Gemlik Havzası Alüvyon çökellerinin deprem yönetmeliklerine dayanarak değerlendirilmesi.

Gemlik County is located in the Marmara Region (NW Turkey), which has been affected by destructive earthquakes sourced from North Anatolian Fault System throughout its history. The bulk of the settlement rests on alluvial deposits of the Gemlik pull-apart basin. So, it is vital to investigate the foundation soils in this basin and the response of them to earthquakes. Many earthquake codes were established by the authorities in different countries of the world to estimate the possible ground shaking and seismic loads which may act on buildings. In this study, Turkish Earthquake Code (TEC-1998) and Eurocode-8 (EN-1998) have been utilized. The analyses showed that EN-1998 results in more conservative estimates relative to TEC-1998, in terms of spectral ordinates. The source of difference between TEC-1998 and EN-1998 has been investigated and three possible reasons have been identified. The variation is probably due to the different seismic characteristics of Turkey and Europe, different soil amplification levels defined by the codes, and different soil classification procedures of the codes.M.S. - Master of Scienc

Sedimentary geochemical evidence of historical tsunamis in the Eastern Mediterranean from oludeniz Lagoon, SW Turkey

In the Eastern Mediterranean and southern Aegean seas, historical records indicate there were 17 tsunamis in the last 2500years with intensities>6 on a 12-point tsunami intensity scale. Regional geologic records of past tsunamis, however, are not sufficiently well-documented to assess tsunami hazards. This study presents geochemical evidence of historic tsunamis in the Eastern Mediterranean for the last 700years, detected in the sedimentary sequence of oludeniz Lagoon, SW Turkey. Sediment chronology was established by Cs-137 and Pb-210 dating, and regional chronostratigraphic correlation reveals that three events observed within the sequence correlate temporally with the AD 1303, 1609, and 1741 tsunamis in the region. The sediment anomalies (tsunami deposits) appear as reddish-brown intercalations within yellowish-brown background sediments of the lagoon, and are enriched in K, Ti, Fe and Zn, but depleted in Ca. This kind of geochemical fingerprint is attributed to a sudden increase in the input of terrigenous sediment to the lagoon, which was swept from oludeniz beach and the sand spit of the lagoon by marine overwash during tsunamis. If the stratigraphic thickness and magnitude of the geochemical anomalies are assumed to be a proxy for tsunami intensity, then the AD 1609 event was stronger in the oludeniz region than the AD 1303 and 1741 tsunamis

Sedimentary Traces of Tsunamis in the Aegean Sea During the Last 1500 Years, (Karine Lagoon, W Turkey)

As high energy tsunami waves reach shallow near-shore environments, the height of the waves increases and sea water propagates towards the land. During this movement, significant amounts of sediment are transported inland from the nearshore, foreshore and beach. While a lagoon that is separated from the sea by a low, thin sand barrier has a relatively calm depositional environment under normal conditions, during a tsunami the sea water climbs over the sand barrier and deposits material from the nearshore, foreshore and sand barrier onto inner parts of the lagoon. This phenomenon is the reason why investigation of sedimentary sequences in lagoons reveals the sedimentary traces of past tsunamis. In this study, the physical and geochemical properties of sediments in two ca. 3.2 m-long cores collected from Karine Lagoon on the coast of Aydin-Soke (western Turkey) were investigated in order to determine the traces of past tsunamis in the Aegean Sea. An ITRAX micro-XRF scanner was used to obtain 0.2 mm-resolution radiographic images and 1mm-resolution XRF data from the cores. High-resolution analysis detected three heterogeneous and high-density intercalations within the relatively homogenous and occasionally laminated background sediments. XRF data revealed that these intercalations had significantly higher Ca/Ti values compared to the background sediments, i.e. they were rich in carbonates. Observation under a stereo-microscope determined that while the background sediments contained fresh bivalve shells smaller than 1 cm in diameter, the intercalations contained weathered/broken bivalve shells approximately 4 cm in diameter. Considering the physical and geochemical observations together, it was concluded that the intercalations containing relatively coarser and intensely-weathered bivalve shells are deposits that were transported from the sand barrier of the lagoon during tsunamis. Radiocarbon dating shows that three intercalations in the sequence of Karine Lagoon were deposited during the tsunamis, from AD 1956, 1650 and 1303.Yüksek enerjili tsunami dalgaları kıyıya yakın sığ bölgelere yaklaştıkça dalga yüksekliği artarak, deniz suyu karasal alanlara doğru tırmanır/ilerler, ve bu ilerleme sırasında yakın kıyı, kıyı önü ve kumsaldan ciddi miktarda sediman karaya doğru taşınır. Normal koşullar altında, alçak ve ince bir kum bariyeri ile denizden ayrılan bir lagün görece sakin bir çökelim ortamına sahipken, tsunami sırasında deniz suyu kum bariyerini aşarak lagünün iç kısımlarına yakın kıyı, kıyı önü ve kum bariyere ait sedimanları taşır. Bu nedenle, lagünlerdeki sedimanter istiflerin araştırılması, geçmişte meydana gelmiş tsunamilerin sedimanter izlerinin bulunmasında önemli rol oynar. Bu çalışmada, Karine Lagünü’nden alınan yaklaşık 3,2 m uzunluktaki iki adet karot boyunca sedimanların fiziksel ve jeokimyasal özellikleri incelenmiş, ve Ege Denizi’nde geçmişte meydana gelmiş tsunamilerin izleri araştırılmıştır. ITRAX mikro-XRF karot tarayıcısı kullanılarak, karotlar boyunca 0,2 mm çözünürlükte radyografik görüntüleme ve 1 mm çözünürlükte XRF taraması yapılmıştır. Yapılan bu yüksek çözünürlüklü analizler ışığında, görece homojen ve bazen ince tabakalanmalı istifin içinde, iki karotta da belirgin bir şekilde gözlenen, yüksek yoğunluğa sahip ve heterojen yapıda üç adet ara katman tespit edilmiştir. XRF verileri incelendiğinde, bu ara katmanlardaki Ca/Ti değerlerinin belirgin bir şekilde istifin geri kalanından daha yüksek olduğu, yani ara katmanların karbonatça zengin olduğu görülmüştür. Stereo mikroskop ile yapılan incelemelerde, istifin genelini temsil eden seviyelerde çökellerin genellikle 1 cm’den küçük bozuşmamış bivalv kavkıları içerdiği, buna karşın ara katmaların ise çapları yaklaşık 4 cm’yi bulan ve yüzeylerinde belirgin bozuşma izleri olan bivalv kavkıları içerdiği görülmüştür. Fiziksel ve jeokimyasal gözlemler birlikte değerlendirildiğinde, görece iri taneli ve bozuşmaya uğramış bivalv kavkıları içeren bu ara katmanların, tsunamiler sırasında lagünün kum bariyerinden taşınan tsunami çökelleri olduğu sonucuna varılmıştır. Radyokarbon tarihlendirmeleri, Karine Lagünü’ndeki üç adet ara katmanın M.S. 1956, 1650 ve 1303 yıllarındaki tsunamilerden kaynaklandığını göstermektedir

