Papers by George Papathanassiou
Applied Sciences
Medicanes, a type of strong hurricanes/cyclones occurring in the Mediterranean, can be the source... more Medicanes, a type of strong hurricanes/cyclones occurring in the Mediterranean, can be the source of major geohazard events in Mediterranean coastal and inland areas. Medicane Ianos that hit Greece during 17–19 September 2020 caused widespread damage, with numerous landsides and floods being the most prominent. Following the landfall of Medicane Ianos, a series of field surveys were launched together with rapid response through satellite imagery. We focused on two of the areas most affected by Medicane Ianos, Cephalonia island and Karditsa, Thessaly, both in Greece. A rapid landslide inventory for the Karditsa region was prepared using Copernicus Sentinel-2 satellite imagery, the first of its kind for a severe weather event in Greece. The mountainous area of Karditsa region in western Thessaly experienced the unprecedented number of 1696 landslides, mapped through satellite imagery and examined in the field. Cephalonia Island experienced a smaller number of landsides but damaging de...
Geosciences
The existence of high potential onshore and offshore active faults capable to trigger large earth... more The existence of high potential onshore and offshore active faults capable to trigger large earthquakes in the broader area of Thrace, Greece in correlation with the critical infrastructures constructed on the recent and Holocene sediments of Nestos river delta plain, was the motivation for this research. The goal of this study is twofold; compilation of a new geomorphological map of the study area and the assessment of the liquefaction susceptibility of the surficial geological units. Liquefaction susceptibility at regional scale is assessed by taking into account information dealing with the depositional environment and age of the surficial geological units. In our case, available geological mapping shows a deficient depiction of Pleistocene and Holocene deposits. Taking into consideration the heterogeneously behavior of active floodplains and deltas in terms of liquefaction, a detailed classification of geological units was mandatory. Using data provided by satellite and aerial i...
On the 3rd and 4th of March 2021, two strong earthquakes of M6.3 and M6.0, respectively occurred ... more On the 3rd and 4th of March 2021, two strong earthquakes of M6.3 and M6.0, respectively occurred at Thessaly, Central Greece. During extensive field survey and mapping, accompanied by UAV aerial surveys, following the strong earthquakes, numerous (more than 400 cases) liquefaction-related features were identified, including sand blows and craters, fissures and lateral spreading cracks/ruptures along the Pinios and Titarisios river banks. A rapid documentation of these features was important, as most of these features were going to be erased or smoothed by the ploughing season that is ongoing in the area.
On March 3, 2021 a Mw=6.3 shallow earthquake occurred in the mountainous region of Damasi, about ... more On March 3, 2021 a Mw=6.3 shallow earthquake occurred in the mountainous region of Damasi, about 20 km to the northwest of Larisa, Thessaly, central Greece, in a region of active crustal extension but of low strain. This event was followed by a Mw=6.0 shallow earthquake on March 4, 2021 about 12 km to the northwest, inside the sedimentary basin of the Titarisios river. On March 12, 2021 a third event of Mw=5.6 occurred 7 km further towards NNW, near the NW edge of the basin. All events show normal-slip kinematics as indicated by the moment tensor solutions, with minor strike-slip components. Because of the shallow depth of the events it was possible to map the surface deformation using InSAR. The preliminary results from InSAR show three main lobes of subsidence, partially overlapping. The deformation pattern indicates the activation of three normal faults, previously unknown in this part of Thessaly. The earthquakes generated numerous secondary phenomena with vast areas of alluvial...
Documentation of landslides is a very critical issue because effective protection and mitigation ... more Documentation of landslides is a very critical issue because effective protection and mitigation measures can be designed only if they are based on the accuracy of the provided information. Such a documentation aims at a detailed description of the basic geomorphological features e.g. edge, traces, scarp etc. while variables such as the landslide area and the volume of the area (that moved) are also measured. However, it is well known that the mapping of these features is not always feasible due to several adverse factors e.g. vertical slopes, high risk. In order to overcome this issue, remote sensing techniques were applied during the last decades. In particular, Interferometric Synthetic Aperture Radar (InSAR), Light Detection and Ranging (LiDAR) and photogrammetric surveys are used for geomorphic mapping in order to quantify landslide processes. The latter one, photogrammetric survey, is frequently conducted by use of Unmanned Aerial Vehicles (UAV), such as multicopters that are ...
