Earthquakes

An earthquake is a sudden rapid shaking of the earth caused by the shifting of rock beneath the earth's surface. Earthquakes can cause buildings and bridges to collapse, disrupt gas, electric and phone lines, and often cause landslides, flash floods, fires, avalanches, and tsunamis. Larger earthquakes usually begin with slight tremors but rapidly take the form of one or more violent shocks, and are followed by vibrations of gradually diminishing force called aftershocks. The underground point of origin of an earthquake is called its focus; the point on the surface directly above the focus is the epicenter. The magnitude and intensity of an earthquake is measured by the Richter scale and the Mercalli scale.

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History of Earthquakes in New England What is the Risk of Earthquakes in New England? When Are Earthquakes Most Likely? Who Is Most At Risk? What Causes an Earthquake? Did You Know? Terms To Know: In The Event Of An Earthquake What is Mitigation? Earthquake Hazard Mitigation Measures for Communities Earthquake Hazard Mitigation Measures for Individuals Links for Additional Information

History of Earthquakes in New England:

The average person may not associate earthquakes with the eastern portion of the United States, yet some of the largest seismic events have occurred east of the Rocky Mountains. In fact, the recorded history of earthquakes in the New World began shortly after the Pilgrims landed, when in 1638, a damaging earthquake rocked Plymouth Colony.

A recently released report by one of New England's foremost seismologists has shed some light on the possible epicenter and magnitude of the 1638 earthquake. He found that the French colonists on the St. Lawrence River and the English along the Massachusetts coast felt this quake with equal intensity. In order for this to happen he believes the most likely epicenter would be central New Hampshire with a magnitude of 6.5 to 7.

The first well documented, damaging earthquake to affect New Hampshire occurred the night of October 29, 1727. This earthquake, with its epicenter located off the New Hampshire and Massachusetts coast, caused damage from Boston, Massachusetts to Portland, Maine. Brick buildings "shattered" in Haverhill, Massachusetts, chimneys toppled and large quantities of sand were ejected from the ground in Newbury, Massachusetts and in Hampton, New Hampshire.

Twenty-eight years later there occurred the Cape Ann Earthquake. This earthquake, with an estimated magnitude of 6.0, caused widespread damage along coastal New England on the night of November 18, 1755. The crew of a vessel sailing 200 kilometers offshore thought they had hit a rock. They "hove-to and cast the lead," only to find plenty of water under the keel. In Boston, twelve to fifteen hundred chimneys toppled, gable ends of brick buildings broke off and fallen bricks blocked the streets. According to John Hyde, a Boston writer, damage was particularly heavy "on the low, loose ground made by encroachments on the harbor.

New England Earthquakes with magnitude 4.2 or more
1924 - 1989

New England Location Date Magnitude
Ossipee, NH December 20, 1940 5.5
Ossipee, NH December 24, 1940 5.5
Dover-Foxcroft, ME December 28, 1947 4.5
Kingston, RI June 10, 1951 4.6
Portland, ME April 26, 1957 4.7
Middlebury, VT April 10, 1962 4.2
Near NH Quebec Border, NH June 15, 1973 4.8
West of Laconia, NH Jan. 19, 1982 4.5

New England States Historical Earthquakes

State Years of Record Number Of Earthquakes
Connecticut 1568 - 1989 137
Maine 1766 - 1989 391
Massachusetts 1627 - 1989 316
New Hampshire 1728 - 1989 270
Rhode Island 1766 - 1989 32
Vermont 1843 - 1989 69
Total Number of Earthquakes within New England = 1215.
Total Number of Earthquakes in the Northeast, 1538-1989 = 4498.
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What is the Risk of an Earthquake in New England?

Potential earthquake losses, when annualized, add up to about $4.4 billion dollars a year, and the Northeast ranks third in the nation for annualized losses, according to a recently released study by the Federal Emergency Management Agency (FEMA).

Northeast cities ranked among the top 40 high-loss potential urban areas include New York and Boston. Earthquake loss estimates are annualized to factor in historic patterns of frequent smaller earthquakes with infrequent but larger events.

The $4.4 billion estimate is extremely conservative and includes only capital losses to buildings and business interruption losses. It does not include damage and losses to critical facilities, transportation, utility lifelines or indirect economic losses.

To arrive at their findings, FEMA utilized a Geographic Information System (GIS) based earthquake loss estimation methodology called Hazards US (HAZUS), developed by FEMA in cooperation with the National Institute of Building Sciences.

