1918 San Fermín earthquake

1918 San Fermín earthquake

Mayagüez San Juan
Date	October 11, 1918 (1918-10-11)
Origin time	10:15 am
Magnitude	7.5 Ms
Epicenter
Areas affected	Puerto Rico
Total damage	$4 million USD
Tsunami	Yes
Aftershocks	14
Casualties	116

The 1918 San Fermín earthquake, also known as the Puerto Rico earthquake of 1918, struck the island of Puerto Rico at 10:15 am on October 11. The magnitude for the earthquake measured 7.5 on the surface wave magnitude scale and level IX on the Rossi–Forel scale. The main-shock 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 116 casualties and $4 million in property damage (about $62,000,000 dollars in 2015 money currency).

Earthquake

The epicenter of the 1918 Puerto Rico earthquake was located in the Mona Passage off the northwestern coast of the island, somewhere along an old left-lateral strike-slip fault. The strongest ground shaking has been estimated at intensity IX on the Rossi–Forel scale. The resulting tsunami affected primarily the west coast towns of the island (primarily Mayaguez).

Damage

File:Terremoto Mayaguez 1918.jpg

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.

File:Inundacion-1918.jpg

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 91 to 116 deaths. Approximately 40 of these deaths were caused by the tsunami which swept shore communities. Also, damages to property were estimated at around $4 million, which was an incredible amount at that time in terms of the island's economy.

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.

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 measured at 20 ft and destroyed several coastal villages. It has been estimated that 40 people were drowned as a direct result of the tsunami. The tsunami reached Galveston, Texas, where it registered as a disturbance on tide gauges.

Aftershocks

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

Gallery

• Iglesia Mayaguez 1918.jpg

  Cathedral of Mayagüez after the first earthquake; further damage toppled the left tower

• Terremoto-pr-2.gif

  Destroyed brick homes in Mayagüez

See also

• List of earthquakes in 1918
• Geology of Puerto Rico
• 1787 Boricua earthquake

References

Sources

External links

• "Puerto Rico Tsunami Warning and Mitigation Program", University of Puerto Rico, Mayaguez
• "Puerto Rico Seismic Network", University of Puerto Rico, Mayaguez
• Significant earthquake – Puerto Rico: Mona Passage – National Geophysical Data Center
• USGS Historic Earthquake: Northwestern Mona Passage – United States Geological Survey