Geotechnical and Geological Engineering, 2020
Soil liquefaction in the free field usually results in the generation of sand craters and volcano... more Soil liquefaction in the free field usually results in the generation of sand craters and volcanoes, as well as in surface ground cracks due to subsidence and lateral displacements. Technical constructions built on or within liquefiable soils may exhibit liquefaction-induced structural damages due to differential settlements, displacements and/or tilting that may lead to their loss of integrity or operational functionality. Oil and gas steel pipelines are typical examples of infrastructures for which appropriate mitigation measures against liquefaction-induced failures are required. For this reason, it is crucial to assess the soil liquefaction susceptibility along the pipeline Right-of-Way (RoW) and evaluate the deformations that may arise due to the occurrence of liquefaction. Since failure prevention and geohazard area avoidance is always preferable in comparison to the design of demanding mitigation measures of the application of post-failure retrofitting, the present study attempts to formulate a protocol that could: (a) be adopted for assessing the liquefaction potential of the various geological formations crossed by a pipeline RoW and, (b) be employed to assess the likelihood of the expected permanent ground displacement (PGD) along or across the proposed pipeline alignment. The proposed approach has been adopted for the studies performed regarding the Front-End-Engineering Design FEED phase of the onshore part of the Trans Adriatic Pipeline (TAP), which crosses the area of Greece and Albania. It is highlighted that this protocol offers a preliminary combined working approach that mainly integrates desktop study and field surveys that should be used for optimizing the pipeline route and define the distribution of the in-situ measurements.
Soil Dynamics and Earthquake Engineering, 2019
The earthquake Mw6.6 (macroseismic intensity VIII, ESI-07 scale) that occurred on July 20, 2017 a... more The earthquake Mw6.6 (macroseismic intensity VIII, ESI-07 scale) that occurred on July 20, 2017 at 22:31 UTC (01:31 local time) in Gökova Bay, SE Aegean Sea, induced minor damages to contemporary structures at the island of Kos, Greece, while severe damages were reported on Venetian and Ottoman-era constructions, causing two deaths. Focusing on the island of Kos, secondary effects were reported in the eastern part, including liquefaction-related phenomena and tsunami. The generation of the latter one indicates the likelihood to this type of effects in the Aegean Sea. Liquefaction-induced lateral spreading caused severe structural damages at the waterfront area of the city of Kos. This area was investigated in detail few days after the event, by performing field measurements using a surveyor's tape and additionally, by applying SfM-based technique using a groundbased digital camera. The values of horizontal deformation, measured by these two techniques are in agreement, while on vertical axis a deviation of 12% is resulted.
Engineering Geology, 2017
a strong, shallow earthquake (Mw = 6.5) occurred on the island of Lefkada along a N20 ± 5°E, east... more a strong, shallow earthquake (Mw = 6.5) occurred on the island of Lefkada along a N20 ± 5°E, east-dipping strike-slip fault with right-lateral sense of slip. The event triggered environmental effects that were mainly mapped at the western part of the island while moving towards the eastern part, the severity of the earthquake-induced failures decreased. The most characteristic geological effects that were triggered by the earthquake were slope failures including rock falls, rock slides and landslides. The spatial density of the failures follows an exponential increase with slope-angle and decreases for values larger than 55°. Small-size liquefaction phenomena such as sand craters and ejection of fine-grained sand through ground cracks were documented at the coastal area of Vassiliki. The epicentral intensity was assessed based on the definitions of Environment Seismic Intensity scale as VIII ESI-07, and the macroseismic epicenter (VIII up to IX) was located at the coastal area of Egremnoi (west of Athani village, south Lefkada). In addition, comparing the severity of earthquake-induced failures on the main road network, triggered by the 2003 and 2015 events, it is concluded that the behavior of the protection measures such as fences and walls, could be generally characterized as satisfactory. On the contrary, the similarity of the structural failures triggered by the 2003 event with the ones triggered by the 2015 earthquake, documented at the port of Vassiliki, indicates that the post-2003 constructed port facilities failed to guarantee the functionality of the port of Vassiliki.
