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Abstract

Loading of the Earth’s surface by the large marine tides in the Bay of Fundy produces a periodic stress field that is an order of magnitude larger that the global-scale, body-tide stress field. Structurally, the Bay is underlain by rock formations, akin to fluid-filled, fractured media. The locally-distributed stress is conducive to the migration of excess pore-pressure into unstable faults. Recent studies on correlations between the tidal stress tensor and focal mechanisms inferred from earthquakes in tectonically active areas have underscored the role of ocean tide loading; this prompts the question whether tidally-induced excess pore-pressure can trigger earthquakes in the Bay of Fundy, even though the area is tectonically passive. Only Beaumont and Quinlan (1977) have addressed this question; however, over the nearly 50 years since, much advances have been achieved in every aspects of the oceanographic and geophysical dynamics of the Bay of Fundy, in parallel with work elsewhere on precisely mapping the displacement field of loaded coastal regions via GNSS data. In this re-assessment, I examine the loading contribution of the predominant tidal constituents, M₂ in particular, about which the Bay of Fundy (and Gulf of Maine) marine system resonates. In assessing the consequences of the regional tidal loading, attention is paid to the permeable nature of the system’s water-rock interface. Moreover, any perturbations of the system’s resonant frequency are examined, particularly in relation to the increase of the amplitude of the M₂ marine tides in the Bay/Gulf system observed over the past century.