6D   Thursday JP

JP:   Make a line graph of the following earthquake data and state what you believe to be the average number of earthquakes per year from this graph:

About the frequency of large earthquakes

    Earthquakes (ground shaking) are caused by relatively fast movement along breaks in the Earth's crust, known as faults. In general, the more movement or displacement along a fault during an event, the greater the amount of ground shaking. Ground shaking is also affected by the properties of the Earth materials through which the vibrations pass; weak soils or loose sediment can enhance ground shaking.

    There are several different methods of measuring the size of an earthquake; a popular measure of earthquake size is the Richter magnitude. The Richter magnitude is based upon the amplitude (height) of ground shaking as recorded on a machine (a seismometer). Earthquakes vary in size over many orders of magnitude, and therefore the Richter scale is logarithmic to accommodate this wide variation in earthquake sizes. On the logarithmic Richter scale, a magnitude 7 earthquake is 10 times bigger than a magnitude 6 earthquake. Earthquakes that are magnitude 7 or above are often (though not always) very damaging earthquakes.

    The United States Geological Survey has compiled information on the number of earthquakes around the globe that have equaled or exceeded magnitude 7. The data are expressed as the number of earthquakes per year for each year starting in 1900. Note that the older data in this table are somewhat suspect, because seismometers did not systematically record earthquakes in a standardized fashion with good spatial coverage until the 1930's or later.

        Save the graph and attach to your weekly JP journal summary for the week...due Friday.