Crustal structure in Nevada and southern Idaho from nuclear explosions

The time of first arrival of seismic waves generated by 4 underground nuclear explosions at the Nevada Test Site (NTS) and recorded along a line extending north into southern Idaho is expressed as T₀ = 0. 00 + Δ/3.0 (assumed), T₁ = 0 .40 + Δ/6.03, and T₂ = 6.15 + Δ/7.84, where time is in seconds and the shot-detector distance (Δ) is in km. Assuming constant velocities and horizontal layers, crustal thickness in the vicinity of NTS was determined to be 28 km. Delays in the traveltime segment T₂, which represents P_n, indicate that the crust may thicken to 32 km in northern Nevada. A third phase, expressed as T₃ = 14.48 + Δ/7.84, was also recognized and has arrival times appropriate for SPS. Amplitudes of P_n were determined at 7 places from recordings of seismic waves from one underground nuclear explosion (ANTLER).