Nature of P waves at the RSTN station RSSD

Technical Report · Fri Aug 20 04:00:00 EDT 1982

OSTI ID:5026761

Taylor, S R

The character of Pn waves recorded at the Regional Seismic Test Network (RSTN) station at South Dakota (RSSD) is investigated using synthetic seismograms. It is demonstrated that anomalous phase shifts and emergent features seen in the records at RSSD are caused by local and regional structure and not the station instrumentation. It is found that the presence of a thin (0.5 km) sedimentary layer can cause an apparent delay of the horizontal components relative to the vertical. This effect is caused by interference between the primary P arrival and a slightly delayed P to SV conversion. The emergent character of Pn arrivals at RSSD from NTS explosions is probably due to effects of Basin and Range structure along major portions of the travel path. The appearance of a large secondary arrival following the weak Pn onset by approximately 1.2 seconds may be another phase critically refracted from the base of the upper mantle low-velocity zone (LVZ). Synthetic seismograms illustrate that, for frequencies up to a few Hz, the waveforms for a surface receiver and one at 100m depth are quite similar, especially for the vertical components. For frequencies above 3 Hz, the differences observed on the radials become more significant. These results are substantiated by comparison of data from an NTS explosion at RSSD recorded at 100m and at the free surface.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5026761
• Report Number(s): UCID-19504; ON: DE82021967
• Country of Publication: United States
• Language: English

Related Subjects

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
450300 -- Military Technology
Weaponry
& National Defense-- Nuclear Explosion Detection
58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
DETECTION
EARTH MANTLE
EXPLOSIONS
FREQUENCY DEPENDENCE
GEOLOGIC STRUCTURES
NATIONAL ORGANIZATIONS
NEVADA TEST SITE
REFRACTION
ROCKS
SEDIMENTARY ROCKS
SEISMIC DETECTION
SEISMIC P WAVES
SEISMIC WAVES
UNDERGROUND EXPLOSIONS
US DOE
US ORGANIZATIONS
WAVE PROPAGATION