Tremor: 3.6 magnitude quake rattles Johannesburg on Friday

Did the earth shake for you on Friday morning? A 3.6 magnitude earthquake was felt in Johannesburg. Here’s what we know.

Joburg tremor details

• The tremor took place at 6:34 SAST on Friday, 30 July, in Kathlehong.
• The hypocentre depth was 10 kilometres.
• Its magnitude measured 3.6 on the Richter Scale
• Coordinates: 26 342 S, 28 227 E

While Volcano Discovery confirmed the 3.6 magnitude quake, EMSC-CSEM, an independent provider of real-time earthquake info, classified it as a 4.2 magnitude quake, with a depth of 5 metres.

A Council for Geoscience spokesperson, Mahlatse Mononela, said: “At this point, it does seem like the earthquake occurred in a mining area, however, more details of the exact location are being gathered”.

Residents who felt the quake reported the following on Volcano Discovery:

• Benoni: The sofa was shaking and there was a rattling sound
• Alberton, Ekurhuleni Metropolitan Municipality, Gauteng: It was just a small vibration with sound…nothing too intense
• Johannesburg South: House shaking. It was concerning
• Boksburg: Lasted for about 3 seconds. It was intense. All windows were shacking. Foundations were shacking.
• Germiston: Deep rumbling followed by a more relaxed roll out.
• Johannesburg South African: All the doors were shaking

Recent earthquakes

It happens more often than you may realise. More than 40 earthquakes were recorded in South Africa this month, including a 4.2 magnitude quake southeast of Springbok in the Northern Cape.

According to Volcano Discovery, there were two quakes of magnitude 8.2 and magnitude 6.1 respectively over the last 24 hours worldwide, as well as 12 quakes between 5.0 and 6.0 magnitude, and 65 quakes between 4.0 and 5.0 magnitude.

The biggest earthquake of the past 24 hours had an epicentre in the Gulf of Alaska – the strongest US quake in 50 years. It sparked tsunami fears for South Alaska and Hawaii.

Alaska earthquake

According to the USGS, the earthquake hit 91km southeast of the town of Perryville, with a tsunami warning in effect for south Alaska and the Alaskan peninsula.

Videos shared on social media showed Kodiak residents evacuating to higher ground while tsunami warning sirens were heard blasting in the background. A buoy southwest in the region recorded “serious changes” in the water height.

Dr Alice-Agnes Gabriel, a seismologist at the Ludwig-Maximilians-Universität (LMU) in Germany, said the earthquake has an intermediate depth of 35km, which is deeper than USGS’s phase estimate of 23km.

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