157 since 1961 Statistical behaviours of earthquake occurrences in the Central Anatolian Region of Turkey: region-time-magnitude analyses Serkan Öztürk Öztürk, S. 2021. Statistical behaviours of earthquake occurrences in the Central Anatolian Region of Turkey: region-time- magnitude analyses. Baltica, 34 (2), 157–173. Vilnius. ISSN 0067-3064. Manuscript submitted 19 April 2021 / Accepted 21 October 2021 / Available online 15 November 2021 © Baltica 2021 Abstract. The main objective of this work is to make detailed region-time-magnitude analyses by describ- ing the statistical behaviours of earthquakes in the Central Anatolian Region of Turkey. In this scope, several seismic and tectonic parameters such as Mcomp, b-value, Dc-value, Z-value, recurrence times and annual probabilities were evaluated. For the analyses, a homogeneous catalogue including 10,146 earthquakes with 1.0 ≤ M d ≤ 5.7 between 30 July 1975 and 29 December 2018 was used and spatio-temporal changes of earth- quake behaviours were mapped for the beginning of 2019. Earthquake magnitudes varied from 1.9 to 3.0 on average, and hence Mcomp was considered to be 2.6. The b-value was calculated as 1.26 ± 0.07, and this relatively large value indicates that small-magnitude events are dominant. The Dc-value was computed as 1.31 ± 0.03. This small value means that distances between epicentres approach the diameter of the cluster, and seismic activity is more clustered at smaller scales or in larger regions. The spatio-temporal analyses of recurrence times suggest that the Central Anatolian Region has an intermediate/long-term earthquake hazard in comparison to occurrences of strong earthquakes in the short term. Several anomaly regions of a small b-value and a large Z-value were found in and around the Tuzgölü Fault Zone, Central Anatolian Fault Zone, Salanda fault and Niğde fault at the beginning of 2019. Thus, a combination of the regions with a lower b-value, a higher Z-value and also moderate recurrence times may give signifcant clues for the future possible earthquakes, and detected regions may be thought to be the most likely areas for strong/large events in the Central Anatolian Region. Keywords: spatio-temporal analysis; Mcomp; b-value; Dc-value; Z-value Serkan Öztürk (serkanozturk@gumushane.edu.tr), Gümüşhane University, Department of Geophysics, TR-29100, Gümüşhane, Turkey BALTICA Volume 34 Number 2 December 2021: 157–173 https://doi.org/10.5200/baltica.2021.2.3 INTRODUCTION Statistical evaluation of region-time-magnitude dis- tributions of earthquake occurrences is a signifcant step to make quantitative the seismic hazard studies, and these types of numerous analyses have been carried out by dif- ferent researchers for different parts of the earth. Many authors have revealed some important results in recent years by considering the basic and the most frequently used seismological parameters such as (i) regional, tem- poral and magnitude distribution of seismic activity, (ii) magnitude completeness, Mcomp, which describes the minimum magnitude of complete reporting, (iii) b-value, which is stated as the power-law distribution of seismic- ity, (iv) Dc-value, which defnes the self-similarity of a geometrical object, (v) standard normal deviate Z-value, which is one of the most frequently used tool in terms of the observation of seismicity rate changes, and (vi) annual probabilities and recurrence times for specifc magnitude values (e.g., Frohlich, Davis 1993; Wiemer, Wyss 2000; Öncel, Wilson 2002; Polat et al. 2008; Roy et al. 2011; Öztürk 2013; Ali 2016; Rodriguez-Perez, Zuniga 2018; Radziminovich et al. 2019; Öztürk, Şahin 2019; Zuniga et al. 2020).