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Previously published focal mechanisms of earthquakes in western Greece (the date of occurrence is shown next to each beachball). The arrows indicate the motion of the plates relative to Europe and the star symbol corresponds to the epicentre of the 2002 Vartholomio mainshock. Strike-slip events are related to the Cephalonia–Lefkada transform fault and are also distributed along the western coast of Peloponnese, whereas thrust events are observed along the Hellenic subduction zone (figure modified after Kiratzi and Louvari, 2003).
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Broadband data from the Greek National Seismological Network are used to study the moderate size (M5.5) earthquake, which occurred on 2 December 2002 near the town of Vartholomio, in western Peloponnese (Greece). Time domain moment tensor inversion applied to retrieve the focal mechanism of the mainshock and of three of the larger aftershocks of th...
Contexts in source publication
Context 1
... (Greece). Most of the damage was reported in Vartholomio, a town located about 9 km north–northeast of the epicenter. At least 17 people were injured when a rockslide near Mega- lopolis caused a train to derail. At least eight houses were destroyed and 100 were damaged, and a monastery partially collapsed in the Vartholomio area. The earthquake was strongly felt on Zakyn- thos Island as well as in Arcadia and Corinth Provinces. The earthquake, even though moderate in size, is of great interest and importance as it occurred in an area characterized by high levels of seismic hazard. The 2002 Vartholomio sequence provided a ple- thora of broadband waveforms that can be incorpo- rated in modern techniques to gain insight into the source process of earthquakes in this area, as well as better knowledge of the general seismotectonic regime. In this work we apply time domain moment tensor inversion to determine the focal mechanism of the mainshock and of the larger aftershocks, as well as the distribution of slip during the mainshock using a source time function inversion scheme. Special effort is given in identifying the causative fault by combining results from independent analyses. As part of the broader Aegean area, western Greece consists a seismotectonically complex area of rapid and intense deformation. The predominant features of the present seismotectonic setting of this area result from the net effect of the relative motions of the Aegean plate, the African plate and the Apulian platform (Fig. 1). The Cephalonia–Lefkada transform fault, in the area of the Ionian Islands, marks the transition zone between the continental collision of the Apulia platform and Eurasia to the north and the Hellenic subduction to the south. In general, the Aegean plate is subject to large-scale extension, which is evidenced by its southwestward motion relative to Europe (e.g. McKenzie, 1972; Le Pichon et al., 1995; McClusky et al., 2000), whereas compression is observed along the Hellenic subduction zone. Kiratzi and Louvari (2003) compiled a database, a part of which includes all known focal mechanisms of earthquakes in western Greece and they showed the domination of strike-slip motions in the area between the Ionian Islands (Cephalonia–Lefkada transform fault) and western Peloponnese (Fig. 1). Although the character of faulting around the Ionian Islands is very well known to be dextral (Louvari et al., 1999 ...
Context 2
... (Greece). Most of the damage was reported in Vartholomio, a town located about 9 km north–northeast of the epicenter. At least 17 people were injured when a rockslide near Mega- lopolis caused a train to derail. At least eight houses were destroyed and 100 were damaged, and a monastery partially collapsed in the Vartholomio area. The earthquake was strongly felt on Zakyn- thos Island as well as in Arcadia and Corinth Provinces. The earthquake, even though moderate in size, is of great interest and importance as it occurred in an area characterized by high levels of seismic hazard. The 2002 Vartholomio sequence provided a ple- thora of broadband waveforms that can be incorpo- rated in modern techniques to gain insight into the source process of earthquakes in this area, as well as better knowledge of the general seismotectonic regime. In this work we apply time domain moment tensor inversion to determine the focal mechanism of the mainshock and of the larger aftershocks, as well as the distribution of slip during the mainshock using a source time function inversion scheme. Special effort is given in identifying the causative fault by combining results from independent analyses. As part of the broader Aegean area, western Greece consists a seismotectonically complex area of rapid and intense deformation. The predominant features of the present seismotectonic setting of this area result from the net effect of the relative motions of the Aegean plate, the African plate and the Apulian platform (Fig. 1). The Cephalonia–Lefkada transform fault, in the area of the Ionian Islands, marks the transition zone between the continental collision of the Apulia platform and Eurasia to the north and the Hellenic subduction to the south. In general, the Aegean plate is subject to large-scale extension, which is evidenced by its southwestward motion relative to Europe (e.g. McKenzie, 1972; Le Pichon et al., 1995; McClusky et al., 2000), whereas compression is observed along the Hellenic subduction zone. Kiratzi and Louvari (2003) compiled a database, a part of which includes all known focal mechanisms of earthquakes in western Greece and they showed the domination of strike-slip motions in the area between the Ionian Islands (Cephalonia–Lefkada transform fault) and western Peloponnese (Fig. 1). Although the character of faulting around the Ionian Islands is very well known to be dextral (Louvari et al., 1999 ...
