If you haven’t set up your V.I. Alert account to receive only notices of moderate and major earthquakes, you’ve probably received a slew of notifications over the past two days as nearby Puerto Rico experienced a spate of minor earthquakes along with a scattering of larger shakes.
“Go in and change your profile,” V.I. Territorial Emergency Management Agency spokesman Christine Lett advised.
The agency is considering whether to discontinue alerts on minor earthquakes, but Lett said no decision has been made. Those minor earthquakes are seldom felt and cause no problems.
She also said that V.I. Alert includes earthquakes in Puerto Rico because larger quakes could cause tsunamis that could affect the Virgin Islands.
Earthquakes are common in Puerto Rico, as well as the Virgin Islands, and most go unnoticed, except by the equipment that measures them. In fact, the Virgin Islands recorded an earthquake at 1:48 p.m. Tuesday: a 3.3 magnitude located at 18.6 degrees north latitude and 64.6 degrees west longitude, or 10 miles north of Road Town in the British Virgin Islands. The depth was a shallow 1.5 miles beneath the ocean floor.
The earthquake information generated by V.I. Alert comes from the U.S. Geological Survey, which gets some, but not all, of its information from Seismic Network’s equipment.
Harold Irizzary, a geologist the Seismic Network, said that reports from both agencies can differ slightly because after the information is automatically recorded the Seismic Network staff manually fine tunes it.
“We verify, so you can get a different magnitude and time,” he said.
Julie Dutton, a geophysicist at the Geological Survey’s National Earthquake Information Center in Golden, Colorado, said that the staff also adjusts data when more information is available.
Additionally, Dutton said that when a larger earthquake occurs, it triggers sensors operated by the Geological Survey. so data from the Geological Survey and the Seismic Network may also differ slightly because they used different equipment.
As of 3 p.m. Tuesday, the Seismic Network listed seven Monday earthquakes on its website that it calls significant.
Irizzary said this means they have a magnitude of over 3.5. However, Irizzary also said that the Seismic Network records many lesser earthquakes, and delving deeper into its website will show them. It lists 62 earthquakes for Monday that ranged from 0 magnitude to 5.2 magnitude.
The recent torrent of earthquakes is not a swarm, but rather the foreshocks and aftershocks of the 5.2 magnitude earthquake that occurred at 6.35 a.m. Monday, centered at 19.1 degrees north longitude and 66.7 degrees west latitude, or 46 miles north northeast of Camuy, Puerto Rico. It occurred at a depth of 9.3 miles.
“The activity stopped at around 10:30 p.m. Monday,” Irizarry said.
Although the earthquake ended, alerts from the Geological Survey didn’t cease arriving in mailboxes until around 5:30 a.m. Tuesday. Dutton said that alerts for major earthquakes go out immediately, but those for the lesser ones are often delayed.
“They don’t generate the same sense of urgency,” she said.
Dutton said the rash of Puerto Rico earthquakes is normal for that region.
Visit www.vialert.gov for more information, or to reset your alert preferences.