A 4.8 magnitude earthquake struck the East Coast on a Friday morning, causing high rises to sway in New Jersey, New York, Pennsylvania, and Delaware.
Residents of California and other Western states may dismiss the concern shown by their East Coast counterparts over what appears to be a minor quake.
However, this tremor hit the most densely populated region of the United States, affecting some of its oldest buildings and alarming people who often assume that the ground is stable.
Therefore, it is important to take it seriously.
Unlike the Western US, the East Coast is less geologically active, with fewer major fault lines that can cause significant earthquakes.
However, there are frequent smaller tremors. According to the US Geological Survey, the eastern part of the country has experienced more than 400 earthquakes with a magnitude greater than 3.5 in the past 50 years. As recently as 2011, a magnitude 5.8 quake in Virginia was felt along the East Coast and caused some damage to buildings in Washington, DC.
One of the differences between earthquakes in the eastern and western US is the nature of the ground below.
The rock beneath the eastern US is older and denser than the subsurface out west, which allows seismic waves to travel further.
"In the Western US, the ground under us is warmer and it’s chopped up by faults and seismic waves get attenuated (filtered out)," said Robert de Groot, who leads public outreach for the US Geological Survey’s ShakeAlert earthquake early-warning system in the western US, in an email.
"Think of the subsurface as a hall of mirrors and lenses.
Waves get scattered, redirected, etc."
While earthquakes are less common in the East, states along the Atlantic coast have updated their building codes over the years to make homes, offices, stores, and warehouses more earthquake-resistant.
However, many older structures, especially in cities like New York, are not protected against earthquakes.
The advice for earthquake safety has also evolved. The old advice of seeking shelter in a doorway is no longer recommended, as doorways are not stronger than other parts of a building.
The new advice is to "Drop, Cover, and Hold On."
This means getting to your hands and knees, covering your head and neck with an arm while taking cover under a table or desk, and holding onto a piece of furniture. Avoid exterior walls, windows, and hanging objects.
If you're in bed, stay there and cover your head and neck with a pillow.
If outdoors, move to an open space away from buildings. If driving, pull over and set the parking brake, avoiding overpasses, trees, and power lines.
Earthquakes can be surprising and dangerous, but with proper precautions, they don't have to be deadly.