Earthquakes in Turkey

North-western Turkey, the county's most densely populated region and industrial heartland, has been struck by two massive earthquakes in less than three months. The first, on 17 August 1999 at 03h02 local, measured 7.4 on the Richter scale and lasted 45 seconds. Izmit, an industrial city of one million in western Turkey, was nearest the epicenter. The official death toll stands at over 18,000, with some 44,000 people injured, nearly 300,000 homes either damaged or collapsed and more than 40,000 business premises similarly affected. On the day of the catastrophe, the Turkish government declared a state of emergency and requested international assistance. The International Federation immediately launched a preliminary appeal, followed by a full appeal for CHF 65 million on 8 September 1999, which remains active.

The disaster was followed by more than 1,300 aftershocks, culminating in the second quake - which shook Düzce and Kaynasli in the north-western province of Bolu, some 100 kilometers (63 miles) to the east of Izmit for 30 seconds - at 18h57 on 12 November 1999 and rated 7.2 on the Richter scale. The jolt was felt both in Istanbul (some 260 km to the west) and Ankara, the nation's capital, 300 km to the east. This situation report concentrates primarily on Red Cross Red Crescent activities in response to this further tragedy in Turkey.

Lately another big earthquake hit the city of Bingöl, Eastern part of Turkey, on 1st of May 2003, killing 176 people (mostly elementary school kids sleeping in their dormitory). The quake came at 03:27 local time lasting for about 17 seconds with a Richter scale of 6.4.

You can click for the latest earthquakes in Turkey based on: Last 24 hours, Last 7 days, Last 30 days, Last 1 year. All links open in a new window. (Provided by Kandilli Observatory of Bogazici University in Istanbul)
Izmit Quake

The Izmit earthquake occurred at 03:02 local time, and was centered at 40.702° N., 29.987° E., which places the epicenter about 11 kilometers, or seven miles, southeast of the city of Izmit. This location indicates that the earthquake occurred on the northernmost strand of the North Anatolian fault system. The earthquake originated at a depth of 17 kilometers, or about 10.5 miles, and caused right-lateral strike-slip movement on the fault. Preliminary field reports confirm this type of motion on the fault, and initial field observations indicate that the earthquake produced at least 60 kilometers (37 miles) of surface rupture and right-lateral offsets as large as 2.7 meters, or almost nine feet.

The earthquake likely occurred on a branch of the North Anatolian fault. Although this is the largest earthquake in the epicenter region in this century, the region of the earthquake has a long history of destructive earthquakes. In 1967, a magnitude 7.1 earthquake caused extensive damage along the North Anatolian fault just east of the current shock.

The 900 km-long North Anatolian fault has many characteristics similar to California's San Andreas fault. These two faults are right-lateral, strike-slip faults having similar lengths and similar long-term rates of movement. If a person is looking across a right-lateral, strike-slip fault during such an earthquake, that person would see the opposite side move to the right.

The North Anatolian fault has produced seven large (MS) 7.0 earthquakes in the period from 1939 through 1999. These earthquakes have ruptured the fault progressively from east to west.

Following are data for the seven large earthquakes that have progressively ruptured the North Anatolian fault:

* 1939 December 26. Magnitude (MS) 7.9 - 8.0. 30,000 deaths. Fault length about 360 km. Initiated the eastward migration of significant earthquakes on the North Anatolian fault. (Termed the 1939 Erzincan earthquake)
* 1942 December 20. Magnitude (MS) 7.1. Fault length about 50 km. (Termed the 1942 Erbaa earthquake)
* 1943 November 26. Magnitude (MS) 7.6. Fault length about 280 km. (Termed the 1943 Tosya earthquake)
* 1944 February 01. Magnitude (MS) 7.3. Fault length about 165 km. (Termed the 1944 Bolu-Gerede earthquake)
* 1957 May 26. Magnitude (MS) about 7. Fault length about 30 km. (Termed the 1957 Abant earthquake)
* 1967 July 22. Magnitude (MS) 7.1. Fault length about 80 km. (Termed the 1967 Mudurnu Valley earthquake)
* 1999 August 17. Magnitude (MS) 7.8; MW 7.4-7.5)

Earthquakes on the North Anatolian fault are caused by the northwards motion of the Arabian plate against the Eurasian plate, squeezing the small Turkish micro plate westwards. Also, compression in this region is due to the northwards motion of the African plate, which produces subduction at the Cyprus and Hellenic arcs. The small Turkish micro plate is bounded on the east by the East Anatolian fault zone (EAFZ), on the north by the North Anatolian fault zone (NAFZ), on the west by a diffuse zone of deformation surrounding the greater Aegean region, and on the south by the Hellenic and Cyprus arcs.

