An Investigation of Seismic Wave Propagation in Eastern North America
Semi-Annual Technical rept. 15 Dec 1977-30 Jun 1978
RONDOUT ASSOCIATES INC STONE RIDGE NY
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Seismic waves propagated and recorded at regional distances in eastern North America are being studies for possible use in discriminating between explosion and earthquake sources. This report deals with a the propagation characteristics of the regional seismic wave designated L sub g and b an evaluation of the usefulness of a particular ocean bottom seismograph system as an aid in discrimination of seismic sources at regional distances. Results of the study of the propagation characteristics of L sub g, with predominant frequencies of 1-3 hertz, is consistently the largest amplitude portion of the short period signal from the Eastern North American events studied. Analysis of the group velocity for each event studied shows a clustering of measurements in the 3.47 kmsec range for the earthquakes studied and a significantly lower 3.24 kmsec mean for measurements from the SALMON explosion. This lower value is believed to be the result of propagation path or source effects. When group velocity information was divided into two regions, E h--high group velocity 4.0-3.4 kmsec energy--and El --low group velocity 3.4-2.8 kmsec energy, the ratios of these areas showed a discrimination between SALMON EhEl .5 and the earthquakes EhEl.5. Phase velocity measurements made using records from Cumberland Plateau Seismic Observatory have a mean of 4.18 kmsec. Analysis of a second event also yields measurements in the 4.0-4.4 kmsec range.
- Seismic Detection and Detectors