The whole house started to shake. It had begun.
At 11:23pm on September 24th, 2019, a 6.0-magnitude earthquake struck 70 kilometers north of Puerto Rico. Then the tsunami warning came on the QuakeFeed app.
We weren’t ready for the earthquake and we weren’t ready for a tsunami. In Camuy, 75 minutes from San Juan, we’d been preparing for Hurricane Karen. Despite the optimistic weather forecast, we’d wanted extra precautions after Hurricane Maria’s devastation.
But we weren’t expecting an earthquake.
We piled into the car and called neighbors to warn them as we followed the evacuation route up the hill.
I quickly downloaded earthquake monitoring apps and pored through research online. After the quake, I found myself fascinated and dove deeper into Caribbean seismology, combing through the science and historic source materials.
People think about earthquakes when they think of California and prepare accordingly: the famous San Andreas Fault, where two tectonic plates meet, runs through almost all of California.
With Puerto Rico, people don’t typically think about earthquakes. But in 2003, scientists discovered the active Bunce Fault along the Puerto Rico Trench, at the boundary of the Caribbean Sea and Atlantic Ocean.
The Bunce Fault is similar in size to its more famous cousin, California’s San Andreas Fault, and it contains the deepest point in the Atlantic Ocean.
When earthquakes hit at sea, they can cause towering waves — tsunamis. The 2003 expedition found multiple submarine slides, which are known sources of tsunamis.
The Chief Scientist at U.S. Geological Survey (USGS), Uri ten Brink, summarized the findings: "The discoveries made during this expedition make clear the potential tsunami hazard to the densely populated northern coast of Puerto Rico...”
It’s happened before.
The magnitude 7.5 San Fermin Earthquake hit off the northwest coast of Puerto Rico in 1918, followed by a 6-meter tsunami. Thousands of buildings were destroyed and more than 100 lives lost.
As I researched more, I found that this type of seismic activity has not been rare.
In 1787, 131 years before San Fermin, Puerto Rico experienced the even more powerful Boricua Earthquake with estimated magnitude of up to 8.5. Tidal waves as tall as 20 meters reached 3 kilometers inland. Due to limited records, the full extent of damage and casualties are unknown — but some suspect the island may have sunk about 3 meters.
As for my experience in Camuy? We were lucky. After an hour passed, there were smaller aftershocks but thankfully no tsunami.
But since then, seismic activity around Puerto Rico hasn’t been the same.
From September to December 2019, the USGS measured earthquakes with magnitudes of 3, 4 and 5 occurring at respective frequencies of 482, 21 and 2. That’s a 391% increase from the same period in 2018. For magnitude 4 and 5 earthquakes, the rate increased by 767%.
Recent seismic activity strongly correlates with known records from both the San Fermin and Boricua earthquakes in terms of magnitude and location.
The next big one could be right around the corner, placing thousands at risk.
But there’s good news. I learned that some very simple preparation in advance can help keep you and your loved ones safe, as detailed here:
Whether you’re a Christian or not, Romans 15:4 can resonate — “For everything that was written in the past was written to teach us.”
When the next earthquake or tsunami hits, let’s have learned the lesson of the past and prepared to keep ourselves and each other safe.