Fault morphology and paleoseismology of the İzmit-Sapanca Lake segment on North Anatolian Fault

The North Anatolian Fault (NAF) is one of the most destructive fault zones of the world and it lies throughout the northern Turkey with 1500 km length nearly in east-west trending arc shape. It is almost totally broken with large earthquakes during 20th century except two main seismic gaps: Yedisu seismic gap in the east and Marmara seismic gap in the west. The last destructive earthquakes occurred in the eastern Marmara region in 17 August and 12 November 1999 and 150 km and 50 km sections of the NAF were ruptured between Yalova and Düzce respectively. North Anatolian Fault has a relatively narrow deformation zone between Erzincan and Bolu, but it bifurcates to the west of Bolu and separates different main tectonic and morphological units from each other in the eastern Marmara Region. These units are; İstanbul-Zonguldak Zone (or Kocaeli peneplain in morphotectonic manner), Armutlu-Almacık Zone (Armutlu-Almacık High or Samanlı Mountains in morphotectonic manner) and Sakarya Continent (or Bursa-Bilecik relief in morphotectonic manner). Between the Gulf of İzmit and the Sapanca Lake the NAF follows an elongated depression and constitutes the boundary between Kocaeli peneplain and the Samanlı Mountains. The 17 August 1999 earthquake ruptured five segments on NAF between Yalova and Gölyaka (Düzce). These segments are named as Yalova, Karamürsel-Gölcük, İzmit-Sapanca Lake, Sapanca-Akyazı and Karadere from west to east. The surface rupture of 1999 İzmit earthquake between the Gulf of İzmit and the Sapanca Lake, the İzmit-Sapanca Lake segment, has mainly followed this elongated depressional morphology. The morphologic features, observed along the surface rupture, indicate that the surface rupture of 1999 İzmit earthquake was also followed by past earthquakes. These features are elongated ridges, offset streams and hills, sag ponds and depressional areas. In the eastern part of the Gulf of İzmit, in the southwestern part of Kullar village, Yaylacık Hill is offset as 420 m by the fault. The measured offset of the river next to the Yaylacık Hill is 380 m in minimum and 450 m in maximum. To the east, Sarımeşe Hill, on the south of Sarımeşe village, is mapped as an elongated ridge. The right step-overs on the west and east of Tepetarla village are represented by depressional swampy areas. To the eastwards, around Acısu village, the deflected streams and the sag ponds are the results of long-term activity of the NAF in the region. The comparison of the measured offset along the segment and the slip rates derived from recent GPS measurements reveals that the NAF has been active along the same traces at least since 20.000 years on İzmit-Sapanca Lake segment. In order to determine the past earthquakes that ruptured the segment, a trench is excavated on the eastern part of the İzmit-Sapanca Lake segment, east side of Acısu village, where the surface rupture follows the northern slope of an east-west trending ridge. On the trench site, 1999 İzmit earthquake surface rupture trends N85ºE direction as two branches and limits a depressed area which is located on the easternmost part of the site. The trench, with a length of 21 m and a maximum depth of 2,5 m, is excavated perpendicular to these two branches of the surface rupture. The stratigraphy of the trench is dominated by clay layers which have different physical properties. According to the stratigraphical and structural relationships three past event horizons are mapped in the trench. The event horizons are dated with radiocarbon dating (C14) of two charcoal samples. The youngest event horizon (ACSP-1) is before A.D.1300 and should represent an earthquake which happened around A.D.1000’s. Merging the results of previous paleoseismic investigations on the segment and correlation with historical records, 26 October 989 earthquake is a good candidate for this event horizon. The older event (ACSP-2) is before A.D.1300 and after A.D.79-140 dates. According to the calculated sedimantation velocity for the trench site with only these two dates, this event horizon may reveal the 15 August 554 historical earthquake. The oldest event horizon (ACSP-3) observed in the trench is before A.D.79-140 according to radiocarbon dating. The A.D.120 historical earthquake, which caused a considerable damage on the region is a possible earthquake for this event horizon. Keywords: North Anatolian Fault, 1999 İzmit earthquake, paleoseismology, fault morphology, İzmit-Sapanca Lake segment.Doğu Marmara Bölgesi’nde Kuzey Anadolu Fayı (KAF), Bolu’dan batıya doğru çatallanarak kollara ayrılır ve farklı ana morfotektonik üniteleri sınırlar. Bu üniteler; Kocaeli penepleni, Çamdağ-Akçakoca yükselimi, Adapazarı-Karasu koridoru, Armutlu yarımadasında yer alan Samanlı Dağları ve doğusundaki Almacık dağından oluşan Armutlu-Almacık yükselimi ile KAF zonudur. İzmit-Sapanca Gölü arasında KAF bir oluk morfolojisini takip eder ve kuzeyde ve güneyde iki farklı özellikte morfolojik alanı birbirinden ayırır. Kocaeli penepleni olarak anılan kuzey kesim oldukça yumuşak bir topografya sunar ve ortalama yüksekliği 250-300 m civarındadır. Güney kesimde ise, Samanlı Dağları, kuzeye göre oldukça yüksek bir topografya izlenir ve bu kesimdeki en yüksek nokta olan Kel Tepe 1602 m yüksekliğindedir. İzmit Körfezi ile Sapanca Gölü arasında kalan bölgede, 1999 İzmit depremi yüzey kırığı yaklaşık doğu batı yönde izlenen bu oluk morfolojisini takip etmiştir. Yüzey kırığı boyunca izlenen uzamış sırt, ötelenmiş dere ve tepeler, fay gölcükleri ve çöküntü alanları faylanmanın bir süredir bu güzergâhı takip ettiğini göstermektedir. Güncel GPS gözlemlerinden elde edilen kayma hızı değerlerine göre bu yapılar, İzmit-Sapanca Gölü segmenti üzerinde en az 20.000 yıldır KAF tarafından takip edilmiş olmalıdır. Segmentin doğu kesiminde eski deprem belirleme amacıyla açılan hendekte izlenen stratigrafik ve yapısal ilişkilerin değerlendirilmesi sonucunda 1999 İzmit depremi öncesi üç eski deprem seviyesi gözlenmiştir. Gözlenen eski deprem seviyeleri, tarihsel depremlerden M.S.120, 15 Ağustos 554 ve 26 Ekim 989 depremleri ile deneştirilmiştir. Anahtar Kelimeler: Kuzey Anadolu Fayı, 1999 İzmit depremi, paleosismoloji, fay morfolojisi, İzmit-Sapanca Gölü segmenti

