Extensional tectonics is concerned with the structures formed, and the tectonic processes associated with, the stretching of the crust or lithosphere. The types of structure and the geometries formed depend on the amount of stretching involved. Stretching is generally measured using the parameter β, known as the beta factor where β = t 0 t 1 t 0 is the initial crustal thickness and it is the equivalent of the strain parameter stretch. In areas of relatively low crustal stretching, the dominant structures are high to moderate angle normal faults, with associated half grabens and tilted fault blocks. In areas of crustal stretching, individual extensional faults may become rotated to too low a dip to remain active. Large displacements may juxtapose syntectonic sediments against metamorphic rocks of the mid to lower crust, in some cases the detachments are folded such that the metamorphic rocks are exposed within antiformal closures and these are known as metamorphic core complexes. Passive margins above a weak layer develop a set of extensional structures.
Large listric regional faults are developed with rollover anticlines and related crestal collapse grabens, on some margins, such as the Niger Delta, large counter-regional faults are observed, dipping back towards the continent, forming large grabenal mini-basins with antithetic regional faults. Areas of extensional tectonics are associated with, Rifts are linear zones of localized crustal extension. They range in width from less than 100 km up to several hundred km, consisting of one or more normal faults. In individual rift segments one polarity normally dominates giving a half-graben geometry, other common geometries include metamorphic core complexes and tilted blocks. Examples of active continental rifts are the Baikal Rift Zone and the East African Rift, divergent plate boundaries are zones of active extension as the crust newly formed at the mid-ocean ridge system becomes involved in the opening process. Zones of thickened crust, such as those formed during continent-continent collision tend to spread laterally, after the collision has finished the zone of thickened crust generally undergoes gravitational collapse, often with the formation of very large extensional faults.
Large-scale Devonian extension, for example, followed immediately after the end of the Caledonian orogeny particularly in East Greenland and western Norway. When a strike-slip fault is offset along strike such as to create a gap i. e. a left-stepping bend on a sinistral fault, such bends are known as releasing bends or extensional stepovers and often form pull-apart basins or rhombochasms. Back-arc basins form behind many subduction zones due to the effects of oceanic trench roll-back which leads to a zone of extension parallel to the island arc. A passive margin built out over a layer, such as an overpressured mudstone or salt. The inboard part of the prism is affected by extensional faulting
An earthquake is the shaking of the surface of the Earth, resulting from the sudden release of energy in the Earths lithosphere that creates seismic waves. Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to people around. The seismicity or seismic activity of an area refers to the frequency, Earthquakes are measured using measurements from seismometers. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe and these two scales are numerically similar over their range of validity. Magnitude 3 or lower earthquakes are mostly imperceptible or weak and magnitude 7 and over potentially cause damage over larger areas. The largest earthquakes in historic times have been of magnitude slightly over 9, intensity of shaking is measured on the modified Mercalli scale. The shallower an earthquake, the damage to structures it causes. At the Earths surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground, when the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami.
Earthquakes can trigger landslides, and occasionally volcanic activity, in its most general sense, the word earthquake is used to describe any seismic event — whether natural or caused by humans — that generates seismic waves. Earthquakes are caused mostly by rupture of faults, but by other events such as volcanic activity, mine blasts. An earthquakes point of rupture is called its focus or hypocenter. The epicenter is the point at ground level directly above the hypocenter, tectonic earthquakes occur anywhere in the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. The sides of a fault move past each other smoothly and aseismically only if there are no irregularities or asperities along the surface that increase the frictional resistance. Most fault surfaces do have such asperities and this leads to a form of stick-slip behavior, once the fault has locked, continued relative motion between the plates leads to increasing stress and therefore, stored strain energy in the volume around the fault surface.
This continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the portion of the fault. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the fault surface and this process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the elastic-rebound theory. It is estimated that only 10 percent or less of a total energy is radiated as seismic energy. Most of the energy is used to power the earthquake fracture growth or is converted into heat generated by friction
It includes oceanic crust extending westward to the Mid-Atlantic Ridge and northward to the Gakkel Ridge. The eastern side is a boundary with the North American Plate to the north and a boundary with the Philippine Sea Plate to the south, and possibly with the Okhotsk Plate and the Amurian Plate. The southerly side is a boundary with the African Plate to the west, the Arabian Plate in the middle, the westerly side is a divergent boundary with the North American Plate forming the northernmost part of the Mid-Atlantic Ridge, which is straddled by Iceland. The geodynamics of central Asia is dominated by the interaction between the Eurasian and Indian Plates, in this area, many subplates or crust blocks have been recognized, which form the Central Asian and the East Asian transit zones
2011 Van earthquakes
The 2011 Van earthquakes occurred in eastern Turkey near the city of Van. The first earthquake happened on 23 October at 13,41 local time, the shock had a moment magnitude of 7.1 and a maximum Mercalli intensity of VIII. It occurred at a depth, causing heavy shaking across much of eastern Turkey and lighter tremors across neighboring parts of the South Caucasus. According to Disasters and Emergency Situations Directorate of Turkey AFAD on 30 October, at least 11,232 buildings sustained damage in the region,6,017 of which were found to be uninhabitable. The other 5,215 have been damaged but are habitable, a separate earthquake within the same earthquake system happened on 9 November at 21,23 local time. Part of the convergence between two plates takes place along the Bitlis-Zagros fold and thrust belt. The earthquakess focal mechanism indicates oblique thrust faulting, consistent with the expected tectonics in the region of the Bitlis-Zagros Fault Zone, where thrust mechanisms dominate. The size of the rupture has been estimated as 60 km x 20 km, consistent with the distribution of aftershocks.
An offset of about 2 metres has been estimated at 10–15 kilometres depth, the rupture lasted for about 50 seconds. Due to its intensity and shallow depth, the earthquake produced significant ground motions across a large area. Violent shaking measuring MM VIII on the Mercalli scale occurred in Van, although widespread strong to severe shaking was observed in many smaller and less populated areas around the epicenter. Lighter but well-felt ground motions spread much farther across the region, extending into surrounding countries such as Armenia, Georgia, Iraq, there have been 1,561 aftershocks above magnitude 2 Mw as of 30 October. The highest magnitude aftershock came at 11,45 pm Local on 23 October, with a MI5.7 and Mw 6.0. The number of reported in ranges as follows,556 ranging from magnitude 2 to 3,832 ranging from magnitude 3 to 4,108 ranging from magnitude 4 to 5. In the first five months there were 9,367 aftershocks with magnitudes in the range 1.5 to 5.8, the earthquakes affected much of eastern Turkey, demolishing hundreds of buildings and burying numerous victims under the rubble.
Erciş, a town near Van, was hardest hit by the violent shaking, at least 55 destroyed buildings,45 fatalities, most of the buildings collapsed along the towns main road and were residential, raising the possibility of a higher death toll. In smaller villages near the epicenter, the shaking demolished almost all the brick houses, in Van city center, at least 100 people were confirmed dead, and 970 buildings collapsed in and around the city. About 200 inmates escaped after the walls of a prison succumbed to the shaking, the natural gas, water and communication systems in Van were all reported affected and in function again within 24 hours after the earthquake
The Aegean Sea is an elongated embayment of the Mediterranean Sea located between the Greek and Anatolian peninsulas, i. e. between the mainlands of Greece and Turkey. In the north, it is connected to the Marmara Sea and Black Sea by the Dardanelles, the Aegean Islands are within the sea and some bound it on its southern periphery, including Crete and Rhodes. The sea was known as Archipelago, but in English this words meaning has changed to refer to the Aegean Islands and, generally. In ancient times, there were various explanations for the name Aegean, a possible etymology is a derivation from the Greek word αἶγες – aiges = waves, hence wavy sea, cf. αἰγιαλός, hence meaning sea-shore. The Venetians, who ruled many Greek islands in the High and Late Middle Ages, popularized the name Archipelago, in some South Slavic languages the Aegean is often called White Sea. The Aegean Sea covers about 214,000 square kilometres in area, the seas maximum depth is 3,543 metres, east of Crete. The Aegean Islands are found within its waters, with the following islands delimiting the sea on the south, Antikythera, Kasos, many of the Aegean Islands, or chains of islands, are actually extensions of the mountains on the mainland.
One chain extends across the sea to Chios, another extends across Euboea to Samos, the International Hydrographic Organization defines the limits of the Aegean Sea as follows, On the South. In the Dardanelles. A line joining Kum Kale and Cape Helles, the dense Mediterranean water sinks below the Black Sea inflow to a depth of 23–30 metres, flows through the Dardanelles Strait and into the Sea of Marmara at velocities of 5–15 cm/s. The Black Sea outflow moves westward along the northern Aegean Sea, Aegean Sea Intermediate Water – Aegean Sea Intermediate Water extends from 40–50 m to 200–300 metres with temperatures ranging from 11–18 °C. Aegean Sea Bottom Water – occurring at depths below 500–1000 m with a uniform temperature. The current coastline dates back to about 4000 BC, before that time, at the peak of the last ice age sea levels everywhere were 130 metres lower, and there were large well-watered coastal plains instead of much of the northern Aegean. When they were first occupied, the islands including Milos with its important obsidian production were probably still connected to the mainland.