Engineering Geology, 2016
Abstract Two earthquakes occurred on January, 26 and February, 3 2014 of Mw 6.1 and Mw 6.0, respe... more Abstract Two earthquakes occurred on January, 26 and February, 3 2014 of Mw 6.1 and Mw 6.0, respectively, onshore the island of Cephalonia, Greece. The environmental effects e.g. rockfalls, liquefaction and ground cracks triggered by the events were widespread at the western part of the island and mainly in the peninsula of Paliki. The most remarkable characteristics of these two events were the generation of strong ground motion, the highest ever recorded in Greece and the recurrent liquefaction phenomena at the waterfront areas of Lixouri and Argostoli. In addition, the grain size distribution curves of soil samples collected along the seafront area at Lixouri indicated a sandy ejecta and are plotted in the range of possibility of liquefaction defined by Tsuchida (1971). By taking into account the data provided by three post-earthquake field trips that took place immediately after the first and the second earthquake, and the information provided by geotechnical boreholes drilled along the shoreline in Lixouri, a quantitative description of the liquefaction-induced deformations and a preliminary failure mode of the waterfront structures in Lixouri are presented in this study. As an outcome, a post-liquefaction induced settlement of ≈ 16 cm at two sites was computed.
, was struck by two strong, shallow earthquakes (NOA local magnitudes M L 5.8 and M L 5.7, respec... more , was struck by two strong, shallow earthquakes (NOA local magnitudes M L 5.8 and M L 5.7, respectively). The earthquakes ruptured two sub-parallel, strike-slip faults, with right-lateral kinematics. During both earthquakes, ground-shaking phenomena such as liquefaction, road failures, rock falls, small/medium size landslides and stonewall failures were widespread all over the western part of the island. No primary fault surface ruptures were observed, however one patch of the rupture of the second event may have nearly reached the surface, because of the abundance of surface cracks with cm-size offsets mapped in the field in north Paliki Peninsula. Liquefaction phenomena were mainly triggered in reclaimed lands in the waterfront areas of Argostoli and Lixouri inducing structural damages to quays, sidewalks and piers. We also present evidence for liquefaction-induced ground disruption in the recently constructed marina of Argostoli, which is situated at the opposite (eastern) shore to the town.
Annals of Geophysics, 2012
Landslides, 2012
Your article is protected by copyright and all rights are held exclusively by Springer-Verlag. Th... more Your article is protected by copyright and all rights are held exclusively by Springer-Verlag. This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your work, please use the accepted author's version for posting to your own website or your institution's repository. You may further deposit the accepted author's version on a funder's repository at a funder's request, provided it is not made publicly available until 12 months after publication.
5th International Symposium on Eastern Mediterranean Geology. Thessaloniki, Ref: S2, 2004
After the Niigata earthquake of 1964 in Japan several researches worked on the phenomena of lique... more After the Niigata earthquake of 1964 in Japan several researches worked on the phenomena of liquefaction and its sequences. For the evaluation of liquefaction potential of an area, several criteria must be examined, such as historical, geologic, compositional and state criteria. Information about liquefaction behavior that has come from field reports shows that liquefaction often recurs at the same location when soil and groundwater have remained unchanged. Thus, liquefaction case histories can be used to identify specific ...
