2019 Mw5.8 Silivri Earthquake Reveals the Complexity of the Main Marmara Shear Zone

2020 ◽  
Author(s):  
A. Ozgun Konca ◽  
Sezim Ezgi Guvercin ◽  
Hayrullah Karabulut ◽  
Figen Eskikoy ◽  
Semih Ergintav
Keyword(s):  
Shear Zone ◽  
Focal Mechanisms ◽  
Seismic Gap ◽  
Marmara Sea ◽  
Central Basin ◽  
The West ◽  
High Background ◽  
North West ◽  
Narrow Zone ◽  
Finite Fault

<p>The North Anatolian Fault (NAF) is a 1600 km dextral transform fault accommodating the motion between Anatolia and Eurasia Plates. The segments beneath the Marmara Sea, are the only part of the NAF that did not break since the 20<sup>th</sup>century. Recent studies show that this 150 km seismic gap is characterized by heterogeneous interseismic behavior and significantly high background seismicity with respect to the other parts of the NAF.</p><p>On September 24 2019, an activity started north of the Main Marmara Fault (MMF) including a M<sub>w</sub>4.7 earthquake, which led to the Mw5.8 mainshock several days later. The 2019 M<sub>w</sub>5.8 Silivri earthquake is the largest since 1963 M<sub>w</sub>6.3 Cinarcik earthquake in the Marmara Sea. This sequence occurred at a location that is immediate north west of the Central Basin; between a zone that is possibly partially creeping (Central Basin) to the west and a possibly locked segment to the east (Kumburgaz Basin).</p><p> </p><p> In this study we used template search for detection of earthquakes, relocated the earthquakes, obtained focal mechanism solutions of earthquakes that are M>4 and obtained a finite-fault slip model of the M<sub>w</sub>5.8 mainshock. Using template cross-correlation, a total of 400 earthquakes were detected in this sequence. The activity started in a relatively narrow zone and spread to larger distances following the M<sub>w</sub>4.7 mainshock. The depth distribution shows that the earthquakes are confined to a narrow zone between the depths of 9-13 km. The focal mechanisms show that there are two clusters; the cluster to the northwest show a ~70°north dipping fault with rake angles about ~160°, while the activity toward east converges to the Main Marmara Fault and dip angle is close to ~70°with rake angles of ~140°. The finite-fault model shows a bilateral rupture that propagated down-dip from the hypocenter.</p><p>We conclude that the seismic activity occurred on a fault that is within the Main Marmara Shear Zone beneath the sedimentary basin. This secondary fault possibly connects to the Main Marmara Fault to the east. There is no evidence that the causative fault continues up-dip into the basin.  Another characteristic of this sequence is that all of the focal mechanisms show significant thrust component in addition to the expected right-lateral motion. The January 2020 M<sub>w</sub>4.7 earthquake that occurred in the same zone  between the two clusters have predominantly thrust mechanism, confirming that this zone is under local compression. The observed thrust component is possibly related to change of the width of the shear zone with narrowing from Central Basin to the west to Central High to the east and/or the change of the interseismic behavior of the fault from partially creeping Central Basin and locked Kumburgaz Basin segments.</p>

The moderate size 2019 September Mw 5.8 Silivri earthquake unveils the complexity of the Main Marmara Fault shear zone

2020 ◽  
Vol 224 (1) ◽  
pp. 377-388 ◽  
Author(s):  
Hayrullah Karabulut ◽  
Sezim Ezgi Güvercin ◽  
Figen Eskiköy ◽  
Ali Özgun Konca ◽  
Semih Ergintav
Keyword(s):  
Shear Zone ◽  
Sedimentary Cover ◽  
Marmara Sea ◽  
Depth Range ◽  
Stress Increase ◽  
The North ◽  
Finite Fault ◽  
Stress Changes ◽  
The City ◽  
The Town

