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Papadimitriou, Eleftheria
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Papadimitriou, Eleftheria
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Papadimitriou, Eleftheria E
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- PublicationRestrictedLong-term seismogenesis in Greece: Comparison of the evolving stress field and precursory scale increase approaches(2006)
; ; ; ; ; ; ;Papadimitriou, E. E.; Geophysics Department, University of Thessaloniki, Thessaloniki, Greece ;Evison, F. F.; Institute of Geophysics, School of Earth Sciences, Victoria University of Wellington, Wellington, New Zealand. ;Rhoades, D. A.; Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand. ;Karakostas, V. G.; Geophysics Department, University of Thessaloniki, Thessaloniki, Greece ;Console, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Murru, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ;; Recent strong (M 6.6) earthquakes in Greece are examined from the point of view of two current, but disparate, approaches to long-term seismogenesis. These are the evolving stress field (ESF) approach, in which earthquakes are considered to be triggered by accumulated stress changes from past earthquakes and tectonic loading on the major faults, and the precursory scale increase (Y) approach, in which a major earthquake is preceded in the long term by an increase in minor earthquake occurrences, with the magnitude of the precursory earthquakes, and the precursor time and area all scaling with the major earthquake magnitude. The strong earthquakes are found to be consistent with both approaches, and it is inferred that both approaches have a relevant role to play in the description of the long-term generation process of major earthquakes. A three-stage faulting model proposed previously to explain the Y phenomenon involves a major crack, which eventually fractures in the major earthquake, being formed before the onset of precursory seismicity. Hence we examine whether ESF can account for the formation of the major crack by examining the accumulated stress changes at the time of the onset of Y for each strong earthquake. In each case, the answer is in the affirmative; there is enhanced stress in the vicinity of the main shock at the time of the onset. The same is true for most, but not all, of the locations of precursory earthquakes.200 29 - PublicationOpen AccessOn the validity of the regional time and magnitude predictable model in China(1999-10)
; ; ; ; ;Qin, C.; Laboratory of Geophysics, University of Thessaloniki, Greece ;Papadimitriou, E. E.; Laboratory of Geophysics, University of Thessaloniki, Greece ;Papazachos, B. C.; Laboratory of Geophysics, University of Thessaloniki, Greece ;Karakaisis, G. F.; Laboratory of Geophysics, University of Thessaloniki, Greece; ; ; A simplified form of the "regional time and magnitude predictable model" gives the time interval, T, between two successive mainshocks in a region and the magnitude, Mf, of the following mainshock by the relations: logT=cMP+a; Mf=CMp+A, where Mp is the magnitude of the preceding mainshock, a, A are constants which depend on the minimum considered mainshock and on the region's tectonic loading (moment rate). The physical meaning of the model is that the larger the magnitude of the preceding main shock, Mp, the longer the time, T, will be till the occurrence of the next one and the smaller its magnitude, Mf. This means that parameters c and C are positive and negative, respectively, when the model has been found valid for a certain area. In order to examine if the above model is appropriate to describe the seismicity behavior in the area of China, a detailed inspection was carried out aiming to show if the estimated values of parameters c and C favor the model. The results show that c tends to the global value 0.33, obtained by Papazachos and Papadimitriou (1997), and that C tends to be within the range [-0.30, -0.23]. The results, which favored the model, greatly outnumber those that do not follow it, the latter being concentrated around the boundaries of the seismically active regions. It is concluded that the results, which favor the model, obviously dominate the whole territory of China.183 189 - PublicationOpen AccessModelling the large earthquakes recurrence times along the North Aegean Trough Fault Zone (Greece) with a physics-based simulator(2021)
; ; ; ; ; ; ; ; ; The recurrence time of large earthquakes above a predefined magnitude threshold on specific faults or fault segments is one of the key parameters for the development of long-term Earthquake Rupture Forecast models. Observational data of successive large earthquakes per fault segment are often limited and thus inadequate for the construction of robust statistical models. The physics-based earthquake simulators are a powerful tool to overcome recurrence data limitations by generating long earthquake records. A physics-based simulator, embodying well known physical processes, is applied in the North Aegean Trough (NAT) Fault Zone (Greece). The application of the simulation is implemented, after defining a five segment source model, aiming at the investigation of the recurrence behaviour of earthquakes with Mw ≥6.5 andMw ≥7.0. The detailed examination of the 544Mw ≥6.5 earthquakes included in the simulated catalogue reveals that both single and multiple segmented ruptures can be realized along the NAT. Results of statistical analysis of the interevent times ofMw ≥ 6.5 and Mw ≥ 7.0 earthquakes per participating segment to the related ruptures indicate the better performance of the Brownian Passage Time renewal model in comparison to exponential model. These results provide evidence for quasi-periodic recurrence behaviour, agreeing with the elastic rebound theory, instead of Poissonian behaviour.83 15 - PublicationRestrictedStatistical seismology: preface to the topical issueIt is widely recognized that Seismology, the quantitative study of which started in the 19th century, has not yet achieved the ambitious target of predicting time, place and intensity of strong earthquakes in such a way as to allow concrete actions to mitigate their disastrous effects. This is mainly due to the intrinsic non-linear and chaotic nature of the earthquake process. In lack of any kind of physics-based and deterministic prediction, seismologists have applied statistical models for seismic hazard assessment that could be useful for earthquake mitigation measures of prevention.
