The 1918 San Fermín earthquake, also known as the Puerto Rico earthquake of 1918, struck the island of Puerto Rico at on October 11. The earthquake measured 7.1 on the moment magnitude scale and IX (''Violent'') on the

Mercalli intensity scale The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

. The mainshock epicenter occurred off the northwestern coast of the island, somewhere along the Puerto Rico Trench. The earthquake triggered a tsunami with waves measured 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 and $4–29 million in property damage.

Earthquake

The epicenter of the 1918 San Fermín earthquake was located in the

Mona Passage The Mona Passage ( es, Canal de la Mona) is a strait that separates the islands of Hispaniola and Puerto Rico. The Mona Passage connects the Atlantic Ocean to the Caribbean Sea and is an important shipping route between the Atlantic and the Panama ...

off the northwestern coast of the island. The strongest ground shaking has been estimated at intensity IX on the

. The resulting tsunami affected primarily the west coast towns of the island (primarily Mayaguez).

Damage

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. 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 Mayagüez, the largest city affected, 700 masonry buildings were damaged and 1,000 wooden houses, so many people were homeless. Major buildings like the church, post office and hall were severely damaged. With fear because of the aftershocks, many people camped out in the hills for weeks.Peter Aviles, "The Earthquake of the Century"
2002, hosted at University of Puerto Rico, accessed 24 October 2013

Tsunami

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 in Point Agujereada, at Point Borinquen, and at Point Jiguero. 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.

Aftershocks

Several

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousand ...

s 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

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.

Gallery

File:Iglesia Mayaguez 1918.jpg,

Cathedral of Mayagüez A cathedral is a church that contains the ''cathedra'' () of a bishop, thus serving as the central church of a diocese, conference, or episcopate. Churches with the function of "cathedral" are usually specific to those Christian denominations ...

after the first earthquake; further damage toppled the left tower File:Terremoto-pr-2.gif, Destroyed brick homes in Mayagüez File:Epicenters of earthquakes around Puerto Rico in last 100 years.jpg, Map showing the epicenters of all the magnitude 5 and greater earthquakes around Puerto Rico for the last 100 years File:Aguadilla Punta Borinquen Lighthouse Ruins.jpg, Aguadilla Punta Borinquen Lighthouse Ruins—an 1889 lighthouse destroyed by the tsunami

References

Sources * * *

External links

"Puerto Rico Seismic Network"
– University of Puerto Rico, Mayaguez
Significant earthquake – Puerto Rico: Mona Passage
– National Geophysical Data Center
M 7.1 - Puerto Rico region
– United States Geological Survey
The Tectonic Setting and Geology of Puerto Rico and Its Surrounding Seafloor
– National Oceanic and Atmospheric Administration
Map of Tsunami wave heights in Puerto Rico by USC Tsunami Research Group

Wave transformation in Coastal Wiki

Earthquakes and Tsunamis in Puerto Rico and the U.S. Virgin Islands by USGS.gov
* {{DEFAULTSORT:1918 San Fermín earthquake Mayagüez, Puerto Rico San Fermin Earthquake, 1918 San Fermin Earthquake, 1918 1918 tsunamis Earthquakes in Puerto Rico