New England Earthquake Facts

  • New England has a population density 10 times greater than California.
  • Most major cities in New England have a greater population density than the major cities in California.
  • The area impacted by an earthquake in New England will be from 4 to 40 times greater than that of California because of intra-plate forces.
  • Much of New England's Built Environment is very old, non-seismically designed and brittle.
  • Predominant structures are built of un-reinforced masonry, which may be as much as 8 stories in height.
  • Most buildings are designed to stand up to the downward force of gravity, but not to the sideways forces of earthquakes, with can be just as strong.
  • In addition to sideways shaking motions, earthquakes can also produce vertical rocking motions like that of a wave. The current model Building Codes, such as BOCA, do not include vertical effects of earthquakes: i.e., Vertical Acceleration, Velocity or Displacement.
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When are Earthquakes Most Likely?

There is no season for earthquakes. They can occur at any time without warning.

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Who Is Most at Risk?

People who live or work in unreinforced masonry buildings built on filled land or unstable soil.

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What Causes an Earthquake?

Earthquakes in the Northeast U.S. cannot be associated with specific known faults, as opposed to the typical seismic activity evident in California. While California earthquakes typically occur at, or near the conjunction of two of the Earth's major tectonic plates ("inter-plate" activity), earthquakes in New England occur in the middle of plates ("intra-plate" activity), far from the plate boundaries .

The immediate cause of most shallow earthquakes is the sudden release of stress along a fault, or fracture in the earth's crust, resulting in movement of the opposing blocks of rock past one another. These movements cause wave-like vibrations to pass through tje ground, just as ripples are generated when a pebble is dropped into a pond.

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Did You Know?

  • New England experiences an average of 30-40 earthquakes per year although most are too small or remote to be felt.
  • Due to the solid bedrock geology of New England, a large earthquake will affect a much wider area than an earthquake of similar magnitude in California.
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Terms to Know:

  • A fault is a fracture in the Earth's crust along which two blocks of the crust have slipped with respect to each other.
  • The focus of an earthquake is the point underneath the earth's surface where an earthquake originates.
  • The epicenter of an earthquake is the point on the Earth's surface directly above the focus.
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In The Event Of an Earthquake:


IF INDOORS:
  • DROP to the ground; take COVER by getting under a sturdy table or other piece of furniture; and HOLD ON on until the shaking stops. If there isn’t a table or desk near you, cover your face and head with your arms and crouch in an inside corner of the building.
  • Stay away from glass, windows, outside doors and walls, and anything that could fall, such as lighting fixtures or furniture.
  • Stay in bed if you are there when the earthquake strikes. Hold on and protect your head with a pillow, unless you are under a heavy light fixture that could fall. In that case, move to the nearest safe place.
  • Use a doorway for shelter only if it is in close proximity to you and if you know it is a strongly supported, load bearing doorway.
  • Stay inside until shaking stops and it is safe to go outside. Research has shown that most injuries occur when people inside buildings attempt to move to a different location inside the building or try to leave.
  • DO NOT use the elevators.
IF OUTDOORS:
  • Move to an open area away from buildings, electric wires, and streetlights or anything that could fall on you. Make sure to look up and watch for falling debris.
IF IN A CAR:
  • Stop and stay in the vehicle away from bridges or overpasses.
  • After the earthquake proceed with caution, roads and bridges may have been damaged.
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What is Mitigation?

Mitigation is the cornerstone of emergency management. It's the ongoing effort to lessen the impact disasters have on people and property. Mitigation involves keeping homes away from floodplains, engineering bridges to withstand earthquakes, creating and enforcing effective building codes to protect property from hurricanes -- and more.


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Earthquake Hazard Mitigation Measures for Communities

FEMA's National Mitigation Action Plan suggests that state and local mitigation plans include the following:
  • Developing and enforcing all-hazards building codes.
  • Adopting incentives to encourage mitigation.
  • Developing administrative structures to support the implementation of mitigation programs.
  • Mitigation should be incorporated into land use management plans.
  • Developing and conducting public information campaigns on hazard mitigation should be a priority.
FEMA's Earthquake Program has four basic goals directly related to the mitigation of hazards caused by earthquakes. They are to:
  • Promote Understanding of Earthquakes and Their Effects.
  • Work to Better Identify Earthquake Risk.
  • Improve Earthquake-Resistant Design and Construction Techniques.
  • Encourage the use of Earthquake-Safe Policies and Planning Practices.
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Earthquake Hazard Mitigation Measures for Individuals

Your first line of protection against earthquakes is the strength of your home. The strength of your home depends largely on the contractor who built it and the building standards that the contractor used. Each state sets minimum quality standards, known as building codes, that contractors and builders must follow. To find out how good your state of community's building codes are, check our NESEC Building Codes Database.

