Measurements of two flavor $\nu_{\mu}$ disappearance were made using K2K, the KEK
to Kamioka long baseline neutrino oscillation experiment, data for
three fiducial volume definitions at the far detector,
Super-Kamiokande. A study was conducted on expanding the fiducial
volume at Super-Kamiokande to show it is possible to expand it both
symmetrically and shifted in the incoming neutrino beam direction.
For the fiducial volume definitions, 112, 143, and 140 events are
observed with an expectation of 158.1$^{+9.2}_{-8.6}$, 183.3$^{+10.7}_{-10.0}$, and
170.9$^{+9.5}_{-9.0}$ events, respectively. A distortion is also seen in the
reconstructed energy spectrum for single ring muon-like events for
each fiducial volume. The probability that the observations are
explained by no neutrino oscillations are 0.0021\% (4.3$\sigma$),
0.018\% (3.7$\sigma$), and 0.042\% (3.5$\sigma$). The best fit values
are $\sin^2 2\theta$=1.0 for all definitions and $\Delta m^2$=0.0027
eV$^2$, 0.0025 eV$^2$, and 0.0024 eV$^2$, respectively. All results
are consistent with other disappearance measurements.
