Variations in seismic Q are sensitive to a much greater extent than are
seismic velocity variations on factors such as temperature, fluid
content, and the movement of solid state defects in the earth. For that
reason an understanding of Q and its variation with position in the
earth and with time should provide information in earth's tectonic
evolution, as well as on aspects of its internal structure. Progress in
understanding Q has suffered from difficulty in obtaining reliable
amplitude data at global and temporary stations. Moreover, laboratory
determinations of Q, until recently, were most often made at frequencies
much higher than those measured by seismologists for waves propagating
through the earth. Recent advances in seismic station distribution and
quality, as well as in methodology at both high and low fequencies, have
greatly improved the quality of observational data available to
seismologists from global stations. Concurrent advances have been made
in measuring Q using laboratory samples at frequencies that pertain to
the earth and in theoretical understanding of seismic wave attenuation.
Papers of this volume present new information on Q in the earth from
several perspectives: methodology, results from global and regional
observations of both body and surface waves, laboratory measurements,
and theoretical understanding. The editors believe that we have reached
a new threshold in Q studies and that advances in data quality and
methodology will spur increased interest in this difficult, but
interesting field.
