Observation and modeling of three-dimensional basin scale acoustics

Abstract

In this paper, an overview of some of the basin-scale recordings of the International Monitoring System of the Comprehensive Test Ban Treaty will be presenting, including observations of distant earthquakes, under-sea volcanoes and cracking ice-sheets. Long range experiments were conducted in 1960 when nearly antipodal receptions were made at Bermuda from SuS charges deployed off the coast of Australia. Three-dimensional propagation effects was an important part of the propagation. For propagation ranges of thousands of kilometers, interaction with islands, ridges and seamounts is expected to influence propagation. Previous modeling approaches have been either a fully 3D ray approach, a hybrid adiabatic mode-ray approach and a hybrid adiabatic mode—PE approach. In this paper, we present the a global scale three-dimensional split-step Pade Parabolic Equation. Model results are compared with several direct observations of arrivals that are clearly in the 2D propagation shadow. The impact of 3D propagation on the coverage maps of the CTBTO are significant, relative to current 2D predictions.