GLG 301 Lecture Notes - Lecture 21: Hypocenter, Elastic Energy, Acoustic Impedance
Document Summary
Travel-time curves: refracted waves i > ic r ecall if the angle of incidence reaches the critical angle (ic), by. Snell"s law you get a critical refraction or head wave along the interface in the faster medium and, by huygen"s principle, each point along the interface becomes a source for up-going rays. Calculate travel time for each leg; path length for down and up- going segments from geometry t(x) = 2h/(v1 cos ic) + x/v2 (2h sin ic)/(v2 cos ic) = x/v2 + (2h/v1 cos ic) ( 1 [v1/v2] sin ic: but, v1/v2 = sin ic, so [v1/v2] sin ic = sin2ic and (1-sin2ic) H can be solved for using cross-over distance (the distance this is an equation of the form y = mx + b at which the direct wave curve crosses the refracted) If velocity increases with depth, the slope gets shallower with distance (recall slope ~ 1/v). Exploration (reflection) seismology: determine subsurface structure.
