Question: I heard you had an earthquake in Arizona yesterday. Did you feel it? How big was it? Did it do any damage? Isn’t Arizona a low-risk area for earthquakes? — Family, Friends, and Colleagues in many different locations.
Answer: So many of you asked about it, I decided to do a post on that event. It’s a little out of the normal scope for Sky Lights, and it runs a little longer than most posts, but it definitely falls into the category of earth science. Plus, it turns out to be an interesting story about how I used science to solve a puzzle.
The graphic above is a composite of a topographic map of Arizona, and an overlay (in red) showing the known faults. Both maps are courtesy of the USGS. The epicenter of the quake and my location (marked by red and yellow dots respectively) are separated by a distance of about 40 km (25 miles).
I was up late that night watching TV at low volume. Around 11:20 pm MST I heard (and also felt) a low rumbling sound. What I felt was around 10 Hz (vibrations per second), and what I heard was an audible harmonic ...