The present coastal arrangement appeared c.7000 BC, with post-ice age sea levels continuing to rise for another 3,000 years after that, the subsequent Bronze Age civilizations of Greece and the Aegean Sea have given rise to the general term Aegean civilization. In ancient times, the sea was the birthplace of two ancient civilizations – the Minoans of Crete and the Mycenean Civilization of the Peloponnese, arose the city-states of Athens and Sparta among many others that constituted the Athenian Empire and Hellenic Civilization. Plato described the Greeks living round the Aegean like frogs around a pond, the Aegean Sea was invaded by the Persians and the Romans, and inhabited by the Byzantine Empire, the Bulgarians, the Venetians, the Genoese, the Seljuq Turks, and the Ottoman Empire. The Aegean was the site of the democracies, and its seaways were the means of contact among several diverse civilizations of the Eastern Mediterranean. Many of the islands in the Aegean have safe harbours and bays, in ancient times, navigation through the sea was easier than travelling across the rough terrain of the Greek mainland
Zagros fold and thrust belt
The Zagros fold and thrust belt is an approximately 1, 800-kilometre long zone of deformed crustal rocks, formed in the foreland of the collision between the Arabian Plate and the Eurasian Plate. It is host to one of the worlds largest petroleum provinces, containing about 49% of the hydrocarbon reserves in fold and thrust belts. The degree of obliqueness reduces southwards along the Zagros, with the collision becoming near orthogonal within the Fars domain, the Zagros FTB extends for about 1800 km from the Bitlis suture zone in the northwest to the boundary with the Makran Trench east of the Strait of Hormuz. The belt varies in width with two main salients in the Lorestan and Fars domains and two main embayments at Kirkuk and Dezful, the distribution of the Hormuz salt is controlled by the extent of late Proterozoic basins. The belt is divided into zones from northeast to southwest. The next zone between the High Zagros Fault and the Main Frontal Fault is known as the Simply Folded Zone, characterised by many elongate folds and very few surface faults.
The zone to the southwest of the Main Frontal Fault is considered to be part of the foreland basin although active structures are observed as far out as the Zagros Frontal Fault. In northern Iraq the Zagros FTB is relatively narrow and this area is referred to as the Kirkuk embayment and this part of the fold belt lacks an effective basal Hormuz salt detachment. The Lorestan domain forms the northerly of the two main salients in the Zagros FTB, the structural style of the simply folded zone is interpreted here to be dominated by detachment folding with some degree of disharmonic folding. The disharmony occurs between a deeper layer bounded by the basal and Dashtak Formation décollement levels and shallower one between the Dashtak décollement and the surface, there is evidence of a thick-skinned element to the deformation. During the Miocene this area became a depocentre in which locally thick Gachsaran salt was deposited, the presence of locally thick Gachsaran salt has caused disharmonic folding between the sequences above and below that layer.
The Fars salient forms the end of the Zagros FTB. It forms the southeastern boundary to the Dezful embayment. In detail the Kazerun fault system consist of a series of en echelon segments within a fan shaped zone. From the focal depth of earthquakes along this zone it is clear that these faults are developed within the basement rocks. The gulf is being infilled by the southeastward prograding delta of the river system. Northeastward subduction of Tethyan oceanic crust continued along this portion of the Eurasian Plate until continental crust of the Arabian Plate became involved in this convergent boundary. Deformation within the Zagros FTB has continued from until the present day and these deformation pulses were associated with southwestward migration of the active deformation front
Common Era or Current Era is a year-numbering system for the Julian and Gregorian calendars that refers to the years since the start of this era, i. e. since AD1. The preceding era is referred to as before the Common or Current Era, the Current Era notation system can be used as a secular alternative to the Dionysian era system, which distinguishes eras as AD and BC. The two notation systems are equivalent, thus 2017 CE corresponds to AD2017 and 400 BCE corresponds to 400 BC. The year-numbering system for the Gregorian calendar is the most widespread civil calendar used in the world today. For decades, it has been the standard, recognized by international institutions such as the United Nations. The expression has been traced back to Latin usage to 1615, as vulgaris aerae, the term Common Era can be found in English as early as 1708, and became more widely used in the mid-19th century by Jewish academics. He attempted to number years from a reference date, an event he referred to as the Incarnation of Jesus.