Remote Sensing
The 6 February 2023 earthquake doublet (Mw 7.7 and Mw 7.6) that occurred on the East Anatolian Fa... more The 6 February 2023 earthquake doublet (Mw 7.7 and Mw 7.6) that occurred on the East Anatolian Fault Zone (EAFZ) triggered a significant amount of soil liquefaction phenomena in SE Türkiye and NW Syria. The great areal extent of the affected area and the necessity of rapid response led to the adoption and improvement of a workflow for mapping liquefaction phenomena based on remote sensing data. Using satellite imagery, we identified 1850 sites with liquefaction manifestation and lateral spreading deformation. We acquired a thorough map of earthquake-triggered liquefaction based on visual mapping with optical satellite imagery (high and very high-resolution) and the aid of radar satellite imagery and interferometry. The majority of sites are found along meandering sections of river valleys, coastal plains, drained lakes, swamps, and lacustrine basins along the East Anatolian Fault, highlighting once again the influence of geomorphology/surficial geology on the distribution of liquefa...
Engineering Geology, 2015
On the 20th and 29th of May 2012, two earthquakes occurred in Emilia-Romagna region (Northern Ita... more On the 20th and 29th of May 2012, two earthquakes occurred in Emilia-Romagna region (Northern Italy) triggering extensive liquefaction of the subsoil units. The consequences of liquefaction have been observed and reported by several agencies in a widespread area. The most impressive liquefaction manifestations were documented in a zone 3-4 km-long and 1 km-wide, where the villages of Sant'Agostino, San Carlo and Mirabello are located. The existing post-earthquake reports and the availability of geotechnical data provided by in-situ tests consist the basic ingredients for a computation of the liquefaction potential parameters within this zone. In particular, the Liquefaction Potential Index (LPI) and Liquefaction Severity Number (LSN) indexes were evaluated and then correlated by considering liquefaction phenomena either observed on site or not. Thus, the existing classifications of the LPI and LSN were evaluated and compared with the observed liquefaction-induced deformations. The latter was applied and validated for the first time within a liquefiable area using post-earthquake data, after the development by Tonkin and Taylor (2013). The outcome of this study shows that a threshold value of LPI around 13 or 14 is better to be taken into account instead of 5 for discriminating sites where liquefaction surface evidences should be expected from the 'non-liquefied' ones. Moreover, from the correlation of the LSN values with the cases of liquefaction-induced ground disruption it is concluded that the proposed threshold value of 10 fits statistically well with our dataset. In addition, a preliminary correlation of LPI and LSN indicates a trend that could be useful in future studies for delineating sites likely to liquefaction.
Tectonophysics
On August 7, 2013 a moderate earthquake (NOA ML= 5.1, NOA Mw= 5.4) occurred in central Kallidromo... more On August 7, 2013 a moderate earthquake (NOA ML= 5.1, NOA Mw= 5.4) occurred in central Kallidromon Mountain, in Pthiotis region of central Greece. 2270 aftershocks were relocated using a modified 1-D velocity model for this area. The b-value of the aftershock sequence was b=0.85 for a completeness magnitude of Mc=1.7. The rate of aftershock decay was determined at p=0.63. The spatial distribution of the aftershock sequence points towards the reactivation of a N70°±10°E striking normal fault at crustal depths between 8 and 13 km. A NNW-SSE cross-section imaged the activation of a steep, south dipping normal fault. A stress inversion analysis of 12 focal mechanisms showed that the minimum horizontal stress is extensional at N173°E. No primary surface ruptures were observed in the field; however, the earthquake caused severe damage in the villages of the Kallidromon area. The imaged fault strike and the orientation of the long-axis of the aftershock sequence distribution are both at hi...
