Options
Kiratzi, Anastasia
Loading...
Preferred name
Kiratzi, Anastasia
Alternative Name
Kiratzi, Anastasia A.
Sissy Kiratzi
ORCID
9 results
Now showing 1 - 9 of 9
- PublicationOpen AccessActive seismic deformation in the Italian peninsula and Sicily(1994-04)
; ;Kiratzi, A. A.; Geophysical Laboratory, University of Thessaloniki, GreeceRecent and historical seismicity as well as reliable fault plane solutions are used in order to perform a moment tensor analysis and estimate the active crustal and sub-crustal deformation of the Italian peninsula and Sicily. The results show that in Northern Italy, along the Alps, the deformation is taken up by compression at N162°E and a rate of 1 mm/yr. The thickening of the seismogenic layer is taking place at a rate of 0.1 mm/yr. In Central Italy, along the Apennines, extension is prevailing at N28°E and a rate of 3 mm/yr which causes thinning of the seismogenic layer at a rate 0.5 mm/yr. In Southern Italy, at Calabria, the deformation is taken up as extension at N40°E and a rate of 11 mm/yr. At the island of Sicily, compression is occurring at N25°E and a rate of 1 mm/yr. These results are in agreement with plate motion models for the area. The analysis of the deep seismicity of the Tyrrhenian Sea showed that the descending slab is in a state of down dip compression at N146°E and a rate of 2 mm/yr.148 332 - PublicationRestrictedA deformation study of Anthemountas graben (northern Greece) based on in situ data and new InSAR results(2020)
; ; ; ; ; ; ; ; ; ; ; The focus of this study is Anthemountas basin in northern Greece, where land subsidence phenomena had been previously identified. The basin has a NNW-SSE orientation, which is optimal to the currently acting ~ N-S extension field in the back-arc Aegean area and is bordered to its north and south edge by two, well-pronounced faults. The region of study is located close to the greater metropolitan city of Thessaloniki and comprises a number of critical facilities including the city’s international airport. The research object is the monitoring of the evolution of the displacement at Anthemountas graben, using InSAR time-series and the investigation of the dominant driving mechanism. We show new surface displacement results from the ENVISAR satellite, and overall, an enhanced dataset of SAR time-series is presented, spanning the period 1992 to 2010, by using the satellites ERS1, ERS2 and ENVISAT. Results indicate a continuously deforming environment in both decades, with an increasing magnitude. The detailed study of the deformation pattern together with the analysis of in situ data defines aquifer overpumping as the main cause of the detected displacement of both decades. Critical regions are examined in detail, as for example: an area close to Thermi, the town of Perea and the Thessaloniki’s international airport, a major hub of the Balkans. The latter was subjected to an increasing deforming velocity during the monitoring period. Overall, we conclude that a water management plan should be of high priority for the area.50 2 - PublicationOpen AccessOn the Segmentation of the Cephalonia–Lefkada Transform Fault Zone (Greece) from an InSAR Multi-Mode Dataset of the Lefkada 2015 Sequence(2019)
; ; ; ; ; ; ; ; ; ; ;; ; ;; We use Interferometric Synthetic Aperture Radar (InSAR) to study the Cephalonia–Lefkada Transform Fault Zone (CTF) in the Ionian Sea. The CTF separates continental subduction to the north from oceanic subduction to the south, along the Hellenic Subduction Zone. We exploit a rich multi-modal radar dataset of the most recent major earthquake in the region, the 17 November 2015 Mw 6.4 event, and present new surface displacement results that o er additional constraints on the fault segmentation of the area. Based on this dataset, and by exploiting available information of earthquake relocation, we propose a new rupture process for the 2015 sequence, complementary to those published already. Our modelling includes an additional southern fault segment, oblique to the segment related with the mainshock, which indicates that the CTF structure is more complex than previously believed.485 47 - PublicationOpen AccessSource parameters of the M 6.5 Skyros Island (North Aegean Sea) earthquake of July 26, 2001(2002)
