Source: Met Dept warns of quake aftershocks | The Herald April 5, 2017
Innocent Ruwende Senior Reporter
Zimbabwe is likely to experience violent aftershocks that can cause damage to buildings and cause debris to fall, endangering people’s lives, following an earthquake that hit Botswana on Monday, the Meteorological Services Department (MSD) has warned.
The earthquake caused tremors that were felt in most parts of Zimbabwe and South Africa.
An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock.
According to the US Geological Survey, which monitors and measures all earthquakes across the world, the Monday earthquake had a magnitude of 6.5 and occurred at a latitude 22.621 degrees South and longitude 25.153 degrees East and around 11.6 kilometres below the surface.
The earthquake occurred in an area holding very few people and the nearest town of the epicentre was Moijabana in eastern Botswana.
“This is a large regional earthquake,” the MSD said in a statement.
“We expect aftershocks hours, days, or weeks after the main earthquakes.
“Aftershocks can cause building damage and falling debris that would injure people.
“People should check for infrastructure damage to their properties as this earthquake was widely felt in Plumtree, Gwanda, Bulawayo, Hwange, Victoria Falls and even in Harare.”
The department said a comprehensive intensity survey would be required to be carried out in areas like Plumtree and most parts of western Zimbabwe.
The earthquake was also felt in South Africa, which had experienced a magnitude of 5,2 earlier.
“The earthquake was felt in most parts of the country, especially in the south western regions, according to people whom we talked over the phone and those who called from Chipinge, Gwanda, Kariba, Mutare and Beitbridge, Wedza, Kezi, Harare, Bulawayo and Plumtree,” said the department.
“The people felt the ground shaking-movements and some also said they had the rumblings, the shaking door panels and rattling of windows. A number of people in Plumtree were frightened as they felt their houses vibrating and door panels shaking heavily.”
The Met Department said at the time of compiling the earthquake report, they had not received any reports of damages to infrastructure.
“This is a big earthquake, thus it has higher chances of causing infrastructure damage,” it said. “A comprehensive intensity survey would be required to be carried out in areas like Plumtree and most parts of western Zimbabwe.
“This would generate a well detailed intensity survey report, thus helping to map the areas the earthquake was felt, an intensity in each area. The most probable cause is pure tectonics. This is a big earthquake in the region, thus the seismic energy that radiated from the hypo-centre (focus or heart of the earthquake) in the form of seismic waves.”
The department said the shaking, which was felt in most parts of the country, was due to the passage of seismic waves generated by the seismic events.
Botswana, the western region of Zimbabwe, Kariba and going as far as Zambia lie in the western extension of the East African Rift System.
The East African Rift System contributes to a number of regional earthquakes recorded so far.
This earthquake was the biggest to be recorded in Botswana and the country, except for the Okavango Delta Region, has always been regarded as a seismic.
“This should give us lessons as a country that we are not safe from earthquakes and earthquakes are a hazard,” the Met Department said.