Fig 1 - uploaded by Efthymis Lekkas
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Simplified Geological Map of the earthquake striken area (1: Alluvial and Scree, 2: PlioPleistocene sediments, 3: "Tsotylion" molassic formation, 4: "Pendalofo" molassic formation, 5: "Vourinos" ophiolitic complex, 6: "Eastern Greece" carbonates, 7: "Flambouron" gneisses and schists, 8: fault zones.
Contexts in source publication
Context 1
... damage has been limited to relatively small area in the form of a triangle extending between the Serbia fault zone to the south, and the Chromion -Varis fault zone to the north (Fig. 1). The western limit was the Aliakmon river. The severe damage is mainly located at the villages lying at the foot of Mt. Vourinos, and some others, as Rymnio and Chromio. However, there still is an "eclectic" distribution, with two groups of highly damaged villages, one at the north (Knidi, Varis, Chromio) and the other at the south ...
Context 2
... morphological unit of Vourinos presents quite intense relief, has a general NW-SE trend and is located between the previous two. At places it is interrupted by E-W trending plateau; that is the case of the area of Knidi-Varis-Chromio (Fig. ...
Context 3
... earthquake stricken area forms a E-W trending zone, from the northwestern border of the Meso-Hellenic Trench at the west, runs through the southern part of the ophiolitic complex of Mt. Vourinos and the carbonates of "Eastern Greece Unit" and ends at the southern part of the post- alpine basin of Kozani. The following formations ( Fig. 1) occur in the area ( Papanikolaou 1986, Mavrides & Kelepertzis ...
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Citations
The Environmental Seismic Intensity (ESI) scale has been officially released in 2007 and is based on the quantification of Earthquake Environmental Effects. Due to its quantitative nature, the scale improves the process of assessing macroseismic intensities, particularly in the epicentral area of those cases in which sole traditional intensity scales prove to be ineffective. Following a large number of publications that applied this relatively newly established scale, there is some need for parametrization. This is because this intensity scale can offer new insights to seismic hazard assessment and has the potential to reduce the uncertainties that stem from traditional macroseismic scales. This study has three main goals. Firstly, to enrich and compile an ESI 2007 database from earthquakes in Greece by adding 4 new events. Secondly, to extract a relationship between Magnitude and the ESI 2007 for Greece and the Mediterranean. Thirdly, to offer a preliminary estimate of how the intensity attenuates with distance, after developing a code in Python language to assist this process. The ESI 2007 scale was applied in the 1995 Ms = 6.6 Kozani-Grevena earthquake, the 1978 Mw = 6.5 Thessaloniki earthquake, the historic 1894 Atalanti earthquake sequence (M = 6.4 and M = 6.8) and the 365AD event in Crete (M = 8.4). These events were selected because they have well documented and extensive co-seismic effects, including primary and secondary surface ruptures, rockfalls, landslides and liquefaction phenomena. For the Kozani earthquake, extracted results were correlated with SAR interferograms, in order to provide a complete and high spatial resolution of the ground deformation. Both the Kozani-Grevena and the Thessaloniki events produced a maximum intensity IX on the ESI 2007 scale, the Atalanti earthquake produced a maximum intensity X and the 365AD Crete earthquake a maximum intensity XII. Overall, the ESI 2007 scale compares fairly well with the traditional macroseismic scales except for some villages in the Kozani-Grevena epicentral area where due to the poor quality of buildings, existing scales overestimated the intensity by one degree compared to the ESI 2007. It is interesting to note that both for Greece and the Mediterranean area a strong correlation exists between Mw and the ESI 2007 scale. In particular, the following relationships between the Mw and the ESI scale have been extracted: i) for Greece Io(ESI 2007) = 3.1427 exp (0.1643Mw) and ii) for the Mediterranean Io(ESI 2007) = 3.3543exp (0.1557Mw).
Fracture-induced electromagnetic emissions (EME) have been observed from the laboratory to the geophysical scale permitting the monitoring of damage evolution. It has been shown that the first appearing MHz EME presents second-order phase transition characteristics and has been attributed to the fracture process of the heterogeneous medium surrounding the family of strong entities (asperities) distributed along the fault sustaining the system. The finally, abruptly, emerged strong avalanche-like kHz EME do not present any footprint of a second-order transition in equilibrium, while they have been attributed to the fracture of the family of the, relatively homogeneous, asperities themselves. In the present work we show that between these two stages of the fracture process, an intermediate stage exists. This is reflected to the tricritical behavior which is revealed for the kHz EME just before the emergence of the strong avalanche-like kHz emission. The identification of this tricritical behavior is performed using the method of critical fluctuations (MCF). The results obtained for the kHz time-series are compatible with the results obtained for an introduced model map which describes the tricritical crossover. A Hurst exponent analysis shows that this crossover indicates the limit of an antipersistence dynamics. It is finally shown, by the MCF, that first-order phase transition characterizes the final rupture of the asperities.
Seismic hazard assessment and seismicity changes are investigated in the
Kozani-Grevena area, at the western margin of internal Hellenides in NW
Greece. The region is of great interest, since it was characterized by
very low seismic activity until 1995, when the "unexpected"
Kozani-Grevena earthquake (Ms = 6.5) occurred. This event is
of significant importance for Greece, since it, along with the 1999
Athens earthquake, initiated the modification of the Greek Building
Code. In order to detect any seismicity changes, the seismicity of the
region was divided into three time windows: the first up to 1973, the
second from 1900 to 1994 and the third covering the entire instrumental
period. For the above mentioned time windows, seismic
hazard assessment was performed using the extreme values method. The
results indicate an increase of the peak ground acceleration (PGA)
values after the impoundment, with the exception of the area in the
vicinity of the NE edge of the Dam. Before the occurrence of the 1995
event, the epicentral region also exhibited higher PGA values than
before the impoundment. The most significant increase in PGA values is
observed SE of the Polyphyto artificial lake, where the largest values
are observed for the second and the third period. The coincident
increase in the number of earthquakes and in the PGA values may be
attributed to the impoundment of the Polyphyto Dam. The
maximum expected magnitude is calculated by the extreme values method
and Gumbel's third asymptotic distribution. The results reveal similar
values of maximum expected magnitudes (Mmax = 6.5),
independent of the seismicity rate, indicating that the 13 May 1995
earthquake was not an "unexpected" event, since the magnitude of an
oncoming earthquake depends mainly on the tectonics of the region and
the characteristics of the active faults.
The usefulness of integration of SAR (ERS-1) and Landsat TM data for study active faults and the corresponding displaced landforms in flat or almost flat areas has been demonstrated. The study area is the Kozani basin which in May 13, 1995 was affected by a strong earthquake (Ms=6.6). After co-registration and resampling the two data sets were merged to form a combined image. The combined image offers the spectral characteristics of the TM data with the spatial resolution and roughness sensitivity of SAR images. The merging method used was the IHS to RGB transform. The criteria and parameters examined were geomorphic features, drainage network analysis, slope processes, terrain analysis, and observations on spatial distribution of soil cover as well as linear features that correspond to fracture zones crossing the basin. The use of the combined image allowed us to identify tectonic terraces in the basin produced by activity of normal faults located in the adjacent relief zone.
