A shallow magnitude 5.1 earthquake struck northern Tanzania on Thursday morning, shaking buildings across the Lake Victoria region and sending tremors into neighbouring Kenya and Rwanda, the United States Geological Survey (USGS) said. The quake struck at 09:22 UTC (12:22 p.m. East Africa Time) at a depth of just 10 kilometres, 19 kilometres north-northwest of Masumbwe in Tanzania's Geita Region, south of Lake Victoria.

Source: Africa Updates (USGS data)

The shallow depth meant the shaking was felt over a wide area. Residents in several towns and cities reported buildings shaking, and the USGS received felt reports from across the region. In Kenya, a moderate tremor was reported in Nairobi and surrounding counties on Thursday afternoon, roughly 986 kilometres from the epicentre, minutes after the quake struck in Tanzania.

Source: EarthquakeTracker (USGS event us7000tw76)

There were no immediate reports of fatalities, injuries or significant structural damage in any of the affected countries, according to emergency authorities cited in regional reporting. No tsunami warning was issued — the epicentre was inland — and no aftershock advisory had been issued at the time of the first reports.

Measurements differed slightly between agencies in the first hours, as is common after a quake. Kenyan reporting based on the European-Mediterranean Seismological Centre (EMSC) put the tremor at magnitude 5.6, centred east of Ushirombo in the same Geita area. Awaaz Punjab is using the USGS figures — magnitude 5.1 at 19 kilometres north-northwest of Masumbwe — which the agency had revised several times by Thursday as more station data came in; the USGS event is recorded as us7000tw76 and was detected by 46 seismic stations.

A rift-valley region that knows strong quakes

The quake is linked to tectonic activity in the East African Rift System, one of the world's most active continental rift zones, which runs through the Lake Victoria region. The area has been hit by damaging quakes before: in September 2016, an earthquake in Tanzania's Kagera region, west of Lake Victoria, killed at least 11 people and injured more than 100, according to reporting at the time.

Thursday's quake was the largest recorded anywhere in the world so far that day in the USGS feed. Authorities in Tanzania, Kenya and Rwanda were continuing to monitor for damage reports from the rural Geita region, where communications are slower, and seismologists said aftershocks were possible in the coming days, as after any shallow quake of this size.