Anatolian tectonic plate, north anatolian fault, historical earthquakes Greece, Attica, Earthquakes, Tsunami, , Hurricanes, Volcanic Eruptions and other Natural and Man-Made Hazards and Disasters - by Dr. George Pararas Carayannis

Tsunami, Earthquakes, Hurricanes, Volcanic Eruptions, Climate Change and other Natural and Man-Made Hazards and Disasters - Disaster Archaeology,

Google

THE EARTHQUAKE OF JANUARY 8, 2006 IN SOUTHERN GREECE

George Pararas-Carayannis

Introduction

On Sunday January 8, 2006, a strong earthquake occurred in the sea along the Hellenic arc, between the islands of Crete and Kythera in Southern Greece. The earthquake, was strongly felt throughout Greece, from Crete in the south to Kastoria in the north. Also, it was felt throughout the Eastern Mediterranean Basin from Italy to Croatia and as far away as Egypt, Cyprus, Israel, Turkey and Jordan.


Damages

The earthquake of 8 January 2006 caused damage to the airport facilities on the Island of Kythera. About 50 old houses on the island eitherwere damaged or collapsed. As with the 1903 magnitude 7.9 earthquake, the village of Mitata suffered the greatest damage on the island. Also, damage occurred at Chania, Crete.

Earthquake Epicenter, Origin Time, Magnitude and Aftershocks

The earthquake's epicenter was at 36.204 N, 23.444 E, in the southwest section of the "Hellenic Arc". It was approximately 90 km (55 miles) NW of Chania, Crete, 150 km (95 miles) SE of Kalamata, 185 km (115 miles) WNW of Iraklion, Crete, and about 200 km (125 miles) of Athens. The epicenter of the earthquake is believed to be very close to that of the 365 A.D. earthquake - which was the largest earthquake to ever occur in Greece, and had an estimated Richter magnitude of 8.3

Epicenter of the January 8, 2006 earthquake (National Observatory of Athens, Geodynamic Institute , Athens, Greece (NOA)

According to the Preliminary Earthquake Report of the U.S. Geological Survey's National Earthquake Information Center, the quake's Moment Magnitude (Mw) was 6.8. The Athens Geodynamic Institute reported the Moment Magnitude to be 6.9. The origin time was 11:34:53 UTC (1:34:53 PM , Sunday, January 8, 2006 Greek local time). The focal Depth was initially reported to be 48.4 km (30.1 miles), byt the Geodynamic Institute in Athens revised it to 69 km. Numerous aftershocks struck the area following the main earthquake, some as large as magnitude 5.

Sattelite Photo of Peloponissos and the Island of Kythira at the lower right

Aftershocks in the days following the Earthaquake of January 8, 2006. Size of circles indicates the magnitudes of the aftershochks Stongest aftershocks ooccurred on January 8, 2006 (Modified graphic of the European-Mediterranean Seismological Center)

Tectonic Setting - The Hellenic Arc

Formation of the Hellenic Arc - Three major tectonic plates, the Eurasia, Africa, and Arabia plates meet in the eastern Mediterranean and have formed broad boundaries of seismic and volcanic activity. Greece is located near the boundary of the two great lithospheric plates of Africa and Eurasia. The interaction of the great plates results in numerous earthquakes.

The northern segment of the African plate south of the Adriatic Sea comprises of the Eastern Mediterranean oceanic lithosphere. Collision of the lighter-density oceanic eastern Mediterranean with the higher density continental lithosphere of Eurasia - part of which is the Aegean Sea subplate - has formed an arcuate zone of subduction along their boundary. Therefore, subduction of the Africa plate beneath the Aegean Sea plate has formed the Hellenic Arc, which is a zone of active seismicity which extends along Western Peloponnesus and continues along the islands of Kythera and Antikythera to south of Crete, then to Rhodes and Western Turkey.

Modified After Nafi Toksoz of MIT/ERL

Paralleling the Hellenic Arc is the volcanic Arc which includes the volcanoes of Methana, Milos, Santorin and Nisyros. The plate movements and the associated earthquakes have also formed a series of sea basins extending from Kefalonia to Rodes.