93 1 - PublicationRestrictedPhysics-Based Simulation of Spatiotemporal Patterns of Earthquakes in the Corinth Gulf, Greece, Fault System(2022)
; ; ; ; ; ; ; ; ; A physics-based earthquake simulation algorithm for modeling the long-term spatiotemporal process of strong (M ≥ 6.0) earthquakes in Corinth Gulf area, Greece, is employed and its performance is explored. The underlying physical model includes the rate- and state-dependent frictional formulation, along with the slow tectonic loading and coseismic static stress transfer. The study area constitutes a rapidly extending rift about 100 km long, where the deformation is taken up by eight major fault segments aligned along its southern coastline, and which is associated with several strong (M ≥ 6.0) earthquakes in the last three centuries, since when the historical earthquake catalog is complete. The recurrence time of these earthquakes and their spatial relation are studied, and the simulator results reveal spatiotemporal properties of the regional seismicity such as pseudoperiodicity as well as multisegment ruptures of strong earthquakes. As the simulator algorithm allows the display of the stress pattern on all the single elements of the fault, we are focusing on the time evolution of the stress level before, during, and after these earthquakes occur. In this respect, the spatiotemporal variation of the stress and its heterogeneity appear to be correlated with the process of preparation of strong earthquakes in a quantitative way.147 2 - PublicationOpen AccessThe 2006 Kythira (Greece), Mw6.7 slab-pull event: tectonic implications and the geometry of the hellenic wadati-benioff zone(2008-10)
; ; ; ; ;Nikolintaga, I.; Geophysics Department, School of Geology, Aristotle University of Thessaloniki, Greece ;Karakostas, V.; Geophysics Department, School of Geology, Aristotle University of Thessaloniki, Greece ;Papadimitriou, E.; Geophysics Department, School of Geology, Aristotle University of Thessaloniki, Greece ;Vallianatos, F.; Technological Educational Institute of Crete, Department of Natural Resources & Environment, Geophysics & Seismology Laboratory, Crete, Greece; ;; A strong (Mw=6.7) intermediate depth earthquake occurred on 8 January 2006 (11:34 UTC) in southwestern Aegean Sea (Greece) causing limited damage to structures on the nearby islands of Kythira and Antikythira, as well as western Crete Island. The epicentral area belongs to the SW segment of the Hellenic Arc, which is known to be associated with the occurrence of large shallow and intermediate depth earthquakes, mainly due to the subduction of the Eastern Mediterranean oceanic lithosphere under the Aegean microplate. The main shock occurred on a dextral strike slip fault at a depth of 75 km, within the descending slab, as it is revealed by both, the spatial distribution of the accurately located aftershocks and its fault plane solution determined in the present study and implying a slab-pull event. The aftershock activity from 8 to 31 January 2006 is distributed in depths ranging from 55 to 75 km, and being comprised in an almost rectangular and vertical plane with a length equal to 28 km and a width of 20 km, which adequately defines the dimensions of the rupture area. The geometry of the Wadati-Benioff zone in this area, namely the southwestern part of the Hellenic Arc, is explored by an exhaustive analysis of all the available phase arrivals gathered from the International Seismological Centre, and the relocation of the earthquakes occurred since 1964 in the South-West Aegean region.377 352 - PublicationOpen AccessSeismic zonation of the Dead Sea Transform Fault area(2000-02)
; ; ; ;Khair, K.; Department of Geology, American University of Beirut, Lebanon ;Karakaisis, G. F.; Geophysics Laboratory, Aristotle University of Thessaloniki, Greece ;Papadimitriou, E. E.; Geophysics Laboratory, Aristotle University of Thessaloniki, Greece; ; The Dead Sea Transform Fault constitutes the northwestern boundary of the Arabian plate, accommodating the plate’s lateral movement relative to the African plate. A complete and homogeneous catalogue of historical earthquakes has been compiled and used in the subdivision of the fault area into the following segments: 1) Araba segment, which extends along Wadi Araba and the southernmost part of the Dead Sea (29.5°-31.3°N) and trends SSW-NNE with scarce historical and instrumental seismicity; 2) Jordan-valley segment, which extends along the central and northern parts of the Dead Sea and the Jordan valley to the Huleh depression (31.3°-33.1° N) and trends S-N with moderate historical seismicity; 3) Beqa’a segment, which extends along the western margin of the Beqa’a valley in Lebanon (33.1°-34.5°N) and trends SSW-NNE with strong historical seismicity; 4) El-Ghab segment, which extends along the eastern flank of the coastal mountain range of Syria (34.5°-35.8°N) and trends S-N with moderate historical seismicity; 5) Karasu segment, which extends along the Karasu valley in SE Turkey (35.8°-37.3°N) and trends SSW-NNE, exhibiting the strongest historical seismicity of the area. Probabilities for the generation of strong (M > 6.0) earthquakes in these segments during the next decade are given, by the application of the regional time and magnitude predictable model.459 2195 - PublicationOpen AccessMonitoring of the geomagnetic and geoelectric field in two regions of Greece for the detection of earthquake precursors(1997-03)
