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Historical faulting in Aghios Konstantinos area (central Greece), based on archaeological indications
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The Greek database of seismogenic sources (GreDaSS): State-of-the-art for northern greece
No full textThe Greek Database of Seismogenic Sources (GreDaSS) is a repository
of geological, tectonic and active-fault data for the Greek territory and its
surroundings. In this report, we present the state-of-the-art of an on-going
project devoted to the building of the GreDaSS, which represents the results
of decades of investigations by the authors and a myriad of other researchers
working on the active tectonics of the broader Aegean Region.
The principal aim of this international project is to create a homogeneous
framework of all of the data relevant to the seismotectonics, and especially
the seismic hazard assessment, of Greece and its surroundings, as
well as to provide a common research platform for performing seismic hazard
analyses, modeling and scenarios from specific seismogenic structures.
In particular, we introduce and synthetically describe the results obtained
(and included in the database) to date in the northern sector of continental
Greece and the Aegean Sea. As a first step we collected all available
(both published and unpublished) historical and instrumental seismicity
data relevant to the determining of the causative faults. Following the experience
of recent 'surprising' earthquakes (e.g. 1995 Kozani, and 1999
Athens), we realized the deficiency of such an approach, and decided to
also include in the GreDaSS active faults (i.e. seismogenic sources) recognized
on the basis of geological, structural, morphotectonic, paleoseismological
and geophysical investigations. A second step is the critical
analysis of all of the collected data for the extraction of the necessary seismotectonic
information, enabling the recognition of as many seismogenic
sources as possible, as well as their characterization and parameterization.
The most updated version of the database consists of numerous seismogenic
sources that are categorized into three types: composite,
individual, and debated. In this report, we describe the major seismotectonic
properties of all of the composite seismogenic sources and individual
seismogenic sources in northern Greece, which imply the partitioning
of the area into five sectors that show similar internal behavior. Northern
Greece was chosen as a pilot area because the parameters and accompanied
metadata of its seismogenic sources show a high level of confidence
and completeness. The amount of information and the degree of uncertainty
is different for the three types
Comparison between single-event effects and cumulative effects for the purpose of seismic hazard assessment. A review from Greece
No full textWhen compiling a database of active and capable faults, or more in general when collecting data for Seismic Hazard Assessment (SHA) purposes, the exploitation of the numerous and different sources of information represents a crucial issue. Also the understanding of their potential and limitations is essential. For example, using only information deriving from historically and/or instrumentally recorded earthquakes, as it has been commonly applied in the past, it is not sufficient and it could be, sometimes, even misleading in terms of SHA. In the present paper, the importance of using geological information for better defining the principal seismotectonic parameters of a seismogenic source is discussed and emphasized. In order to show this, four case studies of active faults recently reactivated by strong earthquakes have been selected from the Greek Database of Seismogenic Sources (GreDaSS). Each seismogenic source is analyzed twice and separately for the two sources of information: firstly, on the basis of the single-event effects as mainly provided by historically or instrumentally recorded data, and secondly, on the basis of the cumulative effects consisting of any, mainly geological, evidence caused by multiple and repeated fault reactivations of the specific seismogenic source. The quality and accuracy of the produced results from both sources of information are then discussed in order to define the reliability of the outcomes and especially for calibrating the methodological approaches based on geological data, which have an intrinsically different degree of uncertainty and resolution, but also a greater potential exploitability. As a matter of fact, an improved geological, in its broader sense, knowledge will help to fill in the gap of the geodetically and/or seismologically determined tectonic activity of hazardous regions. Moreover, including in a catalogue also the seismogenic sources that are not associated with historical and/or instrumental earthquakes will have a remarkable impact in future SHA analyses either probabilistic and deterministic ones
Surface effects of the strong June 8, 2008, NW Peloponnese earthquake
