Current Earthquake Hazard in and around the Southeastern Part of Türkiye: Evaluation of the Multiple Parameters

Abstract

The southeastern end of Türkiye is formed with the multi-segmented large fault systems accommodated by strike-slip faults oriented NW-SE and NE-SW, thrust/reverse faults oriented EW and NS-oriented extension fissures or normal faults. This zone has not produced large/destructive earthquakes for a long time. The last earthquake with a magnitude of 5.0 occurred near the Konalga segment in 2012. Therefore, based on several seismotectonic parameters such as b-value, recurrence times, earthquake probability and Coulomb stress changes, we investigate the earthquake hazard in and around the southeastern part of Türkiye. To achieve a statistical evaluation, a homogeneous catalog according to moment magnitude (Mw) which includes 2818 earthquakes with 1.0<Mw5.9 between October 26, 1958 and December 27, 2022, is used. b-value is determined as 0.830.05 and it is smaller than the mean value of b=1.0, which is accepted for the Gutenberg-Richter scaling law. This b-value means that an increasing stress situation may exist in this part of Türkiye. Also, probabilities of the earthquakes for Mw=5.0, 5.5 and 5.9 in the intermediate term (10 years) are determined as 68.39%, 35.79% and 18.64%, respectively. Recurrence times of earthquakes with Mw=5.0, 5.5 and 5.9 are estimated as 9, 23 and 48 years, respectively. The results show that the regions with smaller b-values are calculated in Beğendik, Konalga, Hakkari, Yüksekova, Şemdinli and Çubuklu segments. Also, Coulomb stress change maps demonstrate 4 positive and 4 negative stress lobes. Positive stress lobes stretch across the Konalga, Hakkari, Işıklar and Çubuklu segments. These regions represent current stress accumulation. According to the stress variation maps, it is observed that stress is transferred towards the end of the Yüksekova-Şemdinli Fault zone, especially at shallow depths. Moreover, this stress increase is caused by the southeast Anatolian Thrust zone. Consequently, these types of multiple parameter analyses are necessary to describe the current and future seismic hazard of the region. Almost all the anomaly regions of seismotectonic parameters are estimated almost in the same parts of the study region and hence, these anomaly regions observed at the beginning of 2023 may be one of the most possible areas for future strong/large earthquake occurrences. Thus, the correlations among these parameters may supply preliminary and useful information for the current earthquake hazard assessment in southeastern part of Türkiye.

Full text

CURRENT EARTHQUAKE HAZARD IN AND AROUND THE SOUTHEASTERN
PART OF TÜRKİYE: EVALUATION OF THE MULTIPLE PARAMETERS
Serkan Öztürk
Dr., Graduate School of Natural and Applied Sciences, Department of Geophysics, Gümüşhane University,
29100, Gümüşhane, Türkiye
serkanozturk@gumushane.edu.tr, +90 535 713 3568
ORCID ID: 0000-0003-1322-5164
Hamdi Alkan (Corresponding Author )
Dr., Engineering Faculty, Department of Geophysics, Van Yüzüncü Yıl University, 65080, Van, Türkiye
hamdialkan@yyu.edu.tr, +90 561 611 8061
ORCID ID: 0000-0003-3912-7503
ABSTRACT
The southeastern end of Türkiye is formed with the multi-segmented large fault systems
accommodated by strike-slip faults oriented NW-SE and NE-SW, thrust/reverse faults
oriented EW and NS-oriented extension fissures or normal faults. This zone has not produced
large/destructive earthquakes for a long time. The last earthquake with a magnitude of 5.0
occurred near the Konalga segment in 2012. Therefore, based on several seismotectonic
parameters such as b-value, recurrence times, earthquake probability and Coulomb stress
changes, we investigate the earthquake hazard in and around the southeastern part of Türkiye .
To achieve a statistical evaluation, a homogeneous catalog according to moment magnitude
(Mw) which includes 2818 earthquakes with 1.0<Mw5.9 between October 26, 1958 and
December 27, 2022, is used. b-value is determined as 0.830.05 and it is smaller than the
mean value of b=1.0, which is accepted for the Gutenberg-Richter scaling law. This b-value
means that an increasing stress situation may exist in this part of Türkiye. Also, probabilities
of the earthquakes for Mw=5.0, 5.5 and 5.9 in the intermediate term (10 years) are
determined as 68.39%, 35.79% and 18.64%, respectively. Recurrence times of
earthquakes with Mw=5.0, 5.5 and 5.9 are estimated as 9, 23 and 48 years, respectively.
The results show that the regions with smaller b-values are calculated in Beğendik, Konalga,
Hakkari, Yüksekova, Şemdinli and Çubuklu segments. Also, Coulomb stress change maps
demonstrate 4 positive and 4 negative stress lobes. Positive stress lobes stretch across the
Konalga, Hakkari, Işıklar and Çubuklu segments. These regions represent current stress
accumulation. According to the stress variation maps, it is observed that stress is transferred
towards the end of the Yüksekova-Şemdinli Fault zone, especially at shallow depths.
Moreover, this stress increase is caused by the southeast Anatolian Thrust zone.
Consequently, these types of multiple parameter analyses are necessary to describe the
current and future seismic hazard of the region. Almost all the anomaly regions of
seismotectonic parameters are estimated almost in the same parts of the study region and
hence, these anomaly regions observed at the beginning of 2023 may be one of the most
possible areas for future strong/large earthquake occurrences. Thus, the correlations among
these parameters may supply preliminary and useful information for the current earthquake
hazard assessment in southeastern part of Türkiye.
Keywords: Earthquake Hazard, b-value, Recurrence Time, Earthquake Probability, Stress.