The residents of Puerto Rico have endured a series of earthquakes over the past two weeks, all centered along the island's southwest coast; to date, the strongest was magnitude 6.4. A brief review of the regional geology and natural history explains why hurricanes are not the only natural threat to this Caribbean island.
Having initially formed as a volcanic island arc off the northwest coast of South America, Puerto Rico and the adjacent Caribbean Plate were forced between the North American and South American Plates as the Atlantic Ocean opened; this process began about 160 million years ago and continues today. Puerto Rico and the Virgin Islands lie on a microplate, bordered by deep-sea canyons, troughs and subduction zones, where pressure builds between it and the Caribbean and North American Plates and is repeatedly released in the form of earthquakes. Indeed, along the northern edge of Puerto Rico, the North American Plate is both scraping past and subducting beneath (via the Puerto Rico Trench) the Puerto Rico-Virgin Islands microplate.
While minor quakes are nearly continuous in this region, most are too weak to cause damage or be noticed by residents. However, more significant earthquakes are far from uncommon and may be associated with a prolonged series of aftershocks (as has occurred this month).
See also: Earthquakes & Tectonic Plates and The Nature of Aftershocks
Having initially formed as a volcanic island arc off the northwest coast of South America, Puerto Rico and the adjacent Caribbean Plate were forced between the North American and South American Plates as the Atlantic Ocean opened; this process began about 160 million years ago and continues today. Puerto Rico and the Virgin Islands lie on a microplate, bordered by deep-sea canyons, troughs and subduction zones, where pressure builds between it and the Caribbean and North American Plates and is repeatedly released in the form of earthquakes. Indeed, along the northern edge of Puerto Rico, the North American Plate is both scraping past and subducting beneath (via the Puerto Rico Trench) the Puerto Rico-Virgin Islands microplate.
While minor quakes are nearly continuous in this region, most are too weak to cause damage or be noticed by residents. However, more significant earthquakes are far from uncommon and may be associated with a prolonged series of aftershocks (as has occurred this month).
See also: Earthquakes & Tectonic Plates and The Nature of Aftershocks
