Measuring Seabed Pressure: a Search for Longuet-Higgins Events

Longuet-Higgins developed a non-linear theory predicting that interacting surface waves could produce bottom pressure fields that were much greater than predicted by prevailing linear theory. Such strong bottom pressure variations could provide extractable energy to power underwater oceanographic sensors. This study was designed to determine (1) whether bottom pressures derived from Longuet-Higgins nonlinear interactions could be detected off San Diego, (2) whether there was a difference in detection off a reflective cliff shoreline versus a low-lying beach, and (3) whether surface wave direction and height could predict such pressure fields, if detected. We found that in all locations surveyed, bottom pressure variations due to surface waves were well predicted by linear theory, rather than Longuet-Higgins non-linear theory.