Dionysius labeled the column of the table in which he introduced the new era as Anni Domini Nostri Jesu Christi, numbering years in this manner became more widespread in Europe with its usage by Bede in England in 731. Bede introduced the practice of dating years before what he supposed was the year of birth of Jesus, in 1422, Portugal became the last Western European country to switch to the system begun by Dionysius. The first use of the Latin term vulgaris aerae discovered so far was in a 1615 book by Johannes Kepler, Kepler uses it again in a 1616 table of ephemerides, and again in 1617. A1635 English edition of that book has the title page in English – so far, a 1701 book edited by John LeClerc includes Before Christ according to the Vulgar Æra,6. A1716 book in English by Dean Humphrey Prideaux says, before the beginning of the vulgar æra, a 1796 book uses the term vulgar era of the nativity. The first so-far-discovered usage of Christian Era is as the Latin phrase aerae christianae on the page of a 1584 theology book.
In 1649, the Latin phrase æræ Christianæ appeared in the title of an English almanac, a 1652 ephemeris is the first instance so-far-found for English usage of Christian Era. The English phrase common Era appears at least as early as 1708, a 1759 history book uses common æra in a generic sense, to refer to the common era of the Jews. The first-so-far found usage of the phrase before the era is in a 1770 work that uses common era and vulgar era as synonyms. The 1797 edition of the Encyclopædia Britannica uses the terms vulgar era, the Catholic Encyclopedia in at least one article reports all three terms being commonly understood by the early 20th century. Thus, the era of the Jews, the common era of the Mahometans, common era of the world
Turkey, officially the Republic of Turkey, is a transcontinental country in Eurasia, mainly in Anatolia in Western Asia, with a smaller portion on the Balkan peninsula in Southeast Europe. Turkey is a democratic, unitary, parliamentary republic with a cultural heritage. The country is encircled by seas on three sides, the Aegean Sea is to the west, the Black Sea to the north, and the Mediterranean Sea to the south. The Bosphorus, the Sea of Marmara, and the Dardanelles, Ankara is the capital while Istanbul is the countrys largest city and main cultural and commercial centre. Approximately 70-80% of the countrys citizens identify themselves as ethnic Turks, other ethnic groups include legally recognised and unrecognised minorities. Kurds are the largest ethnic minority group, making up approximately 20% of the population, the area of Turkey has been inhabited since the Paleolithic by various ancient Anatolian civilisations, as well as Assyrians, Thracians, Phrygians and Armenians. After Alexander the Greats conquest, the area was Hellenized, a process continued under the Roman Empire.
The Seljuk Sultanate of Rûm ruled Anatolia until the Mongol invasion in 1243, the empire reached the peak of its power in the 16th century, especially during the reign of Suleiman the Magnificent. During the war, the Ottoman government committed genocides against its Armenian, following the war, the conglomeration of territories and peoples that formerly comprised the Ottoman Empire was partitioned into several new states. Turkey is a member of the UN, an early member of NATO. Turkeys growing economy and diplomatic initiatives have led to its recognition as a regional power while her location has given it geopolitical, the name of Turkey is based on the ethnonym Türk. The first recorded use of the term Türk or Türük as an autonym is contained in the Old Turkic inscriptions of the Göktürks of Central Asia, the English name Turkey first appeared in the late 14th century and is derived from Medieval Latin Turchia. Similarly, the medieval Khazar Empire, a Turkic state on the shores of the Black.
The medieval Arabs referred to the Mamluk Sultanate as al-Dawla al-Turkiyya, the Ottoman Empire was sometimes referred to as Turkey or the Turkish Empire among its European contemporaries. The Anatolian peninsula, comprising most of modern Turkey, is one of the oldest permanently settled regions in the world, various ancient Anatolian populations have lived in Anatolia, from at least the Neolithic period until the Hellenistic period. Many of these peoples spoke the Anatolian languages, a branch of the larger Indo-European language family, in fact, given the antiquity of the Indo-European Hittite and Luwian languages, some scholars have proposed Anatolia as the hypothetical centre from which the Indo-European languages radiated. The European part of Turkey, called Eastern Thrace, has been inhabited since at least forty years ago. It is the largest and best-preserved Neolithic site found to date, the settlement of Troy started in the Neolithic Age and continued into the Iron Age