Footage released by the National Disaster Mitigation Agency showed streams of people in a village on Mentawai Island fled to the highlands by foot and motorcycles under the rain in darkness, while some patients at the village’s hospital were evacuated to its yard as cracks showed in the facility’s floor.

The shocks were felt in districts and cities of West Sumatra and North Sumatra provinces, and some places ordered evacuations to higher ground.

Residents in parts of West Sumatra province, including the provincial capital of Padang, felt the earthquake strongly for about 30 seconds, agency spokesperson Abdul Muhari said. “Many residents in several villages on Mentawai island chose to stay displaced in higher ground although the tsunami alert was ended due to fears of aftershocks,” he said, adding that authorities were still collecting information about the damage.

The magnitude 7.1 earthquake was centered 170 kilometers (105 miles) southeast of Teluk Dalam, a coastal town in the South Nias regency of North Sumatra, at a depth of 15 kilometers (9 miles), the US Geological Survey said. Aftershocks measured as strong as 5.8.

After an initial tsunami alert, Indonesia’s Meteorology, Climatology and Geophysical Agency lifted it just before dawn, about two hours after the quake. The agency initially put a preliminary magnitude at 7.3, but later revised it to 6.9. Variations in early measurements are common.

The agency’s head of the Earthquake and Tsunami Center, Daryono, who goes by a single name, said that based on sea-level observations, minor tsunamis of 11 centimeters (4.3 inches) were detected in Tanah Bala coastal area of South Nias regency.

Indonesia, a vast archipelago of 270 million people, is frequently struck by earthquakes, volcanic eruptions and tsunamis.

In November, a magnitude 5.6 killed at least 340 people and damaged more than 62,600 homes in part of West Java.