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coxre <br />historical evolution of regional structural or deformational fea- <br />lures. <br />'hrust fault An inclined fracture along which the rocks above the <br />fracture have apparently moved up with respect to those beneath <br />The 1964 Alaska end 1971 San Fernando earthquakes oaurred on <br />thrust fealty. <br />`ime-d[stance curve. Fquels T-X curve: A plot of the arrivsl time <br />of refracted events against the source-receiver distance. <br />.`ime dependent. f)escribiag an operation in which the physical <br />perameten vary with time. <br />.tansfer.funcdon. Filter characteristice in the frequency domain <br />e' represented by the amplitude-versus-frequency and phase <br />angle-versus-frequency curves. Contains the same information u <br />the impulse response in the time domain end is convertible iato <br />the impulse response thrpugh the Fourier transform. <br />!Yansform. To convert information from one form into enot6er, as <br />with the Fourier transform. <br />.Tansverse wave. See Shear wave. <br />Jpper•bound earthquake. The hypothetical earthquake that v <br />considered to be the most severe reasonably possible on the basis of <br />cempreheasive studies of historic seismicity end structural geology. <br />Jibration. An oscillation. The motion of a mechanical system. <br />Jiscoelastic. Having a svess-strain relation that includes terms <br />proportional to both the strain and the rate of strain. Leeds to <br />frequencydependent atteauetioa for seismic waves. Materials <br />with this property are also called Votgt solids. <br /> <br />N75 ~ :III <br />Vincelastic medium. A stress-strain relation in which li rtress <br />is a function of both strain and atraia rate, although not necessar- <br />ily proportional to both. <br />Vinosity, The cohesive force between particles of a fluid that <br />causes the fluid to oRer resistance to s relative eliding motion <br />behveen particles; internal fluid friction. <br />Viscous damping. The dissipation of energy that occurs when e <br />particle in a vibrating system is resisted by a Cora that has a <br />magnitude proportional to the speed of the psrticle end a direction <br />opposite to the direction of the particle. <br />Void ratio. The proportion of void space is a given soil mass. <br />Voigt solid. See Visccelsstic. <br />Waveform. A plot of voltage, current, seismic displacement, ek., ea <br />a funMion of time. <br />Wave guide. A geologic situation which permits surface waves. <br />Wave length. Normal ditance between two wave fronts with peri- <br />odic characteristics end a phase difl'ereoce of one complete cycle. <br />R'avelet A seismic pulse usually consisting of 15S to 2 cycles. <br />H'eveaumber. The number of wave cycles per unit distance; recip- <br />rocal of wavelength. <br />R'hile noise. Random energy containing ell frequency components <br />in equal proportions. <br />Young's modulus. E. The ratio of unit stress W unit strain within <br />the elastic range of a materiel under a given loading condition, <br />numerically equal to the elope of the tangent of astress-strain <br />curve. <br />