Empirical and Numerical Modeling of T-Phase Propagation from Ocean to Land
Abstract
We use empirical and numerical methods to model propagation of T-phases from ocean to land. The empirical study uses data from pressure sensors in the ocean and coastal and island seismometers to measure the T-phase transfer function. The numerical study uses finite difference calculations to model T-phase propagation and conversion. We perform a detailed empirical and numerical study of the transition from the Point Sur IMS station to seismic stations along the California coast, and perform numerical calculations for IMS stations VIB, Tristan da Cunha and Ascension Island. We find both empirically and numerically the unusual result that converted surface waves arrive at coastal stations earlier than body waves. T-phases propagate primarily as P-waves once they are well inland from the coast. Calculations for slopes varying from 10 to 30 degrees are very similar. All IMS T-Phase stations are located in areas where the offshore slope is less than 30 degrees. We perform an analysis of observed waveforms under water and on land recorded during the Ascension Island experiment and find good agreement with the calculations. T-phase conversion attenuates higher frequencies, however high frequency energy from underwater explosion sources can still be observed at T-phase stations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2003
- Accession Number
- ADA417727
Entities
People
- G. E. Baker
- Gerald D'spain
- Heming Xu
- Jeffry Stevens
- Ron Cook