The lack of historical and instrumental reports of strong earthquakes in Connecticut suggests that State to be a region of very minor seismic activity, even when compared to other States in the northeast region.
The cause of "rumblings" in the area near Moodus, a few miles north of East Haddam, had been a matter of scientific speculation for years. Native Indians called East Haddam Morehemoodus, or place of noises, and the town name "Moodus" derived from the Indian word. The earth noises, a peculiar type of earthquake rumbling, apparently have been occurring in that region for years, even prior to the advent of Europeans.
The most severe earthquake in Connecticut's history occurred at East Haddam on May 16, 1791.
Describing that earthquake an observer said: "It began at 8 o'clock p.m., with two very heavy shocks in quick succession. The first was the most powerful; the earth appeared to undergo very violent convulsions. The stone walls were thrown down, chimneys were untopped, doors which were latched were thrown open, and a fissure in the ground of several rods in extent was afterwards discovered. Thirty lighter ones followed in a short time, and upwards of one hundred were counted in the course of the night.
"The shock was felt at a great distance. It was so severe at Clinton, about 12 miles south, that a Capt. Benedict, walking the deck of his vessel, then lying in the harbor at that place, observed the fish to leap out of the water in every direction as far as his eyes could reach."
Still another report states: "the day after the earthquake in 1791, it is said that apertures and fissures were observed in the earth and rocks near Moodus River Falls, and that stones of several tons in weight were thrown from their places."
The record shows the next moderate tremor occurred at Hartford in April 1837. It jarred loose articles, set lamps swinging, and rang bells. Alarmed residents rushed from their homes into the streets.
In August 1840, an earthquake of similar intensity centered a few miles southwest of the 1837 tremor. It shook Hartford quite strongly, and was felt at many points in Connecticut. No damage resulted, however. At Chester, not far from East Haddam, observers compared the tremor "to the rumble of thunder." Its origin was apparently 10 to 20 miles north of New Haven.
On June 30, 1858, New Haven was shaken by a moderate tremor at 10:45 in the evening. Residents reported rattling of glasses and a noise "like carriages crossing a bridge." Derby residents were also shaken strongly by this earthquake.
Seventeen years later, on July 28, an early morning tremor shook 2,000 square miles of Connecticut and Massachusetts. Rumbling noises were heard during this intensity V earthquake.
The strongest tremor since that in 1791 hit near Hartford on November 14, 1925, at about 8 a.m. Plaster was knocked from walls, and many residents were frightened. At Windham, dishes were shaken from shelves, and at East Haddam, the familiar "Moodus" rumblings were noted.
In March 1953, Stamford sustained a minor tremor that alarmed many. "Radiators beat a weird tattoo against the floor of the police station," notes one report. Houses were jarred, and earth noises were heard. The tremor caused no damage.
An intensity V earthquake in southern Connecticut occurred on November 3, 1968, at about 3:30 in the morning. Plaster cracked at Madison, furniture shifter at Chester, and small items fell and broke. Loud earth noises accompanied the tremor. The Moodus noises were noted once again at East Haddam.
A few damaging shocks centering in neighboring States, and several Canadian tremors, have been noted by Connecticut citizens the past three hundred years.
A devastating earthquake near Tros-Rivieres (Three Rivers), Quebec, on February 5, 1663, caused moderate effects in some areas of Connecticut. Sketchy accounts of this quake relate fantastic tales of mountains being thrown down and great forests sliding into the St. Lawrence River near its Quebec Center.
Massachusetts shocks in November 1727 and November 1755 were felt strongly by some Connecticut citizenry. Both were intensity VIII at their epicenters, leaving behind collapsed walls, flattened chimneys, and other broken reminders common to most strong earthquakes.
The Timiskaming, Ontario, earthquake in November 1935 was quite noticeable in Connecticut and other New England States. Several cracked windowpanes were noted at Cornwall, Connecticut. Because of the sparse population, damage at the epicenter of this tremor was insignificant. However, an indication of its severity was the large felt area - one million square miles of Canada and the United States.
An earthquake near Massena, New York, in September 1944 was felt over a wide region. Mild effects were noticed by residents of Hartford, Marion, New Haven and Meriden, Connecticut. At its epicenter, the shock destroyed nearly all chimneys, crippled several buildings, and caused $2 million property damage in that region.
Abridged from Earthquake Information Bulletin, January - February 1971.
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