NEW ZEALAND (BNO NEWS) — A powerful earthquake rocked New Zealand’s second largest city on early Saturday morning, seismologists said, and widespread damage is being reported.

The 7.4-magnitude earthquake at 4.35 a.m. local time (1635 GMT Friday) was centered 30 kilometers (19 miles) northwest from Christchurch, the country’s second-largest city. It struck about 33 kilometers (20 miles) deep, making it a shallow earthquake, according to the GeoNet Data Center, the country’s seismological agency.

The United States Geological Survey (USGS) estimated the strength of the earthquake at 7.0 on the Richter scale.

The USGS estimated that around 22,000 people likely perceived ‘extreme’ shaking, which could potentially result in ‘very heavy damage’. Another 187,000 people were estimated to have perceived ‘violent’ shaking, which could result in ‘heavy’ to ‘very heavy’ damage.

The agency further estimated that about 202,000 people perceived ’severe’ shaking, while 24,000 others perceived ‘very strong shaking. Thousands more felt less intense shaking.

There was no immediate word on casualties, but officials reported widespread damage and power outages. Photos posted to the social networking website Twitter showed debris spread over roads.

The country’s Ministry of Civil Defence and Emergency Management said it was still assessing the situation and activated the National Crisis Management Center. It advised people to prepare for aftershocks.

Fairfax Media Publications-owned Stuff reported major damage and said buildings had been destroyed. “Oh my God. There is a row of shops completely demolished right in front of me,” a resident told Stuff.

A person who answered the phone at Christchurch International Airport told BNO News he felt ‘major shaking’ that was followed by several aftershocks. He said people were evacuated from the airport, but were starting to re-enter the terminals about an hour later. He said there was no major damage at the airport.

Soon after the earthquake, at 4.53 a.m. local time (1653 GMT Friday), a moderate 5.7-magnitude earthquake struck about 50 kilometers (30 miles) west-northwest of Christchurch. It struck about 17.4 kilometers (10.8 miles) deep.

No tsunami warning was issued. “No destructive widespread tsunami threat exists based on historical earthquake and tsunami data,” the Pacific Tsunami Warning Center said in a bulletin.