Öztürk, S.

Variations of the recent seismicity in and around the Central Anatolian region of Turkey were evaluated based on the seismic b-value, standard normal deviate Z-value, GENAS modelling, annual probabilities and return periods of the earthquakes. The catalog includes 16,702 earthquakes between 1974 and 2019 with magnitudes from 1.0 to 6.3. Time distribution of b-value shows that there is a tendency to decrease after the year of 2002 and b-value decreased from 1.58 ± 0.03 to 1.25 ± 0.05 at the beginning of 2019. Annual probabilities for magnitude ranges of 3.0–4.0 have the values between 3 and 30. Return periods for magnitude levels of 5.0–5.5 have the values from 5 to 20 years, and a value of 80 years for magnitude level of 6.0. The GENAS results show the significant temporal variations in the number of earthquakes smaller and larger than specific magnitude intervals by supplying the beginning periods of increases and decreases in the earthquake activity rate. Remarkable reductions in region-time distribution of b-value at the beginning of 2019 were detected in the regions covering Niğde fault and its vicinity along the south, west, northwest and southwest directions, among the Mut Fault Zone, Karsantı-Karaisalı Fault Zone and Karataş-Osmaniye Fault Zone, in and around Sürgü fault and along its northwest direction, between Sürgü fault and East Anatolian Fault Zone. Significant seismic quiescence areas in Z-value distribution include the northwest ends of the Tuzgölü Fault Zone and study area including Akpınar fault, the northeast of Salanda fault, between Salanda fault and the Central Anatolian Fault Zone, the northeast parts of the Central Anatolian Fault Zone, the west of Malatya fault, between Sürgü fault and the East Anatolian Fault Zone, the southeast end of the Tuzgölü Fault Zone, Karsantı-Karaisalı Fault Zone and its vicinity, the southwest of Tuzgölü. Thus, these anomaly areas observed in the Central Anatolian region and its vicinity at the beginning of 2019 may be one of the most likely zones for the next strong/large earthquake occurrences.

Öztürk, S.

The Eastern Anatolian Region of Turkey is one of the most seismically and tectonically active regions due to the frequent occurrence of earthquakes. Thus, the main goal of this study is to analyze the regional and temporal characteristics of seismicity in the Eastern Anatolia in terms of the seismotectonic b-value, fractal dimension Dc-value, precursory seismic quiescence Z-value, and their interrelationships. This study also seeks to obtain a reliable empirical relation between b and Dc-values and to evaluate the temporal changes of these parameters as they relate to the earthquake potential of the region. A more up-to-date relation of Dc = 2:55–0:39*b is found with a very strong negative correlation coefficient (r =–0.95) by using the orthogonal regression method. The b-values less than 1.0 and the Dc-values greater than 2.2 are observed in the Northeast Anatolian Fault Zone, Aşkale, Erzurum, Iğdır and Çaldıran Faults, Doğubeyazıt Fault Zone, around the Genç Fault, the western part of the Bitlis-Zagros Thrust Zone, Pülümür and Karakoçan Faults, and the Sancak- Uzunpınar Fault Zone. In addition, the regions having small b-values and large Z-values are calculated around the Genç, Pülümür and Karakoçan Faults as well as the Sancak-Uzunpınar Fault Zone. Remarkably, the combinations of these seismotectonic parameters could reveal the earthquake hazard potential in the Eastern Anatolian Region of Turkey, thus creating an increased interest in these anomaly regions.

Kaya, A. A.; Üçüncü, O.; Ilter, S. M.; Baltaci, C.; Öztürk, S.

In this study, the chemical composition and antimicrobial activities of the essential oil of the Rhinanthus angustifolius subsp. grandiflorus plant were investigated. Essential oil was obtained from all parts of the plant by hydrodistillation and was analyzed by GC-FID and GC-MS. 31 components representing 99.46% of the total oils were characterized. The main components of these species were found to be 2,3-dihydro-5-methyl-1H-indene (25.14%), alpha-cubebene (19.27%), 1-hexadecene (15.59%) and hexadecanoic acid (12.14%). The antimicrobial activity of the isolated essential oil was investigated. Antimicrobial activity was observed against B. cereus, E. coli, E. coli O157:H7 and S. Aureus microorganisms. Moreover, an effect on the ferments of B. cereus, E. coli, E. coli O157:H7 and S. Aureus was detected.

Öztürk, S.; Sari, M.

A statistical evaluation of earthquake activity for Tunceli province of Turkey was made by applying standard normal deviate Z-test. For this purpose, regional and temporal changes of the seismicity rate at the beginning of 2017 was analyzed by using ZMAP software.The data set is compiled from Bogaziçi University, Kandilli Observatory and Earthquake Research Institute.There are 5462 events from September 21, 1970 to December 30, 2016 with magnitude larger than and equal to 1.1. Completeness magnitude is estimated as 2.8. Three regions indicating important quiescence anomaly were observed at the beginning of 2017.These anomalies are found centered at (a) 39.24°N-39.51°E (around city center, and between Ovacik and Pülümür), (b) 38.98°N-39.41°E (including Pertek) and (c) 38.96°N-39.78°E (region including Mazgirt).These quiescence anomalies are observed in the recent years and they start approximately at the years of 2012 and 2015.The regions in which seismic quiescence are found may be the possible areas for the future earthquakes and for this reason, special attention should be given to these regions. As an important result, the estimation of seismicity rate changes and detecting the precursory seismic quiescence can be used as an important tool in the assessment of earthquake potential.

