The strength of structures, including houses and other infrastructures in Yinchuan, Ningxia Hui autonomous region, is at Level 8, which means they can withstand earthquakes of around magnitude 6 on the Richter scale of quake power, according to a report on the website of Ningxia's earthquake agency on Friday.

Chinese authorities activated an emergency response in Ningxia after successive temblors of magnitude 4.8 and 4.6 jolted Yinchuan on Thursday.

A team has been dispatched to aid with local rescue and relief efforts in affected areas, the Ministry of Emergency Management announced on its website.

The local firefighting department sent 105 personnel and 20 vehicles to conduct on-site assessments around the epicenters. Additionally, two heavy and four light rescue teams, comprising 440 personnel, 86 vehicles and 13 rescue dogs, are in reserve to be used if needed.

According to the China Earthquake Networks Center, the epicenter of the first quake in Yongning county at 10:01 am was located at 38.43 degrees north latitude and 106.28 degrees east longitude, at a depth of 10 kilometers. The epicenter of the other, in Jinfeng district at 4:43 pm, was 38.41 degrees N latitude and 106.26 degrees E longitude.

At 9:27 am on Friday, another quake of magnitude 2.1 struck Yinchuan's Jinfeng district at a depth of 15.2 kilometers.

No casualties or house collapses have been reported so far.

Guo Yanqi contributed to this story.