Seismic risk in Turkey, the Aegean and the eastern Mediterranean: the occurrence of large magnitude earthquakes

Abstract

The file of Turkish seismicity developed by Kandilli Observatory, Istanbul, for earthquakes to 1970 is extended here up to 1978 using 1SC and PDE data. Entries into this file are maintained on the surface wave magnitude scale M,, and conversion of body wave magnitude mb t o M , has been carried out where necessary using a formula derived for Turkish earthquakes. Completeness analysis suggests that magnitudes M,> 4.5 may be used for statistical evaluation of seismic risk. This file is analysed by a range o f methods to provide a suite of risk forecasts.Forecasting results from least squares and maximum likelihood estimates of the whole process Gutenberg-Richter cumulative frequency law of earthquake magnitude occurrence, and from the part process of Gumbel's first extreme value distribution, all show small systematic differences in forecasts, but all three methods lead to magnitude forecasts which fall well within the range of standard deviation. However, these forecasts are obtained by subdividing Turkish seismicity in a cellular manner, and many of these cells show curvature of the earthquake frequency magnitude distribution curve concave with respect t o the origin: Gumbel's third asymptotic distribution of extreme values is chosen as an appropriate statistical description. Approximate upper bounds o t o earthquake surface wave magnitude occurrence are evaluated and estimates of largest magnitudes expected over an interval of 7 5 y r are forecast with uncertainties. Values of w are asymptotic, uncertain, and theoretically correspond t o infinite return periods. Strain energy release diagrams are then invoked t o estimate empirically the large magnitude M , which is equivalent to the total strain energy which may be accumulated in a region. This equivalent magnitude M , is consistently less than w and there is a finite 'waiting time', typically ranging from about 15 to 7 0 yr, during which the energy equivalent to M3 may be accumulated. 476 P. W. Burton et al.Combination of the Gumbel I11 earthquake occurrence statistics for each cell with an inferred intensity attenuation law leads to a suite of perceptibility curves which give the probability of perceiving specific intensity levels from each possible earthquake magnitude up to the local upper bound magnitude w. This family of curves generated for an individual cell is seen t o be nested, and shows a peak probability for each intensity level which typically occurs at similar magnitudes defined as the 'most perceptible' earthquake. These 'most perceptible' earthquakes show values which range from an M, o f about 5.5 t o 7.5 for regional seismicity cells in Turkey; local values may be used as a criterion for choosing engineering design time histories.The seismic risk parameters from the cellular analysis of seismicity are interpreted as contoured seismic risk maps. These maps show that contoured values of the maximum strain energy earthquake M3 usually exceed the 75 yr earthquake by about one-half magnitude for similar geographic locations, but there is overall s...

Estimation of Seismic Hazard Parameters in the Northern Part of Algeria

“…The problem to determine the time period of completeness has been resolved by STEPP (1971), who has proposed a method, which is based on the selection of subinterval, in which the mean recurrence rate is stable for a particular magnitude range. BURTON et al (1984) extend a simple modification of Stepp's method to resolve this problem.…”

Block‐like plate movements in eastern Anatolia observed by InSAR

“…After compiling 70 years of seismic data, however, Jackson and McKenzie [1988] pointed out that the seismicity recorded during the twentieth century was low and probably not representative of a longer period. Similarly, Burton et al [1984] stated, based on analysis of the seismicity between 1900 and 1978, that the seismic activity of the EAF seemed surprisingly low and that it might be an area where seismic creep is dominant. In addition, Bulut et al [2012] recently found low seismicity rates along the eastern half of the EAF (38 ı E-41 ı E) for the time period 2007-2011.…”

Pathways to seismic hazard evaluation: Extreme and characteristic earthquakes in areas of low and high seismicity

“…This general methodology outlined above may be used to assess seismic hazard for one group of earthquakes or to evaluate and map it throughout a region or country. The map in Figure 4 illustrates a successful example for Turkey [17]. Values of the 75 yr earthquake, m(75), were evaluated.for 4 ° cells of seismicity moving on a 1 ° grid.…”

“…Defined using macroseismic intensity as the shaking parameter generates mp = 51 in the U.K. [19], whereas mp is 6.5-6.9 in the Central and Eastern United States [21]. In Turkey [17], the most perceptible earthquake has surface wave magnitude reaching as high as mp = 7.75 on the North Anatolian Fault, whereas in parts of southern Turkey it drops to mp = 6.0.…”