  We perform molecular dynamics simulation of water using the TIP5P model to
quantify structural order in both the first shell (defined by four nearest
neighbors)and second shell (defined by twelve next-nearest neighbors) of a
central water molecule. We find the anomalous decrease of orientational order
upon compression occurs in both shells, but the anomalous decrease of
translational order upon compression occurs {\it mainly in the second shell}.
The decreases of translational and orientational orders upon compression
("structural anomaly") are thus correlated only in the second shell. Our
findings quantitatively confirm the qualitative idea that the thermodynamic,
dynamic and structural anomalies of water are related to changes in the second
shell upon compression.