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Citations
... The characteristics of the observed S a were reproduced well after site amplification correction. At stations 51JLN and 51LDJ, the simulation results of S a were underestimated over a short period, which may be due to the inherent limitation of the H/V method, which tends to underestimate the actual amplification at higher frequencies (Castro et al. 2003;Roumelioti et al. 2004). The aforementioned bias obviously decreased after the introduction of site amplification correction, demonstrating that the improvement in this study can effectively account for the variability of the site amplification effect at different locations. ...
The development of ground motion models is an essential part of seismic hazard analysis. Based on the stochastic finite-fault method, this study conducted a scenario-based seismic hazard analysis of the Moxi fault. Because of the variability in amplification coefficients caused by the complex terrain, a genetic algorithm based on four previous earthquakes was used to identify site amplification. The simulations of the Ms 6.8 Luding earthquake in 2022 indicated that the correction of site amplification effectively reduced the model deviation and resulted in a close match between the simulated 5%-damped spectral acceleration and the observations. Subsequently, utilizing the calibrated input parameters and a hybrid source model, the ground motion of the Mw 7.1 scenario earthquake was synthesized to reflect uncertainties in the source parameters. To represent the dynamic properties of the structures, effective peak acceleration was used as a ground motion intensity measure. The source model with the synthetic effective peak acceleration closest to the average simulation result from 30 hybrid source models was selected and used to generate a seismic hazard map for the entire area. The prediction of earthquake scenarios provides a basis for earthquake disaster loss evaluation and seismic fortification of engineering structures.
... A surface fault trace of limited length and attaining a maximum offset of~25 cm, which appeared with the 2008 earthquake, constitutes only re-activation of the subsidiary Nisi Fault (Figure 1) that can be considered as a splay of the main fault at depth [26]. Fault plane solutions [27] indicated that the moderate earthquake (M w 5.63, [12]) of 2 December 2002 ( Figure 2) was associated with a possibly sinistral strike-slip fault. ...
... Therefore, significant room exists for the reexamination of the earthquake intensity field. of the subsidiary Nisi Fault (Figure 1) that can be considered as a splay of the main fault at depth [26]. Fault plane solutions [27] indicated that the moderate earthquake (Mw5.63, [12]) of 2 December 2002 ( Figure 2) was associated with a possibly sinistral strike-slip fault. ...
Studies on earthquakes that occurred in the early instrumental period of seismology are of importance for the seismic hazard assessment and are still under investigation since new data are being increasingly revealed. We study the case of a moderate-to-strong earthquake that occurred on 15 July 1909 in NW Peloponnese, Greece. Although the earthquake event was quite destructive, it remains little-known so far in the seismological tradition. We compiled a variety of documentary sources and showed that the earthquake caused extensive building destruction in Chavari and in many other villages with an estimated maximum intensity IX (in EMS-98 scale) and a death toll as high as 55. We also assigned macroseismic intensities in several observation points and drew isoseismal lines by applying the nearest-neighbor technique. From empirical relationships between magnitude and intensities, we estimated the macroseismic magnitude of proxy Ms5.9. Our examination also revealed a variety of earthquake associated phenomena including several types of precursors and abundant co-seismic hydrological changes and ground failures, such as soil liquefaction, surface ruptures, and rock falls. Since no surface fault-trace was reported, the determination of the causative blind fault remains an open issue for future investigation.
... Considering the lack of knowledge on velocity structure information and the presence of vast earthquake recordings at stations it is decided to calculate horizontal to vertical spectral ratio method (HVSR) (Nakamura 1989) to account for site response. Even though it is now well known that the HVSR method underestimates the real site amplification (e.g., Castro et al. 2003;Roumelioti et al. 2004), it is still commonly used to quickly portray the average frequency-amplification behaviour. The strong motion recordings from 36 earthquake (mostly aftershocks; 3.9 < ML < 5.1 between July to November 2017) are collected ( Table 5). ...