SUMMARY The unbroken section of the North Anatolian Fault beneath the Sea of Marmara is a major source of seismic hazard for the city of İstanbul. The northern and currently the most active branch, the Main Marmara Fault (MMF), is segmented within a shear zone and exhibits both partially creeping and locked behaviour along its 150 km length. In 2019 September, a seismic activity initiated near MMF, off-coast the town of Silivri, generating 14 earthquakes ≥ Mw 3.5 in a week. The Mw 5.8 Silivri earthquake, is the largest in the Marmara Sea since the 1963 Mw 6.3 Çınarcık earthquake. Our analyses reveal that the activity started in a narrow zone (∼100 m) and spread to ∼7 km following an Mw 4.7 foreshock within ∼2 d. The distribution of relocated aftershocks and the focal mechanisms computed from regional waveforms reveal that the Mw 5.8 earthquake did not occur on the MMF, but it ruptured ∼60° north-dipping oblique strike-slip fault with significant thrust component located on the north of the MMF. Finite-fault slip model of the main shock shows 8 km long rupture with directivity toward east, where the ruptured fault merges to the MMF. The narrow depth range of the slip distribution (10–13 km) and the aftershock zone imply that the causative fault is below the deep sedimentary cover of the Marmara Basin. The distribution of aftershocks of the Mw 5.8 event is consistent with Coulomb stress increase. The stress changes along MMF include zones of both stress decrease due to clamping and right-lateral slip, and stress increase due to loading.

Excavations at Fishbourne, 1963. Third Interim Report

1964 ◽  
Vol 44 (1) ◽  
pp. 1-8
Keyword(s):  
Interim Report ◽  
The West ◽  
Civic Society ◽  
North West ◽  
The Third ◽  
North East ◽  
The North ◽  
The Future ◽  
Set Up

Early in 1963 much of the land occupied by the Roman building at Fishbourne was purchased by Mr. I. D. Margary, M.A., F.S.A., and was given to the Sussex Archaeological Trust. The Fishbourne Committee of the trust was set up to administer the future of the site. The third season's excavation, carried out at the desire of this committee, was again organized by the Chichester Civic Society.1 About fifty volunteers a day were employed from 24th July to 3rd September. Excavation concentrated upon three main areas; the orchard south of the east wing excavated in 1962, the west end of the north wing, and the west wing. In addition, trial trenches were dug at the north-east and north-west extremities of the building and in the area to the north of the north wing. The work of supervision was carried out by Miss F. Pierce, M.A., Mr. B. Morley, Mr. A. B. Norton, B.A., and Mr. J. P. Wild, B.A. Photography was organized by Mr. D. B. Baker and Mrs. F. A. Cunliffe took charge of the pottery and finds.

An Iron Age A site on the Chilterns

1951 ◽  
Vol 31 (3-4) ◽  
pp. 132-148 ◽  
Author(s):  
K. M. Richardson ◽  
Alison Young
Keyword(s):  
Water Supply ◽  
Iron Age ◽  
The West ◽  
North West ◽  
The North ◽  
Roman Villa ◽  
Adjoining Area ◽  
Cursory Examination ◽  
A Site ◽  
The Hill

In 1946 a visit to the barrow, which lies on the edge of the western scarp of Chinnor Common, and a cursory examination of the adjoining area, cultivated during the war, resulted in finds of pottery and other objects indicating Iron Age occupation. The site lies on the saddleback of a Chiltern headland, at a height of about 800 ft. O.D. Two hollow ways traverse the western scarp, giving access to the area from the Upper Icknield Way, which contours the foot of the hill, then drops to cross the valley, passing some 600 yards to the north of the Iron Age site of Lodge Hill, Bledlow, and rising again continues northwards under Pulpit Hill camp and the Ellesborough Iron Age pits below Coombe Hill. The outlook across the Oxford plain to the west is extensive, embracing the hill-fort of Sinodun, clearly visible some fourteen miles distant on the farther bank of the Thames. The hollow way at the north-west end of the site leads down to a group of ‘rises’ hard by the remains of a Roman villa, and these springs are, at the present day, the nearest water-supply to the site.

