Sep 26,2019 | Marmara Earthquake
A powerful earthquake struck the Turkish metropolis Istanbul on Thursday, according to Turkey's Disaster and Emergency Management Authority (AFAD). AFAD said a 5.8-magnitude earthquake centered in the Sea of Marmara hit at 1.59 p.m. (1059GMT).
"Eight people were slightly injured in the earthquake," President Recep Tayyip Erdogan told reporters at Istanbul’s Ataturk Airport returning from his visit to the UN General Assembly in New York.
"According to AFAD, the magnitude of the earthquake is 5.8 and 28 aftershocks are recorded so far," Erdogan said. Erthquake, off Silivri district, occurred at a depth of 6.99 kilometers (4.3 miles), some 22 km (13.6 mi) from Silivri. The region was also shaken by aftershocks.
A 3.6-magnitude earthquake also shook Istanbul earlier today, at 10.32 a.m. (0732GMT), said AFAD. The epicenter of the quake was the Sea of Marmara.
Date & time: Thursday, 26 September 2019 10:59 UTC
Magnitude: 5.7 | Depth: 11.0 km
Epicenter latitude / longitude: 40.88°N / 28.18°E
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BOGAZICI UNIVERSITY
KANDILLI OBSERVATORY AND EARTHQUAKE RESEARCH INSTITUTE (KOERI)
REGIONAL EARTHQUAKE-TSUNAMI MONITORING CENTER (RETMC)
Mavi Boncuk |
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Between 1939 and 1999 a series of devastating M7+ strike-slip earthquakes propagated westward along the North Anatolian Fault Zone, beginning with the 1939 M7.8 Erzincan earthquake on the eastern end of the North Anatolian Fault system. The 1999 M7.6 Izmit earthquake, located on the westward end of the fault, struck one of Turkey's most densely populated and industrialized urban areas killing, more than 17,000 people.
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The Mediterranean region is seismically active due to the convergence of the Africa Plate with the Eurasia plate. Present day Africa-Eurasia motion ranges from ~4 millimeters per year (mm/yr) in a northwest-southeast direction in the western Mediterranean to ~10 mm/yr (north-south) in the eastern Mediterranean. The Africa-Eurasia plate boundary is complex, and includes extensional and translational zones in addition to the dominant convergent regimes characterized by subduction and continental collision. This convergence began at approximately 50 million years ago and was associated with the closure of the Tethys Sea; the Mediterranean Sea is all that remains of the Tethys. The highest rates of seismicity in the Mediterranean region are found along the Hellenic subduction zone of southern Greece and the North Anatolian Fault Zone of northwestern Turkey, but significant rates of current seismicity and large historical earthquakes have occurred throughout the region spanning the Mediterranean Sea.
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Along the eastern margin of the Mediterranean (near Turkey), the Sea of Marmara is a transition zone between the extensional regime of the back-arc of the Hellenic subduction system to the west, and the strike-slip regime of the North Anatolian Fault to the east. The North Anatolian Fault accommodates much of the right lateral strike-slip motion between the Anatolian Block and Eurasia Plate. Between 1939 and 1999, a sequence of 11 M6.7+ strike-slip earthquakes propagated westwards along the North Anatolian Fault.
The most recent and farthest west of these earthquakes was the 17 August 1999, M7.6 Izmit earthquake, which killed approximately 17,000 people. At the southern edge of the Anatolian Block lies the east-west trending Cyprian Arc, which hosts moderate levels of seismicity. The Cyprian Arc represents the convergent boundary between the Anatolian Block to the north and the Africa Plate to the south. The boundary is thought to join with the East Anatolian Fault zone in eastern Turkey; however no certain geometry or sense of relative motion along the entire boundary is widely accepted.
SOURCE: https://pubs.usgs.gov/of/2010/1083/q/ofr20101083q.pdf
LINK
Earthquake magnitude is a measure of the size of an earthquake at its source. It is a logarithmic measure. At the same distance from the earthquake, the amplitude of the seismic waves from which the magnitude is determined are approximately 10 times as large during a magnitude 5 earthquake as during a magnitude 4 earthquake. The total amount of energy released by the earthquake usually goes up by a larger factor: for many commonly used magnitude types, the total energy of an average earthquake goes up by a factor of approximately 32 for each unit increase in magnitude.
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A powerful earthquake struck the Turkish metropolis Istanbul on Thursday, according to Turkey's Disaster and Emergency Management Authority (AFAD). AFAD said a 5.8-magnitude earthquake centered in the Sea of Marmara hit at 1.59 p.m. (1059GMT).
"Eight people were slightly injured in the earthquake," President Recep Tayyip Erdogan told reporters at Istanbul’s Ataturk Airport returning from his visit to the UN General Assembly in New York.
