The usage of historical seismograms: The 1912 earthquake records

Modern sismolojik yöntemlerle gerçekleştirilen deprem kayıtları son 40 yıllık dönemi kapsamaktadır, ancak aletsel sismolojik gözlemlerin başlangıcı 1880’lere dayanmaktadır. 1960’larda dünya standart sismograf ağının (WWSSN) kurulumuna kadar geçen süre içinde depremler ilksel mekanik sismograflar tarafından kaydedilmiştir. Bu deprem kayıtlarının modern metotlarla yeniden incelenmesi sismolojinin aletsel dönemini belirgin bir oranda genişletecektir. Bu çalışmada Ganos Fayı üzerinde meydana gelen 9 Ağustos (Ms = 7.4), 10 Ağustos (Ms = 6.2 ve 5.3) ve 13 Eylül 1912 (Ms = 6.9) ve çalışılmıştır. O tarihte 143 deprem istasyonun faal olduğu tespit edilmiş ve araştırmalar sonucunda bu depremlere ait 73 adet tarihsel sismogram elde edilmiştir. Sismogramlardan Bergen, Ebro ve Taranto istasyonlarına ait kayıtlar TESEO2 yazılımıyla sayısallaştırılmış, geometrik düzeltmeye tabii tutulmuş ve SAC (sismik analiz kodu) formatına dönüştürülmüştür. Toplamda 15 adet deprem kaydı, cihaz parametrelerine ihtiyaç duymayan Green Fonksiyonu hesabı yöntemiyle incelenmiştir. Taranto istasyonu kaydından elde edilen göreceli kaynak-zaman fonksiyonu 9 Ağustos depremi için 40 saniyelik bir kaynak süresi vermiştir ki bu süre 3 km/sn’lik ortalama kırılma hızıyla yaklaşık 120 km’lik bir kırık uzunluğu ifade eder. Bununla birlikte, düşey bileşen kaydı yapan Göttingen Toledo Ebro Pulkovo ve Hongo istasyonlarının P dalgası ilk varışları incelenmiş ve saha gözlemleriyle birleştirilerek 9 Ağustos 1912 şoku için bir fay mekanizması çözümü verilmiştir. Bu çalışmada tarihsel deprem kayıtları ve saha gözlemlerinin birleştirilmesi sonucunda 1912 depremleri için toplamda 150 km’lik bir fay kırığı hesaplanmıştır. Bu kırık boyu Marmara denizindeki sismik boşluğun boyutunun belirlenmesinde önemli bir sınır teşkil etmektedir. 9 Ağustos 1912 ve Kuzey Anadolu fayı üzerinde meydana gelen tarihsel depremlere ait tarihsel sismogramların yeniden incelenmesi bu depremler hakkında yeni parametreler sağlayacak ve deprem olgusunun anlaşılmasına yardımcı olacaktır. Anahtar Kelimeler: Sismoloji, tarihsel sismogram, 1912 depremi, Ganos Fayı, Kuzey Anadolu Fayı. Large earthquakes (M>7) occur with intervals more than hundreds of years. Quantitative data of large earthquakes are available through recordings of modern (digital) seismographs since the last 40 years. However historical (analog) seismograms encompass nearly 100 years of seismicity and document significant large earthquakes of the world. Contemporary analyses of old seismograms predate fundamental developments in quantitative seismology, while present techniques and methods in modern seismology allow comprehensive analysis of the earthquake phenomena (Kanamori and Brodsky, 2004). A reanalysis of old seismograms, integrated with modern methods will expand considerably the instrumental period of earthquake seismology and may provide key information for regional tectonics, kinematics of faults, earthquake parameters, recurrence intervals and seismic hazard (Batllo et al., 2008). In this work, it is here provided a short guideline how to collect and process historical seismograms by presenting a case study of the 1912 earthquake sequence along the North Anatolian Fault. The 9 August 1912 Mürefte earthquake (Ms=7.4) occurred at an early stage of seismological research. At that time, at least one primitive seismograph was active at 143 stations. 73 seismic records have been collected for the 9 August, 10 August and 13 September 1912 shocks, which occurred along the Ganos Fault. The majority of the records are from European stations located northwest and west of the epicentre. However, other recordings from Japan, Australia and Russia were also obtained. The SISMOS online database was the major source of the collected seismograms. The TESEO software has been used to vectorize and correct the waveforms and to convert them to SAC files. Signals were processed using the Empirical Green Function approach proposed by Vallee (2004), which avoids complexities due to unknown instrument parameters. The method uses the signal of a smaller event to model the Green function of the main earthquake. Comparable signal pairs 9 August and 13 September shocks from the Bergen, Ebro, and Taranto stations were digitized and corrected. 