Fundamental Investigations of Propagation through the Land–Air–Water Interface in a Controlled Littoral Environment

Abstract

ABSTRACT Interpreting signals from mechanical waves that cross material media boundaries is challenging due to the historical development of instrumentation suitable to study waves in each distinct medium, leading to discrepancies in boundary and adjacent media descriptions and governing physics related to each media. Nowhere is this more significant than in littoral zones at the convergence of land–air–water (LAW) domains. In short, a comprehensive physics framework does not exist that can accurately predict how waveforms freely traverse these media boundaries resulting in a critical fundamental science knowledge gap that can correlate received waveforms to actual source generators. Furthermore, the preponderance of research has treated media boundaries as lossy reflectors rather than poor transmitters, resulting in a rudimentary understanding of wave transformation over subsurface inhomogeneities and boundaries. This article details the experimental component of a new transdisciplinary effort to characterize the full LAW wavefield within a littoral zone to overcome the mixed media challenges. The fusion of disciplines, including air and underwater acoustics, geophysics, and hydrology, aims to develop a full-wavefield description of coupled media in the environment. Beginning with a simplified scenario, the experimental design accommodates for measurements of wave transmission across land–water, air–water, and land–air boundaries in a controlled, constructed, and prototypical littoral zone. This article reviews the test site design, construction, and preliminary experimental results. The challenges of designing and implementing an experiment that explicitly observes signal propagation across the media boundaries without distorting the boundaries and includes sources and sensors in all three environments are discussed.