The seismotectonics of Greece's southern region are controlled primarily by the interaction of the Africa tectonic plate with the small Aegean Sea plate along the Hellenic Arc. Most of the earthquakes near the Arc are shallow but further away from it the focal depths are intermediate.

The rate of subduction along the Hellenic Arc is estimated to be 35- 40 mm/year. Most of the earthquakes that occur west and northwest of Crete near the Hellenic arc plate boundary are relatively shallow, with focal depths of less than 50 km.

Differences in the rates of extension of two adjacent major segments of the external Western Hellenic Arc have created the Kythera Strait - a zone of complex, active, transform-extensional deformation and rotation (Lyberis et al.,1982). Oblique, en echelon, normal faulting indicates a pattern of dextral deformation.

The seismic slip along the Kythira Strait is estimated at about 30 mm/yr (Papadopoulos 1989). With such high rate of seismic slip, the Kythera Strait can generate large shallow and intermediate-depth earthquakes - with Richer magnitudes of up to about 8.0 (Papazachos, 1996 ; Papazachos and Papazachou, 1997) . The earthquake of January 8, 2006 occurred along the Kythera Strait deformation zone and its focal depth of 48.4 km was close to the upper limit for earthquakes in this region.

TYPE OF CRUSTAL DISPLACEMENTS AND RUPTURE ASSOCIATED WITH THE EARTHQUAKE OF JANUARY 8, 2006

Most of the earthquakes in this particular region of the Greek Arc involve reverse as well as strike slip motion and some normal faulting motion. The earthquake of January 8, 2006 involved inverse but mostly lateral movement. The African plate is estimated to have moved in a northern direction by about 90 centimeters in relation to the Aegean Sea plate and to have subducted beneath it. The long duration of the shaking (about 30 seconds), indicates a long rupture (perhaps as 50-60 km or even more).

( Seismicity of Greece - Epicenters of the September 7, 1999 earthquake - Modified USGS map)

The energy of the 8 January 2006 earthquake was 33 times greater than that of the September 7, 1999 earthquake in Central Greece which had a Richter magnitude of 5.9.

HISTORICAL EARTHQUAKES ALONG THE WESTERN HELLENIC ARC AND IN THE STRAIT OF KYTHIRA

The historical record indicates that the southwestern region of Greece is vulnerable because of the high seismic potential of the southwestern segments of the Hellenic Arc. The Kythera Strait zone of deformation has a particularly high seismic potential. Many large earthquakes have occurred in this region in the past. Unfortunately, there is no adequate documentation for events prior to 1750. Some of the earliest large earthquakes occurred in 66 A.D., in 365 AD (near Crete), in 800 A.D., and in 1303 AD.

There is better documentation for the more recent events. At least ten strong earthquakes were documented for the period from 1750 to 1910 with magnitudess Ms+6.0 or more. The mean recurrence was estimated to be of about 18±18 years (Papadopoulos & Vasssilopoulou 2001).

Best known of the more recent events is the destructive Kythera earthquake of 11 August 1903. After 1910, when systematic instrumental seismic recording begun in Greece, the documentation of earthquakes in the region improved.

Since 1910, the Institute of Geodynamics, National Observatory of Athens, recorded three strong earthquakes in the Kythera Strait - on March 18, 1937 (Ms = 6.0), on June 21, 1984 (Ms = 6.2), and November 21, 1992 (Ms = 6.5).

Recently, a historical data bank of earthquakes in the region was compiled from various sources in support of an experimental regional tsunami warning system for the Kythera Strait (Papadopoulos & Vasssilopoulou 2001). The Catalog of historical earthquakes for the region of Kythera Island that has been compiled shows about 55 events. Some of these earthquakes generated tsunamis. Most noteworthy of the earthquakes that were destructive at Kythira are the following:

Earthquake of 5 June 1750 - An earthquake on June 7, 1750 killed about 2,000 people at Kythera and caused considerable destruction on the island.

