Jack Xie, while a graduate student at SLU, developed a method for obtaining estimates of Lg coda Q that permitted more stable and precise measurements than had been previously possible. He also developed a method for obtain tomographic maps of Lg coda Q for continent-size regions. These methods have allowed us to obtain new insights on regional variation of Q in the crusts of continents. Tomographic maps of Lg coda Q have now been obtained for Africa, Eurasia, Australia, South America, the Middle East, and the United States.

Xie, J., and B.J. Mitchell, A back-projection method for imaging large-scale variations of Lg coda Q with application to continental Africa, Geophys. J., 100, 161-181, 1990.

Xie, J., and B.J. Mitchell, Attenuation of multiphase surface waves in the Basin and Range province, Part I: Lg and Lg coda, Geophys. J. Int., 102, 121-137, 1990.

Mitchell, B.J., Frequency of QLg and its relation to crustal anelasticity in the Basin and Range province, Geophys. Res. Lttrs., 18, 621-624, 1991.

Mitchell, B.J., Anelastic structure and evolution of the continents from seismic surface wave attenuation, Rev. Geophys., 33, 441-462, 1995.

Mitchell, B.J., J. Xie, and Y. Pan, Attenuation and blockage of Lg in Eurasia, in Monitoring a Comprehensive Nuclear Test Ban Treaty, edited by E. Huseby and A. Dainty, Kluwer Publ., Dortrect, The Netherlands, 645-654, 1996.

Xie, J., L. Cong, and B.J. Mitchell, Spectral charactistics of the excitation and propagation of Lg from underground nuclear explosions in central Asia, J. Geophys. Res., 101, 5813-5822, 1996.

Mitchell, B.J., Y. Pan, J. Xie, and L. Cong, Lg coda Q variation across Eurasia and its relation to crustal evolution, J. Geophys. Res., 102, 22767-22779, 1997.

de Souza, J., and B.J. Mitchell, Lg coda Q variations across South America and their relation to crustal structure and evolution, in Q of the Earth: Global, regional, and laboratory studies, edited by B.J. Mitchell and B. Romanowicz, in press, 1999.

Baqer, S., and B.J. Mitchell, Regional variations of Lg coda Q in the continental United States and their relation to crustal structure and evolution, in Q of the Earth: Global, regional, and laboratory studies, edited by B.J. Mitchell and B. Romanowicz, in press, 1999.

Cong, L., and B.J. Mitchell, Lg coda Q and its relation to the geology and tectonics of the Middle East, in Q of the Earth: Global, regional, and laboratory studies, edited by B.J. Mitchell and B. Romanowicz, in press, 1999.

Mitchell, B.J., and L. Cong, Lg coda Q and its relation to the structure and evolution of continents: A global perspective, in Q of the Earth: Global, regional, and laboratory studies, edited by B.J. Mitchell and B. Romanowicz, in press, 1999.