Tamer Y. Duman

Assessment of Landslide Susceptibility by Decision Trees in the Metropolitan Area of Istanbul, Turkey

The main purpose of the present study is to investigate the possible application of decision tree in landslide susceptibility assessment. The study area having a surface area of 174.8 km2 locates at the northern coast of the Sea of Marmara and western part of Istanbul metropolitan area. When applying data mining and extracting decision tree, geological formations, altitude, slope, plan curvature, profile curvature, heat load and stream power index parameters are taken into consideration as landslide conditioning factors. Using the predicted values, the landslide susceptibility map of the study area is produced. The AUC value of the produced landslide susceptibility map has been obtained as 89.6%. According to the results of the AUC evaluation, the produced map has exhibited a good enough performance.

Step-Over and Bend Structures along the 1999 Duzce Earthquake Surface Rupture, North Anatolian Fault, Turkey

The 12 November 1999 Duzce earthquake (M w 7.1), which occurred on the Duzce fault of the North Anatolian Fault Zone, formed a 40-km-long surface rupture, which extended between Golyaka in the west and Kaynasli in the east. The earthquake nucleated close to the Beykoy step-over, a 0.8-km-wide and 1.8-km-long pressure ridge, with bilateral rupture propagation both to the west and the east. The Beykoy, Kaynasli, and Cevizlik step-overs, through which the 1999 Duzce rupture propagated, are less than 2.5 km wide. The Eften and Bakacak step-overs, where the rupture was arrested, are more than 4 km wide. These exceptional dimensions of step-overs associated with the 1999 Duzce rupture were investigated for their influ- ence on rupture propagation. The earthquake broke three distinct geometric segments, from west to east, the Eften, Dagdibi, and Kaynasli fault segments, separated by left-restraining step-overs at Beykoy and Kaynasli. To the west of the main shock, 3.5 m of average slip on the Eften fault segment propagated into the 2-km-wide Cevizlik releasing double bend, where it was largely arrested, with smaller (0.5 m) slip continuing westward on the Golyaka intervening segment, west of Lake Eften. This is similar to the ter- mination of slip observed on the Karadere fault segment in the 1999 Izmit earthquake, where 1.5 m of slip was largely terminated by a releasing double bend at the Golyaka intervening segment, with minor slip continuing eastward near Lake Eften. To the east of the main shock, 5 m of slip decreased along the Dagdibi fault segment to about 3.5 m at the 1-km-wide Kaynasli step-over. From here to the east, the 2.5 m of average slip on the Kaynasli fault segment continued to decrease, reaching zero at the releasing step-overs to the Elmalik fault. The terminations of the 1999 Duzce surface rupture are defined by distinct struc- tural complexities. The rupture was arrested in the west at the 4-km-wide Eften releasing double bend, where the eastern termination of the 1999 Izmit rupture also occurred. To the east, the rupture terminated at the 4- to 5-km-wide Bakacak releasing double step-overs. Both eastern and western ends of the Duzce rupture have short fault segments that experienced minor rupture during the 1999 Duzce earthquake. The Golyaka intervening segment experienced minor rupture, during both the 1999 Izmit and Duzce earthquakes. The Duzce rupture propagated across 0.8- to 2-km- wide step-overs, but it was arrested at step-overs 4 km wide or wider. These results agree with the observations on ratios between step-over width (in kilometers) and strike-slip displacement (in meters) collected along strike-slip faults worldwide (Let- tis et al., 2002).

The East Anatolian Fault: geometry, segmentation and jog characteristics

Abstract A detailed account is given of the fault geometry and segment structure of the East Anatolian Fault Zone as a whole based on mapping of active faults, supported by available seismological and palaeoseismological data. We divide the East Anatolian Fault into two main strands: southern and northern. The main southern strand is c. 580 km long between Karlıova and Antakya, and connects with the Dead Sea Fault Zone and the Cyprus Arc via the Amik triple junction. The northern strand, termed the Sürgü–Misis Fault system, is c. 350 km long and connects with the Kyrenia–Misis Fault Zone beneath the Gulf of İskenderun. We infer that slip partitioning between the main and northern strands of the East Anatolian Fault accommodates 2/3 and 1/3 of the slip rate of the lateral motion between the Arabian and Anatolian plates, respectively in the Çelikhan–Adana–Antakya region. Taking account of the time elapsed from the latest events on the East Anatolian Fault, we suggest that the Pazarcık and Amanos segments have the potential to produce destructive earthquakes in the near future. Supplementary material: The data and interpretations given here are supported by five additional annotated field photographs and two tables of factual data, these are available at www.geolsoc.org.uk/SUP18568

An assessment on the use of Terra ASTER L3A data in landslide susceptibility mapping

Abstract The main purpose of the present study is to evaluate the potential use of Terra ASTER data—the L3A DEM and its derivatives in landslide susceptibility mapping. For the purpose, an appropriate application site from the Western Black Sea region of Turkey—the Kelemen catchment area was selected. During the analyses, a two-stage comparative evaluation was carried out. In the first stage, the differences between the DEMs obtained from Terra ASTER L3A data and the conventional topographic data; and their first and second derivatives were investigated. Subsequently, different susceptibility maps were produced by using the DEMs and the topographic attributes obtained from both source of data in addition to the spectral information acquired from satellite sensor. According to the results of the comparative evaluations, a strong correlation between Terra ASTER L3A DEM and the conventional topographic data was obtained. However, depending on the increment of the degree of the derivative, an evident decrease in the spatial correlations was observed. On the contrary, the final model performance, prediction capacity, and the spatial performance statistics for the landslide susceptibility maps produced by using both source of data were found as very high and close to each other.