Paleoseismology of the North Anatolian Fault at Güzelköy (Ganos segment, Turkey): Size and recurrence time of earthquake ruptures west of the Sea of Marmara

International audienceThe Ganos fault is the westernmost segment of the North Anatolian Fault that experienced the Mw = 7.4 earthquake of 9 August 1912. The earthquake revealed 45-km-long of surface ruptures inland, trending N70 E, and 5.5 m of maximum right lateral offset near Güzelköy. The long-term deformation of the fault is clearly expressed by several pull-apart basins and sag ponds, pressure and shutter ridges and offset streams. In parallel with detailed geomorphologic investigations, we measured co-seismic and cumulative displacements along the fault, and selected the Güzelköy site for paleoseismology. A microtopographic survey at the site yields 10.5 AE 0.5 m and 35.4 AE 1.5 m cumulative lateral offsets of stream channels and geomorphologic features. Seven paleoseismic parallel and cross-fault trenches document successive faulting events and provide the timing of past earthquakes on the Ganos fault segment. Radiocarbon dating of successive colluvial wedges in trench T1, and the fresh scarplet above (probably 1912 surface rupture) indicate the occurrence of three faulting events since the 14th century. Parallel trenches (3, 5, 6 and 7) expose paleo-channels and show a cumulative right-lateral offset of 16.5 AE 1.5 m next to the fault, and 21.3 AE 1.5 m total channel deflection. Radiocarbon dating of past channel units and fault scarp-related colluvial deposits imply an average 17 +/À 5 mm/year slip rate and 323 AE 142 years recurrence interval of large earthquakes during the last 1000 years on the Ganos fault. The succession of past faulting events and inferred slip rate west of the Marmara Sea provide more constraint on the long-term faulting behavior in the seismic gap of the North Anatolian Fault and may contribute to a better seismic hazard assessment in the Istanbul region

