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their instrumentation was 15 Hz which would filter out a major portion of the energy spectrum and result in significant underestimation of total ground motion. The report does not provide any supporting data regazding the spectral response of the seismometer, calibration corrections for sensor coupling to the ground, filters employed in the recording instrument, or impulse response tests of the system that allow independent analysis of the system spectral response. Without documentation on the calibration of sensor response to ground motion for the specific site, the reported displacements and velocities cannot be considered to be reliable. 4) There is no discussion regarding the type of waves (compressional, shear, and Rayleigh) produced by various equipment and their relative amplitudes and decay rates. Seismic energy generated by heavy equipment can take several forms including compressional waves, horizontal and vertical sheaz waves, and Rayleigh surface waves. Each wave type produces a different ground motion, has a different decay rate, and can impact the stability of jointed blocks in the Rollins cliff in a different manner. Vertical loading of the ground surface generates compressional waves, vertical sheaz waves, and Rayleigh surface waves. Surface waves propagate in two dimensions and have low attenuation rates, low frequencies, and can transmit significant amplitudes at large distances. Depending upon the geometry between the direction of propagation and the orientation of a joint face, each wave type can produce a component of shear and compressional motion on joint surfaces (Dobrin 1976, Grant and West 1965). The Revey report fails to discuss the nature and potential impact of various forms of motion and only relates impacts to dilation of cracks. The nature of the interaction of induced vibrations with rock fractures and slope stability is far more complex than depicted in the Revey report (see Coates, 1970, chapter 8). 5) The analysis of simple harmonic motion in the Revey report does not account for mechanisms that produce the highest amplitude ground motions such as waveguides, normal mode propagation, and natural resonance. Local seismic velocity structure can have a strong influence upon the mode of propagation of seismic energy and can create waveguides and standing waves that amplify ground motion and reduce attenuation rates dramatically relative to propagation in a homogeneous half-space. These effects are site specific and dependent upon the geologic setting, variation of seismic velocity with depth, and geometry of the source relative to local features. The presence of the quartz cemented Rollins sandstone at shallow depths below the proposed quarry site should produce a low velocity waveguide in the overlying sediments that could create standing wave propagation confined between the free surface at the Rollins outcrop and the continuous source produced by the rock crusher. Certain frequencies in the source could resonate with this fundamental length producing standing waves that would have amplitudes faz greater than that predicted from measurements made in a homogeneous environment such as the Austin site (sce Figure 2). The simple harmonic motion model used in the Revey report cannot account for many