Frost Quakes

 

     Today we woke up to drizzling rain in a 300 mile wide by 1,300 mile long system that arrived over night from down in Texas. Today's weather conditions will have us feeling more like spring than winter with potentially record-breaking high temperatures of near 65 degrees. But, it also comes with some strong winds with gusts predicted to be up to 60 mph...that's near hurricane strength (!) and that could produce damages and power outages. Just another typical crappy day where I live. 

     There is no danger of frost quakes, or ice quakes, today although a while back when we had zero degree temperatures and even below in some nearby locations they were a real possibility. 

     Technically known as cryoseisms, a frost quake is a seismic event caused by a sudden cracking action in frozen soil or rock saturated with water or ice or by stresses generated at frozen lakes. 

     As water drains into the ground, it may freeze and expand under colder temperatures, putting stress on its surroundings. This stress builds up until relieved explosively in the form of a frost quake. 

     There are numerous requirements for one to occur and so accurate predictions are not possible. Interestingly, their possibility may be a factor in structural design and engineering when constructing in an area historically known for such events. And, needless to say, Speculation has been made between global warming and their frequency. 

     Frost quakes occur when very cold air interacts with soil that is saturated after recent rain or snow has seeped into the ground. They are triggered by a rapid temperature drop in a short amount of time when the air is at or below freezing. The cold air suddenly freezes the water in the ground, causing expansion, which then causes stress and pressure to build up. The result causes soil and rocks to crack, which can make a booming sound and produce minor shaking. 

     They are most likely to happen in locations that are susceptible to cold air masses, like Canada and the northern states in the U.S. They have been reported in recent years in Connecticut, Massachusetts, Maine, Vermont, Michigan, Wisconsin, Ohio, Indiana, Missouri and Tennessee. 

     A 2016 study concluded that frost quakes could become more frequent because as winters continue to get warmer and the ground remains thawed for longer with a higher prevalence of unfrozen water in the soil. 

      Frost quakes are often mistaken for minor earthquakes because the initial indications may appear similar...tremors, vibrations, ground cracking and noises such as cracking, popping, thundering or booming sounds.  

 

     However, they can be distinguished from earthquakes through meteorological and geological conditions.

     Frost quakes can have an intensity of up to 6 (out 0f 10) on the Modified Mercalli Scale which means they are considered "strong" and felt by all and many people will be frightened. Some heavy furniture may be moved and there may be a few instances of fallen plaster, but damage is considered "slight." 

     Also, frost quakes often exhibit high intensity only in a very localized area in the immediate proximity of the epicenter as compared to the widespread effects of an earthquake. And, because they happen at the ground's surface they cause effects right at the site, often strong enough to jar people awake. 

     Some reports have included the presence of distant flashing lights before or during a frost quake; this is possibly because of electrical changes when rocks are compressed. Cracks and fissures may also appear as surface areas contract and split apart. Sometime superficial to moderate occurrences may range from cracks of a few inches to several miles long.