Geology and Mineral Resources

Natural Hazards - Earthquake Awareness Page

Earthquakes in Vermont?!?

Introduction:
Earthquakes are not a common occurrence in Vermont, but they do happen here. In 1994, Vermont Emergency Management Agency (VEMA ) funded a study of Vermont to determine the potential types and severity of damage that could result from earthquakes in Vermont. Excerpts from this study, A Report on the Seismic Vulnerability of the State of Vermont by J. E. Ebel, R. Bedell and A. Urzua, are presented here. Although damaging earthquakes are infrequent in Vermont, there is a some risk to our population and there are precautions that people can take to reduce the injury and damage that could result from ground shaking. Nationally, most serious damage from ground shaking (i.e. an earthquake) results from the collapse of buildings or bridges, damage to utility lines and resulting fires, shelves and items suspended from the ceilings falling on people, and broken glass. Due to the rural nature of Vermont, most communities are not concerned with collapse of large bridges and overpasses. Geologists are not able to predict when and where an earthquake will occur, but can give probability statistics for ground shaking based on recorded human observations during the past several hundred years. Geologists can also model and predict the severity of quakes. These models are used to help citizens prepare for and to allow governments and communities to plan for this type of emergency.

Some questions and answers about earthquakes are listed below, based on information from Federal Emergency Management Agency (FEMA) publications: H-34, September, 1991, Are You Ready? Your Guide to Disaster Preparedness; and 88A, March 1990, Earthquake Safety Activities for Children; A Report on the Seismic Vulnerability of the State of Vermont by Ebel and others, 1995; and Why Does the Earth Quake in New England by Alan Kafka, 2004. For more links to past and real-time earthquakes, go to our Hazards Index Page.

What is an earthquake?
An earthquake is the sudden shaking of the earth caused by shifting of rock beneath the surface.

Where do earthquakes occur?
Worldwide, 98% of earthquakes occur at plate boundaries. In the United State most earthquakes occur west of the Rocky Mountains, although some have occurred in the east.

What causes an earthquake?
The cause of earthquakes in Vermont is not clear. The majority of quakes worldwide occur at plate boundaries. The earth's lithosphere or outer shell is believed to be comprised of thin slabs or plates which move over, under, and past each other sliding about over the upper mantle (a 2800 km thick dense layer surrounding the earth's core) at rates of 10 to 130 mm per year. The activity and collisions at plate boundaries are varied: one plate may dive beneath another along a subduction zone; one plate may be thrust over the other; or plates may slide past each other. The earthquake zones along plate boundaries are well defined and are the cause for most of the earthquakes in the world, but do not explain the earthquakes in Vermont. Vermont is located within a plate rather than at a plate boundary and the cause for intraplate earthquakes is poorly understood. Perhaps quakes occur along ancient plate boundaries where faults are reactivated or serve as a surface along which tectonic stress is released. However, at the present time the locations of recorded earthquakes do not correspond to known fault surfaces mapped in the state or neighboring states.( Why Does the Earth Quake in New England by Alan L. Kafka, 1997).

What would an earthquake feel like and what happens during an earthquake?
You may notice a gentle shaking, a swaying of plants, light fixtures and shelves, and a sudden jolt or a low rumbling noise. It is difficult to move or walk around. Cabinets and shelves are likely to fall, light fixtures and anything on the ceiling may come down, and doors and windows may jam shut, bend and break. There is usually a smaller aftershock associated with an earthquake.

What type of damage occurs during an earthquake?
During an earthquake, buildings may collapse, foundations may crack, telephone and power lines may collapse causing fires, and there may be explosions and landslides. In coastal areas, there may be huge ocean waves called tsunamis.

What are the major causes of injury from earthquakes?
Most injuries are caused by collapsed buildings, flying glass, and fire resulting from broken chimneys and ruptured gas and power lines.

What are the risks for Vermonters?
In Vermont, we do not have many large urban areas where collapse of skyscrapers and overpasses would be a problem. We do, however, have old masonry buildings and buildings which have not been engineered with earthquakes in mind. Our lack of preparedness is a concern. The Federal Emergency Management Agency (FEMA) and the New England States Emergency Consortium (NESEC) provide information on emergency preparedness.

What should people do during an earthquake?