The use of high-resolution stratigraphy and derived lithoclasts to document structural inversion; a case study from the Paleogene, Isle of Wight, U.K.

2021 ◽  
pp. jgs2020-156
Author(s):  
Andy Gale
Keyword(s):  
The West ◽  
North West ◽  
Geologic Time ◽  
Northern Limb ◽  
The North ◽  
Basement Faults ◽  
Structural Inversion ◽  
Geologic Time Scale ◽  
Radiometric Ages

The effects of structural inversion, generated by the Pyrenean Orogeny on the southerly bounding faults of the Hampshire Basin (Needles and Sandown Faults) on Eocene sedimentation in the adjacent regions were studied in outcrops by sedimentary logging, dip records and the identification of lithoclasts reworked from the crests of anticlines generated during inversion. The duration and precise age of hiatuses associated with inversion was identified using bio- and magnetostratigraphy, in comparison with the Geologic Time Scale 2020. The succession on the northern limb of the Sandown Anticline (Whitecliff Bay) includes five hiatuses of varying durations which together formed a progressive unconformity developed during the Lutetian to Priabonian interval (35-47Ma). Syn-inversion deposits thicken southwards towards the southern margin of the Hampshire Basin and are erosionally truncated by unconformities. The effects of each pulse of inversion are recorded by successively shallower dips and the age and nature of clasts reworked from the crest of the Sandown Anticline. Most individual hiatuses are interpreted as minor unconformities developed subsequent to inversion, rather than eustatically-generated sequence boundaries:transgressive surfaces. In contrast, the succession north of the Needles Fault (Alum Bay) does not contain hiatuses of magnitude or internal unconformities. In the north-west of the island, subsidiary anticlinal and synclinal structures developed in response to Eocene inversion events by the reactivation of minor basement faults. The new dates of the Eocene inversion events correspond closely with radiometric ages derived from fracture vein-fill calcites in Dorset, to the west (36-48Ma).

Recession and the Regions in Great Britain, 1976–1980: Analyses of Redundancy Data

1982 ◽  
Vol 14 (10) ◽  
pp. 1389-1404 ◽  
Author(s):  
A R Townsend
Keyword(s):  
Great Britain ◽  
Poor Performance ◽  
Regional Data ◽  
The West ◽  
Industrial Composition ◽  
British Economy ◽  
North West ◽  
The North ◽  
West Midlands ◽  
Policy Interest

The severe downturn in the British economy in 1980 is apparent in regional data for employment (provisional), redundancies, and unemployment. Five shift-share analyses are used here to explore the data on employment and redundancies, three of them conducted at ‘minimum list heading’ level. The period 1976 to 1979 is one of poor performance by regions of traditional policy interest, whereas the events of 1980 are seen as essentially a national phenomenon. However, bias in the industrial composition of the recession towards manufacturing in general and towards certain individual products is sufficient to focus its very worst effects on Wales, the West Midlands, and the North West.

scholarly journals Marmara Island earthquakes, of 1265 and 1935; Turkey

2006 ◽  
Vol 6 (6) ◽  
pp. 999-1006 ◽  
Author(s):  
Y. Altınok ◽  
B. Alpar
Keyword(s):  
Fault Zones ◽  
Marmara Sea ◽  
Sea Waves ◽  
Rock Falls ◽  
The West ◽  
Moderate Size ◽  
Northwestern Turkey ◽  
Earthquake Ruptures ◽  
Fundamental Understanding

Abstract. The long-term seismicity of the Marmara Sea region in northwestern Turkey is relatively well-recorded. Some large and some of the smaller events are clearly associated with fault zones known to be seismically active, which have distinct morphological expressions and have generated damaging earthquakes before and later. Some less common and moderate size earthquakes have occurred in the vicinity of the Marmara Islands in the west Marmara Sea. This paper presents an extended summary of the most important earthquakes that have occurred in 1265 and 1935 and have since been known as the Marmara Island earthquakes. The informative data and the approaches used have therefore the potential of documenting earthquake ruptures of fault segments and may extend the records kept on earthquakes far before known history, rock falls and abnormal sea waves observed during these events, thus improving hazard evaluations and the fundamental understanding of the process of an earthquake.