"According to AFAD, the magnitude of the earthquake is 5.8 and 28 aftershocks are recorded so far," Erdogan said. Erthquake, off Silivri district, occurred at a depth of 6.99 kilometers (4.3 miles), some 22 km (13.6 mi) from Silivri. The region was also shaken by aftershocks.
A 3.6-magnitude earthquake also shook Istanbul earlier today, at 10.32 a.m. (0732GMT), said AFAD. The epicenter of the quake was the Sea of Marmara.
Date & time: Thursday, 26 September 2019 10:59 UTC
Magnitude: 5.7 | Depth: 11.0 km
Epicenter latitude / longitude: 40.88°N / 28.18°E
BOGAZICI UNIVERSITY
KANDILLI OBSERVATORY AND EARTHQUAKE RESEARCH INSTITUTE (KOERI)
REGIONAL EARTHQUAKE-TSUNAMI MONITORING CENTER (RETMC)
Mavi Boncuk |
Between 1939 and 1999 a series of devastating M7+ strike-slip earthquakes propagated westward along the North Anatolian Fault Zone, beginning with the 1939 M7.8 Erzincan earthquake on the eastern end of the North Anatolian Fault system. The 1999 M7.6 Izmit earthquake, located on the westward end of the fault, struck one of Turkey's most densely populated and industrialized urban areas killing, more than 17,000 people.
The Mediterranean region is seismically active due to the convergence of the Africa Plate with the Eurasia plate. Present day Africa-Eurasia motion ranges from ~4 millimeters per year (mm/yr) in a northwest-southeast direction in the western Mediterranean to ~10 mm/yr (north-south) in the eastern Mediterranean. The Africa-Eurasia plate boundary is complex, and includes extensional and translational zones in addition to the dominant convergent regimes characterized by subduction and continental collision. This convergence began at approximately 50 million years ago and was associated with the closure of the Tethys Sea; the Mediterranean Sea is all that remains of the Tethys. The highest rates of seismicity in the Mediterranean region are found along the Hellenic subduction zone of southern Greece and the North Anatolian Fault Zone of northwestern Turkey, but significant rates of current seismicity and large historical earthquakes have occurred throughout the region spanning the Mediterranean Sea.
Along the eastern margin of the Mediterranean (near Turkey), the Sea of Marmara is a transition zone between the extensional regime of the back-arc of the Hellenic subduction system to the west, and the strike-slip regime of the North Anatolian Fault to the east. The North Anatolian Fault accommodates much of the right lateral strike-slip motion between the Anatolian Block and Eurasia Plate. Between 1939 and 1999, a sequence of 11 M6.7+ strike-slip earthquakes propagated westwards along the North Anatolian Fault. The most recent and farthest west of these earthquakes was the 17 August 1999, M7.6 Izmit earthquake, which killed approximately 17,000 people. At the southern edge of the Anatolian Block lies the east-west trending Cyprian Arc, which hosts moderate levels of seismicity. The Cyprian Arc represents the convergent boundary between the Anatolian Block to the north and the Africa Plate to the south. The boundary is thought to join with the East Anatolian Fault zone in eastern Turkey; however no certain geometry or sense of relative motion along the entire boundary is widely accepted.
SOURCE: https://pubs.usgs.gov/of/2010/1083/q/ofr20101083q.pdf
LINK
Earthquake magnitude is a measure of the size of an earthquake at its source. It is a logarithmic measure. At the same distance from the earthquake, the amplitude of the seismic waves from which the magnitude is determined are approximately 10 times as large during a magnitude 5 earthquake as during a magnitude 4 earthquake. The total amount of energy released by the earthquake usually goes up by a larger factor: for many commonly used magnitude types, the total energy of an average earthquake goes up by a factor of approximately 32 for each unit increase in magnitude.
There are various ways that magnitude may be calculated from seismograms. Different methods are effective for different sizes of earthquakes and different distances between the earthquake source and the recording station. The various magnitude types are generally defined so as to yield magnitude values that agree to within a few-tenths of a magnitude-unit for earthquakes in a middle range of recorded-earthquake sizes, but the various magnitude-types may have values that differ by more than a magnitude-unit for very large and very small earthquakes as well as for some specific classes of seismic source. This is because earthquakes are commonly complex events that release energy over a wide range of frequencies and at varying amounts as the faulting or rupture process occurs. The various types of magnitude measure different aspects of the seismic radiation (e.g., low-frequency energy vs. high-frequency energy). The relationship among values of different magnitude types that are assigned to a particular seismic event may enable the seismologist to better understand the processes at the focus of the seismic event. The various magnitude-types are not all available at the same time for a particular earthquake.
