August 31, 1926 Earthquake: Fayal Island, Azores

Name: August 31, 1926 Earthquake: Fayal Island, Azores
Start: 1926-08-31
Location: Fayal Island, Azores

August 31, 1926 · M5.8 · 9 deaths

A magnitude 5.8 earthquake struck Fayal Island, Azores on August 31, 1926 at 10:40:09 UTC, 10 km below the surface. It killed 9 people.

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: August 31, 1926
Time: 10:40:09 UTC
Place: Fayal Island, Azores
Magnitude: 5.8 (Mw)
Magnitude scales: Mw 5.8 · Ms 5.6
Focal depth: 10 km (6 mi)
Intensity: X, extreme shaking, on the Modified Mercalli scale
Tsunami: Yes: the tsunami it caused
Epicenter: 37.973° N, 28.590° W
Country: Azores
Region: Atlantic Ocean
USGS record: The USGS’s page for this earthquake

Mw: moment magnitude, based on the slip on the fault and the area that slipped. Ms: surface-wave magnitude. NCEI’s headline magnitude is the best of these for the earthquake.

The toll

Deaths: 9
Injuries: 200
Damage: Moderate (about $1 to $5 million)
Houses destroyed: Many (101 to 1,000)
Houses damaged: Few (about 1 to 50)

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.

From Wikipedia

The 1926 Horta earthquake (Portuguese: Sismo da Horta de 1926/Terramoto da Horta), occurred at 8:42 a.m. (local time) on 31 August. It caused the destruction of many of the buildings located in the city of Horta, the central group of the Portuguese autonomous region of the Azores, resulting in the death of nine and the partial or complete destruction of 4,138 buildings.

Text from Wikipedia, “1926 Horta earthquake”, licensed CC BY-SA 4.0. Quoted as written; the full article has the rest.

What the record says

NCEI’s account, from the sources it cites.

Reference #130 lists earthquake on Aug 31, 1926, 10:40:08 UTC, 38.5 N, 28 W.

Reference #3933 lists a destructive earthquake on August 31, 1926. All but ten of the thirteen villages on Fayal Island were damaged. One village of 1,200 population had only twenty houses standing. On September 2nd the civil governor reported that the known deaths at that time were nine and the number of wounded about 200. The main shock was followed by many aftershocks of lesser intensity.

On August 31, 1926, Faial Island was struck by an earthquake of Ms 5.6 and MMI X, and the epicentre was located in the channel between Faial and Pico Islands. Horta city, as well as Flamengos and Praia do Almoxarife, suffered heavy damage that caused 9 deaths. (reference #12490)

37.973, -28.59. Mw 5.8. 10 depth. (reference # 10476)

It should be noted that the earthquake of August 31, 1926, which destroyed a large part of the city of Horta and several villages in Faial, did not produce any trace of tidal waves. (reference #1919)

Concerning the event in 1926, Agostinho (1927) described a ", .. damaging earthquake on Fayal and Pico islands .... The people aboard the ships in the harbor [Horta--Faial Island] felt violently the earthquake, but only small waves nearly two feet high were formed which vanished in a two minutes. No tsunami was remarked in any other of the islands". This account suggests that the violence of the seismic shock had no direct correspondence in tsunami development. (reference #5046)

On the morning of the 31st. August 1926 the inhabitants of some of the Azores islands were frightened by a su1den motion of the soil which was most violent on the islands of Faial and Pico where with in five or six seconds the shock caused much damage, a few hundred buildings having been ruined in Horta and suburbs, minor destructions occurring in some distant places of Pico. (reference #12492)

Nine deaths, >200 injured. Severe damage in the eastern part of Faial and major damage in the rest of the island and in Pico. (reference #13058)

Note: reference #41 lists 22 August

Sources NCEI cites

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

#130 Gutenberg, B. and C.F. Richter (1965). Seismicity of the earth and associated phenomena. Princeton University Press, 1954 (second edition); Hafner Publishing Company, New York and London (facsimile edition), 310 p.
#3933 Seismological Society of America (1926). Seismological Notes, 1926. Bulletin of the Seismological Society of America, Vol. 16, no. 3, p. 197-202.
#5046 Andrade, C., P. Borges, and M.C. Freitas (2006). Historical tsunami in the Azores archipelago (Portugal). Journal of volcanology and geothermal research, vol. 156, no. 1-2, p. 172-185.
#1919 Agostinho, Jose (1935). Notice Sur Quelques Raz de Maree aux Azores. Annales de la Commission Pour l'Etude des Raz de Maree, Union Geodesique et Geophysique Internationale, no. 5, p. 21-25.
#10476 International Seismological Centre (2013). Final Scientific Report of the ISC-GEM Instrumental Earthquake Catalogue, ISC-GEM Global Instrumental earthquake Catalogue (1900-2021). Versions 1-12 downloaded beginning 18 March 2013. DOI: 10.31905/D808B825
#12490 Caldeira, B., Fontiela, J., Borges, J. F., & Bezzeghoud, M. (2017). Grandes terremotos en Azores. Física De La Tierra, 29, 29-45. DOI:10.5209/FITE.57601
#13058 Gaspar, J.L., Queiroz, G., Ferreira, T., Medeiros, A.R., Goulart, C. and Medeiros, J. (2015). Earthquakes and volcanic eruptions in the Azores region: geodynamic implications from major historical events and instrumental seismicity. Geological Society, London, Memoirs, 44(1), 33-49. DOI: 10.1144/M44.4
#41 Berninghausen, William H. (1964). Tsunamis and seismic seiches reported from the eastern Atlantic south of the Bay of Biscay. Bulletin of the Seismological Society of America, vol. 54, no. 1, p. 439-442.
#12492 Agostinho, Jose (1927). The earthquake in the Azores Islands, on the 31st August 1926. Zeitschrift fur Vulkanologie. Pages 268-272.

Other significant earthquakes nearby

Within 200 km, the deadliest first.

Significant earthquakes of 1926 The 1900s Every quake the USGS located in 1926 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 7864. The written accounts and the magnitude estimates are from the USGS earthquake catalog, event iscgem910078, matched to this record by time, place and magnitude.