; ; ; ; ;Benetatos, C.; Department of Geophysics, Aristotle University of Thessaloniki, Greece ;Roumelioti, Z.; Department of Geophysics, Aristotle University of Thessaloniki, Greece ;Kiratzi, A.; Department of Geophysics, Aristotle University of Thessaloniki, Greece ;Melis, N.; Institute of Geodynamics, National Observatory of Athens, Greece; ; ; Teleseismic body wave modelling, time domain moment tensor inversion of regional waveforms and spectral analysis of the far-field P-wave pulses are used to derive the source parameters of the July 26, 2001 Skyros earthquake (M 6.5). Its epicentre is located south of the Sporades Islands in the North Aegean Sea (Greece). Previous focal mechanism solutions indicate motion on strike-slip faults. The time domain moment tensor inversion is applied for the first time to the regional waveforms of the recently established broadband network in Greece. Its application gave results which are highly consistent with teleseismic waveform modelling. The results of this study, in combination with the distribution of aftershocks, indicate left-lateral strike slip motion on a NW-SE striking fault with parameters: fault plane (strike = 151°, dip = 83°, rake = 7°) and auxiliary plane (strike = 60°, dip = 84°, rake = 173°), depth 12 km and M 0 = 5.98e18 N m. Moreover, the time domain moment tensor inversion technique yielded a pure double couple source with negligible CLVD. The spectral analysis of the far-field P-wave pulses resulted in a fault length L ~ 32 km, stress drop ~ 9 bars and average displacement u ~ 30 cm.These values are in very good agreement with those estimated from empirical scaling relations applicable to the Aegean area.170 224 - PublicationOpen AccessStress tensor inversion in Western Greece using earthquake focal mechanisms from the Kozani-Grevena 1995 seismic sequence(1999-08)
; ;Kiratzi, A. A.; Department of Geophysics, Aristotle University of Thessaloniki, GreeceStress tensor inversion has been applied to estimate principal stress axes orientations in Western Greece, from 178 earthquake fault plane solutions from the Kozani-Grevena May 13, 1995 sequence. All focal mechanisms were previously determined through the deployment of a dense portable array. The magnitude range is 2.7-6.5 and the depth range is 4.0-15 km. A single stress tensor with an average misfit of 6.5°, small enough to support the assumption of stress homogeneity, can describe the stress field. The maximum compressive stress, s1, has a NNE-SSW trend (N26°E) and a nearly vertical plunge (80°) while the minimum compressive stress, s3, has a NNW-SSE orientation (N159°E) and a shallow plunge (7°) southwards. The scalar quantity, R (stress ratio) was found equal to 0.4 suggesting a transtensional regime (normal faulting with strike-slip motions) in which s2 is compressional. The identification of the fault plane from the auxiliary plane was achieved for 99 fault plane solutions out of 178 in total (56%). Vertical cross sections support previous results concerning the north dipping main fault segments and the south dipping antithetic faulting. The strike-slip motion is mainly dextral, along NNE-SSW structures, which follow the direction of the main neotectonic faults while the scarce sinistral strike-slip motion is connected to NW-SE trending zones of weakness pre-existing the old phase of compression in the Aegean. The strong strike slip motion that supports the transtensional regime probably reflects the effect of the motions of the North Anatolian Fault, taken up by normal faulting in the area of Western Greece.164 348 - PublicationOpen AccessEarthquake Source Investigation of the Kanallaki, March 2020 Sequence (North-Western Greece) Based on Seismic and Geodetic Data(2021)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The active collision of the Apulian continental lithosphere with the Eurasian plate charac- terizes the tectonics of the Epirus region in northwestern Greece, invoking crustal shortening. Epirus has not experienced any strong earthquakes during the instrumental era and thus there is no detailed knowledge of the way the active deformation is being expressed. In March 2020, a moderate size (Mw 5.8) earthquake sequence occurred close to the Kanallaki village in Epirus. The mainshock and major aftershock focal mechanisms are compatible with reverse faulting, on NNW-ESE trending nodal planes. We measure the coseismic surface deformation using radar interferometry and investi- gate the possible fault geometries based on seismic waveforms and InSAR data. Slip distribution models provide good fits to both nodal planes and cannot resolve the fault plane ambiguity. The results indicate two slip episodes for a 337 ◦ N plane dipping 37 ◦ to the east and a single slip patch for a 137 ◦ N plane dipping 43 ◦ to 55 ◦ to the west. Even though the area of the sequence is very close to the triple junction of western Greece, the Kanallaki 2020 activity itself seems to be distinct from it, in terms of the acting stresses.486 14 - PublicationOpen AccessA comparative study of a stochastic and deterministic simulation of strong ground motion applied to the Kozani-Grevena (NW Greece) 1995 sequence(2000-10)
