I've written a paper titled "A tutorial on gravitational pendulum theory
applied to seismic sensing of translation and rotation" for a special
edition of the Bull. Seism. Soc. Amer. concerned with rotation,
technical editor Willie Lee.  I don't know if it is too technical for
the majority of folks but figured I would let you know about it anyway.
The paper has been posted to my webpage at
http://physics.mercer.edu/hpage/BSSA-tutorial/pend-theory.pdf
The request for me to generate this paper originated with John Lahr's
mentioning my research to Willie, with whom John worked for a long time
(before he retired from the USGS).  Without John's passionate
involvement with amateur seismology and science education (reason I came
to know him) none of this would have happened.