Geological Hazards in Connecticut 


There are several small earthquakes in and near Connecticut every year, most being so small that they are not felt, only recorded on seismometers.  Earthquakes can have a variety of causes, including fault movements, landslides, volcanic eruptions, etc., but most earthquakes are pretty much due to slip of the solid earth along faults.  The faults may be exposed on the surface, but many earthquakes apparently occur along buried faults that do not show movement on the surface.

The tectonic map of Connecticut (below, click for a lager version) shows the major terranes by different patterns, and the boundaries between terranes are generally faults of various sorts.  The terrane boundary faults have been well stuck for hundreds of millions of years, but younger, steep-angled faults are common within the terranes, as shown by heavy solid lines on the map.  The ones in the Hartford basin, in the middle of Connecticut, are especially prominent.  It could be that some of these faults are still active and generate some modern earthquakes, but no earthquake has been directly related to a known fault. 
 CT Tectonic Map_Reduced   New England EQ Prob Map

The map with green spots was prepared by the Weston Observatory in Massachusetts, which operates a network of seismographs in New England.  According to a statistical analysis of earthquakes between 1975 and 1998, there is a 66% chance that the next earthquake of magnitude 2.7 or greater in New England will occur in one of the green areas.  That's a pretty small earthquake, but larger ones are so rare that it is very hard to make any reasonable prediction about the next one in New England.  In other words, earthquake risk is real but very small.

Notice that most of the green circles in Connecticut cluster between Moodus and New Haven, but the large zone around and north of the greater New York City area includes a little bit of westernmost Connecticut. Other likely areas for earthquakes are in southeastern Massachusetts and southern New Hampshire, and Maine is surprisingly active as well.  Vermont is blessed with seismic quietness.  Here in Connecticut, areas with lots of faults do not match up very well with our earthquake risk map.  You can check on recent earthquakes in New England at the New England Seismic Network web site.



Radon (chemical symbol Rn) is a colorless, odorless, heavy gas that seeps up to the surface out of the rocks of the earth.  Radon is a product of the decay of uranium (U), which is present in most rocks in small amounts, but U is also fairly concentrated in some areas of granite, pegmatites, and mineral veins in Connecticut. Although radon is quite radioactive, it is not very dangerous itself because it has a neutral electromagnetic charge (not ionic), so it does not stick well to other molecules.  You breath it into your lungs, but you also breath it back out again.  However, radon has a short half-life (3.8 days), meaning it rapidly breaks down into other radioactive elements, which are ionic and do stick to your lung cells.  Some of these "daughter" ions are radioactive isotopes of lead, bismuth, and polonium.  Being so close up to your lung cell DNA, the radioactive particles can and do cause damage that eventually leads to tumors.

We need to pay more attention to radon, because it probably causes most of the lung cancer deaths that are not directly due to smoking.  The National Academy of Science concluded in 1998 that about 15,400 to 21,800 lung cancer deaths per year in the United States are caused by breathing high levels of indoor radon.  That means hundreds of deaths in Connecticut every year.  In addition, there may be other problems such as stomach and esophagus cancer, and even if you are not killed there are likely to be years of pain and misery.

Radon Map

This map shows potential indoor risk levels from radon in various areas of our state, based on many measurements of radon in water wells and in the air of our  buildings.  No matter where you are on the map, you will not know if your house has high radon until you test for it, which is pretty cheap and easy.  The Ct. Department of Public Health is the source of this map, and it has a good website about radon in Connecticut.

If you do find radon in your house, the problem can be fixed, and the cost is not extreme.

Check this website to understand reality versus myths about radon: http://www.epa.gov/radon/index.html