Average P and PKP Codas for Earthquakes
Abstract
An analysis of 418 small-event (m sub b < or = 5.8) seismograms recorded at 17 world-wide stations, and of 148 large-event (m sub b, M sub s (NOS), or m sub b from Pasadena or Berkeley > or = 7.0) seismograms recorded at 8 worldwide stations and TFO indicates that coda shape is primarily a function of the arrival times and relative amplitudes of significant secondary arrivals. However, for times greater than 10 to 20 seconds into the coda, large-event codas are approximately 0.14 m sub b units greater in amplitude at any given time relative to their maxima, than the corresponding relative amplitude for small-event codas. This suggests that large events are, in fact, multiple events, with the nominal period of source activity for a given sequence estimated to be on the order of 1 to 2 minutes. Correspondingly, large events also tend to be emergent, displaying a 0.2 to 0.3 m sub b increase in amplitude between 5 and 30 seconds into the P-wave arrival over that observed in the first 5 seconds of the arrival. Because of their differences, large-event and small- event coda observations cannot be combined.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 12, 1973
- Accession Number
- ADA004960
Entities
People
- E. I. Sweetser
- M. F. Tillman
- T. J. Cohen
Organizations
- Teledyne Technologies