Reports of unidentified “booms” have emerged from different places around the world for hundreds of years, and although many of the “boom stories” remain a mystery, others have been explained. Most of the booms that people hear or experience are the result of human activity, such as an explosion, a large vehicle going by, nearby construction, or sometimes a sonic boom, but there have been many reports of booms that cannot be explained by man-made sources. Some of those booms are associated with a variety of interesting natural phenomena, including earthquakes.

In the United States most reports of mysterious booms come from the Northeast and along the East Coast, but there have also been observations along the West Coast. Those on the East Coast have not been directly studied and explained, but we can deduce from observations and measurements in West Coast locations that at least some of the East Coast booms are associated with very small earthquakes. Small shallow earthquakes sometimes produce rumbling sounds or booms that can be heard by people who are very close to them. High-frequency vibrations from the shallow earthquake generate the booming sound; when earthquakes are deeper, those vibrations never reach the surface. Sometimes the earthquakes create booming sounds even when no vibrations are felt.

Booms Around the World

Eastern U.S.

The term “Seneca Guns” is commonly used for booms that residents hear near Lake Seneca in the Finger Lakes region of New York. The name has also been applied to similar sounds along the coasts of North Carolina, South Carolina, and Virginia (possible origins of this term). The 1886 Charleston, South Carolina earthquake (approximately M6.9) was accompanied by well-documented booming sounds. The observations describe a roaring sound that was heard as the seismic waves rolled across the region. For several weeks after the Charleston Earthquake, there were many aftershocks that were reportedly accompanied by "loud detonations".

Midwestern U.S.

There are accounts of "artillery"-like sounds that were said to have occurred before or during the New Madrid earthquakes of 1811-1812 (M 7.4-7.9).

Reports of booms throughout the Midwest often coincide with low temperatures of -20 F or colder and are sometimes described as “ice quakes” or “frost quakes” . A frost quake is a result of shallow groundwater freezing, expanding, and then causing surrounding frozen rock and soil to crack. These events are not recorded on seismographs. Another explanation for booms during cold snaps is the expansion and contraction of houses and other structures due to the extreme temperatures.

Western U.S.

In 2001, a swarm of small earthquakes accompanied by booming sounds unnerved the city of Spokane. The shallow location of the earthquakes in Spokane (sometimes only 1-2 miles deep) probably contributed to all the noise heard by residents.

In 1989, USGS seismologists working on Mammoth Mountain in California heard muffled booming sounds but felt no shaking . Seismographs showed that several small, shallow earthquakes (<M2) occurred at the same time. Another group of USGS scientists heard low rumbling sounds and felt shaking while they were installing seismic stations in Imperial Valley, CA during an earthquake swarm. During the 1906 San Francisco earthquake (M7.9), many citizens described sounds of all types, from “roaring” to “rushing”.

Outside the U.S.

Historical reports of earthquake sounds in Europe include anecdotes from as early as 1857 from a M6.9 earthquake in Italy. The sounds from that earthquake were described as both “explosive” and “rushing and rolling” by witnesses. Accounts of sounds from small- to moderate-size earthquakes in England from 1880 to 1916 were collected in a publication in 1938. The observations include descriptions of booming, blowing wind, muffled sounds, and “an immense covey of partridges on the wing”, according to one report.

Non-Earthquake Booms

Of course, most booming sounds that people hear are not caused by earthquakes. Some other common and not-so-common natural causes are lightning, storm and tsunami waves, meteors, and sand dunes. Man-made causes include sonic booms, explosions, and construction.

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