Earthquake Shakes Eastern Canada, U.S

June 23, 2010

Ontario quake

Ontario Earthquake Area. Credit: USGS.

An earthquake with the following parameters has occurred:

Time: Wednesday, June 23, 2010 at 17:41:42 UTC, 13:41:42 EDT (1:42 PM in NY)

Location: 45.862 °N, 75.457 °W (Southern Ontario), approximately 53 KM (33 mi) NNE from Ottawa

Depth: 18 km (11.2 mi) set by location program

Magnitude 5.0

Parameters are calculated by the National Earthquake Information Center, U.S. Geological Survey, using data from US and Canadian Earthquake Monitoring Networks, including the Lamont Cooperative Seismic Network. THESE PARAMETERS MAY CHANGE AS MORE DATA ARE ANALYZED.

This earthquake occurred near the Ontario-­‐Quebec boundary, in what seismologists call the Western Quebec Seismic Zone. Earthquakes in this zone are commonly felt over a much broader region than earthquakes of similar size in the west. This earthquake is generating felt reports as far away as Long Island, Northern New Jersey, Northern Pennsylvania, Western New York, and Western New England. No significant damage has been reported so far, but more information may soon be available.

Initial felt reports indicate moderate to strong shaking near the epicenter (Modified Mercalli Intensity VI). Most felt reports in New York State are MMI II-­‐IV (weak to light).

An earthquake of this size is likely to generate an aftershock sequence lasting several days to weeks. The rate of aftershock occurrence will decay in inverse proportion to the time since the mainshock, although the magnitude may not.

Previous large earthquakes in this zone:

1935, (magnitude 6.1), well to the northwest of today’s quake

1732 (magnitude 7.2 (est)) near Montreal (damage reported)

The Western Quebec Seismic Zone is not near a present-­‐day plate boundary, where most earthquakes occur. However, earthquakes can and do occur in the middle of tectonic plates. Such “intraplate” seismicity often concentrates in zones, such as the Western Quebec Seismic Zone. Though infrequent, they can still cause significant damage, especially to fragile infrastructure and buildings.

There are other intraplate earthquake-­‐generating zones in the Eastern US, including measureable activity in the NY City metropolitan area, in western New York State, and in the Adirondacks. Lamont-­‐Doherty Earth Observatory operates the Lamont Cooperative Seismic Network as part of the Advanced National Seismic System of the U.S. Geological Survey.

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