Wave Scattering Theory in Analysis of P‐wave Anomalies at NORSAR and LASA

Abstract

Observed travel time and amplitude anomalies at the NORSAR and LASA arrays are significantly larger than the measurement errors, and cannot be explained in terms of deterministic crust and upper mantle structural models for the respective siting areas. In this paper the Chernov theory is used in modelling the crust and upper mantle as a random medium, and also to estimate to what extent such models can account for the observed anomalies. We find that the random medium modelling can explain 50–60 per cent of the variance of the time and amplitude anomalies at NORSAR. The corresponding results for LASA are 50–60 per cent and 25 per cent respectively. In contrast, reasonable deterministic models cannot account for even 25 per cent of this variance. While the random medium model can provide a satisfactory explanation of the observational data, extensive tests have revealed that the parameters characterizing the random medium cannot be uniquely determined from the data. The reasons underlying this limitation are discussed. Copyright © 1975, Wiley Blackwell. All rights reserved