Seismic risk in southern Europe through to India examined using Gumbel's third distribution of extreme values

Abstract. 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 (M s = 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 (M max = 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.

Section: Seismic Hazard Assessmentmentioning

confidence: 99%

Seismic hazard assessment in Polyphyto Dam area (NW Greece) and its relation with the "unexpected" earthquake of 13 May 1995 (Ms = 6.5, NW Greece)

Pavlou

Κaviris

Chousianitis

et al. 2013

“…Annual extremes are seen only in few occasions, and generally we have extreme intervals of duration of N-years (Burton, 1977) and these intervals referred as "extreme years". On the other hand (Burton, 1979) suggested that in the case of N-year extremes if the missing entries (years) must be less than or equal to 25% the parameters of Gumbel I or III distribution may be estimated without noticeable loss of accuracy. Then we estimated the extreme years and the percentage (%) of the missing years (≤25%) in order to obtained reliable results, as we aforementioned.…”

Section: Resultsmentioning

confidence: 99%

“…Equation (9) is the most proper one for the 1-type and 3-type asymptotic distribution of extremes (Burton, 1979). The commonest description of earthquake occurrence is provided by the Gutenberg-Richter law.…”

Section: Brief Descriptions Of the Methods Appliedmentioning

confidence: 99%

Seismicity assessment for the different regions in and around Turkey based on instrumental data: Gumbel first asymptotic distribution and Gutenberg-Richter cumulative frequency law

Bayrak

Öztürk

Koravos

et al. 2008

Abstract. The evaluation of the seismicity in 24 seismic regions, in which Turkey and adjacent areas divided, is carried out. For this purpose two methods are adopted. The first is the "whole process" which follows the Gutenberg and Richter distribution frequency-magnitude law, while the second one is the "part process" which is well known as the theory of extreme values. This theory was developed by Gumbel in order to solve many geophysical problems. The first asymptotic distribution of extremes was used in the present study. The advantage of the method is that it does not required analysis of the whole data set. It uses, instead, the sequence of earthquakes with the largest magnitudes in a set of predetermined equal-time intervals. The parameters a and b were estimated from both methods. For the goodness of fit, to the Gutenberg-Richter frequency-magnitude law, the maximum likelihood approach is applied. The b-values calculated from Gutenberg and Richter frequency-magnitude law, reveal a better fit to the tectonic environment of the 24 seismic regions of Turkey and its surroundings examining in this study. On the other hand b-values evaluated from Gumbel's first distribution, do not adjust to the particular tectonics of the 24 seismic regions. The modal value a 1 /b adopted from Gutenberg-Richter for the 24 seismic regions were calculated, as well.An effort made to correlate the tectonics of the area with the spatial distribution of the various computed seismic parameter, while maps were produced for this purpose. These maps provide a detail image of seismicity and local tectonics for the whole investigated area. The results showed that the Aegean arc and the North Anatolian fault zone ranked among to the first positions between the 24 seismic regions researched.

“…(1), and σ ω , σ µ and σ λ the square root of the diagonal elements of the covariance matrix (Burton, 1979;Burton and Makropoulos, 1985;Makropoulos and Burton, 1985a). …”

Section: Methodsmentioning

confidence: 99%

“…First we update the MB earthquake catalogue for Greece 1900-1978(Makropoulos and Burton 1981Makropoulos et al, 1989) to include 1979-1999(Burton et al, 2003c. The basic references for this updated work are ISC, NEIC and CMT Harvard catalogues.…”

Section: Shield Regional Working Area Of Revithoussa and Datamentioning

confidence: 99%

Regional seismic hazard for Revithoussa, Greece: an earthquake early warning Shield and selection of alert signals

Burton

Tselentis

2003

Self Cite

Abstract. The feasibility of an earthquake early warning Shield in Greece is being explored as a European demonstration project. This will be the first early warning system in Europe. The island of Revithoussa is a liquid natural gas storage facility near Athens from which a pipeline runs to a gas distribution centre in Athens. The Shield is being centred on these facilities. The purpose here is to analyze seismicity and seismic hazard in relation to the Shield centre and the remote sensor sites in the Shield network, eventually to help characterize the hazard levels, seismic signals and ground vibration levels that might be observed or create an alert situation at a station. Thus this paper mainly gives estimation of local seismic hazard in the regional working area of Revithoussa by studying extreme peak ground acceleration (PGA) and magnitudes.Within the Shield region, the most important zone to be detected is WNW from the Shield centre and is at a relatively short distance (50 km or less), the Gulf of Corinth (active normal faults) region. This is the critical zone for early warning of strong ground shaking. A second key region of seismicity is at an intermediate distance (100 km or more) from the centre, the Hellenic seismic zone south or southeast from Peloponnisos. A third region to be detected would be the northeastern region from the centre and is at a relatively long distance (about 150 km), Lemnos Island and neighboring region. Several parameters are estimated to characterize the seismicity and hazard. These include: the 50-year PGA with 90% probability of not being exceeded (pnbe) using Theodulidis & Papazachos strong motion attenuation for Greece, PGA NTP ; the 50-year magnitude and also at the 90% pnbe, M 50 and M P50 , respectively. There are also estimates of the earthquake that is most likely to be felt at a damaging intensity level, these are the most perceptible earthquakes at intensities VI, VII and VIII with magnitudes M VI , M VII and M VIII . Example results (from many) include the corresponding parameters describing the hazard for Revithoussa as follows: PGA NTP : 203 cm s −2 , M 50 : 6.5, M p50 : 6.9, M VI : 5.8, Correspondence to: Y. Xu (y.b.xu@uea.ac.uk) M VII : 6.1 and M VIII : 6.4. These data are also useful in selecting expected alert-signals i.e. examples of strong ground vibration histories that might be expected at a Shield station in the alert situation.