kammeni. Global Positioning System (GPS) observations from a local geodetic network confirm the DInSAR findings.

Unrest

Volcanology

10.1109/jstars.2012.2198871

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Uplift Dynamics of the Obducted Northeastern Continental Margin of the Arabian Peninsula, Sultanate of Oman

Geochemistry Geophysics Geosystems (2023)

Kosmas Pavlopoulos Daniel Moraetis Michael Foumelis Andreas Scharf Frank Mattern

Abstract Eustatic sea level changes and vertical tectonic movements are producing uplifted paleoshorelines. Along subduction zones, uplifted terraces are used to study fault activities and, overall, allow to interpret the tectonic history of plate convergence. Northeastern Oman is experiencing plate convergence following the late Cretaceous obduction of the Semail Ophiolite. Post‐obduction shallow‐marine carbonates have been uplifted to different elevations from 133 to >2,000 m. The present study employs a multidisciplinary approach to elucidate the variability in relief and to introduce a geodynamic model that extends beyond the temporal constraints imposed by the late Quaternary age of the sediments found on the uplifted terraces. Stratigraphic and fault analyses produced a post‐obductional geodynamic model to advance the existing regional models in the framework of the subduction of the Arabian Plate in the Makran Zone. In addition, we rely on imaging geodesy, geomorphology and dating to explain the late Quaternary uplift scenario. Overall, analyses of geomorphology, stratigraphy, and fault patterns reveal spatially heterogeneous post‐late Cretaceous uplift in the region. Compartmentalization by major faults created individual blocks and relief variability. Within the timeframe of marine terrace formation (late Quaternary), we also observed spatially varied displacements. Ground displacements by Interferometric Synthetic Aperture Radar document an ongoing spatial heterogenous uplift at approximately 1.3 mm/a. Finally, temporal variability was evident during the late Quaternary by unusually high late Pleistocene (<40 ka) uplift rates averaging ≥2 mm/a in younger terraces, while for older terraces (>40 ka) the uplift rate is distinctly lower (<1 mm/a).

Obduction

Continental Margin

Tectonic uplift

10.1029/2023gc011054

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Vertical & horizontal ground deformation of Santorini island deduced by DGPS measurements

Bulletin of the Geological Society of Greece (2018)

Elena Papageorgiou Ε. Λάγιος Spyridoula Vassilopoulou Vassilis Sakkas

Santorini is considered to be a dormant volcano with fairly high geodynamic unrest. Two major tectonic NE-SW trending fault zones, Kammeni and Columbo Lines, which intersect the main part of the volcanic edifice, have affected the magma flow at relatively shallow depths enabling the appearance of individual volcanic centers on the island. GPS measurements on a network of 18 stations were carried out in 1994 and 2005 in order to estimate the ground deformation, both in vertical and horizontal component. The results show that the highest amplitude of subsidence (45 mm) and uplift (51 mm) is noticed on Nea Kammeni and Cape Columbo, respectively. Considering the horizontal displacements, it appears that these sites were strongly affected by the above major faulting zones. They vary between 4 mm and 37 mm, where the highest amplitudes are observed at the south-western corner of Thera and Therassia Islands. Their directions seem to correlate with the observed subsidence in the caldera (deflation) and a probable inflation around the area of the sub-marine Columbo Volcano.

Caldera

Magma chamber

Unrest

Tiltmeter

10.12681/bgsg.16874

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Citations (3)

Monitoring Santorini volcano (Greece) breathing from space

Geophysical Journal International (2013)

Michael Foumelis Elisa Trasatti Elena Papageorgiou Salvatore Stramondo Issaak Parcharidis

Since its last eruption in 1950, Santorini volcano (Greece) remained in a dormant state. This is also evidenced for the period 1992–2010 by the gradual deflation signal over Nea Kameni as measured by satellite Synthetic Aperture Radar Interferometry (InSAR) with low rates of about 5–6 mm yr–1 as well as by the absence of seismic activity within the caldera. However, at the beginning of 2011 the volcano showed signs of unrest with increased microseismic activity and significant ground uplift, reaching 14 cm within a year (2011 March–2012 March), according to InSAR time-series. ALOS PALSAR data indicate the onset of the phenomenon in early 2010 where an aseismic pre-unrest phase of increased subsidence (1–3 cm) preceded the uplift. Joint inversions of SAR and GPS velocities using spherical and spheroidal magmatic source types indicate their location offshore at about 1 km north of Nea Kameni and between 3.5 and 3.8 km depth. The estimated volume variation rate is 6 × 106 m3 yr-1 to 9 × 106 m3 yr-1. A gradual slowing in the rate of inflation within the first quarter of 2012 is apparent by ENVISAT data, while subsequent observations from RADARSAT-2 confirm the observed trend.