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Düzce Quake

A major earthquake occurred 70 kilometers (45 miles) east of Adapazari or 170 km (105 mi) northwest of Ankara, Turkey at 18:57 local time on November 12th, 1999. A magnitude of 7.2 was computed for this earthquake. This earthquake is located about 110 km (70 miles) east of the magnitude 7.4 main shock on August 17 which killed over 17,000 people and injured another 50,000 around Izmit.

Casualty figures from this last earthquake stand around 845 confirmed dead and around 5,000 injured. The destruction in Bolu and Düzce was widespread, with the total affected population between 150,000 and 180,000. Some assessments indicated that over 18 thousand buildings have been heavily damaged and the Government has estimated the financial cost of the quake at 10 billion US dollars. Industrial facilities in the area have stopped their production due to power shortages and some have suffered major material damage.

During the morning of 17 November (Wednesday) two major aftershocks (4.9 at 02h00 and 5.0 at 10h10) were felt in the provincial capital of Bolu bringing more fear and despair to the population as damaged buildings collapsed. About 24,000 families (80% of the town's population) were homeless. The local crisis centre in Bolu called upon rescue and humanitarian workers in Düzce for help in the middle of the night. The Prime Minister's Crisis Centre (PMCC) urgently sent 10,000 tents for the affected area. Temporary houses were constructed as well.

Besides Bolu and Düzce, the neighboring districts of Kaynasli (70% of the town is considered to be destroyed), Akcakoca, Cumayeri, Gümüsova, Yigilca and Gölkaya have been affected. With night-time temperatures dropping as low as minus two degrees Celsius, the majority of the region's population remained outdoors either because their homes were damaged or for fear of entering buildings even though many appeared structurally sound. Population movements away from the region were also increasing on a daily basis. According to the PMCC, 1,000 prefabricated houses constructed in Düzce for victims of the August earthquake were been immediately reassigned to the locality.

Meanwhile, many hospital facilities in the affected area were damaged and were no longer functioning. Field facilities surrounding the hospital buildings were set up immediately after the quake, with volunteer doctors and nurses coming from nearby towns to treat the injured. Severe cases were referred to hospitals both in Ankara and Istanbul. All schools in Düzce and Kaynasli were closed due to damage and they continued to teach in winterized tents or temporary buildings.

Government crisis centers established in Düzce and Bolu, coordinating search and rescue teams from all over the world. To date, some 12,000 rescue workers came to the area and the total number of people pulled alive from collapsed buildings is estimated at 300. Rescue activities were ceased after some period giving way to the process of debris removal.

For a list of earthquakes that caused more than 10,000 deaths in Turkey, please Click Here.

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The Richter Magnitude Scale

Seismic waves are the vibrations from earthquakes that travel through the Earth; they are recorded on instruments called seismographs. Seismographs record a zigzag trace that shows the varying amplitude of ground oscillations beneath the instrument. Sensitive seismographs, which greatly magnify these ground motions, can detect strong earthquakes from sources anywhere in the world. The time, locations, and magnitude of an earthquake can be determined from the data recorded by seismograph stations.

The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value.

At first, the Richter Scale could be applied only to the records from instruments of identical manufacture. Now, instruments are carefully calibrated with respect to each other. Thus, magnitude can be computed from the record of any calibrated seismograph.

Earthquakes with magnitude of about 2.0 or less are usually call micro earthquakes; they are not commonly felt by people and are generally recorded only on local seismographs. Events with magnitudes of about 4.5 or greater - there are several thousand such shocks annually - are strong enough to be recorded by sensitive seismographs all over the world. Great earthquakes, such as the 1964 Good Friday earthquake in Alaska, have magnitudes of 8.0 or higher. On the average, one earthquake of such size occurs somewhere in the world each year. Although the Richter Scale has no upper limit, the largest known shocks have had magnitudes in the 8.8 to 8.9 range. Recently, another scale called the moment magnitude scale has been devised for more precise study of great earthquakes. The Richter Scale is not used to express damage. An earthquake in a densely populated area which results in many deaths and considerable damage may have the same magnitude as a shock in a remote area that does nothing more than frighten the wildlife. Large-magnitude earthquakes that occur beneath the oceans may not even be felt by humans.