15 digital seismic signals have been modelled with the related method. Due to limitations by the applied method and majorly because of inadequate signal corrections our modelling revealed reliable results only for the Taranto station. The modelling of the 9 August and 13 September shocks provide a relative source time function and indicate that the moment ratio between the two shocks is about 30 which corresponds to 1 degree difference in magnitude and infer 40 second source duration for the 9 August. In addition to the modelling, we use the P-wave polarities at 5 stations to construct a focal mechanism. The vertical component seismograms from Göttingen, Toledo, Ebro, Pulkovo and Hongo and field based N68°E fault strike allow us to construct the focal mechanism solution for the 9 August 1912. The pure strike slip solution we obtained is in agreement with the known fault kinematics and slip measurements. The 40 second source duration implies ~ 120 km coseismic rupture length if a unilateral rupture propagation at 3 km/sec is attributed to the 9 August earthquake. On the other hand, the size of the 9 August shock corresponds to 1.5 x 1027 dyn*cm seismic moment which also suggests a 120 ± 20 km rupture length, assuming an average slip of 2.5 m and a fault width of 15 km. The size of the 13 September shock (Ms=6.9) implies 30 ± 10 km of surface rupture with similar fault parameters. As a result, the combined analysis of seismology, field observation and historical data suggest that the 1912 sequence caused a 150 km of surface faulting. This length is equal to the distance of the two major geometrical complexities of the Ganos Fault on its east and west; the Central Marmara Basin and the Saros Trough respectively. Therefore, it may be concluded that the eastern rupture end of 9 August 1912 Mürefte earthquake is located in the Central Marmara Basin and defines the western limit of the seismic gap in the Sea of Marmara. The comprehensive reanalysis of historical seismograms for the large earthquakes along the North Anatolian Fault will considerably extend our knowledge of the characteristics each earthquake and will provide new constraints to understand the earthquake behaviour along this large continental strike slip fault. Keywords: Seismology, historical seismogram, 1912 earthquake, Ganos Fault, North Anatolian Fault

Kuzey anadolu fayi Ganos fay segmentinin aktif tektonigi ve paleosismolojisi ve 9 agustos 1912 Mürefte depreminin sismik karakteristikleri (Bati Türkiye)

Au cours de la dernière centaine d'années, la faille nord-anatolienne (FNA) a déjà généré 9 séismes de magnitude supérieure à 7 en Turquie. Dans cette thèse nous investiguons la faille de Ganos qui est le segment occidental de la FNA. Cette faille fût responsable du séisme de Mürefte du 9 août 1912 (M 7.3). la faille de Ganos est visible en surface sur 45-km alors que le reste est en mers Egée à l'est et Marmara à l'ouest. Cette faille de Ganos forme la section occidentale d'une large zone en step-over qui correspond au bassin losangique (pull-apart) de Marmara où le séisme de Kocaeli de 1999 fût localisé dans sa partie est. Les deux extrémités des ruptures de 1912 et de 1999 définissent une lacune sismique dans la mer de Marmara. Des analyses géomorphologiques sur les 45-km à terre de la faille de Ganos ont permis de décrire des structures typiques des failles en décrochement (ex : pull-apparts, bombements, step-over, rides de compression et décalage de rivières). La section à terre de la faille de Ganos est d'azimut ~N68°E, segmentée en deux step-over extensifs au niveau de Gölcük and Kavak. La combinaison entre les analyses morphologiques à terre et en mer suggèrent