Ormeni, Rrapo; öZtürk, Serkan; Fundo, Akli; çElik, Kemal

Spatial and temporal evaluation of current seismic activity throughout the Vlora- Lushnja-Elbasani-Dibra (VLED) transversal fault zone were carried out at the beginning of year 2016. The seismotectonic b-value, fractal dimension Dc-value and precursory seismic quiescence Z-value are considered for a detailed statistical analysis. Completeness magnitude Mc-value varies from 2.5 to 2.7 for different parts of the VLED fault zone. The b-value is calculated as 1.10±0.04 for the south western part and 1.13±0.05 for the middle part, whereas it is estimated as 0.94±0.07 for the north eastern part of the study region. These results reveal that b-values for all regions are well represented by a b-value typically close to 1.0. There are clear decreasing trends in temporal changes of b-values before the occurrences of some strong main shocks. On the contrary, no earthquakes are observed in some periods after decrease of b-value. Dc-values are computed as 2.66±0.04 for the south western part, 2.64±0.03 for the middle part and 2.15±0.02 for the north eastern part of the VLED fault zone. These rather large values show that earthquake activity is more clustered at larger scales or in smaller areas in the study area. Considering the phenomenon of seismic quiescence as a precursor of the main earthquakes gives successful outcomes in defining the potential anomalies and possible locations of future earthquakes. Quiescence analysis of current seismicity at the beginning of 2016 in the VLED fault zone is performed with the test of standard normal deviate Z-value. Distributions of resulting Z-values show six anomalous regions along the different parts of the VLED fault zone. These quiescence areas are detected at (i) 40.81°N- 19.86°E (including Kuc-Bubullim, southeast of Lushnja town), (ii) 41.00°N-20.01°E (in the Cerriku, south of Elbasani town), (iii) 41.31°N-20.13°E (around Bene-Qafe, northeast of Elbasani town), (iv) 41.43°N-20.21°E (Krasta-Batra, south of Bulqiza town), (v) 41.28°N-20.49°E (including Carrishta-Stebleve, northeast of Librazhdi town), (vi) 41.51°N-20.51°E (including Qerrenec-Gjorica, west of Dibra town). As an important result, analyses of spatial and temporal characteristics of the earthquake activity may supply significant clues for revealing the future seismic hazard along the VLED fault zone, and these anomaly regions may be interpreted as the locations of next possible earthquakes.

Öztürk, Serkan

The Western Anatolian region is one of the most seismically active sectors of Turkey where small-magnitude events with considerable clustering occur frequently. The spatial and temporal behaviors of seismic activity as quantified by the fractal dimension Dc-value, seismotectonic b-value and seismic quiescence Z-value are investigated for the Western Anatolian region. For this purpose, a statistical relationship is developed between b and Dc-values, and regional and temporal changes of these parameters are analyzed in order to reveal the potential of future earthquakes in the study region. By using standard deviate Z-value, current seismicity rate changes are estimated in the beginning of 2014. The Western Anatolian region is divided into 18 different seismogenic subregions. Orthogonal regression fit is preferred in order to estimate more up-to-date and reliable statistical correlation between two seismotectonic parameters. The relationship of Dc=2.74-0.29*b is computed with a significant negative correlation (r = -0.73) between b and Dc-values for the Western Anatolian earthquake distributions. There are clear fluctuations in the temporal changes of these two parameters and the same results are relatively obtained in previous studies in literature. Lower b-values smaller than 1.0 and also higher Dc-value are observed in the Burdur fault zone and Kütahya graben. In addition, the regions in which the lower b-values and the higher Z-values are estimated cover the Burdur fault zone, Aliağa-Dumlupınar faults and Bakırçay grabens. Consequently, the relationships between seismic bvalue, fractal dimension Dc-value and seismic quiescence Z-value may provide important evidences to put forth the next earthquake potential in Western Anatolia. In addition, monitoring of microseismic activity and behaviors of some other geophysical parameters should be analyzed in space and time and evaluated carefully.

Öztürk, Serkan

The variations of the current seismicity rate on the North Anatolian Fault Zone in the beginning of 2009 have been analyzed based on the phenomenon of precursory seismic sequence before crustal main shocks. For this purpose, a statistical assessment is made to detect the seismic quiescence situation by using the standard normal deviate Z-value. Eight seismic quiescence regions are observed and quiescence anomalies in these regions have been observed since the beginning of 2005. On the Marmara part of the North Anatolian Fault Zone, four quiescence areas have been found on Silivri, in the Black Sea, around Izmit region and Çanakkale, Saros Gulf. On the Anatolian part of the North Anatolian Fault Zone, two quiescence areas have been observed on the Düzce fault and around the city of Amasya. Other anomalies have been observed around Erzincan, Elaziǧ and Bingöl regions on the eastern part of the North Anatolian Fault Zone. Due to the occurrences of the last strong earthquakes "MW = 6.0-Elaziǧ earthquake, 2010 March 08; MW = 5.2 - Çanakkale (Saros Gulf) earthquake, 2010 November 03; MW = 5.5-Erzincan earthquake, 2011 September 22 and MW = 5.1-Marmara Ereǧlisi (Tekirdaǧ) earthquake, 2012 June 07", other seismic quiescence regions may contribute to the forecasting of impending main shocks. Spatial and temporal estimates of the future seismic hazard of the North Anatolian Fault Zone are provided based on the results.