scholarly journals Before the Celts: Cosmology, Landscape and Folklore in Neolithic Northwest Iberia

2018 ◽  
Vol 22 (1) ◽  
pp. 29-45
Author(s):  
Fabio Silva
Keyword(s):  
Iberian Peninsula ◽  
Bronze Age ◽  
Mountain Range ◽  
The West ◽  
North West ◽  
The North ◽  
Celtic Studies ◽  
The Bronze Age ◽  
Northwest Iberia

This paper applies a combined landscape and skyscape archaeology methodology to the study of megalithic passage graves in the North-west of the Iberian Peninsula, in an attempt to glimpse the cosmology of these Neolithic Iberians. The reconstructed narrative is found to be supported also by a toponym for a local mountain range and associated folklore, providing an interesting methodology that might be applied in future Celtic studies. The paper uses this data to comment on the ‘Celticization from the West’ hypothesis that posits Celticism originated in the European Atlantic façade during the Bronze Age. If this is the case, then the Megalithic phenomenon that was widespread along the Atlantic façade would have immediately preceded the first Celts.

scholarly journals La moneda como ofrenda en los manantiales

1992 ◽  
Author(s):  
Manuel Abad Varela
Keyword(s):  
Thermal Springs ◽  
The West ◽  
North West ◽  
The North ◽  
Sobre Todo ◽  
Península Ibérica

A la vista de como se han producido la mayoría de los hallazgos analizados y según se desprende de las fuentes escritas, diríamos que en la península ibérica y sobre todo en la parte Occidental se realizaron en la Antigüedad ofrendas monetales a divinidades de las aguas y fundamentalmente, por las referencias que tenemos, a las divinidades de las fuentes termales. Únicamente nos queda la duda de si la fuente de Peña Cutral en Retortillo (Reinosa, Santander) es termal o no, pues si no lo fuese sería el único hallazgo dentro de una fuente no termal. Se podría entender, con ciertos reparos en algún caso, que también se hicieron arrojándolas al curso de los ríos, depositándolas en la orilla y lanzándolas a las charcas o pantanos. Por otro lado, las monedas que se han encontrado en las fuentes, en contraposición con las recogidas en los ríos, suelen estar en muy mala conservación, hasta el punto de que muchas se desintegran en las manos al estar muy atacadas por los ácidos. A juzgar por algunos de los hallazgos, se podría creer que las ofrendas más valiosas se procuró depositarlas en lugares seguros o resguardados, como es el caso de la Hermida, de la Fuente de El Sarso, del Balneario de Fortuna y podríamos recordar también el hallazgo del conocido depósito de Oñate. De acuerdo con la cronología de las monedas y según sus resultados estadísticos, la costumbre o rito de depositar o arrojar «stips» a las aguas, principalmente termales, se practicó en la península Ibérica más intensamente entre los siglos i a. C. al ii d. C. Este período coincide con el momento que más estuvo en boga el uso de las aguas termales, a juzgar por lo que se trató el tema en las fuentes escritas. Al mismo tiempo que se percibe esta moda en la vida diaria, pues Suetonio nos dice que Augusto, a pesar de que por su naturaleza enfermiza no abusaba de los baños, sin embargo, cuando necesitaba templar los nervios tomaba baños de mar o las aguas termales de Albula ^'. De Nerón nos dice que cuando reconstruyó su casa en Roma después del incendio, la famosa domus áurea, hizo llegar a las salas de baño agua de mar y de Albula *"*. Por las aras recogidas en las fuentes termales, sabemos que las divinidades que más se sintieron favorecidas con estas ofrendas monetales fueron las Ninfas y las aguas que más beneficios causaron o por las que se sintieron más agradecidos los visitantes fueron las de aguas sulfuradas- cálcicas, es decir, las que se recomiendan principalmente para los problemas de dermatosis herpética, neurosis y catarros crónicos de las vías respiratorias ^^ sin que ésto signifique que hubiese alguna relación entre las cualidades de las aguas y las divinidades a quienes se dedicaron las aras. Finalmente, conviene señalar que son éstas las únicas conclusiones a las que nos atrevemos a llegar partiendo de las informaciones que tenemos. No obstante, deseamos que en un futuro se produzcan más hallazgos en lugares tan particulares como los señalados, fuentes, ríos y lagos, que nos permitan confirmar o desmentir con más precisión nuestras hipótesis. Para que ésto suceda animo desde aquí a los arqueólogos para que busquen este tipo de yacimientos y tengan en cuenta sus ofrendas, tratándolas con cuidado por su mal estado, y no tardando en darlas a conocer como tales.This paper deals with the finding of thirty one cases of possible monetary offerings to the divinities in the waters of the Spanish península. The largest number of cases involve springs, which make up 74.19 % of the total, of which 78.26 % are hyperthermal springs with temperatures ranging between 15 and 70 C. Most of these springs are to be found ín the West of Spaín. They are mainly connected with the Nymphis, except in the North West, where they are offered up to Apollini, to judge from the devotional alters which can be sean. It would appear, from the coins collected, that the custom of throwing stipes to the deities of the springs was mostly practiced between the 1st century B.C. and the 2nd century A. D., although a slight increase can be seen towards the middie of the 4th century A. D. The thermal springs which benefitted nnost from the profits of these offerings were those with suifuric-caicic waters.