Seismotectonic database of Turkey

Turkey is located in one of the most seismically active regions in the world. Characterizing seismic source zones in this region requires evaluation and integration of geological, geophysical, seismological and geodetical data. This first seismotectonic database for Turkey presented herein was prepared, under the framework of the National Earthquake Strategy and Action Plan—2023. The geographic information system (GIS)-based database includes maps of active faults, catalogues of instrumental and historical earthquakes, moment tensor solutions and data on crustal thickness. On the basis of these data, 18 major seismotectonic zones were delineated for Turkey and the surrounding region. The compilation and storage of the seismotectonic data sets in a digital GIS will allow analyses and systematic updates as new data accrete over time.

The Bekten Fault: the palaeoseismic behaviour and kinematic characteristics of an intervening segment of the North Anatolian Fault Zone, Southern Marmara Region, Turkey

The Bekten Fault is 20-km long N55°E trending and oblique-slip fault in the dextral strike-slip fault zone. The fault is extending sub-parallel between Yenice-Gönen and Sarıköy faults, which forms the southern branch of North Anatolian Fault Zone in Southern Marmara Region. Tectonomorphological structures indicative of the recent fault displacements such as elongated ridges and offset creeks observed along the fault. In this study, we investigated palaeoseismic activities of the Bekten Fault by trenching surveys, which were carried out over a topographic saddle. The trench exposed the fault and the trench stratigraphy revealed repeated earthquake surface rupture events which resulted in displacements of late Pleistocene and Holocene deposits. According to radiocarbon ages obtained from samples taken from the event horizons in the stratigraphy, it was determined that at least three earthquakes resulting in surface rupture generated from the Bekten Fault within last ~1300 years. Based on the palaeoseismological data, the Bekten Fault displays non-characteristic earthquake behaviour and has not produced any earthquake associated with surface rupture for about the last 400 years. Additionally, the data will provide information for the role of small fault segments play except for the major structures in strike-slip fault systems.

Paleosismolojik bulgular ışığında Orhaneli Fayının Holosen aktivitesi, Bursa, KB Anadolu

Orhaneli Fayi, Biga Yarimadasi’nda yer alan yaklasik 30 km uzunlugunda, ters bileseni baskin, sag yonlu dogrultu atimli bir faydir. Kuvaterner yasli Orhaneli Havzasi’nin guney sinirini bu fay kontrol etmektedir. Bununla birlikte soz konusu fay ayni zamanda Tavsanli Zonu’na ait metamorfik kayaclari, Kretase yasli ofiyolitik birimleri ve Neojen/Kuvaterner yasli sedimanlari kesmekte olup hava fotografl arinda ve arazide belirgin cizgiselligi ve fay sarpliklari ile kolayca takip edilebilmektedir. Fay boyunca gozlenen uzamis sirtlar, otelenmis vadiler ve topografik boyunlar, fayin aktivitesine isaret eden onemli jeomorfolojik unsurlardir. Bu calismada Orhaneli Fayi uzerinde gerceklestirilmis olan ilk paleosismolojik calismalarin sonuclari yer almaktadir. Bu kapsamda fay uzerinde iki adet hendek acilmistir. Serceler ve Kusumlar olarak adlandirilmis bu hendeklerde, Tavsanli Zonu’na ait metamorfik kayaclarin fay tarafindan Kuvaterner yasli sedimanlar uzerine itildigi belirlenmistir. Yapilan calismada, Kuvaterner’de yuzey yirtilmasiyla sonuclanmis dort buyuk depremin izlerine rastlanmistir. Serceler hendeginde, en eski depremin MO 22.000±3.200 ile MO 6.600±800 arasinda, son depremin ise MO 770-415 den once gerceklestigi belirlenmistir. Kusumlar hendeginde ise, en eski depremin MO 6.600 ile MO 3.085 arasinda, son olayin ise MS 650 tarihinden sonraki bir donemde gerceklestigi belirlenmistir. Soz konusu eski depremler arasinda tekrarlanma periyoduna iliskin bir yorum yapilamamistir. Bu calisma ile Orhaneli Fayi’nin Holosen aktivitesi kanitlanmistir. Toplam uzunlugu 30 km olan ve iki segmentten olusan bu fayin tek parca halinde kirilmasi halinde, Mw= 6,87 buyuklugunde bir deprem uretme potansiyeline sahip oldugu belirlenmistir.

