Source: Earthquake rattles Harare, Bulawayo | The Herald April 4, 2017
MOST parts of Zimbabwe, including Harare and Bulawayo, were yesterday shaken for more than a minute by tremors from an earthquake that occurred in central Botswana which started at 7:40:15pm, almost 350 kilometres southwest of Plumtree.There were no reports of injuries or damage last night, and intensity estimates suggested very low risk of these, although the most severely affected parts of Zimbabwe were Bulilima, Lupane, Nyamandlovu, Tsholotsho, Inyathi, Bulawayo and parts of Hwange.
According the US Geological Survey, which monitors and measures all earthquakes across the world, the earthquake had a magnitude of 6.5 and occurred at latitude 22.621°S and longitude 25.153°E and around 11,6km below the surface in an area holding very few people.
The nearest town to the epicentre is Moijabana, population 2000, about 132km to the east.
Besides magnitude, scientists also measure the intensity of earthquakes on the surface on a scale using Roman numerals that ranges from I, which means it is not felt, through to X which is called extreme.
This intensity scale gives a better indication of how much the ground shakes, while the magnitude gives an indication of how much energy was released.
In Zimbabwe there was a lobe of intensity V, which is moderate, contained within a line running due north of Plumtree almost to Lupane and then west back to the Botswana border. Most a wide belt of land felt the earthquake at intensity IV, classified as light, before intensities petered out into II and III, jointly called weak.
Even within Botswana there was only a small circle around the epicentre containing about 2000 people which felt the earthquake at a VII very strong intensity, and a larger circle with around 54 000 people which felt the earthquake at a VI strong to VII very strong intensity. Most Botswana towns and cities are in the V moderate zone, the same as central west Zimbabwe.
People in Harare’s Central Business District were seen running out of buildings fearing for their lives as tables and chairs were shaking.
The tremor was also felt in Gweru, Harare, Murehwa and Gokwe, among others.
In separate interviews residents said it all started with a sound like a train and suddenly houses were shaking vigorously.
“It was around 7:35pm when I heard a sound like a goods train then suddenly the whole house was shaking. Fortunately nothing was broken in our kitchen display unit,’’ said Mr Mthokozisi Dube.
Mr Mcebisi Ncube of Marriage Quarter said; “Our windowpanes cracked when suddenly the whole house was shaking and initially we were wondering what was happening to us until someone shouted from the next house that it was an earthquake.”
The Meteorological Services Department yesterday said it would issue a statement today.
The earthquake was also felt in South Africa, which had already had a 5.2 magnitude quake early yesterday morning. Magnitudes are on a logarithmic scale so a magnitude 6 is 10 times as powerful as a magnitude 5.
Last year tremors shook Chipinge, after an earthquake measuring 5,6 hit Mozambique.
Earlier a 4,6 magnitude earthquake hit the Kariba area and parts of neighbouring Zambia .
Kariba residents and their northern neighbours woke up to the rattling effects of the quake which lasted for about 15 seconds.
Seismologists say the main causes of effects of earthquakes in Zimbabwe are largely plate tectonics closely related to the east African Rift Valley system.