Investigation of Land Subsidence in Eastern Thrace (Turkey) using Multi Temporal InSAR

2021 ◽  
Author(s):  
Tohid Nozadkhalil ◽  
Semih Ergintav ◽  
Ziyadin Cakir ◽  
Ugur Dogan ◽  
Thomas R. Walter
Keyword(s):  
Natural Gas ◽  
Ground Motion ◽  
Deformation Source ◽  
Seismic Gap ◽  
Marmara Region ◽  
Marmara Sea ◽  
Gas Extraction ◽  
Triangular Elements ◽  
Natural Gas Extraction ◽  
Thrace Region

<p>Westward migration of M>7 earthquakes along North Anatolian fault with the latest one, Izmit 1999 event, led focus of studies to the seismic gap in the main Marmara fault. For this purpose, the coastal ranges of the Marmara Sea, mainly Istanbul megacity, are renowned for earthquake and ground motion hazards, associated with faulting, landslides and sediment compaction processes. Ground motion associated with man-made activities, however, have been barely studied. The Thrace region of Turkey, some 50 km to the North of the Marmara Sea, expresses pronounced ground motions affecting large areas. We use the Persistent InSAR technique to monitor the Marmara region using Sentinel-1 satellites’ TOPSAR data between 2014 and 2020. Results for both ascending (T131 and T58) and descending (T36) tracks reveals 10 mm/yr rate of subsidence in the Thrace region of Turkey, affecting an area ~15400km² with dimensions of ~110 km by ~140 km. There are two plausible mechanisms for this deformation; (1) excessive pumping of groundwater for agricultural purposes, or (2) natural gas extraction activities taking place in the region. To better understand the observed deformation source, as a first step, we model potential gas extraction by volume change. No piezometric data are available for this region for the time being. Thick sediments including sandstone, reefal carbonates, amongst others, are aimed for gas exploration in the Thrace basin for more than half century. Depth of gas extraction wells and sediment thickness is compiled from previous studies to compare the subsided area with sediment and well depth variations. </p><p>We use  the Poly3D boundary element method to model the surface. Poly3D uses planar triangular elements of constant model to model displacement’s source. Using triangular elements provides models with complex and smooth 3D surfaces avoiding overlaps or gaps, and hence allowing one to construct realistic models. Poly3dinv inverse model applies a fast non-negative/non-positive least squares solver to optimize the solution. We construct a surface enveloping tips of the wells and use it to produce deformation at surface due by allowing opening on it. Small residuals between the observation and model based on opening suggests that deformation is likely caused by natural gas extraction.</p>

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