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New Hampshire Earthquakes

History of Earthquakes in New Hampshire

In 1638, only 18 years after they landed at Plymouth Rock, the Massachusetts Pilgrims felt their first earthquake.  The earthquake shaking was so strong that the people had trouble standing without holding on to something.  Recent seismological research has suggested that this earthquake was about a magnitude 6.5 event centered in New Hampshire between the city of Concord and just west Laconia.  Thus, New Hampshire’s first historic earthquake was also the first significant earthquake in colonial New England.

Map of Earthquakes of the Northeastern US and Southeastern Canada 1975 to 2017

From that first earthquake in 1638 through the end of 2016 a total of 320 felt earthquakes are known to have been centered in New Hampshire, and many more earthquakes that have been too small to be felt have been detected during recent decades by modern instrumental seismic monitoring.  Since the 1970s the area just north of Concord, NH has been the most seismically active locality in all of New England.

Since 1638 the strongest earthquakes that were centered in New Hampshire took place on December 20 and 24, 1940, both of which had an estimated magnitude of 5.6.  The December 20 shock took place at 2:27 a.m., awakening residents in central New Hampshire, whereas the December 24 event occurred at 8:43 a.m.  At Tamworth in the Ossipee Mountains approximately where the earthquakes were centered, many chimneys were damaged, plaster was cracked, tombstones were rotated, some furniture was broken, and many items were thrown from shelves.  Other nearby towns suffered similarly but with fewer reports of damage.  The second earthquake was reported to be a sharper and shorter shake and more terrifying than the first shock.  Many smaller aftershocks were reported, with one person claiming to have felt 129 earthquakes through January 31, 1941.  These Ossipee earthquakes had been preceded by an earthquake in the same area on October 9, 1925.  This earlier shock, which had an estimated magnitude of 4.0, knocked goods and dishes from shelves and damaged chimneys in New Hampshire and nearby Maine.  On July 23, 1843 an earthquake with estimated magnitude 4.1 occurred with an epicenter probably offshore southeast of Portsmouth.  Stone walls were thrown down in the Portsmouth area, and this earthquake was felt from Portland, ME to Kingston, MA.  Another probable offshore earthquake that broke windows in Portsmouth occurred on November 9, 1810.  This earthquake had an estimated magnitude of 4.0 and was felt as far away as Boston, MA.  Another earthquake of magnitude 4.0 was centered at Gaza west of Laconia on January 18, 1982.  This earthquake caused a chimney fire that destroyed one building, and it was felt strongly throughout central New Hampshire.  On April 25, 1928, an earthquake of estimated magnitude 3.9 was centered near Berlin.  This event shook central New England but caused no damage.  On November 23, 1884 an earthquake of  an estimated magnitude 3.8 was centered at Contoocook. Although widely felt in New Hampshire and neighboring states, this event caused no damage.  The same can be said for an earthquake also of estimated magnitude 3.8 from the same epicentral area on May 1, 1891.  On October 25, 1986, a magnitude 3.7 earthquake was centered at Tilton.  This earthquake was felt throughout New Hampshire and into nearby states, but no damage was reported.

Earthquakes Outside of Massachusetts Having Notable State Impacts

Several earthquakes from outside of New Hampshire have had significant effects in the state.  The November 18, 1755 magnitude 6.2 earthquake with a probable epicenter east of Cape Ann, MA cause damage to a many chimneys and cracks in brick walls in Portsmouth.  The October 29, 1727 magnitude 5.6 earthquake that was centered at Newburyport, MA damaged chimneys and stone walls in southeastern New Hampshire was well as causing a landslide and a sand blow at Hampton.  On June 14, 1973 a magnitude 4.7 earthquake with an epicenter near the place where the New Hampshire, Maine and Quebec borders meet rattled New Hampshire with some reports of cracked plaster, broken windows, and items knocked from shelves reported from the northern part of the state.  A magnitude 5.9 earthquake that had an epicenter near Montreal on September 16, 1732 on the Gregorian calendar strongly shook all of New Hampshire, although no damage was reported due to the very sparse population in northern and central parts of the state at the time.  Other large earthquakes that were felt noticeably throughout New Hampshire were the September 5, 1944, a magnitude 5.9 earthquake with an epicenter at Massena, NY, the magnitude 5.8 earthquake on January 9, 1982 with an epicenter in central New Brunswick, the magnitude 5.9 earthquake on November 25, 1988 centered north of Quebec City, and the magnitude 5.0 earthquake on April 20, 2002 centered at Au Sable Forks, NY.  In addition, some strong earthquakes in the Charlevoix seismic zone in Quebec on October 17, 1860 (magnitude 6.0), October 20, 1870 (magnitude 5.9) and March 1, 1925 (magnitude 6.2) were felt throughout New Hampshire but caused no damage.

New Hampshire Information and Links

Prepared in Consultation with Professor John E. Ebel PhD. Boston College, Weston Observatory