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 Modified Mercalli Intensity (MMI) scale, respectively.

The USGS generates a real-time map of earthquakes that have occurred over the past 7 days in the United States. The map includes the age and strength of any earthquake with a magnitude over 1.0 (updated hourly).

History of Earthquakes in the Northeast:

Believe it or not, the Northeast US is earthquake country! No it does not have the high frequency of earthquakes of California. However, the Northeast has experienced damaging earthquakes in the past and they will occur again in the future.

The Northeast has a long history of earthquakes. Some of the first explorers were startled when they experienced strong shaking and rumbling of the earth beneath their feet. The Pilgrims felt their first earthquake in 1638. A recently released report by one of the Northeast's foremost seismologists Dr. John Ebel 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.

In 1727, an earthquake rattled the east coast from Maine to Delaware. The shock was epicentered off the New Hampshire and Massachusetts coast and 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.

An even stronger earthquake rocked the region in 1755 of the coast of Cape Anne Massachusetts. 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.

More recent earthquakes of particular note that have affected the Northeast include a pair of damaging earthquakes (magnitude) that occurred in 1940 near Ossipee, NH. Since 1975 moderate size earthquakes have occurred in Central New Brunswick, central NH, northern NY State and Quebec. The map below depicts earthquake activity in the Northeast from October, 1975 - March, 2010

Northeast seismicity from October, 1975 - March, 2010 Source: Weston Observatory

Click on your state below for state-specific earthquake information and links.

Total Earthquakes by State
1638 - 2007

State	Years of Record	Number Of Earthquakes
Connecticut	1668 - 2007	137
Maine	1766 - 2007	544
Massachusetts	1668 - 2007	355
New Hampshire	1638 - 2007	360
New Jersey	1738 - 2007	141
New York	1840 - 2007	755
Rhode Island	1776 - 2007	38
Vermont	1843 - 2007	73
Total Number of Earthquakes in Northeast = 2403

* Northeast is defined here as CT, ME, MA, NH, NJ, NY, RI and VT only. Seismic data from other proximate states (e.g., PA, MD, DE) and border regions of Canada is not included. All data is obtained from Weston Observatory and compiled by NESEC.

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What is the Risk of an Earthquake in the Northeast?

Potential earthquake losses, when annualized, add up to about $5.3 billion dollars a year, and the Northeast ranks fourth 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 $5.3 billion annual 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.

Northeast Earthquake Facts

• The cities in the Northeast are among the most densely populated areas in the United States, which places more people at risk in the event of an earthquake.
• The area impacted by an earthquake in the Northeast can be up to 40 times greater than the same magnitude event occurring on the West coast due to our regional geology.
• Approximately 40-50 earthquakes are detected annually in the Northeast.
• The Northeast is home to many older and historic structures that are not designed to withstand the impacts of an earthquake.
• Many older structures in the Northeast, such as schools, hospitals and fire stations, are built of un-reinforced masonry (i.e., "red brick") and are particularly vulnerable to damage or collapse in the event of an earthquake.
• Most states in the Northeast have adopted some seismic provisions into their state building codes for certain types of new construction. However, the coverage, scope and enforcement of these codes vary by state and community.
• Unlike other areas of the country where earthquakes occur along known fault lines (e.g., California), Northeast earthquakes do not correlate with the many known faults that exist in the region.
• While there are many uncertainties about what causes earthquakes in the Northeast, one thing is certain: earthquakes will continue to occur in this region.

(Modified from Stearns & Miller, 1977)
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When are Earthquakes Most Likely?

There is no season for earthquakes. They can occur at any time without warning. The probability of an earthquake occurring today in New England are computed by the Weston Observatory based on an analysis of the earthquake activity from 1975-1999 and are presented here on an experimental basis for informational purposes only.

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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 the ground, just as ripples are generated when a pebble is dropped into a pond.

What Causes The Earth to Quake in New England provides an excellent overview of why we have earthquake in the Northeast.

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Did You Know?

• The Northeast experiences an average of 40 - 50 earthquakes per year.
• Due to the solid bedrock geology of the Northeast, a large earthquake will affect a much wider area than an earthquake of similar magnitude in California.

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Earthquake Glossary

IN THE EVENT OF AN EARTHQUAKE

What to do Before an Earthquake

What to During an Earthquake

What to Do After an Earthquake

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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 Everyone

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 or community's building codes are, check our NESEC Building Codes Database.
Below are the main categories of FEMA earthquake mitigation publications and tools.

• Individuals and Families
  Practical guides and checklists describing how you can prepare yourself, your family, and your home to reduce the likelihood of damage or injuries during earthquakes and the risk of hardships and disruptions following disasters
• Teachers and Kids
  Interactive lessons and other instructional materials that engage students in learning about earthquakes and earthquake safety; also practical preparedness information for child care providers
• Public Policy Makers and Planners
  Reports, handbooks, case studies, and tools for use in planning, promoting, developing, and implementing seismic risk-reduction policies and programs at state and local levels
• Seismic Design and Construction Professionals
  Technical guidance and training materials focusing on the evaluation, design, and construction of earthquake-resistant structural and nonstructural elements for new and existing buildings, lifelines, and other structures; includes the latest NEHRP recommended provisions for seismic design standards
• Building Codes and Seismic Rehabilitation
  Among the most important strategies for earthquake risk reduction are the development, adoption, and enforcement of seismic building codes and standards, and the seismic rehabilitation of existing structures; these publications and tools address the public policy, socioeconomic, and technical aspects of these strategies
• Training
  Presentation materials, student manuals, and online instruction designed for adult learners interested in designing earthquake-resistant buildings, assessing the seismic vulnerability of buildings, and coordinating seismic risk-reduction programs and activities

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Links to Additional Information:

• Boston College Weston Observatory
• Lamont-Doherty Earth Observatory