IN THE NEWS
The August 2011 Knox, NY Earthquakes
The Albany, New York area experienced 24 small, deep earthquakes between Monday, August 22 and Sunday, August 28. These minor earthquakes occurred below the Helderberg plateau in the Town of Knox, approximately 12 miles west of Albany. The earthquakes had magnitudes of 1.6 to 2.9, and occurred at depths of 17.6 to 24.0 kilometers (10.9 to 14.9 miles).
Earthquake (“seismic”) records for the region, available beginning in the late 1970s, indicate an unusual number of small, deep earthquakes occur in the Helderbergs. Between 1980 and 2007, 30 earthquakes were recorded beneath the Town of Berne, immediately south of Knox. Between February 2009 and March 2010, 37 additional earthquakes occurred below Berne. The Berne earthquakes had magnitudes between 1.1 to 3.1, and occurred at depths of 4-22 kilometers (2.5 to 13.7 miles).
The latest series of 24 earthquakes represent the first recorded earthquakes in Knox.
Earthquakes generally occur when there is sudden movement along a break in rocks, called a fault. Earthquakes with a magnitude of 2.0 to 2.9 or less are generally not felt; those between 3.0-3.9 are more commonly felt, but rarely cause damage.
The pattern of earthquake activity in the Helderbergs west of Albany points to small amounts of slip along deeply-buried faults. The rocks at those depths are over a billion years old, and are seen exposed in the Adirondack Mountains to the north. Two known fault zones extend toward the Helderbergs from the southern Adirondacks and the Saratoga-Ballston Spa area. Bedrock mapping in the Helderbergs has not found any significant faults that reach the surface; vertical faults found in the Helderbergs so far show only a vertical slip of a few tens of centimeters (up to one to two feet), and could have formed anytime from recently to hundreds of millions of years ago.
In and around New York, most earthquakes occur in the area of the central to northern Adirondacks and adjacent parts of Quebec and Ontario, or in the greater New York City area. The reason for such a concentration of earthquakes deep below the Helderbergs is not known, and is catching the attention of seismologists, geologists who specialize in the study of earthquakes.
To read more about the Knox and Berne earthquakes, and earthquake activity in general:
Albany Times Union:
U.S. Geological Survey:
Lamont-Doherty Earth Observatory: