Figure F4. Comparison of vertical Guralp and geophone spectra for the same time interval (1500 hr) (high- and low-gain channels) in a window just after the gain change on JD360/2001. Because the Guralp and geophone spectra differ from one another (which is unexpected) but are the similar before and after the gain change (compare with Figure F3, which is expected), we suspect that there is a discrepancy between the Guralp and geophone transfer functions for the vertical component. For each item listed, the first letter stands for geophone (E) or Gurlap (H), the second stands for high (H) or low (L) gain channels, and the third stands for vertical component (Z). Numbers in the third position indicate horizontal components.

Figure F4. Comparison of vertical Guralp and geophone spectra for the same time interval (1500 hr) (high- and low-gain channels) in a window just after the gain change on JD360/2001. Because the Guralp and geophone spectra differ from one another (which is unexpected) but are similar before and after the gain change (compare with Figure F3, which is expected), we suspect that there is a discrepancy between the Guralp and geophone transfer functions for the vertical component. For each item listed, the first letter stands for geophone (E) or Guralp (H), the second stands for high (H) or low (L) gain channels, and the third stands for vertical component (Z). Numbers in the third position indicate horizontal components.