Electronic Supplement to
The Seismic Response of a Steep Slope: High Resolution Observations with a Dense, Three-Component Seismic Array

by Christian Poppeliers and Gary L. Pavlis

    This supplement contains animations of three-dimensional and four-dimensional visualizations used to analyze data from the experiment at Glendora Lake near Sullivan, Indiana, that is the subject of this paper.  The paper contains still images from these visualizations and we cross reference figures in the parent paper to allow the reader to connect between the two elements of the paper.  These movies allow one to see features of the data that are not evident from a static display.

     Movie 1.  P-wave particle motion for the entire Glendora experiment.   Figure 8 of the paper is a still image from this movie.   As the movie advances the visualization draws a grossly exaggerated trace of the particle motion at each station in the array.   The data have been time-aligned to remove the effect of normal moveout of the first arrival and amplitude has been corrected to have approximately equal particle motion amplitude at all stations using an empirically derived power low decay curve.   The movie advances to show the first full cycle of the first arrival P wave from a fixed perspective and then rotates to give a three-dimensional perspective of the particle motion tracks for each station.  The coordinate axes are drawn to provide a spatial perspective.  The x-axis (red) points toward east, the y-axis (green) points toward north, and the z-axis (blue) points up. The  spatial scale can be understood by recognizing the nominal station spacing on all the linear profiles is 50 m.  This visualization demonstrates that across the entire array the first arrival phase is nearly vertically polarized with an orientation consistent with a head wave propagating through the bedrock refracted to near vertical incidence by low velocity materials in the near-surface.

     Movie 2.  Particle motion of a secondary phase interpreted as a direct water wave displayed for the larger Glendora array.   The initial viewpoint is similar to Movie 1, but focused initially on a limited area directly east of the dense array that is the focus of the paper.   The time alignment and amplitude scaling is the same as used for Movie 1.  The spatial scale can again be gleaned from the nominal station spacing of 50 m.  The start time of this movie is approximately the end time of Movie 1.  Figure 9 of the paper is a still image from this animation.  This visualization shows that the particle motion of this phase is complex compared to the first arrival P, but it is more nearly horizontally polarized.  The tilt of the axis of the particle motion ellipse, however, is not consistent with a S head rock on the bedrock interface.  We use this to argue that this phase is a P wave propagating through water that couples into a direct wave in mining spoil areas on the right side of view at the start of the movie.  The direct P wave through the water hits array 3 (Movie 3 below) polarized nearly horizontally.  On the mining spoil areas this phase is more complex.

     Movie 3.    Three-dimensional particle motion of a P-wave recorded on the dense array at Glendora.  This animation is identical to Movie 1, but focused on the dense array we call array 3 in the paper.  That is, it illustrates the particle motion of the first cycle of the first arrival at this array.
The coordinate axes are now described as radial transverse and vertical, and the view is greatly magnified.  The nominal spacing of stations in the array here is 10 m.    Figure 10 of the paper shows still images from this animation.  As in Movie 1 we see that the particle motion is nearly vertically polarized.  Note, however, that the stations at the slope break edge have a more elliptical particle motion than those on the flat ground to the left.

     Movie 4.   Same as Movie 3 but focused on the time period of the secondary P arrival we interpret as a direct wave through the water of the lake.  The time frame is similar to Movie 2 and other elements are as in Movie 3.  Note that this phase is almost purely horizontally polarized while the first arrival P-wave seen in Movie 3 is almost vertically polarized.    If you watch carefully and at reduced playback speed you can also see this phase propagating upslope on the right side of the figure.  Figure 11 of the paper is a still from this animation.

     Movie 5.   4D visualization of spectral ratio results for full seismogram records of data recorded by array 3.  The average spectral ratio results at a given frequency for each station are presented as a combined ``jack figure'' and a transparent sphere as described in a previous paper by Wilson and Pavlis [2000].   Each graphical object is drawn in a three-dimensional perspective at the location of a corresponding seismic station for array 3.  The arms of the ``jack figures'' point in the cardinal directions (i.e. NS, EW, and Vertical) and the length of each arm is proportional to the logarithm of the spectral ratio of the corresponding component (NS, EW, or Z).  The sphere displays the spectral ratio computed from the total power.  Colors are used to indicate the sign of the logarithm of the corresponding spectral ratio.  Blue is negative (lower amplitude) while red or yellow are positive (higher amplitude) spectral ratios.   The animation plays through the entire frequency band of analysis.  The number at the lower left side of the movie shows the frequency of each movie frame.   In this and Movies 6 and 7 the view is to the northeast, with flat ground to the left and the slope breaking to the right.  We argue that the spatial pattern seen in results around 8 Hz suggest this is a fundamental mode of the slope with amplification at the slope break.  There is a suggestion of a possible overtone at double this frequency.

     Movie 6.   Same as Movie 5, but with spectral ratios computed for a shorter, 0.25 s window focused on the first arrival P wave.

     Movie 7.   Same as Movie 5, but with spectral ratios computed for a 1.0 s window focused on the secondary phase we interpret as a direct wave propagating through the water.

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