Caldera

Unrest

10.1093/gji/ggs135

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Citations (36)

DGPS AND MAGNETOTELLURIC CONSTRAINTS ON THE CONTEMPORARY TECTONICS OF THE SANTORINI VOLCANIC COMPLEX, GREECE

Bulletin of the Geological Society of Greece (2017)

Elena Papageorgiou A. Tzanis P. Sotiropoulos Ε. Λάγιος

The study of vertical and horizontal crustal movements at the Santorini Volcanic Complex (SVC), as deduced by Differential GPS measurements revealed that an intricate pattern of five distinct domains with different horizontal kinematics: The West SVC (Akrotiri peninsula and Therassia) with very significant NNW-ward motion, North Thera with rather significant NW-ward motion, East Thera (Monolithos), with significant SE-ward motion, South Thera with significant NW-ward motion and, finally, central Thera with small westward motion. An apparently dextral, NNW-SSE oblique-to-strike-slip fault emerges as a prominent tectonic structure, separating the West SVC from the rest of the complex; this is the “Santorini Fault Zone”. Additional insight is afforded by the results of MT and GDS surveys: a significant NNW-SSE conductive zone was detected, which is collocated with the purported NNW-SSE fault zone indicated by DGPS analysis and may be explained as an epiphenomenal conductivity anomaly. The observed deformation pattern enables the drafting of a qualitative model of contemporary tectonics, which is also presented and discussed. The model is plausible but certainly incomplete and pending verification with numerical modelling and additional observations

Peninsula

10.12681/bgsg.11186

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Citations (8)

Episodic ground deformation signals in Thessaly Plain (Greece) revealed by data mining of SAR interferometry time series

International Journal of Remote Sensing (2016)

Michael Foumelis Elena Papageorgiou Constantine A. Stamatopoulos

The Eastern Thessaly Plain presents an area of severe settlement phenomena, owing to the over-exploitation of the underground aquifer systems, causing significant damages to national infrastructures and private properties annually. Herein, both Persistent Scatterers (PS) and Small Baselines (SB) interferometric techniques were applied to study the history of ground deformation along the entire plain. Although the area consisted mostly of agricultural land, a sufficient number of point targets was obtained, well-distributed over the entire plain, permitting the recognition of spatial variations of the displacement field in addition to temporal trends. Our findings outline the southern part of the basin as the mostly affected area, whereas local subsidence patterns of lower magnitude were also recognized elsewhere. Episodes of significant ground subsidence, reaching several centimetres within a few months, characterize the deformation pattern of the area. Although average ground deformation rates do not exceed 2 cm year−1, line-of-sight (LOS) displacements of up to 13 cm were observed, occurring during the summer–autumn periods. A geographic information system (GIS)-based post-processing approach for the analysis of synthetic aperture radar (SAR) time series is presented, by which these abrupt settlement episodes can be identified in both temporal and spatial domains. The analysis allows the separation between rapid subsidence phenomena during the summer–fall season and annual deformation rates, thereby providing valuable information regarding the actual deformation pattern of the area. The results confirm in situ geological observations, highlighting the unique behaviour of the area due to intense water pumping. The study underlines that average SAR displacement rate maps might be inadequate to describe complex deformation scenarios and could lead to misinterpretations. Exploitation of the full capacity of SAR time series by detailed examination of the displacement histories, through a tailored data-mining strategy, could provide valuable information to geotechnical engineers and planners.

Settlement (finance)

10.1080/01431161.2016.1201233

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Citations (26)

SNAPPING Services on the Geohazards Exploitation Platform for Copernicus Sentinel-1 Surface Motion Mapping

Remote Sensing (2022)

Michael Foumelis José Manuel Delgado Blasco Fabrice Brito Fabrizio Pacini Elena Papageorgiou

We are communicating recent developments regarding the Surface motioN mAPPING (SNAPPING) service for the Sentinel-1 mission on the Geohazards Exploitation Platform (GEP) platform in support of the scientific community as well as of EO practitioners. We present the processing scheme adopted for the service and the designed implementation on the GEP, and we discuss in detail the user-defined processing parameters and service outputs. SNAPPING is offered through three independent services, namely the SNAPPING IFG for the generation of interferometric stacks, utilized consequently as input for the SNAPPING PSI Med and SNAPPING PSI Full services, which execute Persistent Scatterers Interferometry (PSI) analyses at medium and full resolutions, respectively. The inter-verification of the SNAPPING results was performed to underline the robustness of the provided measurements, and several showcases from diverse environments are demonstrated. The service aims to pave the way towards the improved acceptance of EO-hosted processing services and deeper community engagement, anticipating operational exploitation in response to geohazards.

Robustness

Copernicus

10.3390/rs14236075

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Εφαρμογή GIS στο ηφαίστειο Σαντορίνης για ανάλυση εδαφικής παραμόρφωσης = Implementation of GIS in Santorini volcano for ground deformation analysis

Πανελλήνια και Διεθνή Γεωγραφικά Συνέδρια, Συλλογή Πρακτικών (2007)

Elena Papageorgiou Σ. Βασιλόπουλος Ε. Λάγιος

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