Earthquake of 11 August 1903 - A major earthquake (Ms about 7.9) on August 11, 1903 - with epicenter at sea south of Kythera - devastated the island. The shock was felt throughout Greece and as far away north as Trieste, as well as in South Italy, Egypt and Turkey. The quake killed four people, injured another ten and inflicted heavy damage on the island pf Kythera.

Hardest hit on the island was the village of Mitata which is located on ground consisting of alluvial deposits. A church and a school building collapsed and about 80 houses were damaged or destroyed. Also destroyed was the villages of Variadika and Kapsali. Many houses were destroyed in Avlemona (Papazachos and Papazachou 1997). Extensive damage occurred in Peloponnisos (Leonidio Kynourgia, Korinth), in the island of Santorin, and as far away as Southern Italy and Sicely.

FUTURE EARTHQUAKES IN THE SOUTHWESTERN REGION OF GREECE

Seismic activity in the area can be expected in the form of diminishing aftershocks following the major earthquake of 8 January 2006. Usually, when a strong earthquake occurs, most of the stress is relieved and another large earthquake may not occur for many years in the same region. However, this is not always the case, as dynamic stress loading can accelerate the occurrence of another earthquake along an adjacent seismic zone.

As a result of such stress load transfer, another earthquake in an adjacent fault along the southwestern segments of the Hellenic Arc is possible. However, such an earthquake may not occur for months or even years from now. When such an event will occur again, is not known with any degree of certainty. The only thing known with certainty is that it will occur in this or an adjacent region. A stress transfer analysis based on the study of rupture parameters and the geometric distribution of aftershocks, could help establish the space-time evolution of stresses and help determine both static and dynamic modifications that could possibly trigger future events along the known faults in this southwestern region of Greece.

WHY NO TSUNAMI WAS GENERATED BY THE EARTHQUAKE OF 8 JANUARY 2006?

The strait of Kythera is an area of high seismicity where major tsunamigenic earthquakes have generated destructive tsunamis in the past and will do so again in the future. Whether a major earthquake will generate a tsunami depends on its magnitude and energy release, its focal depth and location of the source area, and the type and extent of crustal displacements on the sea floor. Depending on the type of faulting motion, net crustal displacements and water depth, tsunami generation is possible in this area.

Most of the earthquakes in the Kythera Strait involve reverse as well as strike slip motion and some normal faulting motion. The earthquake of January 8, 2006 occurred east of the subduction boundary and involved mostly lateral strike slip movement. Also, it had a greater focal depth (48.4 km, revised later to 69 km) and occurred in a region where the water was quite deep. All these were reasons - particularly the earthquake's focal depth - why no tsunami was not generated. If indeed a small tsunami was generated - there may be some evidence of it. It is possible that tide gauges that may have been operating at some port facility may have recorded a small sea oscillation.

TSUNAMIS IN THE SOUTHWESTERN REGION OF GREECE

The Kythera Strait is an area of high seismicity in Greece where strong earthquakes have occurred with frequency. Some of these earthquakes generated tsunamis. The historic record documents that earthquakes generated at least five destructive tsunamis since the 1st Century. These five do not include a tsunami from the questionable earthquake of 800 AD or the tsunami (s) associated with the eruptions, explosion and collapse of the volcano of Santorin around 1625 B.C.

As already mentioned, the Geodynamic Institute of Athens has included in its historical earthquake data bank tsunami data from various sources in support of an experimental regional tsunami warning system for the Kythera Strait. Based on the limited available historic data, the mean recurrence frequency of tsunamis in the Kythira strait has been estimated to be 130 years (Papadopoulos & Vasssilopoulou 2001). Additional data on historical tsunamis in the Eastern Mediterranean, the Aegean and the Ionian Seas can be found at this web site under the title "Tsunami Potential of Greece"

Tsunamis that Have Affected the Island of Kythera.

