Staff members of the National Earthquake Response Support Service contact with the command center at Huanglong Airport in Jiuzhaigou County, southwest China's Sichuan Province, Aug. 9, 2017. A 7.0-magnitude earthquake jolted Jiuzhaigou on Tuesday. (Xinhua/Li Xin)

A 7.0-magnitude earthquake struck the county of Jiuzhaigou in southwest China's Sichuan Province Tuesday night.

With rescue operations in full swing, Xinhua journalists have gathered some facts about the earthquake and the latest developments to provide a brief overview of the situation on the ground.

-- How serious was the earthquake?

The quake, measuring 7.0 on the Richter scale, hit Jiuzhaigou County at 9:19 p.m. Tuesday. The epicenter was recorded at a depth of 20 km below the township of Zhangzha. The population density of the county is 15 people per square km.

As of 9:30 a.m. Wednesday, 13 people had been confirmed dead while 175 reported injuries.

The casualties may continue to rise as rescuers have not yet reached all villages as some roads and communications remain cut off.

Seismologists warned that 6.0-magnitude aftershocks may strike in the coming days.

-- Where is Jiuzhaigou?

Jiuzhaigou is a popular tourist destination in the mountains on the eastern edge of Qinghai-Tibet Plateau. It is part of the Tibetan and Qiang Autonomous Prefecture of Aba and is known for its ethnic minority communities, mountainous landscape, and stunning scenery.

The Jiuzhaigou Nature Reserve covers 720 square km and includes plateau lakes, waterfalls and mountains. It has been open to tourists since 1984 and has seen visitor numbers rise each year. In 2016, it logged 5.14 million visits.

When the quake hit, 35,000 tourists were in Zhangzha. Thousands have already been evacuated. The authorities aim to relocate all tourists by the end of Wednesday.

-- Why do so many quakes hit this part of China?

At least three major tectonic earthquakes have struck mountainous areas of Sichuan in the past decade.

In 2008, an 8.0-magnitude earthquake in Wenchuan claimed more than 80,000 lives. Five years later, a 7.0-magnitude quake hit Lushan, killing 196.

Jiang Haikun from the China Earthquake Networks Center said although the quakes are not related, they all occurred on the same seismic belt and were caused by crustal movement of Bayan Har block of the Qinghai-Tibet Plateau, pushing towards the borders of the low-lying Sichuan Basin.

The seismic belt, known as Longshan, is one of China's most active quake zones.

-- Are the tourist sites damaged?

The nature reserve has been closed to the public since early Wednesday.

Water drained from the plateau lake, known as Wuhuahai or five flower lake, during th earthquake. Some tourist facilities have been damaged, according to Sangye, an employee of the nature reserve. Small landslides have occurred.

However, authorities have denied claims that barrier lakes had formed at two popular tourist areas. They said it remains too early to tell the full scale of damage.

-- Are the pandas OK?

Sichuan Province is the main habitat for giant pandas and location of China's leading panda breeding and research institutes.

China Conservation and Research Center for the Giant Panda, which has breeding bases across the province, Wednesday reported that all pandas and staff in their bases are unaffected.

-- How are the rescue efforts progressing?

China has experienced devastating natural disasters in recent years and its rescue services have become extremely well prepared.

The rescue operations are now in full swing. A wide spectrum of state units have been mobilized -- disaster relief, police, fire fighters, armed forces, geologists, medical staff, infrastructure maintenance teams, transport authorities, and fuel suppliers.

Rescue dogs, life detectors, drones and laser sensors are among the equipment being used.

Rescue teams are moving -- at times on foot -- to reach every village in the quake zone.