No full textThe main goal of this paper is the description of the quantitative and qualitative characteristics of the secondary effects triggered by the June 8th, 2008 earthquake. The earthquake-induced ground deformations were spread into a large area up to 25Km of epicentral distance. Surface ruptures were mapped at the areas close to the villages of Mihoi, Psari and Nisi where the maximum horizontal and vertical displacement was equal to 15cm and 20cm, respectively. Furthermore, typical liquefaction-induced surface disruptions were reported at the coastal area of the villages Kato Achaia, Alikes and at the shore of the lake Pinios close to the villages Roupakia and Kalivia. Moreover, small scale liquefaction phenomena were observed at the banks of the river Pinios and at the area of Nisi. In addition, landslides and rockfalls were mapped into a large area and caused damages to the road network of Peloponnesus, particularly to the roads connecting the villages of Santomeri, Portes at the mountain Skollis
An updated database of Holocene relative sea level changes in NE Aegean Sea
No full textThe reconstruction of Holocene relative sea levels has several implications, ranging from the investigation of coastal vertical movements to the calibration of earth rheology models and ice sheet reconstructions. The North Eastern Aegean Sea is among the tectonically complex sectors of the Eastern Mediterranean, mainly influenced by the activity of the North Anatolian Fault. In this paper, we created a relative sea level (RSL) database by expanding upon the previous compilation with recently published geological and archaeological data. We reconstruct the RSL history in those Aegean coastal sectors located within the South Marmara microplate, a broad shear zone located between western Anatolia and central Greece and affected by dominant strike-slip faulting, at times combined with a normal component. Then, we compared it with the RSL histories obtained for the surrounding coastal sectors. The analysis of the database indicated that it is not possible to define a common Holocene RSL curve for the entire NE Aegean, as RSL history here is majorly influenced by changes in deformation patterns. In addition, data in our database are consistent with a continuous RSL rise in the last 6.0 ka BP in the whole NE Aegean Sea and cannot support the hypothesis of a mid-Holocene RSL highstand in the area. Finally, we present our best estimates of late Holocene rates of RSL prior to any possible acceleration during the twentieth century in the broad area of NE Aegean. Here we identified the fastest rising rate (~0.9 mm a-1) in that sector whose active tectonic deformation is mainly controlled by the North Anatolian Fault activity. © 2013 Elsevier Ltd and INQUA
Using geological quantitative data for the assessment of the seismic hazard in Greece and the surrounding region.
No full textEmpirical relationships among earthquake magnitude, surface ruptures and maximum displacement in the broader Aegean Region
No full textPalaeoseismological studies carried out in the Aegean Region during the past decade or so, mainly from faults lying in mainland Greece, are reconsidered and their results re-evaluated. We focus on active normal faults and particularly on the principal seismotectonic parameters, such as the coseismic displacement associated to past events and the length of the seismogenic structures. Based on new both field observations and existing data and following few assumptions, we attempt to calculate the maximum seismic moment possibly associated to past earthquakes and documented from palaeoseismological studies. These seismic moments are compared with those estimated from historical earthquakes for which both maximum vertical displacement and surface rupture length are known. Similarities and differences of the two datasets are discussed, showing that palaeoseismologically-calculated magnitudes and displacements per event appear to be systematically underestimated in the Aegean Region as well as their seismic potential. For selected faults, we also obtained reliable values of the recurrence interval of moderate to large earthquakes and estimates of the slip-rate. Differences in these parameters are attributed to the different geotectonic settings
Palaeoseismological investigations of Aegean-type active faults.
No full textPalaeoseismological studies carried out in the Aegean Region during the past decade or so, mainly from faults lying in mainland Greece, are reconsidered and their results re-evaluated. We focus on active normal faults and particularly on the principal seismotectonic parameters, such as the coseismic displacement associated to past events and the length of the seismogenic structures. Based on new both field observations and existing data and following few assumptions, we attempt to calculate the maximum seismic moment possibly associated to past earthquakes and documented from palaeoseismological studies. These seismic moments are compared with those estimated from historical earthquakes for which both maximum vertical displacement and surface rupture length are known. Similarities and differences of the two datasets are discussed, showing that palaeoseismologically-calculated magnitudes and displacements per event appear to be systematically underestimated in the Aegean Region as well as their seismic potential. For selected faults, we also obtained reliable values of the recurrence interval of moderate to large earthquakes and estimates of the slip-rate. Differences in these parameters are attributed to the different geotectonic settings
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