27 Analyzing the DataStep 1: Determine the number of seconds between the arrival time of the first P-wave and the first S- wave. This time difference is know as “Lag Time”. The lag time must be calculated from at least 3 different recording stations.
28 Analyzing the Data Continued Step 2: Plot the lag times found from the three recording stations on a (S-P) Lag Time Graph in order to determine the distance to the epicenter.
30 Analyzing the Data Continued Step 3: Using a ruler and a map scale to measure the distance between the seismometer and the earthquakes epicenter. Step 4: Place the point of a compass on the seismometer location and the pencil on the distance away from the epicenter. Next, draw a circle around the seismometer. Repeat this step for the other two recording stations.
31 The epicenterWhere the three triangulated circles intersect is the location of the epicenter of the earthquake.
32 Determining an earthquakes magnitude Scientists use three different scales to measure and describe an earthquakes magnitude. Magnitude is a measure of the amount of energy released during an earthquake.Richter Magnitude ScaleMoment Magnitude ScaleModified Mercalli Scale
33 Richter ScaleThe Richter scale is used to interpret two different values recorded by the seismometer.The amount of ground motion.The amount of energy released by the earthquake
34 Ground MotionThe Richter scale begins at zero but has no upper limits. Each increase of 1 unit represents ten times the amount of ground motion. Example: A magnitude 8 produces ten times greater ground shaking than a magnitude 7. The ground motion value is the measure used to alert the general public.
35 Energy ReleaseThe Richter scale also measures the energy released by the earthquake. On this scale each increase of one whole number, is represented by a 31-fold increase in energy. Example: A magnitude 8 is 31 times more powerful than a magnitude 7
36 Moment magnitude scale The moment magnitude scale measures the total amount of energy released by an earthquake. The energy released depends on three factors:The size of the faultThe amount of motion that occurs along the faultThe strength of the rocks that break during the earthquake.
37 Moment magnitude scale continued On this scale for each increase of one unit the earthquake releases 31.5 times more energy. Example: A magnitude 8 earthquake releases more than 992 times more energy than a magnitude 6.
38 Modified Mercalli Scale On the Modified Mercalli scale, an earthquakes magnitude is measured by the amount of damage caused by ground motion. This scale ranges from 1 – being minimal and 12 being total destruction.
40 Largest recorded earthquake The largest ever recorded earthquake occurred in Chile. May 22nd 1960 at 11:19:14 UTC a magnitude 9.5 earthquake was recorded. Approximately 1,655 killed, 3,000 injured, 2,000,000 homeless, and $550 million damage in southern Chile; tsunami caused 61 deaths, $75 million damage in Hawaii; 138 deaths and $50 million damage in Japan; 32 dead and missing in the Philippines; and $500,000 damage to the west coast of the United States.
44 How can earthquakes be used Seismologists have used earthquakes to map the Earth’s interior. P and S waves change speed and direction depending on the density of different materials. Scientists have found that S-waves cannot travel through the outer core, proving it is liquid. By studying the P-waves scientists were also able to determine that the inner core is composed of iron and nickel.