A 7.6 magnitude earthquake off the coast of Honduras Tuesday night triggered a tsunami scare that impacted the Cayman Islands and raised new questions about the islands’ emergency alert capability.
Hazard Management Cayman Islands officials confirmed Wednesday morning that the territory had been impacted by a small tsunami, bringing sea level rises of less than a foot.
The quake hit at 9:52 p.m., 25 miles east of Swan Island, Honduras, and registered as a minor tremor 190 miles away in Grand Cayman. Residents reported feeling vibrations, in some cases shaking furniture, knocking pictures off the wall and causing minor wave action in condo swimming pools.
The U.S. Tsunami Warning Center briefly placed the Cayman Islands on an advisory watchlist Tuesday night, warning of potential wave impact between 1 and 3 feet at around 10:30 p.m.
Information about the quake and the scale of the anticipated tsunami was not immediately available locally, prompting speculation and some concern among residents, who feared a more serious wave impact.
The first official notification from government’s Hazard Management unit dropped at 10:46 p.m. – 15 minutes after the anticipated wave impact.
Simon Boxall, education and communications officer at Hazard Management, acknowledged that public concern about emergency communications was justified. He said government does not currently have an effective and efficient system of notifying the public in the case of “rapid onset events,” like a tsunami, major fire or a toxic spill.
He said the team had reacted swiftly, briefing journalists and updating their social media pages, but acknowledged more universal communication was needed.
“It re-emphasizes what we have been saying for a while. We need a mass notification system. It is fairly standard in other countries …. The public need and expect to be informed if a threat is coming their way,” he added.
He said government was working on a solution that will enable much swifter access to information in emergency scenarios.
Even with sharper communications, he acknowledged, residents may not have much time to prepare if a more serious tsunami struck the Cayman Islands. Depending on the location of the earthquake, the lead time for residents in the Cayman Islands could be anything from a few minutes to eight hours.
Danielle Coleman, acting head of the Hazard Management unit, said part of its focus was a public education campaign to ensure residents knew what to do.
“We are not used to having tsunamis. It is a mysterious topic for a lot of people, but they are a realistic threat. If you feel an earthquake, you need to go inland and up – it might be nothing but it is much better to be safe than sorry.”
Boaters are advised to stay on the water and go out to sea, she added.
The likelihood of a more serious tsunami impacting Cayman is considered to be remote but not impossible.
Mr. Boxall said, “We are in a seismically active area. These things don’t happen very often, but that’s part of the problem. We need people to know if these things do happen, how are you going to react to keep yourself and family safe.”
The deep water around the Cayman Islands provides some degree of protection, because major tsunamis require shallower depths to build height
But Mr. Boxall said there were enough such areas, including in the North Sound, for tsunamis to be considered a credible threat to the territory.
Tuesday night’s event was the first time a tsunami has officially been recorded in the Cayman Islands, though the history books suggest there may have been previous events, before the advent of modern recording equipment.
Mr. Boxall said there were documented accounts of a serious earthquake at sea in 1843 and an incident in 1856 where Cayman was “sunk” by an earthquake.
In his book, “Islands from the Sea,” on the geology of Cayman, author Murray Roed documents a tsunami in Jamaica in 1692 which he says impacted Cayman.
He told the Cayman Compass Tuesday that the conditions did exist for tsunamis to impact the island.
“A tsunami can be generated in several ways: movement along faults, especially near continental edges, major landslides into water and also major submarine slides in places like the Cayman Trough,” Mr. Roed said.
He added, “The Jamaica tsunami impacted Cayman. The Cayman Islands are near major transform faults trending east-west and also are at the edge of the North American Plate. So there are plenty of opportunities for tsunamis but are nevertheless very rare.”