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IV. Seismic waves A. Waves produced by earthquakes 1. Earthquakes occur when rocks beneath earths surface moves. Pressure in rock build up enough, rocks break or change shape releasing energy in waves. 2. Ripple out in all directions from point of earthquake 3. 3 types of waves I. P waves ii. S waves iii. surface waves B. P waves 1. longitudinal seismic waves 2. primary waves 3. move faster that other seismic waves 4. Made up of compressions and rarefactions of rock inside 5. travel directly through earth C. s waves 1. traverse seismic waves 2. secondary waves 3. shake ground not through liquids 4. cannot travel through liquids 5. do not travel directly through earth like P waves I. Cannot be detected on opposite of earthquake D. Surface waves- combination of longitudinal and traverse waves that travel along the surface of a medium 1. slower than p and s waves 2. cause most severe ground movements I. make ground move like ocean waves 3. can produce huge surface waves on ocean tsunamis I. can travel thousands of miles across oceans ii. varied sizes - 2 cm to 30m E. Detecting seismic waves 1. seismograph- an instrument to detect and measure earth quakes 2. Records ground movements caused by seismic waves as they move thru earth 3. Measure time between arrival of P wave and S wave- can tell how far the earth quake was 4. compare at least 3 seismographs in different locations to pinpoint 5. Geologists use seismographs data to locate underground recourses Traverse wave Crest

wave movement trough

Study guide 1 seismic waves 2 antinode waves 9 seismic waves 10 the time between the arrival of P waves and the arrival of S waves 25 The amplitude of a wave is the measure of the waves energy The more energy the wave has the the larger the amplitude is 28 In the open ocean waves move forward more freely When they reach land the waves travel more slowly as they enter shallow water. This allows waves to catch up to one another combine and increase energy and therefore their amplitude 29 P waves travel thru earth faster than S waves/ P waves arrive at seismograph before S waves. By finding the difference in arrival times of P and S waves they can tell how far away the earthquake was

Quiz 1 S waves 2 longitudinal 3 slower than P or S waves 4 all mediums or solid and liquid rocks 5 waves produced by earthquakes 6 instrument used by scientist to record ground movement caused be seismic waves as they move thru earth 7 huge surface wave on the ocean caused by an underwater earthquake