Earthquake off Crete 2009

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The earthquake off Crete in 2009 occurred on July 1 at 12:30:09 p.m. local time. The quake reached a moment magnitude of M w = 6.4 and a sky wave magnitude of M B = 6.6. Its epicenter was off the south coast of Crete .

epicenter

Map with the location of the epicenter and the course of the Mercalli intensities

The coordinates of the epicenter are given as 34 ° 14'25``N and 25 ° 28'40''E. This corresponds to a position in the Libyan Sea around 100 kilometers south of Ierapetra . The depth of the quake was 19 kilometers. An intensity of VII was determined at the epicenter, but only V on the Cretan mainland.

A recalculation of the seismological data by Moshou and colleagues (2010) produced improved results. The intensity of the quake was downgraded to m w = 6.2. The coordinates of the epicenter changed to 33 ° 55'12 '' and 25 ° 28'12 '' and are therefore around 35 kilometers further south. The focal depth could now be set at H = 22 ± 3 kilometers. The compression waves had arrived at a speed of v p = 6600 meters / second. The focal area was determined by an inversion of the moment tensor : its stroke direction runs more or less east-west with ϕ = 92 ± 5 ° and its angle of incidence is δ = 67 ± 3 ° to the south. The initial movement at the focal surface was also determined; it is more or less identical to the maximum angle of incidence (λ = 90 °) and directed to the north. It is therefore a matter of a postponement that was slightly offset (λ = 80 ± 5 °) to the west. Since the focus is in the area of ​​the back thrust zone on the northern edge of the Mediterranean Ridge, this result is to be expected.

Effects

The main quake itself was preceded by foreshocks over three days, which had even triggered a small tsunami the day before . After the main quake, several swarms of aftershocks set in, the depth of which could be determined to be 15 to 25 kilometers and which were also postponements. The main quake was still felt in Cairo , but not in Athens . Very clear vibrations could be perceived in Lasithi and in Heraklion on Crete. The property damage from the quake was only minor and there were no human lives to be mourned.

Geodynamics

The quake occurred at the plate boundary between the Aegean Plate and the African Plate , with the latter moving north and being crossed by the Aegean Plate advancing to the southwest. In front of the Aegean Plate is the Hellenic Deep Sea Trench and the Mediterranean Ridge, under which the African Plate is subducted .

See also

Individual evidence

  1. ↑ Moshou, A. et al.: Moment tensor determination using a new waveform inversion technique . In: Bulletin of the Geological Society of Greece . 2010.
  2. ↑ Meier, T. et al .: A Model for the Hellenic Subduction Zone in the area of ​​Crete based on seismological investigations . Ed .: Taymaz, Tuncay and Dilek, Yildirim The Geodynamics of the Aegean and Anatolia. Geological Society, London, 2007, ISBN 978-1-86239-239-7 , pp. 183-200 .