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1918 San Fermín earthquake

Coordinates: 18°48′N 67°13′W / 18.8°N 67.22°W / 18.8; -67.22
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1918 San Fermín earthquake
1918 San Fermín earthquake is located in Puerto Rico
San Juan
San Juan
1918 San Fermín earthquake
UTC time1918-10-11 14:14:42
ISC event913306
Local dateOctober 11, 1918 (1918-10-11)
Local time10:14:42 [1]
Magnitude7.1 Mw[1]
Depth15 km (9.3 mi) [1]
Epicenter18°48′N 67°13′W / 18.8°N 67.22°W / 18.8; -67.22 [1]
Areas affectedPuerto Rico
Total damage$4–29 million USD [2][3]
Max. intensityMMI IX (Violent) [3]
Casualties76–118 [2][4]

The 1918 San Fermín earthquake,[5][6] also known as the Puerto Rico earthquake of 1918, struck the island of Puerto Rico at 10:14:42 local time on October 11. The earthquake measured 7.1 on the moment magnitude scale and IX (Violent) on the Mercalli intensity scale. The mainshock epicenter occurred off the northwestern coast of the island, somewhere along the Puerto Rico Trench.

The earthquake triggered a tsunami that swept the west coast of the island. The combined effects of the earthquake and tsunami made it one of the worst natural disasters that have struck the island. The losses resulting from the disaster were approximately 76–118 casualties[4] and $4–29 million in property damage.


The epicenter of the 1918 San Fermín earthquake was located in the Mona Passage off the northwestern coast of the island. The strongest ground shaking has been estimated at intensity IX on the Mercalli intensity scale. The resulting tsunami affected primarily the west coast towns of the island (primarily Mayaguez).


Damage caused to the "La Habanera de Infanzón y Rodríguez" building in Mayagüez

Numerous structures in the west coast suffered irreparable damage. Factories and production facilities were virtually destroyed, while bridges and roads were severely damaged. The earthquake caused several mudslides in areas where the intensity exceeded Level VII, but none caused numerous deaths. Also, the river currents were affected, which, in many cases affected the foundations of many bridges, resulting in their collapse. Telegraph cables under the ocean were damaged, cutting off the island from outside communication for a time.[7]

Simulation of the results of the tsunami on the coast of Aguadilla, Puerto Rico

The reported casualties of the earthquake have been estimated somewhere between 76 and 116 deaths. Approximately 40 of these deaths were caused by the tsunami which swept shore communities. Damage to property was estimated to be between $4 and 29 million.

In Aguadilla, the closest town to the earthquake epicenter, the parish church and most of the stone and concrete buildings were either destroyed or partially damaged.[8] The nearby Spanish-built Punta Higuero lighthouse of Rincón also was severely damaged.[9][10]

In Mayagüez, the largest city to be directly affected, 700 masonry buildings were damaged and 1,000 wooden houses, so many people were homeless. Major buildings like the church, post office, municipal theater and city hall were severely damaged. With fear because of the aftershocks, many people camped out in the hills for weeks.[7] Some of the buildings of the recently founded University of Puerto Rico campus were also damaged or destroyed. The Edificio José de Diego suffered structural damages and the Degetau Hall was destroyed with its main entrance portico being the only standing structure left intact.[11] These ruins were later preserved, and its portico would later on become a local landmark and the official emblem of the institution today.[12][13]

The historic center of San Germán was also badly affected, with reported damages to notable structures such as the main town church.[14] Cities throughout the southern coast were also affected. The United States Customs House was destroyed[15] while the Ponce city hall for example was damaged, prompting the mayoral office to temporarily relocated to the Parque de Bombas until 1920.[16] Other damaged buildings in Ponce were the Tricoche Hospital and the Armstrong-Poventud House.[17][18]

There were damages reported further afield throughout Puerto Rico, for example the original bell towers of the cathedral of Humacao and the main town church of Vega Baja also collapsed.[19][20] The Corregimiento Plaza Theater, the cathedral and the city hall in Arecibo also sustained damages.[21][22]


As a result of the earthquake, a tsunami lashed the west coast of the island, probably 4–7 minutes after the main shock. The highest waves were estimated at 6.0 m (19.7 ft) in Point Agujereada, 4.5 m (15 ft) at Punta Borinquen (where it destroyed the lighthouse),[23] and 5.2 m (17 ft) at Point Jiguero.[24] Several coastal villages were destroyed, and it has been estimated that 40 people drowned (32 in Aguadilla alone) as a direct result of the tsunami.[25] The earthquake and consequent tsunami destroyed most historic vernacular residences in downtown Aguadilla with only a few, such as the Amparo Roldán residence,[26] surviving. Many of the historic tombs and mausolea of the historic cemetery were also badly damaged by the waves.[27]


Several aftershocks were reported immediately after the main earthquake. On October 24 and November 12, two strong aftershocks were reported on the island. However, no damage was reported as a result.