MANYAS GÜNEYİNİN (BALIKESİR) JEOLOJİSİ VE MAVlŞlSTLERlN TEKTONİK KONUMU

Çalışılan bölge esas olarak Sakarya zonuna ait Karakaya kompleksi birimlerinden ve Neojen çökel ve magmatik kayalarından oluşur. Bunlar dışında ufak bir mavişist klibi Karakaya kompleksi üzerinde yer alır. Karakaya kompleksi, incelenen alanda Nilüfer biriminden ve bunu tektonik olarak üzerleyen Triyas kırıntılı kayalarından (Hodul birimi ve Orhanlar grovakı) yapılmıştır. Nilüfer biriminin alt kesimlerini metabazit-metapelit-mermer ardalanması, üst kesimlerini ise tekdüze mermerler oluşturur. Yeşilşist fasiyesinde metamorfizma geçirmiş olan Nilüfer birimin metamorfizma yaşı muhtemelen Geç Triyastır. Nilüfer biriminin üzerinde tektonik dokanakla Permiyen ve Karbonifer yaşta neritik kireçtaşı ve seyrek spilit blokları kapsayan kırıntılı kayalar bulunur. Bunun dışında mavişist metabazitlerinden oluşan ufak bir klip Manyas güneyinde Nilüfer birimi ve Triyas kırıntılı kayaları üzerinde yer alır. Mavişist metamorfizmasmın yaşı Mustafakemalpaşa güneyindeki mavişistlerde yapılan yaş tayinlerine göre Geç Kretasedir. Mavişistlerin satha doğru yükselmeleri de büyük ölçüde Geç Kretasenin sonlarında gelişmiştir. Bu durumda mavişistlerin Karakaya kompleksi birimleri üzerine bindirmesi muhtemelen Paleosende kıta-kıta çarpışması sırasında meydana gelmiştir. Esas mavişist kuşağının klibin güneyinde yer aldığı düşünülürse, bindirme yönünün kuzeye doğru olduğu ortaya çıkar. Bu durum, Alpler'de olduğu gibi, Batı Anadoluda da kıta-kıta çarpışması sırasında çarpışma kuşağının ana verjansına ters yönde, ters bindirmelerin (retroşariyaj) geliştiği gösterir

Geodynamic importance of the strike-slip faults at the eastern part of the Anatolian Scholle: Inferences from the uplift and slip rate of the Malatya Fault (Malatya-Ovacık Fault Zone, eastern Turkey)

Controversy remains over when present-day configuration of the Anatolia boundary faults came into existence, and the issue of what are the driving forces of the Anatolian westward motion. The NW-striking dextral and NE-striking sinistral second-order strike-slip faults at the eastern part of the Anatolian Scholle play a crucial role within these long-lasting discussions, and the NE-striking sinistral Malatya–Ovacık Fault Zone (MOFZ) is particularly important in this ongoing debate. Although the MOFZ is defined as one of the intra-plate structures, it has been proposed that it was an inter-plate fault between the Anatolia and Arabian plates from the latest Miocene to mid-Pliocene and that it has been inactive during the last ca. 3.5 Ma. This study provides results from the first morphochronology-based uplift and slip rate estimates on the Malatya Fault within the southern section of the MOFZ. The cosmogenic isochron burial and cosmogenic depth burial of ages from the sinistrally offset Tohma River remnant terraces enabled us to calculate 1.0 ± 0.01 and 1.12 ± 0.01 mm/yr minimum and maximum horizontal slip rates, respectively, for the last 1.4 ± 0.1 Ma. Furthermore, we conclude that the 96 ± 11 m/Ma mean uplift has been driven by the Malatya Fault. Integrated interpretation of the findings of this study and available data on both the MOFZ and other strike-slip faults at the eastern part of the Anatolian Scholle support the hypothesis that they are plate-boundary related active deformation belts that originated from paleotectonic structures during the tectonic escape of the Anatolian Scholle

Mechanics of plio-quaternary faulting around the Karliova triple junction: implications for the deformation of Eastern part of the Anatolian Scholle