Öztürk, S.

An evaluation based on Gutenberg-Richter b-value, fractal dimension Dc-value, completeness magnitude Mc-value, annual probability and recurrence time of earthquakes is carried out for Tunceli province of Turkey. Earthquake catalog covers the years between 21 September 1970 and 30 December 2016, and contains 5462 earthquakes with magnitude equal to and greater than 1.1. Magnitude completeness is estimated as 2.8 and b-value is found as b=0.98+/-0.01. This b-value is smaller than average value of b=1.0 given for Gutenberg-Richter relation. So, this low b-value may be an indicator of stress to build up over time at the beginning of 2017. Dc-value is obtained as 1.63+/-0.04 with 95% confidence limits. This high Dc-value indicates that seismicity in Tunceli and vicinity is more clustered at larger scales or in smaller areas. Annual probability of the earthquakes between 4.5 and 5.5 magnitude levels exhibits a value between 1 and 10. Recurrence time of the earthquakes has a value between 10 and 30 years for magnitude levels between 5.5 and 6.0, and a value between 30 and 100 years for magnitude levels between 6.0 and 6.5. Consequently, this part of Turkey may have an earthquake potential for the possibility of intense earthquake occurrences in the next future.

Öztürk, S.

In this study, a statistical analysis is carried out to reveal the current earthquake potential in the Eastern Anatolia region of Turkey. For this purpose, a space-time assessing based on the recent changes in Gutenberg-Richter b-value, seismic quiescence Z-value, cumulative moment, annual probability and recurrence time of earthquakes is achieved. Temporal variation of b-value indicates that average b-value decreased from 1.25±0.02 between 2002 and 2010 to 1.08±0.02 between 2011 and 2015. A clear quiescence in the seismic moment in recent years may be a clue foretelling the occurrence of an intense event. Annual probability of the earthquakes between 3.5 and 4.0 magnitude levels exhibits a value equal to and larger than 30. Recurrence time of the earthquakes has a value between 2.0 and 3.0 years for magnitude level of 6.0, and a value between 6.0 and 7.0 years for magnitude level of 7.0. A significant decrease in b-value and clear quiescence anomalies in Z-value at the beginning of 2015 are observed in the several same regions. These areas cover the Central Anatolia Fault Zone, Malatya and Ovacık faults, the southeastern part of the Eastern Anatolia Fault Zone, and the junction of the Eastern Anatolia and Dead Sea Fault Zones. In these anomaly regions, a decreasing trend in b-value may be an indicator of stress increases and an increasing trend in Z-value may show the quiescence areas before the next earthquake occurrences. As a remarkable fact, these areas in the Eastern Anatolia region may be interpreted as one of the most likely locations for the major earthquakes in the future.

Öztürk, S.; Sari, M.

An evaluation of recent seismicity behaviors in the East Anatolian Fault Zone, eastern part of Turkey, is made by using Gutenberg-Richter b-value and fractal dimension Dc-value. Reasenberg's algorithm is used in order to separate the dependent events from independent ones. The completeness magnitude in study region is calculated as 2.8. b-value is calculated as 1.02+/-0.01 by maximum likelihood estimation and matches the Gutenberg-Richter law with a b-value typically close to 1. Dc-value is found as 2.34+/-0.04 with 95% confidence limit by linear regression and this large value suggest that seismicity is more clustered at larger scales in the East Anatolian Fault Zone. The smallest b-values and the highest Dc-values are found in the same areas covering the East Anatolian Fault Zone, Aşkale Fault, Sancak-Uzunpinar Fault Zone, Pülümür Fault, Göynük Fault Zone and Genç Fault, in and around Karataş-Osmaniye Fault Zone and in the southeast part of the study region. Thus, low b-value in these regions may be an indication of low degree of heterogeneity, high-strain due to the active tectonics and stress to build up over time and to be released by events. Thus, special attention should be given to these regions where low b-value and large Dc-value are observed.

Öztürk, S.; Sariçiçek, I.

In the scope of this study, an evaluation of recent seismic quiescence in the East Anatolian Fault Zone, eastern part of Turkey, is made by using the standard deviate Z-value. For this purpose, a statistical assessment of the spatial and temporal variations of the seismicity rate changes in the beginning of 2013is performed by using ZMAP software package. Results show that four areas with an apparently seismic quiescence may be important in the East Anatolian Fault Zone in the beginning of 2013. These anomalies are observed centered at 39.48°N-39.712°E (between Ovacik and Pülümür, Tunceli), the second one is found centered at 39.06°N-40.297°E (including Karakoçan, Sancak-Uzunpinar and Göynük fault zones), the third one is found centered at 38.55°N-38.763°E (between Malatya fault and EAFZ, north of Pötürge, Malatya) and the last one is found centered as 39.95°N-35.647°E (between Ceyhan-Yumurtalik-Karatas, Adana). The beginnings of these seismic quiescence anomalies are recently observed and nearly started in the beginning of 2007.For this reason, special attention should be given to these regions where the seismic quiescence is observed.