The 1787 Boricua earthquake struck offshore of the island of Puerto Rico on May 2. The magnitude of the earthquake was believed to have been around 8.0–8.25, however there is evidence that it was only about 6.9. The epicenter is thought to have been somewhere north of Puerto Rico, probably on the Puerto Rico Trench.Earthquake History of Puerto Rico and the Virgin Islands on USGS Puerto Rican geomorphologist José Molinelli considers it "the strongest" in the seismic history of the country.
Effects
According to some sources, the earthquake was felt all across the Island. It demolished some structures like the Arecibo church,Arecibo on EdicionesDigitales along with monasteries like El Rosario and La Concepcion. It is also reported that it damaged the churches at Bayamon, Toa Baja and Mayagüez. It also caused considerable damage to the forts of San Felipe del Morro and San Cristobal, breaking cisterns, walls and guard houses.El Morro, San Cristobal y San Geronimo en peligro en caso de terremoto on NoticiasOnline (6/7/2009) Apparently, the earthquake did not cause major damage in the South of the island, but did crack the walls of the Our Lady of Guadalupe church in Ponce.Historia sísmica de Puerto Rico: Terremotos significativos en la zona de Puerto Rico. SalonHogar.com Accessed 22 March 2018.
There are no historical records of damage to the surrounding islands, adding to the evidence that the quake was smaller than previously thought.
Evidence
The earthquake that struck the island has little historical record itself, but some of the little evidence that exists suggests that effects were done to the topography of the ocean floor. Also, soil deposits give evidence that the event may have had a physical effect on the island; this evidence suggests that the island may have sunk about 3 meters. It is estimated that the tsunami produced by the earthquake may have been some 40–60 ft (12–18 m) high, mostly because the Caribbean ocean in particular is quite shallow. Coastal regions of the island were swamped, producing a thin layer of the crust, showing that salt water had reached almost 2 miles inland.
See also 1867 Virgin Islands earthquake and tsunami 1918 San Fermín earthquake List of earthquakes in 1918 List of earthquakes in Puerto Rico List of earthquakes in the Caribbean
References
External links Historia sísmica de Puerto Rico