Wondering what to do if and when earthquakes and tornadoes threaten to strike in and around Delaware? Here’s what to know.
On a national scale, Delaware charts near the bottom in terms of natural disasters. (Florida, Texas, California and Washington are among the most at-risk.) But that doesn’t mean impervious. The Delaware coastline is especially vulnerable to extreme weather events.
Over the coming years, our state is projected to face higher temperatures, more high-heat days, increased heavy precipitation and sea level rise. The impacts from each of these threatens industries, infrastructure, natural resources and health of residents, according to Delaware Natural Resources and Environmental Control (DNREC).
That means greater risks of floods and other disasters as time progresses. We rounded up four of the best-known natural disasters and filtered them through a Delaware lens. These experts told us how to prepare for flooding as well as hurricanes and cyclones in the First State. Now, they share insight on how to prepare for some of the less common, but equally devastating disasters: tornadoes and earthquakes.
For more comprehensive disaster planning, visit PrepareDe.org, maintained by the Delaware Emergency Management Agency (DEMA).
Threat Level: 2/5
Tornadoes are infrequent but steady in Delaware— we average around one a year. “We’ve had a couple tropical systems that have spawned tornadoes; the main one was Isaias from two hurricane seasons ago,” says Dan Leathers, Delaware’s state climatologist and a professor at UD.
The storm spawned the state’s most wickedly long tornado. As the Washington Post reported, the record-breaking tornado spanned nearly 30 miles, from Dover to Middletown. The twister threw debris 10,000 feet into the air, tore up the roof at William Henry Middle School and clocked in at 96 miles per hour from a nearby Delaware Department of Transportation weather station.
Thankfully, no injuries were reported, though the National Weather Service said two tornadoes hit the area. Delaware has only two tornado fatalities on record dating back to 1950. A record six tornadoes touched down in 1996.
In our part of the country, tornadoes typically result from tropical storms and hurricanes. When the force of the storm whips around, extreme wind shear creates a sudden change in wind speed and/or direction. Tornadoes spawned by landfalling hurricanes can cause enormous destruction, according to NOAA. As a hurricane moves shoreward, tornadoes often develop on the fringes of the storm.
“We get tornadoes [here] regularly, but a very small number if you look back in time,” Leathers adds. “Not all tropical cyclones give you tornadoes. And it’s a fairly small percentage, about 1 out of 3 that gives you a tornado somewhere in the mid-Atlantic.”
And although a handful have struck the First State in recent years, there’s no long-term trend tornadoes are increasing, Leathers says.
Threat Level: 1/5
Ask around, and most Delawareans can probably tell you where they were at 1:51 p.m. on August 23, 2011, when a magnitude 5.8 earthquake (according to the United States Geological Survey, or USGS) struck a couple hundred miles away in central Virginia.
While that area is known for seismic activity, our state is rarely impacted.
Then, in the early evening of Thanksgiving 2017, a rumbling emanated from around 6 miles northeast of Dover in Bombay Hook National Wildlife Refuge, according to data reported by the USGS. Dishes rattled in cabinets. Patio chairs wobbled slightly. People remembered the sensation all too well.
But at a magnitude of 4.1, the earthquake—Delaware’s largest ever— wasn’t much of a disaster. Unless you were near the Dover epicenter, the quake might’ve been confused with a passing truck. The memes that followed are perhaps the enduring legacy of the 2017 event.
“There are not very many that you can feel around Delaware,” says David Wunsch, our state geologist and director of the Delaware Geological Survey (DGS), “and the last big one from 2017 was an oddity.”
The shifting tectonic plates that helped form the Atlantic coast around 190 million years ago have been fairly quiet ever since. But over time, even quiet areas can accumulate some tectonic stress that gets released in the form of an earthquake. Unlike California and its famous San Andreas Fault system, Delaware lies on no such geological phenomenon.
“The bedrock underneath us on the East Coast and mid-Atlantic is old and just not as active,” Wunsch explains. “We do get these small quakes because the crust does adjust over time, but this is a quiet part of the country.”
The 2017 earthquake was just the 58th such documented event in Delaware since 1871, according to the DGS. It represented a once-in-a-decade event in Delaware: a quake that people could feel. Around 98 percent of the nearly 3 million earthquakes that occur worldwide each year fall under a magnitude of 3. The largest previously recorded event hit Delaware in 1973 and had an estimated magnitude of 3.8.
But we don’t actually know a lot about what lies deep beneath Delaware’s earth. Unlike some of our southern and Appalachian neighbors, we don’t sit on rich natural gas or oil wells, so companies haven’t drilled as deeply into our ground, Wunsch adds, other than for research purposes.