Crustal structure from the Nevada test site to Kingman, Arizona, from seismic and gravity observations

Abstract

The time of the first arrival of seismic waves generated by explosions at the Nevada Test Site and recorded along a 300‐km line southeastward through Kingman, Arizona, is expressed as T0 = Δ/5.2, T1 = 0.34 + Δ/6.15, and T2 = 5.82 + Δ/7.81, where time is in seconds and the shot‐detector distance (Δ) is in kilometers. Assuming constant velocities for the layers, the thicknesses are H0 = 1.7 km, H1 = 26.7 km, and H0 + H1 ≐ 28 km (below a 1‐km datum). The average Bouguer anomaly is about −120 milligals, and the average elevation is about 1.1 km. Seismograms were examined for P waves indicating the presence of other discontinuities within and below the H2 layer, but the separation between seismic stations was too great to establish the presence of such discontinuities. A questionable alignment of weak arrivals following the T2 refraction time by less than 1 second may indicate the presence of a discontinuity below 28 km. Fair alignments of strong second arrivals in the range 200 to 400 km might be interpreted as direct P waves or channel waves in the H1 layer.

Regional Geophysics of the Basin and Range Province

“…Verification came from Berg et al (6), Diment et al (16), and Press (54), although these authors initially used a different definition of the crust. They found abnormally low P-wave velocities of 7.6 to 7.8 km/sec at shallow depth for what we have now come to identify as Pn' the wave traveling in the uppermost mantle below the M discontinuity.…”

A Study of Ps Converted Waves

“…-49" At WMAZ, using the cru; al section of Diment, Stewart and Roller (1961), the first good indication of shear on the particle-motion diagrams is at 4.4 sec after the first motion. This coincides wel 1 yith cc expected arrival of PK a convertt«; head ■ , ?e from the base ov i he crust.…”

Structure of the crust and upper mantle in the western United States

“…Earlier Ryall (1962 ), and still earlier Byerly (1956) observed significant variat ions in t he speed of Pn in the western United States. Press (1960 ), Ber g and others (1960 ) , and Diment, Stewart, and Roller (1961) have also observed compr essional-wave speeds in the range 7.6 to 7o8 km/sec i~ the Basin and Range province (see Pakiser and Hill, 1963, for discussion).…”