Scales for Reporting Earthquakes Size and Severity

Until about a century ago, only historical records accounted for the severity of an earthquakes shaking and destruction.   When scientist used these reports, it was very difficult for them to make an accurate comparison of earthquakes sizes.   This was due to the reports being gathered using a system that had no established standards for reporting.   Over time many versions of intensity scales were created and tested, some scales monitored the damage done to buildings, individual descriptions of earthquakes and also the secondary effects of earthquakes such as landslides and the extent of ground breakage.   Mr. Guiseppe Mercalli developed more dependable intensity scale which is called the Mercalli Intensity Scale and a modified version is still used today.   This scale is used mostly through out the United States and Canada to estimate the strength of an earthquake; for instance, if well-built wood structures and masonry buildings are destroyed by an earthquake, the region would be assigned an intensity of X, meaning disastrous, on the scale.   Although this scale is a very useful tool to compare earthquake severity in regions that do not have seismographs, its problems are plenty.   The problems with the Mercalli Scale is that the information gathered is based on the damage of earthquakes that depends on the severity of the shaking, and on other factors such as the amount of people, design of the buildings in the area, and nature of external materials.   The Richter Scale was designed in 1935 and was better then he Mercalli Scale because the Mercalli Scale was mostly based on what people saw and felt, when the Richter Scale is based on the volume of seismic waves; which is measured by instruments giving the results a more scientific, objective basis.
Lutgens, F.K. and Tarbuck, E.J. 2006. Foundations of Earth Science. Fifth ed. Pearson Hall. Upper Saddler River, NJ.