Schoenberg's angle on fractures and anisotropy: A study in orthotropy

ACKNOWLEDGMENTS

I thank Atilla Aydin, Vladimir Grechka, Mark Kachanov, Francis Muir, Seiji Nakagawa, Steven R. Pride, Colin Sayers, Leon Thomsen, Ilya Tsvankin, and especially Michael Schoenberg -- to whose memory this paper is dedicated -- for many helpful, stimulating, and enlightening discussions about fractures and anisotropy.