Amplitude variations of Rayleigh waves—horizontal refraction

摘要: abstract Amplitudes of the vertical component ground motion caused by Rayleigh waves with periods about 20 sec were measured over an array consisting 25 stations WWSSN in United States; produced shocks selected regions Pacific and one area along Mid-Atlantic Ridge. plotted as a function azimuth from epicenter to station on outline maps centered epicenters. Patterns amplitude are highly sensitive epicentral location; pattern appears change continuously epicenter. The amplitudes generally show variations factor 10 or more within array. These striking fluctuations appear be focusing due lateral phase velocity; they cannot explained other factors such asymmetrical radiation at source. Analysis based simple model horizontal variation velocity yields theoretical patterns that explain size character most prominent amplitude. marked here presented can effect horizontally varying coincide obvious features Pacific, notably, island Hawaii. long-period P vary one-fourth much those