Frequency of Earthquakes 7.5 and Greater
The graph shown above depicts the number of earthquakes larger than 7.4. These can be regarded as significant earthquake events that often result in substantial property damage and human casualties. The earthquake statistics were taken from the United States Geological Survery (USGS), and their yearly assessment of earthquakes around the world.
The graph shows the period of record, extending from 1900 to 2009 inclusive. And although the number of sites monitoring earthquakes has increased manifold during this period, the number of earthquakes (particularly the larger magnituded quakes) is not thought to be affected. The graph shown represents a five year running mean, that despite smoothing the data, best shows the trends in numbers. The main feature of the graph to be noted is the recent (past twenty plus years) increase in quakes.
The question that might be asked is: Does the increase merely show a short-term trend, or instead a much more dire longer term increase in earthquake activity?
