For a while yesterday, city lifeguards at beaches around O'ahu were bracing for the possible aftereffects from a magnitude-7.8 earthquake that hit off the coast of New Zealand about 11:20 p.m. Tuesday Hawai'i time.

But concerns about possible rip currents, tidal surges and other unusual ocean conditions brought about by the quake did not materialize here.

Lt. James R. Sloane of the city Ocean Safety and Lifeguard Services Division was at Hanauma Bay at noon yesterday and said lifeguards there and across O'ahu had reported "nothing out of the ordinary."

Sloane said lifeguards were ready just in case the New Zealand temblor caused problems similar to those generated by an 8.3-magnitude earthquake in Japan in November 2006.

"Back then, there were visible changes in the water, and we closed Hanauma for two or three days," Sloane said.

Those changes included strong currents and sudden drops in water levels that left usually submerged reef areas sticking out above the water.

The effects of an earthquake thousands of miles away are usually small but can be amplified in areas like Hanauma due to the surrounding topography, Sloane said.

A tsunami advisory was issued shortly after the New Zealand earthquake struck but was canceled at 12:52 a.m. yesterday Hawai'i time.

There were no reports of widespread damage or deaths resulting from the quake.