un minimum de 04 sous-segments limités par des complexités géométriques qui est de l'est à l'ouest comme suit : Le bassin central de Marmara, le coude de Ganos, step-over de Gölcük, step-over de Kavak and la dépression Saros. La dépression de Saros et le basin central de Marmara sont les plus importantes complexités structurales le long de la faille de Ganos et peuvent as ir comme barrière à la propagation de la rupture.Le déplacement cumulé calculé sur 69 localités, de la reconstruction tectonique permettent d'avoir un aperçu sur les caractéristiques de déformation du segment de Ganos à long terme et à court terme. Les mesures des déplacements de chenaux, des crêtes et une partie d'ancienne routes nous conduisent à évaluer un décalage entre 8 et 575m. Par ailleurs, nous suggérons un décalage (offset) plus important de 200m à 9000m basé sur la reconstruction du système hydrologique actuel. Une classification des décalages de chenaux montre 8 classes distinctes d'offset de glissement cumulée. Nous avons aussi utilisé les courbes de fluctuations du niveau de la mer noire afin de contraindre les période de fortes précipitations qui peuvent générer des incisions de chenaux. 5 groupes de glissement cumulé (de 70 à 300m) montrent une bonne corrélation avec un rehaussement du niveau de la mer conséquent à 4 ka, 10.2 ka, 12.5 ka, 14.5 ka et 17.5 ka. Les estimations du taux de glissement conduisent à un taux de glissement constant de of 17.9 mm/an pour les dernières 20.000 années et un taux de glissement variable de 17.7 mm/an, 17.7 mm/an, 17.9 mm/an et 18.9 mm/an pour les dernières 10.2 ka, 12.5 ka, 14.5 ka et 17.5 ka, respectivement.La paléosismologie a montré sur 03 sites (Güzelköy, Yeniköy and Yörgüç) des évidences de 8 événements sismiques, 5 datés entre 1043 835 BC et 1500 830 BC à Güzelköy et Yeniköy respectivement. Une meilleure datation a été contrainte pour les trois derniers événements à Güzelköy qui sont vraisemblablement des séismes en (1) 1343 ou 1344 (2) 1659 ou 1766b and (3) 1912. Nous suggérons deux scénarios de récurrence de séismes pour les derniers séismes en relation avec la faille de Ganos. Le scénario (1) conduit à une moyenne de récurrence de 285 +- 36 ans et englobe les événements de 1912, 1659, 1354/1344, 824, 484 alors que le scénario (2) est aussi valable si une récurrence non périodique des séismes est acceptée. La combinaison entre les analyses géomorphologiques et des résultats des tranchées conduit à un taux de glissement de la faille nord anatolienne au niveau de la région de Ganos. A Güzelköy deux paleo-chenaux présentement un décalage de 16 m et 21 m et conduit à un taux de 22.3 +- 0.5 mm/an pour ce dernier ~700 années et 26.9 mm/an pour les 781 dernières années respectivement. A Yeniköy des datations des couches les plus profondes montre de 46 +- 1 m de décalage de chenal et donnant ainsi un maximum de 17 mm/an de taux de glissement.Le 9 août 1912 la région de Mürefte a été secouée par un séisme (M = 7,3) a frappé le long de la faille de Ganos et a provoqué de graves dégâts (Io = X) entre Tekirdag et de Çanakkale. Un deuxième grand choc s'est produit le 13 Septembre 1912 (M = 6,8) avec une zone épicentrale à l'ouest du choc principal, causant des destruction Io = VII à l'ouest de dommages Gaziköy et le long de la péninsule de Gallipoli. Des rupture en surface ont été enregistrées le long de la totalité des 45-km de la section en surface. Nous avons déterminé un glissement maximum de 5,5 m qui a été précédemment suggéré à 3 m par Ambraseys & Finkel et al. (1987). Nous prolongeons les mesures de glissement de Altunel et al. (2004) à partir de 31 localités à 45 avec une meilleure répartition le long de la faille. La distribution d'offsets indique qu'une certaine partie de la rupture est au large, c'est à dire dans la baie de Saros et Mer de Marmara.73 enregistrement de sismogrammes historiques ont été collectés pour les événements du 9 août, 10 août et le 13 Septembre 1912. Des paires comparables ont été numérisées à l'aide du