Massive earthquake strikes seabed off SA’s Cape coast

It’s hard to believe, but an “atomic bomb”-scale earthquake shook the ocean floor a mere 2000km from Mossel Bay this morning.

The earthquake – measuring 6.7 on the Richter scale – was recorded at 6.55am on Wednesday, 10 July about 2,140km south of Mossel Bay in the Indian Ocean.

Volcano Discovery reported that very strong shaking near the epicentre was detected with the estimated seismic energy activity of the earthquake measured at 197 gigawatt hours, which is equivalent to 10.6 atomic bombs.

The quake was at a depth of 10km, which, according to USGS Quakes, is considered a “shallow earthquake”.

Strongest earthquake in area since 1900

According to scientists, the area where this quake occurred, has a high level of seismic activity. This was however, the strongest earthquake to hit this area since at least the beginning of the 1900s.

No aftershocks have been recorded so far. 

What is an earthquake?

According to the Council for Geoscience’s (CGS) website, an earthquake occurs when there is a build-up of stresses in the Earth’s crust that need to be released and this can occur through weakness in the rock, such as a fault. This sudden release of stress is what we experience as an earthquake.

What is considered a tremor?

The CGS states that seismic events measuring less than 4 on the Richter scale are considered as tremors in South Africa because they happen frequently and are felt in most mining towns and nearby areas.

The most recent tremor (with a magnitude of 2.6) was recorded on Monday, 30 June in Gauteng with its epicentre near Johannesburg south.