A cursory field survey of Kythera Island was undertaken by the author in October 2005 to examine suspected past collapses of coastal areas and possible evidence of palaiotsunami inundation. The geologic formations and coastal geomorphology indicated that large scale landslides and mass edifice coastal collapses have indeed occurred on the island. Such coastal failures and subsidence appear to have occurred in the region of Palaiopolis and elsewhere on the island - where Minoan or Mycenean settlements existed. There is also evidence of tsunami inundation from past events - probably from the Minoan and subsequent tsunamis - in Agia Pelagia, Palaiopolis, Kastri and Avlemonas, on the east side of the island and at Kapsali on the southern coast.

No volcanic ash from the great eruption of Santorin was found - as expected. However the survey was preliminary and will be continued in the future on both Kythera and Antikythera island to the south. It is very possible that the prevailing winds at the time of the great Minoan eruption of Santorin carried the vocanic ash mostly in a southern rather than a westerly direction.

Depositional patterns on the Island of Santorin (at Akrotiri) - also examined in September 2005 - indicate that the prevailing winds were from the north, which would indicate that the great paroxysmal eruption and tsunami occurred during the summer months.

The following listing of tsunamis that have affected the island of Kythera, Crete and islands of the Cyclades is based on cursory review of existing literature including the thorough study by the Athens Geodynamic Institute (Papadopoulos and Vassilopoulou, 2001). Unfortunately, even though the literature is extensive, no specific details are provided for most of the known tsunamis that have struck the island.

1625 B.C. - The paroxysmal eruptions and explosion of the Santorin volcano around 1625 B.C. generated a large tsunami which undboutedly reached and caused damage to any Minoan or Mycenean settlements on the east coast of the island of Kythira.

66 A.D. - An earthquake in the Kythera Strait generated a tsunami. The island of Kythera was impacted by the combined effects of the earthquake and the tsunami. No details available.

365 A.D. - The earthquake of 365 A.D. in the Kythera Strait is believed to be the strongest historical earthquake that ever occurred in Greece. Its Richter magnitude is estimated to have been about 8.3. and it impacted the greatest part of the Roman empire. Knossos on Crete was destroyed by the earthquake. There was heavy damage from the earthquake at Gortyna and in Patra and throughout the provinces of Ahaia and Viotia on Peloponissos. The destructive tsunami that was generated struck the islands of Kythera, Crete and Cyclades, Peloponissos and many other coastal areas in the Aegean and Ionian Seas and as far away as Epirus, Sicely and elsewhere in the Metiterranean. The tsunami struck and destroyed at least ten coastal cities on Crete.

Skandia, the ancient harbour of Kythera on the east side of the island , was destroyed by the combined effects of the earthquake and the tsunami. No specific information for this event is available in the historic records.

800 A.D. - The occurrence of another large tsunamigenic earthquake in the year 800 A.D. remains questionable. It may have been confused with an earthquake which occurred in 796. It must be assumed that if indeed the earthquake occurred - whether in 796 or in 800 A.D. - it must have generated a destructive tsunami that struck Ancient Skandia and other coastal settlements on the island of Kythera.

Cliffs at Palaiapolis, on the East Coast of Kythera Island, near ancient settlements, where massive coastal edifice failures have occurred and tsunamis have struck (photo: G Pararas-Carayannis, Oct. 2005)

1629 or 1630 - An earthquake in the Kythera Strait generated a tsunami. Serious damage and some deaths occurred at Heraklion and elsewhere in Crete. No details are available on whether the damage and the deaths on Crete were caused by the tsunami or what the effects of the earthquake and of the tsunami were on Kythira Island.

1866 - A strong earthquake in the Kythera Strait on 6 February 1866 generated a tsunami. There was significant earthquake damage to Kythira The tsunami reached a runup height of 8 meters at Avlemonas on the eastern side of Kythera island and caused damage to houses (Fuchs 1886, Leonhard 1899).

1867 - A strong earthquake on 20 September 1867 with epicenter near Mani in south Peloponisos generated a strong tsunami. There was heavy damage in Peloponisos and slight damage at Kythira. The tsunami affected coastal areas at Kythira, Crete and Cyclades and reached islands in the Ionian and south Adriatic seas (Papazachos and Papazachou, 1997).

