Map

Where it struck, with the other significant earthquakes within 200 km. Circles are sized and colored by magnitude; select one for its page.

The earthquake

Date: September 25, 478
Place: Marmara Sea, Turkey
Magnitude: 7.2 (Ms)
Intensity: IX, violent shaking, on the Modified Mercalli scale
Tsunami: Yes: the tsunami it caused
Epicenter: 40.800° N, 29.200° E
Country: Turkey
Region: Middle East

The toll

Deaths: Many (about 101 to 1,000)
Damage: Moderate (about $1 to $5 million)
Houses destroyed: Some (about 51 to 100)

Where the literature gives no number, NCEI records a description on a scale of 1 to 4, printed here in its words. Damage is in millions of US dollars of the year of the event, not adjusted for inflation.

What the record says

NCEI’s account, from the sources it cites.

477 or 478, September 25. Constantinople; also at the Hellespont, the Cyclades, Cos, and Cnidos. The shocks lasted for four days. Several cities overwhelmed. (reference #521)

478, September. Vicinity of Istanbul, 41.04 N, 28.98 E, intensity VIII. (reference #1071)

478. 40.3 N, 26.6 E, magnitude 7, intensity IX. According to the excerpt by the Great Chronographer, in the reign of Zeno, a strong earthquake damaged, in the area of Hellespont, most of the cities of Abydos and Lampsacos. In Thrace, it reduced Callipole and Sestos to ruins as well as most of Tenedos. Fifty towers of the Long Walls were also demolished and all those who had fled there were buried in them. In the area around Sestos a sort of mud welled up from the earth and immediately became stiff and solid (Schreiner, 1975; Guidoboni et al., 1994). (reference #4408)

478, September 25. A destructive earthquake in the eastern part of the Sea of Marmara in which Helenopolis (n.Karamtirsel) and Nicomedia(Izmit) were totally destroyed with great loss of life; Constantinople was seriously damaged. (reference #13999)

478 Sep 25. A destructive earthquake in the eastern part of the Sea of Marmara in which Helenopolis (n.Karamtirsel) and Nicomedia (Izmit) were totally destroyed with great loss of life; Constantinople was seriously damaged. The earthquake was followed by a damaging seawave and by aftershocks that continued for 40 days. The emperor fled the capital and took refuge in Chalcedon(Kadikoy). The shock caused damage in Thrace and in Bithynia and the towns destroyed received financial assistance from the imperial treasury for reconstruction. (reference #14000)

A.D 478 Sept 24 Nicomedea. In Bithynia, its capital Nicomedea (lzmit) was totally destroyed for the sixth time with great loss of life; and the same happened to Helenoupolis (now Karamursel). Constantinople was seriously damaged for the second time and much of the destruction was in the district of the Forum of Tauri […] Guidaboni et al. (1994, 302-305) date this event under different years, probably duplicating it or conflating it with the destructive earthquake of AD 484 in the western part of the Sea of Marmara, west of Constantinople, to produce an epicentral area of an abnormally large earthquake with an east-west axis 300 km long. (reference #9116)

Sources NCEI cites

The publications NCEI lists for this record. The numbers match the “reference #” notes in its account above.

#521 Mallet, Robert (1853). Catalogue of Recorded Earthquakes from 1606 B.C. to A.D. 1850, Part I, 1606 B.C. to 1755 A.D. Report of the 22nd Meeting of the British Association for the Advancement of Science held at Hull, Sept., 1853, John Murray, London, p. 1-176.
#1071 Ergin, Kazim, Ugur Guclu, and Zeki Uz (1967). A Catalogue of Earthquakes for Turkey and Surrounding Area (11 A.D. to 1964 A.D.). Istanbul Teknik Universities (Technical University of Istanbul), Istanbul, Turkey.
#1151 Magnaki, D.V. (1688). Historical Information on Earthquakes Having Occurred in the Past Centuries and Present Century, translated by R.M. Davis, Jr. (1945), Antonio Bulifon, Naples, Italy.
#14000 Ambraseys, N. N., and Finkel, C. F. (1991). Long‐term seismicity of Istanbul and of the Marmara Sea region. Terra Nova, 3(5), 527-539.
#13999 Triantafyllou, I., & Papadopoulos, G. A. (2024). New Observational Material about Seismic and Non-Seismic Tsunamis in Greece and Surrounding Areas from 1900 to 2023. GeoHazards, 5(1), 233-254. DOI: 10.3390/geohazards5010012
#9116 Ambraseys, Nicolas (2009). Earthquakes in the Mediterranean and Middle East, A Multidisciplinary Study of Seismicity up to 1900. Cambridge University Press, 947 p.
#11164 Maramai, Alessandra, Beatriz Brizuela, Laura Graziani (2014). The Euro-Mediterranean Tsunami Catalogue. Annals of Geophysics, vol. 57, no. 4. DOI:10.4401/ag-6437
#2427 Papadopoulos, Gerassimos A. (2000). Tsunamis in the East Mediterranean: 1. A Catalogue for the Area of Greece and Adjacent Seas. Institute of Geodynamics, National Observatory of Athens, Greece. Online listing of events through 2000 at: http://www.gein.noa.gr/services/catalogue.htm

Other significant earthquakes nearby

Within 200 km, the deadliest first.

More

Significant earthquakes of 478 The 400s Recent earthquakes near here This day in weather history

Sources

Significant earthquakes from NOAA’s National Centers for Environmental Information, Global Historical Hazard Database, cited as NCEI/WDS, doi:10.7289/V5PN93H7. Public domain. Read 2026-10-01. NCEI earthquake 5888.