A strong earthquake with Mw 6.6 occurred on 20 July, 2017 in Gökova Bay at the southwest part of the Turkey, accompanied by a local tsunami which impacted Bodrum (Turkey) and Kos (Greece). This paper presents simulation of strong ground motions from this earthquake to visualize the extent of spectral acceleration over the region. A stochastic finite fault method based on a dynamic corner frequency is utilized as a simulation tool. For validation of simulation, strong motion recordings from 10 closest stations within 76 km are used. Horizontal to vertical spectral ratio and near surface attenuation parameter (kappa) of shear waves at strong motion recording stations are calculated to account for site effects. The most suitable source parameters; stress drop and pulsing area percentage are found as 2.5 MPa with 30–36% based on the residuals analyses. In general, an acceptable level of consistency is found between observed and simulated ground motions. Simulation is more successful at frequencies of 2 Hz and above. Distribution of spectral accelerations at a larger region is calculated with the best validated model parameters and compared with ground motion prediction equations. In spite of significant scatter of synthetics particularly in the near fault region, at longer epicentral distances the median values of Turkish empirical prediction better approximates the synthetics. The current results and further scenario simulations for the region are believed to complement normal faulting synthetic strong ground motion library of Turkey.
... The application of the moment tensor inversion method produced results slightly different than the previously published by Roumelioti et al. (2004) for the same event (strike:50 o , dip: 68 o , rake: -166 o ). ...
On the 2 December 2002 an earthquake (Mw=5.5) occurred near the city of Vartholomio (western Greece) causing damage in more than 1000 buildings. The University of Patras Seismological Laboratory permanent network stations recorded the mainshock and the aftershocks. Furthermore, twenty-six sites were instrumented to study the aftershock sequence. We identified more than 500 aftershocks with Md ranging from 2.0 to 4.3 during the first 30 days following the mainshock. The spatial and temporal evolution of the aftershock sequence is presented. We use the 370 earthquakes recorded at a minimum of 20 stations, with RMS less than 0.1 s and uncertainties less than 1 km, to infer the precise distribution of the seismicity in the fault region. The mainshock moment tensor inversion results are used in parallel to the aftershock sequence distribution in order to identify the causative fault. The results suggest a strike slip fault with dextral movement, which is trending NNE-SSW and fits the regional tectonics.
... The 2nd December 2002, M w 5.5 earthquake caused damage in the town of Vartholomio. Preliminary analysis of aftershock locations and macroseismic data support a NW-SE trending fault plane, which is connected with sinistral strike-slip motion (Roumelioti et al. 2004). The activated area seems to occupy a fault segment adjacent to the 1988 Killini segment, with similar strike. ...
On 8 June 2008 an earthquake of Mw6.4 took place
in the northwestern part of Peloponnese, Greece. The main shock
was felt in a wide area and caused appreciable damage along the
main rupture area and particularly at the antipodal of the main
shock epicenter fault edge, implying strongly unilateral rupture and
stopping phase effects. Abundant aftershocks were recorded within
an area of *50 km in length in the period 8 June 2008–end of
2014, by a sufficient number of stations that secure location
accuracy because the regional network is adequately dense in the
area. All the available phases from seismological stations in epicentral
distances up to 140 km until the end of 2014 were used for
relocation with the double difference technique and waveform
cross-correlation. A quite clear 3-D representation is obtained for
the aftershock zone geometry and dimensions, revealing the main
rupture and the activated adjacent fault segments. SAR data are
processed using Stanford Method for Persistent Scatterers
(StaMPS) and a surface deformation map constructed based on PS
point displacement for the coseismic period. A variable slip model,
with maximum slip of *1.0 m located at the lower part of the
rupture plane, is suggested and used for calculating the deformation
field which was found in adequate agreement with geodetic measurements.
With the same slip model the static stress changes were
calculated evidencing possible triggering of the neighboring faults
that were brought closer to failure. The data availability allowed
monitoring the temporal variation of b values that after a continuous
increase in the first 5 days, returned and stabilized to 1.0–1.1
in the following years. The fluctuation duration is considered as the
equivalent time for fault healing, which appeared very short but in
full accordance with the cessation of onto-fault seismicity.
