GeoNet said that was because deeper and offshore quakes often took a bit longer to analyse all the information and get the correct magnitude.
Jennifer Harris, in Auckland's Mt Eden, felt a "decent jolt", while Jim Maddock, in Kawakawa Bay, felt a "gentle swaying motion".
Linda Keesing-Styles said she was woken just after 5.30am by the quake, which was "unusual" for Auckland.
She lived in an apartment building which had creaked under the pressure.
Theresa Mullan said she could hear the quake coming in a "rolling motion" before it arrived.
"It was coming from the north of Napier. There was absolute stillness and then it gave the house a good shake," Mullan said.
GeoNet tweeted it had received more than 5000 reports, with the quake waking many people up.
"Deeper quakes such as this are often widely felt, especially down the East Coast where the rigid subducting Pacific Plate is good at transmitting seismic energy."
People should remember to "drop, cover, and hold" in a quake, the agency tweeted.
"Remember in an earthquake to Drop, Cover, and Hold. If the quake was long or strong, get gone to higher ground or as far inland as possible."