logiciels TESEO. La modélisation et deconvolution de la forme d'ondes sismiques a permis la récupération d'une fonction temps source en utilisant les événements du 13 Septembre et du 9 Août et fourni une fonction temps source de 40 secondes pendant le tremblement de terre du 9 août. Considérant une propagation unilatérale de la rupture de 3 km/s, cette durée implique longueur de rupture de 120 km, cohérente avec la dimension du séisme (Mw 7.4). Les polarités P des ondes à 5 stations et des N68°E d'azimut de faille nous permet de déduire un mécanisme au foyer pour l'événement du 9 aout. L'ampleur du choc Septembre 13 exige 30 +- 10 km de rupture de surface et des contraint la terminaison ouest pour les 120 +- 20km de longueur de la rupture du 9 Août. Prenant en compte les deux événements, une position de l'épicentre dans la baie de Saros pour le choc du 13 septembre de 150 +- 20 km de longueur totale de rupture et s'étendrait de Saros en propageant vers l'est et rejoignant ainsi le bassin de Marmara central, en accord avec la complexité géométriques importantes le long de cette section de la faille nord-anatolienne. Par conséquent, la terminaison est de la rupture du 09 aout 1912 et la terminaison ouest de la rupture de 1999 impliquent un minimum de 100-km de lacune sismique dans la mer de Marmara. Cette longueur de faille suggère un séisme de magnitude M>7 qui devra être pris en compte dans l'évaluation du risque sismique de la région d'Istanbul.The North Anatolian Fault generated 9 large earthquakes (M>7) in Turkey during the last 100 years. We investigate the Ganos fault, the westernmost segment of the North Anatolian Fault that was responsible for the 9 August 1912 Mürefte earthquake (M 7.3). The Ganos fault is exposed onland for 45 km while the rest is covered up by the Aegean and Marmara seas to the west and east respectively. The Ganos fault forms the western section of a large step-over area that corresponds to the Marmara pull-apart and experienced the 1999 Kocaeli earthquake on its east. The two ends of the 1912 and 1999 earthquake ruptures define the seismic gap in the Sea of Marmara. Geomorphic analysis along the 45-km-long onland section of the Ganos fault allowed documenting typical structures of strike slip faulting; i.e. step-overs, pull-aparts, bends, pressure ridges, sag-ponds, offset ridges, shutter ridges and stream displacement. The onland section of the Ganos fault is expressed as ~N68°E striking linear geometry, segmented by two extensional step-overs at Gölcük and Kavak. The combined analysis of offshore and onland fault morphology suggests a minimum of 4 sub-segments limited by geometrical complexities which are from east to west, the Central Marmara basin, Ganos bend, Gölcük step-over, Kavak step-over and Saros Trough. The Saros Trough and the Central Marmara basin are the largest structural complexities along the Ganos fault and may serve as barriers to earthquake rupture propagation.Cumulative displacements determined at 69 localities and tectonic reconstructions provide insights on the long-term and short-term deformation characteristic of the Ganos fault segment. Measurements of displaced streams, ridges and partly ancient roads yield right lateral offsets ranging from 8 to 575 m. Furthermore, we suggest larger offsets from 200 to 9000 m based on reconstructions of the present-day drainage system. A classification of the stream offsets shows 8 distinct classes of cumulative slip. We used sea level fluctuation curves of the Black Sea in order to constrain the timing of high precipitations periods which can trigger channel incisions. Consecutive 5 cumulative slip groups (from 70 to 300 m) show well correlations with subsequent sea level rise periods at 4 ka, 10.2 ka, 12.5 ka, 14.5 ka and 17.5 ka. Slip rate estimations yield a constant slip rate of 17.9 mm/yr for the last 20.000 years and a variable slip rate of 17.7 mm/yr, 17.7 mm/yr, 17.9 mm/yr and 18.9 mm/yr for the last 10.2 ka, 12.5 ka, 14.5 ka and 17.5 