... MT solutions of 145 events (Table 3) were first time computed using TDMT inversion technique (Dreger, 2003). This technique was widely exploited for earthquakes occurring in Italy (Scoganmiglio et al., 2009), Utah (Whidden and Kristine, 2012), California Hector mine (Dreger and Kaverina, 2000), Greece (Roumelioti et al., 2004(Roumelioti et al., , 2008, Aegean Sea between mainland of Greece and Turkey (Roumelioti et al., 2011). The results of earlier MT solutions (Table 4) are also compared with the analyzed solutions in this study. ...
Time domain moment tensor analysis of 145 earthquakes (Mw 3.2 to 5.1), occurring during the period 2006-2014 in Gujarat region, has been performed. The events are mainly confined in the Kachchh area demarcated by the Island belt and Kachchh Mainland faults to its north and south, and two transverse faults to its east and west. Libraries of Green’s functions were established using the 1D velocity model of Kachchh, Saurashtra and Mainland Gujarat. Green’s functions and broadband displacement waveforms filtered at low frequency (0.5 - 0.8 Hz) were inverted to determine the moment tensor solutions. The estimated solutions were rigorously tested through number of iterations at different source depths for finding reliable source locations. The identified heterogeneous nature of the stress fields in the Kachchh area allowed us to divide this into four Zones 1-4. The stress inversion results indicate that the Zone 1 is dominated with radial compression, Zone 2 with strike-slip compression, and Zones 3 and 4 with strike-slip extensions. The analysis further shows that the epicentral region of 2001 MW 7.7 Bhuj mainshock, located at the junction of Zones 2, 3 and 4, was associated with predominant compressional stress and strike-slip motion along ∼NNE-SSW striking fault on the western margin of the Wagad uplift. Other tectonically active parts of Gujarat (e.g. Jamnagar, Talala and Mainland) show earthquake activities are dominantly associated with strike-slip extension/compression faulting. Stress inversion analysis shows that the maximum compressive stress axes (σ1) are vertical for both the Jamnagar and Talala regions and horizontal for the Mainland Gujarat. These stress regimes are distinctly different from those of the Kachchh region.
... Regional and local recordings have been used for studying the characteristics of the seismicity in the region (Hatzfeld et al., 1990Haslinger et al., 1999;Louvari et al., 1999;Tselentis et al., 2006;Slejko et al., 2010). Clustered seismicity involving mainshock-aftershock series and swarms has also been studied using regional (Scordilis et al., 1985;Roumelioti et al., 2004;Benetatos et al., 2005;Kiratzi Fig. 1. Map presenting seismicity (GI-NOA catalogue; Makropoulos et al., 2012) and focal mechanisms of crustal earthquakes (CMT solution Project). ...
... Regional and local recordings have been used for studying the characteristics of the seismicity in the region (Hatzfeld et al., 1990;Haslinger et al., 1999;Louvari et al., 1999;Tselentis et al., 2006;Papoulia et al., 2008). Clustered seismicity involving mainshock-aftershock series and swarms has also been studied using regional (Scordilis et al., 1985;Roumelioti et al., 2004;Benetatos et al., 2005;Kiratzi et al., 2008;Konstantinou et al., 2009a;2009b;Karakostas and Papadimitriou, 2010;Konstantinou et al., 2011;Papadimitriou et al., 2012) and local recordings (Sachpazi et al., 2000;Kassaras et al., 2014a;Kassaras et al., 2014b;Serpetsidaki et al., 2014;Papadopoulos et al., 2014). ...
We analyzed a large number of focal mechanisms and relocated earthquake hypocenters to investigate the geodynamics of western Greece, the most seismically active part of the Aegean plate-boundary zone. This region was seismically activated multiple times during the last decade, providing a large amount of enhanced quality new information that was obtained by the Hellenic Unified Seismological Network (HUSN). Relocated seismicity using a double-difference method appears to be concentrated above ∼35 km depth, exhibiting spatial continuity along the convergence boundary and being clustered elsewhere. Earthquakes are confined within the accreted sediments escarpment of the down-going African plate against the un-deformed Eurasian hinterland. The data arrangement shows that Pindos constitutes a seismic boundary along which large stress heterogeneities occur. In Cephalonia no seismicity is found to be related with the offshore Cephalonia Transform Fault (CTF). Onshore, NS crustal extension dominates, while in central and south Peloponnesus the stress field appears rotated by 90°. Shearing-stress obliquity by 30° is indicated along the major strike-slip faults, consistent with clockwise crustal rotation. Within the lower crust, the stress field appears affected by plate kinematics and distributed deformation of the lower crust and upper mantle, which guide the regional geodynamics.