; ; ; ; ; ;Vargemezis, G.; Geophysical Laboratory, University of Thessaloniki, Greece ;Zlotnicki, J.; Laboratoire de Geophysique d'Orleans, France ;Tsokas, G.; Geophysical Laboratory, University of Thessaloniki, Greece ;Papazachos, B. C.; Geophysical Laboratory, University of Thessaloniki, Greece ;Papadimitriou, E. E.; Geophysical Laboratory, University of Thessaloniki, Greece; ; ; ; Two magnetotelluric stations have been installed in the South-Eastern Thessaly basin (Central Greece), which have recorded the geomagnetic and geoelectric fields since 1993. The aim is to detect long lasting abnormal changes of the geoelectric field which may be due to impending earthquakes. The geoelectric recordings were checked against the climatic changes such as temperature changes and precipitation and no correlation was observed. Ten anomalies were observed with characteristics similar to seismoelectric signals which have been reported in the literature and thus we can assume that these changes constitute precursory phenomena. The duration of these signals varies from several days to a few weeks. Some of them keep on developing until the occurrence of an earthquake, and others appear like transient changes several days before. The high seismicity of the area where the stations are located creates difficulties in the correlation of the signals with certain shocks.155 141 - PublicationOpen AccessStatistical study of epicentre alignment in the broader Aegean area(1994-09)
; ; ; ; ;Tosi, P.; Istituto Nazionale di Geofisica, Roma, Italy ;De Rubeis, V.; Istituto Nazionale di Geofisica, Roma, Italy ;Papadirnitriou, E.; Laboratory of Geophysics, Aristotelian University of Thessaloniki, Greece ;Dimitriu, P.; Laboratory of Geophysics, Aristotelian University of Thessaloniki, Greece; ; ; Accurate data concerning shallow (h = 60 km) earthquakes (Ms =4.5) that occurred in the broader Aegean area are used to point out the presence of linear seismogenic structures (seismolineaments). The earthquake data were analyzed by the use of a specific algorithm, and the directions of the best alignment of epicentres were found. The algorithm is based on statistical criteria applied within a circular area with the aim of searching for the best direction of alignment; this is then tested, to discriminate whether or not the pattern could stem from a random distribution of epicentres, or whether it is effectively the result of a linear seismic structure; the procedure is repeated to cover the whole area examined. The resulting lineaments can be regarded as individual tectonic units, as they usually coincide with known active faults or fault systems. An interpretation is given of the spatio-temporal evolution of the seismicity along the lineaments in terms of the asperity model.165 156 - PublicationOpen AccessAn Earthquake-Clustering Model in North Aegean Area (Greece)The investigation of short-term earthquake-clustering features is made feasible through the application of a purely stochastic Epidemic-Type Aftershock Sequence (ETAS) model. The learning period that is used for the estimation of the parameters is composed by earthquakes with M>= 2.6 that occurred between January 2008 and May 2017. The model predictability is retrospectively examined for the 12 June 2017 Lesvos earthquake (Mw6.4) and the subsequent events. The construction of timedependent seismicity maps and comparison between the observed and expected earthquake number are performed in order to temporally and spatially test the evolution of the sequence, respectively. The generation of 127 target events with M >= 3.0 in the period June–July 2017, just before the main shock occurrence, is examined in a quantitative evaluation. The statistical criteria used for assessing the model performance are the Relative Operating Characteristic Diagram, the R-score, and the probability gain. Reliable forecasts are provided through the epidemic model testifying its superiority towards a time-invariant Poisson model.
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