Magnitude versus Intensity of earthquakes

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Do you know the difference between magnitude and intensity? A lot of people don't. So why did the Pakistan earthquake of 5.6, which is not a terribly large magnitude, cause so much damage? Do you want to know? Read on. Magnitude tells the power that is released by the earthquake. There are various ways of measuring it but they all come out about the same. It has to do with the length of the fault, how far it slips, how fast, how much power was put out at the initial point of breakage, etc. Intensity tells how much the earth shook at any given spot, and how much damage it could cause. Intensity changes according to depth of the earthquake, distance from the earthquake, what the soil and substrata are made of and how they react to the seismic waves. So, the USGS "shake map" gives a VII (seven) as the intensity of the Pakistan earthquake. That is plenty enough to cause damage. The earthquake magnitude scales are logarithmic, that is, they increase by a power of 10 for every magnitude. They also increase in power by 33 times for each magnitude. Hummm, that is complicated. But if you consider intensity, it is on a 12-point scale and calculated by how much damage was or could be caused (if it is in a populated area). This is called the Mercalli scale and it will probably tell you more that you need to know than the magnitude itself. You can have a magnitude 7 in an unpopulated area with no damage, and a magnitude 5 in a populated area with soft soil and stone-stack buildings, and the 5 will do much more damage. In Japan, modern buildings are built to flex but not break with earthquakes. So they can take much more shaking. Does this help you understand why a 5 can cause so much damage in Pakistan? It all depends on the intensity and the readiness of buildings.