LAHORE - Experts have attributed the confusion regarding difference in magnitude of earthquake to taking readings from different places.
United States Geological Survey first reported that magnitude of earthquake was recorded 7.7 on Richter Scale and later revised it to 7.5. Pakistan Meteorological Department, however, conveyed that the intensity of earthquake was 8.1.
“Pakistan measures intensity of earthquake through its seismic network on the fault line. The US Geological Survey takes readings from equipment installed in the US over thousands of miles away from the epicenter. So the difference in readings may be due to the distance,” said meteorological expert Shaukat Ali Awan. He claimed that Pakistan Meteorological Department was using state of the art seismic equipment for measuring intensity of earthquakes at different locations. “There is no question of any inaccuracy as reading is taken at more than 40 locations in Pakistan close to the fault line,” he affirmed, adding, that the reading taken by the US Geological Survey could be different from those taken by the PMD mainly because of long distance. World over there are mainly two methods of measuring magnitude of an earthquake: the Richter Scale and Moment Magnitude Scale. The widely in vogue Richter Scale uses a formula based on amplitude of the largest wave recorded on a specific type of seismometer and the distance between the earthquake and the equipment.
The Moment Magnitude Scale is preferred because it works over a wider range of earthquake sizes and is also applicable globally. It is based on the total moment release of the earthquake. In the technical jargon, moment is a product of the distance a fault moved and the force required to move it. Its estimates are about the same as Richter magnitudes for small to large earthquakes. But the only difference being that it is used to measure events of 8 magnitude or above.