Dispersion of short period Rayleigh waves in the Atlantic Ocean
Eighteen earthquakes, recorded at Bermuda, from in front of and behind the West Indian Island Arc and near the Mid-Atlantic Ridge were analyzed. Short-period Rayleigh waves propagating from earthquakes in front of Puerto Rico and the Virgin Islands have apparent velocities which indicate that the energy travels from the epicenters as a P-phase to the steep wall of the Puerto Rico trench where it is transformed to Rayleigh first shear mode. Short-period Rayleigh waves from the Windward Passage exhibit slower apparent velocities indicating that they travel from epicenter through the Bahamian Platform in the fundamental Rayleigh mode where they are transformed to travel through oceanic structure in the first shear mode. Earthquakes from the Mid-Atlantic Ridge between 22Â°N and 31Â°N latitude produced only Rayleigh waves with periods of 16 seconds or greater. These waves are in fundamental Rayleigh mode in an environment of high attenuation of short period energy. Earthquakes in the Windward and Leeward Islands behind the West Indian Arc produce only Rayleigh waves with periods of 17 seconds or greater which are also propagated in the fundamental mode, and short-period energy is strongly attenuated before transformation to the first shear mode becomes possible.