How to Protect Your Property:

  • Bolt bookcases, china cabinets, and other tall furniture to wall studs. Brace or anchor high or top-heavy objects. During an earthquake, these items can fall over, causing damage or injury.
  • Secure items that might fall (televisions, books, computers, etc.). Falling items can cause damage or injury.
  • Install strong latches or bolts on cabinets. The contents of cabinets can shift during the shaking of an earthquake. Latches will prevent cabinets from flying open and contents from falling out.
  • Move large or heavy objects and fragile items (glass or china) to lower shelves. There will be less damage and less chance of injury if these items are on lower shelves.
  • Store breakable items such as bottled foods, glass, and china in low, closed cabinets with latches. Latches will help keep contents of cabinets inside.
  • Store weed killers, pesticides, and flammable products securely in closed cabinets with latches, on bottom shelves. Chemical products will be less likely to create hazardous situations from lower, confined locations.
  • Hang heavy items, such as pictures and mirrors, away from beds, couches, and anywhere people sit. Earthquakes can knock things off walls, causing damage or injury.
  • Brace overhead light fixtures. During earthquakes, overhead light fixtures are the most common items to fall, causing damage or injury.
  • Strap the water heater to wall studs. The water heater may be your best source of drinkable water following an earthquake. Protect it from damage and leaks.
  • Bolt down any gas appliances. After an earthquake, broken gas lines frequently create fire hazards.
  • Install flexible pipe fittings to avoid gas or water leaks. Flexible fittings will be less likely to break.
  • Repair any deep cracks in ceilings or foundations. Get expert advice if there are signs of structural defects. Earthquakes can turn cracks into ruptures and make smaller problems bigger.
  • Check to see if your house is bolted to its foundation. Homes bolted to their foundations are less likely to be severely damaged during earthquakes. Homes that are not bolted have been known to slide off their foundations, and many have been destroyed because they are uninhabitable.
  • Consider having your building evaluated by a professional structural design engineer. Ask about home repair and strengthening tips for exterior features, such as porches, front and back decks, sliding glass doors, canopies, carports, and garage doors. Learn about additional ways you can protect your home. A professional can give you advice on how to reduce potential damage.
  • Follow local seismic building standards and safe land use codes that regulate land use along fault lines. Some municipalities, counties, and states have enacted codes and standards to protect property and occupants. Learn about your area's codes before construction.

How to Plan for an Earthquake:

  • Pick "safe places" in each room of your home. A safe place could be under a sturdy table or desk or against an interior wall away from windows, bookcases, or tall furniture that could fall on you. The shorter the distance to move to safety, the less likely you will be injured. Injury statistics show that persons moving more than 10 feet during an earthquake's shaking are most likely to experience injury.
  • Practice drop, cover, and hold-on in each safe place. Drop under a sturdy desk or table, hold on, and protect your eyes by pressing your face against your arm. Practicing will make these actions an automatic response. When an earthquake or other disaster occurs, many people hesitate, trying to remember what they are supposed to do. Responding quickly and automatically may help protect you from injury.
  • Practice drop, cover, and hold-on at least twice a year. Frequent practice will help reinforce safe behavior.
  • Talk with your insurance agent. Different areas have different requirements for earthquake protection. Study locations of active faults, and if you are at risk, consider purchasing earthquake insurance.
  • Inform guests, babysitters, and caregivers of your plan. Everyone in your home should know what to do if an earthquake occurs. Assure yourself that others will respond properly even if you are not at home during the earthquake.
  • Get training. Take a first aid class from your local Red Cross chapter. Get training on how to use a fire extinguisher from your local fire department. Keep your training current. Training will help you to keep calm and know what to do when an earthquake occurs.
  • Discuss earthquakes with your family. Everyone should know what to do in case all family members are not together. Discussing earthquakes ahead of time helps reduce fear and anxiety and lets everyone know how to respond.
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Links for Additional Information about New England Earthquakes:

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