Frost Quakes!!

This is so wild. It goes with other things I love, including ball lightning and will-o-the-wisps. I've been through a frost quake!

Local Indiana station WTHR reported:

Many WTHR viewers reported hearing a loud boom early Thursday morning.

We've heard from people in Geist, Avon, Mooresville, Anderson, Noblesville, Decatur Township and in Randolph County. Residents described hearing a loud booming sound that woke them up, and some said their dishes rattled. One person says they thought their roof was collapsing.

An expert says the loud booms are probably something called "frost quakes" from all of the ice built up during the ice storm. The frost quake phenomenon is caused by a sudden cracking in soil or rock caused by the freezing and expanding of water.

"It's like a very soft explosion actually. It's like someone ran into something outside," said Dr. Gabriel Filippelli, IUPUI geology professor. "Unlike an earthquake where you feel it across hundreds or thousands of miles, these frost quakes are really localized because it doesn't freeze very deep."

The technical term is cryoseism - also known as a frost quake.

How neat! Here's what Wikipedia said about cryoseism. There apparently two types of cryoseisms, one caused by frost and one caused by ice:

A cryoseism known as a frost quake may be caused by a sudden cracking action in frozen soil or rock saturated with water or ice. As water seeps down into the rock, it freezes and expands, putting stress on surrounding rock. This builds up until it is relieved explosively in a cryoseism.

...

Cryoseisms are often mistaken for minor or intraplate earthquakes.Although the outward signs often appear similar to those of an earthquake, with tremors, vibrations, ground cracking and related noises such as thundering or booming sounds,

There were booming sounds.

cryoseisms can be distinguished from earthquakes through meteorological and geological conditions. ... [C]ryoseisms often exhibit high intensity in a very localized area, in the immediate proximity of the epicenter, as compared to the widespread effects of an earthquake.

Some reports have indicated the presence of "distant flashing lights" before or during a cryoseism, possibly due to the electrical changes when the rocks are compressed. Cracks and fissures can also appear, as the ground may contract and split apart from the cold.

...

Cryoseisms typically occur when temperatures rapidly decrease from above freezing to subzero, in the first cold snap of spring. They usually occur between midnight and dawn, during the coldest part of the night. ... In general, cryoseisms occur 3 to 4 hours after significant changes in temperature. Due to the perennial or seasonal frost conditions involved with cryoseisms, these events are limited to temperate climates which experience seasonal variation with subzero winters. Furthermore, the ground must be saturated with water, which can be caused by snowmelt, rain, sleet or flooding and the site of a cryoseism generally has little or no snow cover to insulate the ground. Geologically, areas of permeable materials like sand or gravel, which are affected by frost action are most susceptible to experience cryoseisms. After large cryoseisms, there is generally no seismic activity detected for several hours, an indication that accumulated stress has been relieved.

Several things I notice in here, like the time these things occur. The strongest one didn't come until almost eight o'clock Thursday morning, but they were going on through out the night. (I can account for this no thanks to my insomnia.) The ground being saturated with water, well, we did have a bit of thawing before this occurred. I wonder where the quake originated from.