Body-wave amplitude and travel-time correlations across North America
Relationships between travel-time and amplitude station anomalies are examined for short- and long-period SH waves and short-period P waves recorded at North American WWSSN and Canadian Seismic Network stations. Data for two azimuths of approach to North America are analyzed. To facilitate intercomparison of the data, the S-wave travel times and amplitudes are measured from the same records, and the amplitude data processing is similar for both P and S waves. Short-period P- and S-wave amplitudes have similar regional variations, being relatively low in the western tectonic region and enhanced in the shield and mid-continental regions. The east coast has intermediate amplitude anomalies and systematic, large azimuthal travel-time variations. There is a general correlation between diminished short-period amplitudes and late S-wave arrival times, and enhanced amplitudes and early arrivals. However, this correlation is not obvious within the eastern and western provinces separately, and the data are consistent with a step-like shift in amplitude level across the Rocky Mountain front. Long-period S waves show no overall correlation between amplitude and travel-time anomalies.
Additional Information© 1983 Seismological Society of America. Manuscript received 3 December 1982. This research was supported in part by the National Science Foundation under Grant NSF EAR 810-8616 and by the Advanced Research Projects Agency of the Department of Defense. This research was also monitored by the Air Force Office of Scientific Research under Contract F49620-81-C-0008.
Published - 1063.full.pdf