Experts Seek Answers Behind Constant Quakes in Puerto Rico
Another magnitude 5 quake shook Puerto Rico Wednesday morning
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Alena L. Leeds, a scientist from the United States Geological Survey, operates earthquake monitoring and recording equipment amid aftershocks across the island’s southern coast where recent quakes have toppled homes and schools in Ponce, Puerto Rico, Tuesday, Jan. 14, 2020. The seismic activity that experts say is unusual but not unexpected has unleashed scientific debate about what’s causing it and drawn international attention to the area, where more than 4,000 people have sought shelter as they wonder when the ground will stop trembling. (AP Photo/Carlos Giusti)
Seismologists in southern Puerto Rico gingerly walked around a patch of dirt that marks the location of recently buried sensors they hope will reveal answers behind the constant and unusual shaking in the region that has terrified residents.
Alena Leeds with the U.S. Geological Survey stopped in front of the sensors on Tuesday afternoon and scrutinized the information that popped up on the screen in front of her.
“Here comes one! There’s an aftershock,” she said as the software showed red, blue and green lines that squiggled up and down.
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Cars drive through an area heavily affected by a landslide after a powerful earthquake hit the island in Ponce, Puerto Rico, Jan. 12, 2020. A 5.9-magnitude earthquake rocked Puerto Rico on January 11, the latest in a series of powerful tremors that have shaken the U.S. territory in recent days.
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People arrive with supplies for affected residents in Guanica, Puerto Rico, on Jan. 12, 2020, after a powerful earthquake hit the island. A 5.9 magnitude earthquake rocked Puerto Rico on January 11, the latest in a series of powerful tremors that have shaken the U.S. territory in recent days.
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A person inspects rubble and destroyed power lines in Guayanilla, Puerto Rico, on Sunday, Jan. 12, 2020. Puerto Rico was hit by a series of earthquakes over the past 15 days, leading to a state of emergency, various power outages and millions of dollars of damage.
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A Caterpillar Inc. excavator sits on a destroyed bridge in Guayanilla, Puerto Rico, on Sunday, Jan. 12, 2020. Puerto Rico was hit by a series of earthquakes over the past 15 days, leading to a state of emergency, various power outages and millions of dollars of damage.
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A barber gives free haircuts to people at a shelter in Guanica, Puerto Rico on Jan. 12, 2020, after a powerful earthquake hit the island. A 5.9 magnitude earthquake rocked Puerto Rico on January 11, the latest in a series of powerful tremors that have shaken the U.S. territory in recent days.
Carlos Giusti/AP
William Mercuchi’s house sits damaged after a 6.4 earthquake hit Yauco, Puerto Rico, the day before, as seen in this Jan. 8, 2020, photo.
Carlos Giusti/AP
A building collapses after the previous day’s magnitude 6.4 earthquake in Yauco, Puerto Rico, Jan. 8, 2020. More than 250,000 Puerto Ricans remained without water on Wednesday and another half a million without power.
Carlos Giusti/AP
Maritza Quiñones Rodriguez, 51, cries as she and other neighbors remain outdoors using camping tents and portable lights for fear of possible aftershocks after a 6.4-magnitude earthquake struck in Guanica, Puerto Rico, Tuesday, Jan. 7, 2020.
Carlos Giusti/AP
Paramedics assist a man suffering from seizures as he and neighbors remain outdoors using camping tents and portable lights for fear of possible aftershocks on their first night after an earthquake in Guanica, Puerto Rico, Tuesday, Jan. 7, 2020.
Carlos Giusti/AP
Volunteers distribute food to neighbors who remain outdoors using camping tents and portable lights for fear of possible aftershocks after a 6.4-magnitude earthquake struck in Guanica, Puerto Rico, Jan. 7, 2020.
Carlos Giusti/AP
Neighbors place Martin Velez, 96, on a bed outside a shelter after an earthquake struck in Guanica, Puerto Rico, Tuesday, Jan. 7, 2020.
Carlos Giusti/AP
Store owners and family help remove supplies from Ely Mer Mar hardware store, which partially collapsed after an earthquake struck Guanica, Puerto Rico, Tuesday, Jan. 7, 2020. A 6.4-magnitude earthquake struck Puerto Rico before dawn on Tuesday, killing one man, injuring others and collapsing buildings in the southern part of the island.
Ricard Arduengo/AFP via Getty Images
The Inmaculada Concepcion church, built in 1841, is seen partially collapsed after an earthquake hit the island in Guayanilla, Puerto Rico, on Jan. 7, 2020. A 6.4-magnitude earthquake hit the island – the latest in a series of tremors that have shaken the island since December 28.
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A view of damages at Guanica town after 6.4-magnitude earthquake hit Puerto Rico on Jan. 7, 2020.
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A view of damages at Guanica town after 6.4-magnitude earthquake hit Puerto Rico on Jan. 7, 2020.
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The Inmaculada Concepcion church, built in 1841, is seen partially collapsed after an earthquake hit the island in Guayanilla, Puerto Rico, on Jan. 7, 2020.
Ricard Arduengo/AFP via Getty Images
The Inmaculada Concepcion church, built in 1841, is seen partially collapsed after an earthquake hit the island in Guayanilla, Puerto Rico, on Jan. 7, 2020.
RICARDO ARDUENGO
Paramedics carry away an injured patient after a earthquake hit the island in Ponce, Puerto Rico on Jan. 7, 2020. Eight people were hurt from the latest quake, with one man dead.