HOLOCENE ACTIVITY OF THE ORHANELI FAULT BASED ON PALAEOSEISMOLOGICAL DATA, BURSA, NW ANATOLIA

Orhaneli Fayi, Biga Yarimadasi’nda yer alan yaklasik 30 km uzunlugunda, ters bileseni baskin, sag yonlu dogrultu atimli bir faydir. Kuvaterner yasli Orhaneli Havzasi’nin guney sinirini bu fay kontrol etmektedir. Bununla birlikte soz konusu fay ayni zamanda Tavsanli Zonu’na ait metamorfik kayaclari, Kretase yasli ofiyolitik birimleri ve Neojen/Kuvaterner yasli sedimanlari kesmekte olup hava fotografl arinda ve arazide belirgin cizgiselligi ve fay sarpliklari ile kolayca takip edilebilmektedir. Fay boyunca gozlenen uzamis sirtlar, otelenmis vadiler ve topografik boyunlar, fayin aktivitesine isaret eden onemli jeomorfolojik unsurlardir. Bu calismada Orhaneli Fayi uzerinde gerceklestirilmis olan ilk paleosismolojik calismalarin sonuclari yer almaktadir. Bu kapsamda fay uzerinde iki adet hendek acilmistir. Serceler ve Kusumlar olarak adlandirilmis bu hendeklerde, Tavsanli Zonu’na ait metamorfik kayaclarin fay tarafindan Kuvaterner yasli sedimanlar uzerine itildigi belirlenmistir. Yapilan calismada, Kuvaterner’de yuzey yirtilmasiyla sonuclanmis dort buyuk depremin izlerine rastlanmistir. Serceler hendeginde, en eski depremin MO 22.000±3.200 ile MO 6.600±800 arasinda, son depremin ise MO 770-415 den once gerceklestigi belirlenmistir. Kusumlar hendeginde ise, en eski depremin MO 6.600 ile MO 3.085 arasinda, son olayin ise MS 650 tarihinden sonraki bir donemde gerceklestigi belirlenmistir. Soz konusu eski depremler arasinda tekrarlanma periyoduna iliskin bir yorum yapilamamistir. Bu calisma ile Orhaneli Fayi’nin Holosen aktivitesi kanitlanmistir. Toplam uzunlugu 30 km olan ve iki segmentten olusan bu fayin tek parca halinde kirilmasi halinde, Mw= 6,87 buyuklugunde bir deprem uretme potansiyeline sahip oldugu belirlenmistir.

The Manyas fault zone (southern Marmara region, NW Turkey): active tectonics and paleoseismology

The Manyas fault zone (MFZ) is a splay fault of the Yenice Gönen Fault, which is located on the southern branch of the North Anatolian Fault System. The MFZ is a 38 km long, WNW–ESE-trending and normal fault zone comprised of three en-echelon segments. On 6 October 1964, an earthquake (Ms = 6.9) occurred on the Salur segment. In this study, paleoseismic trench studies were performed along the Salur segment. Based on these paleoseismic trench studies, at least three earthquakes resulting in a surface rupture within the last 4000 years, including the 1964 earthquake have been identified and dated. The penultimate event can be correlated with the AD 1323 earthquake. There is no archaeological and/or historical record that can be associated with the oldest earthquake dated between BP 3800 ± 600 and BP 2300 ± 200 years. Additionally, the trench study performed to the north of the Salur segment demonstrates paleoliquefaction structures crossing each other. The surface deformation that occurred during the 1964 earthquake is determined primarily to be the consequence of liquefaction. According to the fault plane slip data, the MFZ is a purely normal fault demonstrating a listric geometry with a dip of 64°–74° to the NNE.

Active tectonic and palaeoseismological features of the western section of Mustafakemalpaşa Fault; Bursa, NW Anatolia

The Mustafakemalpaşa Fault (MF), located among Manyas, Ulubat and Orhaneli faults, is a right lateral strike-slip and 47 km in length. The MF begins with a pressure ridge at the west and exhibits complex jog terminations at east ends in restraining left stepovers. The western section of the fault bounds Miocene and Quaternary units and continues towards İlyasçılar. The central segment of the fault, starts with approximately 750-m leftward stepover, exhibits a sinusoidal geometry between Kapaklıoluk and Kabulbaba. In this section, MF traverses mountainous terrain and cuts Ophiolite, Jurassic limestones and Miocene detritals, forming dextral faulting features and gaining reverse component. The eastern section exhibits left stepping en-echelon pattern and consists 2.5-km offset on the Orhaneli River. In this study, palaeoseismological findings related to the Holocene activity and active tectonic properties of the MF are presented. The trenches exposed mismatched stratigraphy, demonstrating evidence of events across the fault. We identified three events (before BC 2190, later AD 1425 and 1850) that have occurred during the past 4000 years. We suggest a long non-characteristic recurrence interval and ~0.7 mm/y slip-rate for MF, based on trench data and offset of the Late Pliocene drainage of Orhaneli River.