; ; ; ; ;Roumelioti, Z.; Department of Geophysics, Aristotle University of Thessaloniki, Thessaloniki, Greece ;Kiratzi, A.; Department of Geophysics, Aristotle University of Thessaloniki, Thessaloniki, Greece ;Theodulidis, N.; Institute of Engineering Seismology and Earthquake Engineering, Thessaloniki, Greece ;Papaioannou, C.; Institute of Engineering Seismology and Earthquake Engineering, Thessaloniki, Greece; ; ; We present the results of a comparative study of two intrinsically different methodologies, a stochastic one and a deterministic one, performed to simulate strong ground motion in the Kozani area (NW Greece). Source parameters were calculated from empirical relations in order to check their reliability, in combination with the applied methodologies, to simulate future events. Strong ground motion from the Kozani mainshock (13 May, 1995, M w = 6.5) was synthesized by using both the stochastic method for finite-fault cases and the empirical Green’s function method. The latter method was also applied to simulate a Mw = 5.1 aftershock (19 May, 1995). The results of the two simulations computed for the mainshock are quite satisfactory for both methodologies at the frequencies of engineering interest (> ~ 2 Hz). This strengthens the idea of incorporating proper empirical relations for the estimation of source parameters in a priori simulations of strong ground motion from future earthquakes. Nevertheless, the results of the simulation of the smaller earthquake point out the need for further investigation of regional or local, if possible, relations for estimating source parameters at smaller magnitude ranges155 1027 - PublicationOpen AccessSource parameters of the Izmit-Bolu 1999 (Turkey) earthquake sequences from teleseismic data(2001-02)
; ; ;Kiratzi, A.; Geophysical Laboratory, Aristotle University of Thessaloniki, Greece ;Louvari, E.; Geophysical Laboratory, Aristotle University of Thessaloniki, Greece; Body waveform modelling and far-field displacement spectral analyses were used to study the source parameters of five of the largest earthquakes of the (Izmit-Bolu) Turkey 1999 sequence. The derived source parameters for the August 17, 1999 M W 7.4 event are: strike = 267°, dip = 85°, rake = – 175°, h = 10 km, M 0 = 1.31×10 20 Nm. The length of the fault was found equal to 76 km, the average displacement 6.4 m and the static stress drop 90 bars. The Bolu November 12, 1999 M W 7.1 event has a focal mechanism with strike = 262°, dip = 53°, rake = –177°, h = 12 km, M 0 = 4.71×10 19 Nm, fault length of 56 km, average displacement 2.1 m and average static stress drop 29 bars. The focal mechanisms of three other aftershocks of the Izmit sequence indicate right lateral strike slip motion, as well. The slip vectors of the events studied are in accordance with the GPS velocity vectors, have a mean azimuth of 269° and reveal the extrusion of the Anatolian plate towards the Aegean.137 621 - PublicationOpen AccessIsolation of swarm sources using InSAR: the case of the February 2017 seismic swarm in western Anatolia (Turkey)(2019)
; ; ; ; ; ; ; ;; We study the surface deformation of a moderate size M5+ earthquake swarm-type activity which burst at the tip of the Biga peninsula (western Turkey) in early 2017. No previous M5+earthquakes have been recorded in the instrumental period on land, however, offshore normal faults, have ruptured to produce strong (M>6) earthquakes.We use the Interferometric Synthetic Aperture Radar (InSAR) technique and exploit a data set of Sentinel-1 and ALOS-2 images, to successfully detect the surface deformation caused by three M5+ events of the sequence and constrain their source models, furtherly strengthened by seismic waveform analysis. The sequence occurred at shallowdepths (<12 km) and is relatedwith the activation of a normal fault. Our geodetic inversions constrained the rupture distribution of the main events and led us to conclude that they belong to a single fault plane, striking N110◦E and dipping ∼40◦ to the SW, compatible with the regional tectonics. Furthermore, the InSAR analysis revealed that no aseismic transients occurred during the Biga swarm. InSAR applications in seismic swarms are limited mainly due to the low displacement signal they produce, which is not always easily detectable by radar satellites. Another obstacle is the time frequency of radar satellites acquisitions that often does not allow the temporal isolation of distinct seismic events. However, here we present a study that exploits InSAR data to isolate seismic sources of a swarm and proposes its use for the understanding of shallow seismic swarms in a systematic manner.328 99