The intersection of the Eurasian and Arabian plates and the smaller Anatolian Scholle created the Karlıova Triple Junction (KTJ) in eastern Turkey. In this study, we present analogue model experiments for this region and compare the results with our field observations and data from remote sensing imagery. Our comparison suggests that the sense of slip along curvilinear faults at the west of the KTJ changes along strike moving away from the principal displacement zones, from strike-slip to oblique normal and then to pure normal slip. Although, the active Prandtl cell model has been proposed to explain the overall regional fault pattern at eastern part of the Anatolian Scholle, the map view orientation of the secondary faults within the Karlıova wedge and performed analogue modelling results suggest that the passive wedgeshaped Prandtl cell model with a normal dip-slip component along slip lines is more appropriate in order to explain not only deformation pattern around the KTJ but also internal deformation of eastern part of the Anatolia. Moreover, these faults accumulate the significant amount of deformation that causes to the irregular earthquake behavior and the relatively lower geologic slip-rates along the main fault branch of boundary faults around the KTJ

Geometry and Paleoseismology of the Malatya Fault (Malatya-Ovacık Fault Zone), Eastern Turkey: Implications for intraplate deformation of the Anatolian Scholle

he sinistral Malatya-Ovacık Fault Zone (MOFZ) is one of the outstanding intraplate deformation belts within Anatolia. The 165-km-long, NE–SW-striking Malatya Fault (MF), which constitutes the southern section of the MOFZ, is separated into five segments according to its surface geometry. These segments have evident morphotectonic features that reflect long- and short-term fault activity, such as morphologic structures offset by as little as 7 m and as much as 7.3 km. This study provides results from the first paleoseismological investigations on the MF. We find that the last earthquake occurred between 965 and 549 BCE and calculate a recurrence interval of 2275 ± 605 years from evidence for four paleo-events over the last 10 ka. Considering fault segmentation and our paleoseismological data, we propose that the accumulated strain on the MF may cause a destructive earthquake (M = 7.4) in the near future. Our results support the hypotheses that the MF and other NW-striking dextral and NE-striking sinistral strike-slip faults within the eastern part of Anatolia are plate boundary-related, active deformational structures

Palaeoseismic history of the eastern part of the North Anatolian Fault (Erzincan, Turkey): Implications for the seismicity of the Yedisu seismic gap

The North Anatolian Fault showed a remarkable seismic activity especially between 1939 and 1999, when the westward migrating earthquake sequence created surface ruptures more than 1000 km, leaving unbroken only the Marmara segments, to the west, and the Yedisu Segment, to the east along the main strand of the fault. To understand the palaeoseismicity of the Yedisu Seismic Gap, we undertook trench investigations close to the village of Balaban Sarıkaya, on the western part of the Yedisu Segment. We found evidence for at least five surface faulting earthquakes, from which only two are correlated with the 18 July 1784 CE and 27 June 1583 CE historical events. Although the surface rupture of the 1784 CE was reported by other trench studies, the evidence of 1583 CE event is presented for the first time. In consideration with other historical earthquakes, affecting the region east of Erzincan, we suggest that this particular section of the North Anatolian Fault may be in a seismically quiescent period, following a cluster of earthquakes in its near history. In order to test this hypothesis, further studies are needed to increase our knowledge on the temporal and spatial seismic behaviour of the Yedisu Segment, which has potential to create an earthquake with Mw ~7.2 in the near futur

Inborn errors of OAS–RNase L in SARS-CoV-2–related multisystem inflammatory syndrome in children

International audienceMultisystem inflammatory syndrome in children (MIS-C) is a rare and severe condition that follows benign COVID-19. We report autosomal recessive deficiencies of OAS1 , OAS2 , or RNASEL in five unrelated children with MIS-C. The cytosolic double-stranded RNA (dsRNA)–sensing OAS1 and OAS2 generate 2′-5′-linked oligoadenylates (2-5A) that activate the single-stranded RNA–degrading ribonuclease L (RNase L). Monocytic cell lines and primary myeloid cells with OAS1, OAS2, or RNase L deficiencies produce excessive amounts of inflammatory cytokines upon dsRNA or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) stimulation. Exogenous 2-5A suppresses cytokine production in OAS1-deficient but not RNase L–deficient cells. Cytokine production in RNase L–deficient cells is impaired by MDA5 or RIG-I deficiency and abolished by mitochondrial antiviral-signaling protein (MAVS) deficiency. Recessive OAS–RNase L deficiencies in these patients unleash the production of SARS-CoV-2–triggered, MAVS-mediated inflammatory cytokines by mononuclear phagocytes, thereby underlying MIS-C