ka, respectively.Paleoseismology at three sites (Güzelköy, Yeniköy and Yörgüç) showed evidence of 8 faulting events, 5 of which post-date 1043 835 BC and 1500 830 BC at Güzelköy site and Yeniköy site, respectively. A better timing was constrained for the last three events at Güzelköy which are most probably the earthquakes in (1) 1344 or 1354 (2) 1659 or 1766b and (3) 1912. We suggest two earthquake recurrence scenarios for the last historical earthquakes attributed to the Ganos fault. Scenario 1 yields an average recurrence interval of 285 +- 36 years and encompasses the 1912, 1659, 1354/1344, 824, 484 events, whereas Scenario 2 gives an average recurrence interval of 285 +- 93 years and includes the 1912, 1766, 1354/1344, 824, 484 events. Considering that earthquakes occur periodic the suitable seismic history corresponds to Scenario 1. However scenario 2 is also valid if a non-periodic earthquake occurrence is accepted. The combination of geomorphic analysis and trenching results provides slip rates for the North Anatolian Fault at the Ganos region. At Güzelköy two paleo-channels offset for 16 m and 21 m yield 22.3 +- 0.5 mm/yr for the last ~700 years and 26.9 mm/yr for the last 781 years, respectively. At Yeniköy dating from the lowermost units of the 46 +- 1 m offset stream provided a maximum 17 mm/yr slip rate for the last 2840 years.The 9 August 1912 Mürefte earthquake (Ms=7.3) struck along the Ganos fault causing severe destruction (Io = X) between Tekirdag and Çanakkale. A second large shock occurred on 13 September 1912 (Ms = 6.8) with an epicentral region to the west of the first main shock, giving rise to Io = VII damage west of Gaziköy and along the Gallipoli peninsula. Surface breaks have been recorded along the entire 45-km-long onland section. We determined a maximum slip of 5.5 m that was previously suggested as 3 m (Ambraseys & Finkel et al, 1987). We extend the slip measurements of Altunel et al., (2004) from 31 localities to 45 with a better distribution along the fault. The offset distribution indicates that a certain length of the rupture is offshore, i.e., in the Saros bay and Sea of Marmara.73 historical seismogram recordings have been collected for the 9 August, 10 August and 13 September 1912 shocks. Comparable pairs have been digitized using TESEO software. The modelling and deconvolution of seismic waveforms allowed retrieving a relative source time function using the 13 September and 9 August shocks and provided a source duration of 40 seconds for the 9 August earthquake. Considering a unilateral rupture propagation of 3 km/s, this duration implies rupture length of 120 km, consistent with the earthquake size (Mw 7.4). P-wave polarities at 5 stations and field based N68°E fault strike allow us to construct the focal mechanism solution for the 9 August shock.The size of the 13 September shock requires 30 +- 10 km of surface faulting and constrains the western limit for the 120 +- 20 km long 9 August rupture. Taking into account the two events, an epicentre location in the Saros bay for the 13 September shock, the 150 +- 20 km long total rupture length would extend from Saros Trough towards east and reach the Central Marmara Basin, consistent with major geometric complexities along this section of the North Anatolian Fault. Therefore, the eastern termination of the 9 August 1912 rupture and the western termination of the 1999 earthquake rupture imply a minimum 100-km-long seismic gap in the Sea of Marmara. This fault length suggests an earthquake size M>7 that should be taken into account in any seismic hazard assessment for the Istanbul region

Kuzey anadolu fayi Ganos fay segmentinin aktif tektonigi ve paleosismolojisi ve 9 agustos 1912 Mürefte depreminin sismik karakteristikleri (Bati Türkiye)

