More than 800,000 earthquakes are recorded every year. Most go unnoticed except by the scientific community. For us, seismic activity matters only when we can feel it. Yet, the possibility of an earthquake always lurks in the back of our minds. It's one reason we keep basic supplies handy like food, water and candles. So, when does an earthquake become a threat? The answer is determined by the Richter scale, devised by geologist Charles Richter in 1935. His magnitude scale ranges from 1 to 8 and each number is a 10-fold increase in strength. Anything below 2 or 3 is hardly felt. Between 3 and 5, we feel minor shaking. A 6 gets into minor interior and structural damage. Readings of 7 and above represent major damage. And that's the On The House tip for today.