Earth Tremor

Today I felt an earth tremor. I first heard this rumbling sound - like thunder in the far distance. Next thing I felt the tremor and even my windows rattled! Immediately the song "If the World was ending" came to mind. It got me thinking. We have never had a major earthquake here in South Africa. What would I do if ever there was one? Scary thought. I would rather not dwell on it. Nope. Let me not even go there!! Update: After some research it turns out it was an earthquake. It measured 3.50 on the Richter scale.