... Recent strike-slip events in this area include the offshore Kyllini earthquake in October 16, 1988 (Mw=5.8), and the offshore Vartholomio earthquake in December 2, 2002 (Mw=5.6) , Mariolakos et al. 1991, Roumelioti et al. 2004 (Figure 1). These events were generated about 30-40 km WSW of the 2008 Andravida event. ...
On June 8, 2008, a strike-slip earthquake (Mw=6.4) was generated NE
of the Andravida town (NW Peloponnese, western Greece) due to the activation
of the previously unknown western Achaia strike-slip fault zone
(WAFZ). Extensive structural damage and earthquake environmental effects
(EEE) were induced in the NW Peloponnese, offering the opportunity
to test and compare the ESI 2007 and the EMS-98 intensity scales in a
moderate strike-slip event. No primary EEE were induced, while secondary
EEE including seismic fractures, liquefaction phenomena, slope movements
and hydrological anomalies were widely observed covering an area
of about 800 km2. The lack of primary effects and the relatively small
surface deformation with respect to the earthquake magnitude is due to
the thick Gavrovo flysch layer in the affected area that isolated and absorbed
the subsurface deformation from the surface. According to the application
of the EMS-98 scale, damage to masonry buildings ranged from
grade 3 to 5, while damage in most of R/C buildings ranged from grade
1 to 3. A maximum ESI 2007 intensity VIII-IX is recorded, while the maximum
EMS-98 intensity is IX. For all the sites where intensity VIII has
been recorded the ESI 2007 and the EMS-98 agree, but for others the ESI
2007 intensities values are lower by one or two degrees than the corresponding
EMS-98 ones, as it is clearly concluded from the comparison of
the produced isoseismals. An exception to this rule is the Valmi village,
where considerable structural damage occurs (IXEMS-98) along with the
lack of significant EEE (VESI 2007). This variability between the ESI 2007
and the EMS-98 intensity values is predominantly attributed to the vulnerability
of old masonry buildings constructed with no seismic resistance
design. Correlation of all existing data shows that the geological structure,
the active tectonics, and the geotechnical characteristics of the alpine
and post-alpine formations along with the construction type of buildings
were of decisive importance in the damage and the EEE distribution.
... The 2nd December 2002, M w 5.5 earthquake caused damage in the town of Vartholomio. Preliminary analysis of aftershock locations and macroseismic data support a NW-SE trending fault plane, which is connected with sinistral strike-slip motion (Roumelioti et al. 2004). The activated area seems to occupy a fault segment adjacent to the 1988 Killini segment, with similar strike. ...
An earthquake with magnitude M=6.4 occurred on 06 June 2008 in NW Peloponnessus Greece. Historical seismicity deciphers that at least two earthquakes with M≥6.0 have occurred in the same area in eighteenth and nineteenth centuries. The main shock triggered a number of landslides and rockfalls and toppled old buildings but no significant surface deformation was observed.
A rather intense aftershock activity of small magnitude aftershocks followed with several felt events since they occurred onshore. Relocation performed in previous studies implies that the main rupture occurred on an almost vertical fault segment, having a length of about 24 km with a NNE-SSW orientation. The epicenter of the main shock is located at the southernmost part of the rupture, whereas adjacent smaller fault segments were activated during the course of this activity, probably triggered by stress perturbation caused by the main event.
Aiming in a better understanding of the rupture process on the activated fault segment, geodetic and SAR data were combined with the obtained seismological ones. This paper focuses on SAR data first results.
InSAR images were formed from data collected by ENVISAT satellite of the European Space Agency. The ENVISAT data set is from ascending track 186 and consist of 13 images spanning 19 Feb 2006 - 19 Apr 2009. The data were processed using Doris and StaMPS /MTI software.
In first step we construct interfergoram based on two images 2008.03.30 and 2008.07.13. Generally interferograms were highly decorrelated. Nevertheless regions near the projected fault plain maintain modest coherence and little interference consistent with coseismic activity is identifiable. On the west side of the fault one can see deformation corresponding with maximum approximately 2.5 cm changing on surface. We decided to use PSI technique instead of InSAR. PS mean velocity displacement for the whole period of time (2006.02 to 2009.04) vary from -19.7 to 18.4 mm/yr. One can observed that times series plots of PS points around the fault show characteristic opposite direction of displacement before and after the earthquake.
