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.

Özturk, S.; Sari, M.

A statistical assessment of recent seismicity in the North Anatolian Fault Zone, Turkey, is made by using seismotectonic b-value and precursory seismic quiescence Z-value. The catalogue including 28,420 earthquakes between 1970 and 2016 is used. Using the Reasenberg declustering process and the earthquakes with MD≥2.7, 51.4% of the events are removed and so, 13,815 events are used for a quantitative evaluation of seismic quiescence in the NAFZ in the beginning of 2016. Completeness magnitude is estimated as 2.7. Resulting values show that significant anomalies are observed in both band Z-values in some parts of the NAFZ. The larger b-values are calculated in Silivri, Black Sea, Izmit and Düzce whereas the smaller b-values are estimated in the western, the eastern and the middle parts of the NAFZ, covering Gulf of Saros, Gelibolu (Çanakkale), Ismetpasa segment, Bingöl, Erzincan, Amasya and Çankiri. Several quiescence regions in and around Tekirdag, Gulf of Saros, Istanbul, Marmara and Black Sea, Izmit, Düzce fault, Mudurnu, Çankiri, Amasya are observed. Consequently, the same regions including Gulf of Saros, Çankiri and Amasya where the smallest b-values and the largest Z-values are obtained may give important evidences to reveal the future earthquake potential in the North Anatolian Fault Zone.

Sari, M.; Seren, A.

It was aimed to identify the permeability of the dam area by collecting the information of 15 boreholes with 450 m depth in totally previously made along the dam axis line and the electric resistivity measurements along four lines vertical to the same axis line. Kirklartepe Dam, planned to be an irrigation dam for agricultural purposes, in the Central district of Bayburt province located in the northeastern region of Turkey was selected as the study area and it was tried to identify the permeability of the units forming the dam area. 2D and 3D underground views of the measurement lines were determined by implementing the inversion process to the electric resistivity measurements. While examining these sections, it was interpreted that anomaly areas with low resistivity values categorize an alluvial cone with permeable slope wash character, while anomaly fields with high resistivity categorize an impermeable metamorphic unit. Moreover, it was tried to reveal the permeability of the dam area by associating with the information of the present boreholes in the study area and creating section maps of 3D views obtained for each 10 m. Thus, it was observed that current boring information and electric resistivity measurement results supported one another.

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.