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