  The X-ray structure of Kepler's supernova remnant shows a rounded shape
delineated by forward shocks. We measure proper motions of the forward shocks
on overall rims of the remnant, by using archival Chandra data taken in two
epochs with time difference of 6.09 yr. The proper motions of the forward
shocks on the northern rim are measured to be from 0.076" (+/-0.032"+/-0.016")
to 0.110" (+/-0.014"+/-0.016") per yr, while those on the rest of the rims are
measured to be from 0.150" (+/-0.017"+/-0.016") to 0.300" (+/-0.048"+/-0.016")
per yr, here the first-term errors are statistical uncertainties and the
second-term errors are systematic uncertainties. Combining the best-estimated
shock velocity of 1660+/-120 km/sec measured for Balmer-dominated filaments in
the northern and central portions of the remnant (Sankrit et al. 2005) with the
proper motions derived for the forward shocks on the northern rim, we estimate
the distance of 3.3 (2.9-4.9) kpc to the remnant. We measure the expansion
indices to be 0.47-0.82 for most of the rims. These values are consistent with
those expected in Type-Ia SN explosion models, in which the ejecta and the
circumstellar medium have power-law density profiles whose indices are 5-7 and
0-2, respectively. Also, we should note the slower expansion on the northern
rim than that on the southern rim. This is likely caused by the inhomogeneous
circumstellar medium; the density of the circumstellar medium is higher in the
north than that in the south of the remnant. The newly estimated geometric
center, around which we believe the explosion point exists, is located at about
5" offset in the north of the radio center.