Au cours de la dernière centaine d'années, la faille nord-anatolienne (FNA) a déjà généré 9 séismes de magnitude supérieure à 7 en Turquie. Dans cette thèse nous investiguons la faille de Ganos qui est le segment occidental de la FNA. Cette faille fût resThe North Anatolian Fault generated 9 large earthquakes (M>7) in Turkey during the last 100 years. We investigate the Ganos fault, the westernmost segment of the North Anatolian Fault that was responsible for the 9 August 1912 Mürefte earthquake (M 7.3)

Investigating the Structure of a Coastal Karstic Aquifer through the Hydrogeological Characterization of Springs Using Geophysical Methods and Field Investigation, Gökova Bay, SW Turkey

The electrical resistivity tomography method has been widely used in geophysics for many purposes such as determining geological structures, water movement, saltwater intrusion, and tectonic regime modeling. Karstic springs are important for water basin management since the karst systems are highly complex and vulnerable to exploitation and contamination. An accurate geophysical model of the subsurface is needed to reveal the spring structure. In this study, several karst springs in the Gökova Bay (SW, Turkey) were investigated to create a 3D subsurface model of the nearby karstic cavities utilizing electrical resistivity measurements. For this approach, 2D resistivity profiles were acquired and interpreted. Stratigraphically, colluvium, conglomerate, and dolomitic-limestone units were located in the field. The resistivity values of these formations were determined considering both the literature and field survey. Then, 2D profiles were interpolated to create a 3D resistivity model of the study area. Medium-large sized cavities were identified as well as their locations relative to the springs. The measured resistivities were also correlated with the corresponding geological units. The results were then used to construct a 3D model that aids to reveal the cavity geometry in the subsurface. Additionally, several faults are detected and their effect on the cavities is interpreted

Prevalence and predictors of gestational diabetes mellitus: a nationwide multicentre prospective study

Cetinkaya, Esra/0000-0003-2415-1236; Taskiran, Bengur/0000-0003-4842-450X; MELEKOGLU, RAUF/0000-0001-7113-6691; pekkolay, zafer/0000-0002-5323-2257; Ozer, Alev/0000-0002-0934-0226; kilinc, faruk/0000-0002-0198-2558; Aygun, Elif Ganime/0000-0003-3737-7250; KARAKILIC, ERSEN/0000-0003-3590-2656; Aydin, Hasan/0000-0003-4246-0681WOS: 000457530200011PubMed: 30402933Aim Prevalence rates of gestational diabetes mellitus (GDM) show considerable variation among different countries and regions of the world. The primary aim of this study was to determine the nationwide prevalence and predictors of GDM in Turkey. Methods We conducted prospective nationwide screening among pregnant women. Between August 2016 and November 2017, a total of 2643 pregnant women from 51 centres in 12 different regions were enrolled. A two-step screening method and Carpenter and Coustan criteria were used in the diagnosis of GDM. Clinical and biochemical data were obtained using electronic database software. Results The national prevalence of GDM was found to be 16.2% [95% confidence intervals (CI) 15.0% to 17.4%] without a significant difference between urban and rural regions. Women with GDM were older (mean age: 32 +/- 5 vs. 28 +/- 5 years, P < 0.001) and heavier (mean BMI: 27.2 +/- 5.1 vs. 24.7 +/- 4.7 kg/m(2), P < 0.001) than their counterparts without GDM. The prevalence of GDM tended to increase with age (< 25 years, 6.9%; 26-35 years, 15.6%; and 36-45 years, 32.7%; P < 0.001). Maternal age, maternal BMI, history of previous GDM and family history of diabetes mellitus were independent predictors of developing GDM (P < 0.05 for all). Low-risk women (age < 25 years, BMI < 25 kg/m(2), no family history of diabetes) comprised 10.7% of the total population and the prevalence of GDM in these women was 4.5% (95% CI 2.4% to 7.8%). Conclusion The results of this nationwide study indicate that GDM is very common, affecting one in seven pregnancies in Turkey. Implementation of international guidelines on screening and management of this public health problem is required