Towards a paleotsunami chronology in the southern Aegean and Levantine seas, Eastern Mediterranean (EASTMED-PALEOTSUNAMI)

In 2004 and 2011, the World witnessed the devastating consequences of Sumatra (Indonesia) and Tohoku (Japan) tsunamis. We realized once again how seriously tsunamis can threaten our lives and infrastructures, and how vital tsunami hazard assessment studies are to reveal especially the recurrence of tsunamis by means of paleotsunami investigations. In the Aegean and the Levantine seas (Eastern Mediterranean), although the historical records report 17 damaging tsunamis during the last 2500 years, the geological records of the paleotsunamis revealed so far in the region are far from providing information useful for reliable tsunami hazard assessments. The proposed research action aims to take a significant step forward towards constructing paleotsunami chronologies in the eastern Mediterranean by investigating the sedimentary sequences of six lagoonal sites located along the south-western and southern coasts of Turkey. The methods for the proposed research comprise piston coring the sequences, high-resolution micro-XRF core scanning, u-channel X-ray radiography, grain-size distribution analysis, and AMS 14C dating. In addition to revealing paleotsunami records in the region, the proposed research will bring new insights on detection of tsunami deposit in sedimentary sequences. Among the methods to be applied, high-resolution micro-XRF core scanning have been utilised in only a few studies before, while u-channel X-ray radiography has never been used in any paleotsunami investigation. Hence, the proposed research will mediate a significant transfer of the knowledge gained in paleolimnology/paleoclimatology/paleoceanography disciplines to paleotsunami research. Another important part of the project will be the organization of stakeholders’ meetings in the important cities of the study area in order to inform people about the scope and the results of the research and to increase the public awareness about tsunamis.MSCA-IF-EF-ST - Standard EF (H2020-MSCA-IF-2015

Contribution of subaqueous paleoseismology to paleoseismic datasets: Examples from the Euro-Mediterranean Region

Besides on-fault paleoseismic trenching techniques, subaqueous paleoseismology have been getting popular in the recent years to contribute paleoseismic data sets. In the regions having high-seismic activity and on-fault paleoseismic trenching is not applicable (e.g., blind reverse/trust faults and offshore faults), subaqueous paleoseismology becomes highly crucial. In moderate-seismicity regions, even though the earthquakes of M∼6 can cause significant damages and loss of life, they usually generate non-distinct surface ruptures, which again limit the application of on-fault trenching. Moreover, recent subaqueous (lacustrine and marine) sedimentary records can provide more precisely dated and longer paleoseismic data. However, sedimentary traces of past earthquakes in lacustrine and marine records can be very similar to the sedimentary events of climatic origin. For this reason, subaqueous paleoseismology needs temporal validation by using information from historical seismicity records and paleoseismic trenches. In this study, I present examples of subaqueous paleoseismological applications from EuroMediterranean region. The lacustrine sedimentary records from the central Europe (e.g., France and Switzerland), which is a low-moderate seismicity region, reveal short-to-moderate length paleoseismic records (i.e. 1000-3000 year long). The North Anatolian Fault (NAF) and the Dead Sea Fault (DSF) are the two main source of high seismic activity in Euro-Mediterranean region. Subaqueous paleoseismicity studies from the Marmara Sea and several lakes on the NAF provide short-to-moderate length paleoseismic records, while the studies from DSF can go ∼50 kyr back in time