United States response[edit]

The response from the United States was to exempt the municipalities most affected from paying taxes for a short period immediately following the quake: those municipalities were Mayagüez, Aguada, Aguadilla, Añasco and Isabela. The U.S. appropriated funds for the repair of municipal buildings of the most affected municipalities.[28]


See also[edit]


  1. ^ a b c d ISC (2016), ISC-GEM Global Instrumental Earthquake Catalogue (1900–2012), Version 3.0, International Seismological Centre
  2. ^ a b USGS (September 4, 2009), PAGER-CAT Earthquake Catalog, Version 2008_06.1, United States Geological Survey, archived from the original on 2020-03-13
  3. ^ a b National Geophysical Data Center / World Data Service (NGDC/WDS) (1972), Significant Earthquake Database, National Geophysical Data Center, NOAA, doi:10.7289/V5TD9V7K
  4. ^ a b "Tsunami Hazards—A National Threat A Real Risk for the United States". USGS.gov. March 6, 2018. Retrieved August 19, 2018.
  5. ^ Subcomite de la Historia de Mayagüez (1960), Historia de Mayagüez 1760–1960 (in Spanish), Talleres Graficos Interamericanos, retrieved September 7, 2010
  6. ^ Millie Gil. A 92 años del Terremoto de San Fermín, 1918. Mayaguez Sabe a Mango. 17 October 2010.
  7. ^ a b Peter Aviles, "The Earthquake of the Century", 2002, hosted at University of Puerto Rico, accessed 24 October 2013
  8. ^ Mari Mut, José A. (28 August 2013). "Los pueblos de Puerto Rico y las iglesias de sus plazas" (in Spanish). Retrieved 19 June 2020 – via archive.org.
  9. ^ "Rincón 1". Ediciones Digitales. Retrieved June 28, 2019.
  10. ^ "Rincón 2". Ediciones Digitales. Retrieved June 28, 2019.
  11. ^ "José de Diego(Rectoría)" (in Spanish). Archived from the original on 2010-07-15. Retrieved 2009-07-23.
  12. ^ "Rincones de Mayagüez - Pórtico del Edificio Degetau". Mayagüez sabe a mangó (in Spanish). 2016. Retrieved 2021-04-05.
  13. ^ Álvarez Cervela, José María (1988). El Pórtico Federico Degetau en la Universidad de Puerto Rico en Mayagüez: Su Historia estética, constructiva y simbólica así como sus influencias arquitectónicas en Mayagüez. Editorial UPRM. p. 91.
  14. ^ "San Germán Historic District". National Park Service. Archived from the original on 2009-04-30. Retrieved 2009-05-20.
  15. ^ National Archives, Records of the Public Buildings Service, Record Group #121; Box #855; "Ponce, P.R., Custom House"
  16. ^ Armando Morales-Pares, State Architect, and Abelardo Gonzalez-Architect, State Historic Preservation Office, 23 May 1984. In National Register of Historic Places Inventory-Nomination Form – Parque de Bombas de Ponce – (Ponce Firehouse). United States Department of the Interior. National Park Service. (Washington, D.C.) Page 3. Listing Reference Number 84003150. 12 July 1984.
  17. ^ Mariano G. Coronas Castro, Certifying Official; Felix J. del Campo, State Historian; and Jorge Ortiz Colom, State Architect, Puerto Rico Historic Preservation Office. (San Juan, Puerto Rico) April 7, 1987. In National Register of Historic Places Inventory - Nomination Form. United States Department of the Interior. National Park Service. (Washington, D.C.) Page 3. Listing Reference Number 87000769. May 14, 1986.
  18. ^ del Campo, Felix Julian; Santiago, Hector F. (1987). "National Register of Historic Places Registration: Residencia Armstrong-Toro / Casa de las Caricitides". National Park Service. with 10 photos from 1987
  19. ^ "National Register of Historic Places Inventory Nomination Form". National Park Service. Retrieved 2011-10-17.
  20. ^ "Iglesia Nuestra Señora del Rosario". Municipio Autónomo de Vega Baja (in Spanish). 2014-04-04. Retrieved 2023-01-09.
  21. ^ Felix J.del Campo (May 1, 1985). "National Register of Historic Places Inventory/Nomination: Corregimiento Plaza Theater / Oliver Theater". National Park Service. Retrieved January 24, 2017. with 12 photos, historical and from 1984
  22. ^ "Casa Alcaldía de Arecibo". Discover Puerto Rico. Retrieved 2022-07-15.
  23. ^ "Punta Borinquen Lighthouse Ruins". Atlas Obscura. Retrieved 15 June 2019.
  24. ^ "1918 PUERTO RICO TSUNAMI". USC Tsunami Research Group. Archived from the original on April 30, 2005. Retrieved August 19, 2018.
  25. ^ "Los Cascos Urbanos Hablan: Aguadilla 2/3". florida.pbslearningmedia.org/ (in Spanish). Puerto Rico National Endowment for the Humanities. Retrieved 9 February 2021.
  26. ^ Jose R. Bourdony (July 30, 1984). "National Register of Historic Places Inventory/Nomination: Casa de Piedra / Residence Amparo Roldan". National Park Service. Retrieved December 28, 2016.
  27. ^ Jose Rafael Bourdony (1984). "National Register of Historic Places Inventory/Nomination: Old Urban Cemetery / Cemeterio Municipal". National Park Service. Retrieved December 24, 2016. with eight photos from 1984
  28. ^ United States. Congress (1919). Congressional Edition. U.S. Government Printing Office. pp. 12–16. Retrieved July 31, 2019.


Further reading[edit]

  • Brink, U.; Chaytor, J.; Flores, C.; Wei, Y.; Detmer, S.; Lucas, L.; Andrews, B.; Georgiopoulou, A. (2023). "Seafloor Observations Eliminate a Landslide as the Source of the 1918 Puerto Rico Tsunami". Bulletin of the Seismological Society of America. doi:10.1785/0120220146. ISSN 0037-1106.

External links[edit]