Ricardo Arduengo/AFP via Getty Images
A man carries a St. Jude statue from the Inmaculada Concepcion church ruins that was built in 1841 and collapsed after an earthquake hit the island in Guayanilla, Puerto Rico, on Jan. 7, 2020. A strong earthquake struck south of Puerto Rico early Tuesday morning – the latest in a series of tremors that have shaken the island since December 28. The shallow 6.4 magnitude quake struck five miles south of the community of Indios, the USGS said.
Carlos Giusti/AP
Debris from a collapsed wall of a building litters the ground after an earthquake struck Puerto Rico before dawn, in Ponce, Puerto Rico, Tuesday, Jan. 7, 2020.
Carlos Giusti/AP
Amir Seneriz, president of the Logia Aurora Organization, inspects damages after an earthquake struck Puerto Rico before dawn, in Ponce, Puerto Rico, Tuesday, Jan. 7, 2020.
Courtesy Fabián Torres
A damaged wall crumbles in Yauco, Puerto Rico, following a 6.4 magnitude earthquake that hit Tuesday morning on Jan. 7, 2019.
Courtesy Fabián Torres
Cracks appeared on a damaged building in Yauco, Puerto Rico, following a 6.4 magnitude earthquake that hit Tuesday morning on Jan. 7, 2019.
Ricardo Arduengo/AFP via Getty Images
San Juan is plunged in darkness after a 6.4 earthquake rattled Puerto Rico early Jan. 7, 2020, leaving the island largely without power.
Courtesy Jesus Ramos
San Juan sits in darkness after power is knocked out following a 6.4 magnitude earthquake that hit Puerto Rico Tuesday morning on Jan. 7, 2019.
Courtesy Jorge Torres Ramos
Products scatter on the floor of a damaged grocery store in San Sebastián, Puerto Rico, after a 6.4 magnitude earthquake hit Tuesday morning on Jan. 7, 2019.
Telemundo Puerto Rico
A damaged house sits in Guanica, Puerto Rico, after a 5.8 magnitude earthquake hit off the southern coast of Puerto Rico on Monday morning, Jan. 6, 2019.
Telemundo Puerto Rico
Guanica, Puerto Rico, residents survey a felled utility pole after a 5.8 magnitude earthquake hit off the southern coast of Puerto Rico on Monday morning, Jan. 6, 2019.
More than 1,280 earthquakes have hit Puerto Rico’s southern region since Dec. 28, more than two dozen of them magnitude 4.5 or greater, according to the USGS. Among them was a 6.4 magnitude quake that hit on Jan. 7, killing one person and injuring nine others, and a 5.9 magnitude aftershock that occurred Saturday, causing further damage.
Government officials say the quakes have caused a preliminary $110 million in damage, toppled part of a famed rock formation landmark and damaged or destroyed more than 550 homes.
The seismic activity that experts say is unusual but not unexpected has unleashed scientific debate about what’s causing it and drawn international attention to the area, where more than 4,000 people have sought shelter as they wonder when the ground will stop trembling.
“I don’t plan on stepping foot in the house for any reason until this stops,” said Adrián Santos, a 45-year-old mechanic who has been living in a tent in the southern coastal city of Ponce for nearly a week with nine other relatives. “The shaking is unbearable.”
Scientists say they don’t yet know much about the faults causing the quakes, although some experts believe at least three faults are involved, including the Punta Montalva one in southwest Puerto Rico that students and professors at the University of Puerto Rico in Mayaguez discovered in the early 2000s.
“There are a lot of different opinions but not a lot of data,” said Elizabeth Vanacore, an associate research professor at the university, which also houses the island’s Seismic Network.
Overall, Puerto Rico is located in a very seismically active area, with the North America and Caribbean tectonic plates converging at a rate of about 2 centimeters a year, said Gavin Hayes, a USGS research geophysicist. To the north part of the island, the North America plate is moving past and sinking below Puerto Rico, while in the southern region, the Caribbean plate is sinking into the mantel underneath the island.
“Essentially, the island is being squeezed between these two tectonic plates,” he said.
In the last 50 years, 10 earthquakes of magnitude 4 and higher have occurred within 50 kilometers of the recent 6.4 magnitude epicenter prior to Dec. 28, said Lindsay Davis, with USGS’s earthquake disaster assistance team manager.
Powerful earthquakes and aftershocks in southern Puerto Rico have left several buildings in ruins. NBC 6's Sheli Muniz reports from Guanica.
She said the rate of aftershocks following the 6.4 magnitude quake is higher than expected, but still within normal range. She also said Saturday’s 5.9 magnitude quake was within the range of what was expected for the aftershock sequence.
Experts say the likeliest scenario is that the frequency of aftershocks will decrease in the next 30 days, noting that moderately sized ones could still further damage structures. A less likely scenario is another earthquake just as strong as the 6.4 one occurs in the same area, an event known as a doublet. A much less likely scenario is that an earthquake significantly larger than the 6.4 one hits Puerto Rico.
Meanwhile, scientists are still investigating the reason behind the constant shaking, fascinated that the aftershocks — in a departure from normal behavior — seem to be occurring along several faults, including the Punta Montalva one.
“Some of them we don’t even know they’re there until they talk,” said Leeds, the USGS seismologist. “And now it’s talking very loudly.”
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