"I was really scared because this is the first time I felt this kind of earthquake," said a manager at the Pacific Casino Hotel, who asked not to be named.
"The building was really violently shaking," she said. "It was really strong, it made you move side to side."
Dozens of staff and guests fled the building to the relative safety of the car park, hoping not to be hit by debris on the way out.
The nation's attorney general, John Muria, posted images on social media of office files that had spilled from several large metal filing cabinets.
Aftershocks
The US Geological Survey revised the earthquake's magnitude down from an initial 7.3.
The quake struck at a relatively shallow depth of 10 kilometres, just off the southwest coast of Guadalcanal island.
A tsunami warning had been issued for an area of the Solomons coast within 300 kilometres (185 miles) of the epicentre, but the UN-backed Pacific warning centre later said the threat had "largely" passed.
Solomon Islands authorities also said the tsunami threat had passed, but urged caution.
"We expect aftershocks so people should stay alert around buildings and tall structures because of the size of the earthquake," said David Hiba Hiriasia, director of the Solomon Islands Meteorological Service.
According to UN data, about 20,000 people live within 50 kilometres of the epicentre.
The Solomons -- a sprawling archipelago in the South Pacific -- is home to about 800,000 people.
The quake hit exactly a year after anti-government riots that killed at least three people and caused tens of millions of dollars in damage.