Macroseismic intensity scales are used in order to measure the size of an earthquake using the im... more Macroseismic intensity scales are used in order to measure the size of an earthquake using the impact of the ground shaking on humans, man made environment and nature. The INQUA scale is a new scale based solely on the earthquake-induced ground deformations, proposed by the INQUA Subcommission on Paleoseismicity. This scale is applied to the Sofades 1954 earthquake in order to test its accuracy and reliability. From the comparison among the evaluated intensities based on MM scale with the degrees of INQUA intensity at several locations, we conclude that, in case of earthquakes which triggered remarkable geological effects, these intensity values are about the same. Nonetheless, the use of INQUA scale is suggested in combination with the existing ones, as an assessing tool of the intensity based only on geological effects Περίληψη Οι µακροσκοπικές κλίµακες έντασης ενός σεισµού έχουν χρησιµοποιηθεί για την εκτίµηση του µεγέθους του, βασιζόµενες στην καταγραφή της επίδρασης την εδαφικής κίνησης στην συµπεριφορά του ανθρώπου και τις µεταβολές που προκαλούνται στο φυσικό και τεχνητό περιβάλλον. Η προτεινόµενη, από την επιτροπή της Παλαιοσεισµολογίας, κλίµακα INQUA λαµβάνει υπόψη της, κατά την εκτίµηση της σεισµικής έντασης, µονάχα τις εδαφικές παραµορφώσεις και µεταβολές τις οποίες προκάλεσε η σεισµική δόνηση. Για τον έλεγχο της ακρίβειας και της αξιοπιστίας της INQUA, αποφασίστηκε η εφαρµογή της κλίµακας στον σεισµό των Σοφάδων το 1954. Από τη σύγκριση των τιµών της έντασης INQUA µε τις αντίστοιχες τιµές της κλίµακας ΜΜ, καταλήξαµε στο συµπέρασµα ότι στην περίπτωση σεισµών οι οποίοι προκαλούν έντονα δευτερογενή φαινόµενα, οι τιµές των εντάσεων είναι περίπου ίσες. Παρόλα αυτά, προτείνεται η χρησιµοποίηση της κλίµακας INQUA, σε συνδυασµό µε τις υπάρχουσες, καθώς δίνει έµφαση στις γεωλογικές παραµορφώσεις, αποφεύγοντας να χρησιµοποιήσει δεδοµένα τα οποία σχετίζονται µε την µεταβαλλόµενη από θέση σε θέση τρωτότητα των κατασκευών.
The aim of this study was to investigate the influence of the non-liquefiable cap layer on the su... more The aim of this study was to investigate the influence of the non-liquefiable cap layer on the surface manifestations of liquefaction phenomena. In order to achieve this information from boreholes in Turkey, Taiwan and Greece, obtained during post-earthquake field investigations, were collected and the value of liquefaction potential index (LPI) at each site was determined. Most of borings were at places where liquefaction phenomena was observed, with a few drilled at non-liquefied sites. Afterwards, a diagram was developed based on the estimated thickness of the cap layer (H) and the value of LPI, where the liquefied and non-liquefied cases were plotted. As a result of this study, zones of likely, possible and unlikely occurrence of liquefaction manifestation were delineated into this diagram of LPI versus the thickness of the cap layer. The outcome of this research can be used for the prediction of liquefaction-induced ground disruption and for the mitigation of this geological hazard.
EXTENDED ABSTRACT The basic goal of the project is to develop two applications for tablets and sm... more EXTENDED ABSTRACT The basic goal of the project is to develop two applications for tablets and smartphones, using either android system or iOS that will be used by earth-scientists and engineers during field surveys in order to document the earthquake-induced environmental effects. In order to achieve this, the project was mainly designed based on the Earthquake Environmental Effects form, proposed by the INQUA TERPRO SubCommission Group for reporting earthquake-induced deformations, and the recommendations of GEER (Geotechnical Extreme Events Reconnaissance) regarding data processing after a post-earthquake reconnaissance field survey. In particular, via this application the user is able to document primary and secondary effects, collect GPS waypoints (in decimal degrees using the WGS84) and thus, geo-tag the collected photos. The type of effects that can be reported and described in detail are Surface faulting, Slope failures, Liquefaction, Tsunami, Ground cracks, Hydrological ano...
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Papers by George Papathanassiou