Texas quakes! Above is a map of an odd series of earthquakes in what may appear as a rifting zone, judging by the parallel mountain ranges and basins. There is some intense land formations in this area, indeed, and further west some craters. Here is a link that will last a week, and then it'll clear. Check out the Texas shakers!
Here is a link showing a cool map of the highly localized earthquakes near Hawthorne, NV.
Here is an article on the nature of volcanic harmonic tremors and why they make the noise that they do, and what that means. Indeed volcanos talk to us before blowing.
And here is an old speculation on Yellowstone supervolcano, and possible harmonic tremors in 2009. This is not scientific and merely a conversation amongst lay people, but it is interesting to read.
Here are sounds someone claims to be harmonic tremors, although that notion is refuted. Great earthquake swarm animations too.