1886 - A large, destructive, earthquake on 2 7 August 1886 in SW Peloponnisos generated a local tsunami(Galanopoulos, 1941 and Papazachos and Papazachou 1997). The quake was slightly felt in Kythera (Galanopoulos, 1953). No details about the tsunami are available.

9 July 1956 - The best documented tsunamigenic earthquake in the Aegean Sea is the one that occurred on 9 July 1956 near the southwest coast of the island of Amorgos, killing 53 people, injuring 100, and destroying hundreds of houses. The waves were particularly high on the south coast of Amorgos and on the north coast of the island of Astypalaea. At these two places the reported heights of the tsunami were 25 and 20 meters, respectively. The tsunami must have struck the island of Kythera but no details are available.

 

References (cited and uncited)

Angelier J., Lyberis N., Le Pichon X., Barrier E. and Huchon P. (1982). The tectonic development of the Hellenic arc and the Sea of Crete : a synthesis. Tectonophysics, 86, 159-196.

Angelier J. (1979). Recent quaternary tectonics in the Hellenic Arc: examples of geological observations on land. Tectonophysics, 52, 267-275.

Fuchs, C. W., 1886. Statistik der Erdbeben von 1865 his 1885, Silzungsberichte der Mathemat. Naturwissenschaftlirhen Classe der Kaiserlirhen Akademie der Wissenschaften. 92, Wien.

Lyberis, N. J. Angelier, E. Barrier, and S. Lallemant, 1982: Active deformation of a segment of arc: the strait of Kythira, Hellenic arc, Greece, J. Structural Geology, 4, 299-311.


Galanopoulos, A., 1953.
Katalog der Erdbeben in Griechenland fur die Zeit von 1879 bis 1892. Ann. Geol. Pays Helleniques, 5, Athens.

Leonhard, R., 1899. Die Insel Kythera - Eine geographische Monographie, Library of Historical Studies, 182, Athens, 47pp.

Pararas-Carayannis, G. 2001. The Tsunami Potentila of Greece, http://drgeorgepc/TsunamiPotentialGreece.html

Papadopoulos, G.A., 1989. Seismic and volcanic activities and aseismic movements as plate motion components in the Aegean area, Tectonophysics, 167, 31-39.

Papadopoulos G.A. and A Vassilopoulou, 2001 HISTORICAL AND ARCHAEOLOGICAL EVIDENCE OF EARTHQUAKES AND TSUNAMIS FELT IN THE KYTHIRA STRAIT, GREECE Institute of Geodynamics, National Observatory ofAthens, 11810 Athens Greece

Papazachos, B.C., 1996. Large seismic faults in the Hellenic arc, Annali di Geofisica, 39, 891-903.

Papazachos, B. C. and K. Papazachou, 1997. The Earthquakes of Greece, Ziti Editions, Thessaloniki, 304pp.

Links to other Web Sites for More Information

Tsunami Potential in Greece.html

National Observatory of Athens, Geodynamic Institute , Athens, Greece (NOA)

Department of Geophysics, University of Thessaloniki Thessaloniki, Greece

European-Mediterranean Seismological Centre

Kandilli Observatory and Earthquake Research Institute Istanbul, Turkey

Return to

Links to other Pages

The Big One - The Next Great California Earthquake (A new edition of the book)

Now available from Amazon, Barnes and Noble and other major bookstores. A signed by the author copy can be also ordered by contacting directly by email Aston Forbes Press.

Other Miscellaneous Non-technical Writings

(©) Copyright 1963-2007 George Pararas-Carayannis / all rights reserved / Information on this site is for viewing and personal information only - protected by copyright. Any unauthorized use or reproduction of material from this site without written permission is prohibited.
Web Site Created By Dr. George Pararas-Carayannis / Copyright © 2000. All Rights Reserved

Template Courtesy of "Budget Office & Facility Supply"

 THANK YOU FOR VISITING