  We describe two different nuclear quadrupole resonance (NQR) based
techniques, designed to measure the local asymmetry of the internal electric
field gradient, and the tilt angle of the main NQR principal axis z from the
crystallographic axis c. These techniques use the dependence of the NQR signal
on the duration of the radio frequency (rf) pulse and on the direction of the
rf field H1 with respect to the crystal axis. The techniques are applied to
oriented powder of YBa$_{2}$Cu$%_{3}$O$_{y}$ fully enriched with 63Cu.
Measurements were performed at different frequencies, corresponding to
different in-plane copper sites with respect to the dopant. Combining the
results from both techniques, we conclude that oxygen deficiency in the chain
layer lead to a rotation of the NQR main principal axis at the nearby Cu on the
CuO2 planes by 20+-degrees. This occurs with no change to the asymmetry. The
axis rotation associated with oxygen deficiency means that there must be
electric field inhomogeneities in the CuO2 planes only in the vicinity of the
missing oxygen.
