Transcript Slide 1
How are Earthquakes Recorded? Educational Materials and Videos are made by: Giovanna Perrone and Alexandra Mair SEYS 753 Spring 2008 Professor Brain Murfin Dynamic Crust The• following clip is a demonstration of how earthquakes occur and they are Do Now: recorded. Using the following worksheet, earthquake video worksheet, answer – Watch the clip and youhave are a class the questions using thefollowing information from the describe video. Afterwhat the video, seeing. discussion on the notes as the lesson will reiterate the concepts of the video. (click the warning to begin the video) – http://www.youtube.com/watch?v=m9RF5eRdG9c Earthquakes •Fault: Earthquakes: a violent shaking of the earth’s crust it is the first place where movement occurs causedthe by the movement of landmasses along between plates and/or subduction zones occurs A faults fault line is where an earthquake Earthquakes Epicenter: is the location on the earth’s Seismic Waves: Seismic waves the surface energy thatan is earthquake directly above the focus an earthquake. that release andofgoes in ALL This is where the seismic waves first reach the DIRECTIONS surface. Richter Scale • The Richter scale is widely used to measure the magnitude (or the amount) of energy of an earthquake. There is no limit as to how strong an earthquake may be. Mercalli Scale • Mercalli Scale is used to determine how much observable damage, also called the intensity, was done by an earthquake Seismograph vs. Seismogram • Seismograph is an instrument that is used to detect (measure) seismic waves • Seismic waves are recorded on a seismogram • A seismogram is a piece of paper that records seismic waves http://www.thetech.org/exhibits/online/quakes/seismo/images/seismograph.gif How to Read a Seismogram http://ww2.lafayette.edu/~malincol/Geol120/earthquaketopics.html Earthquake Waves • P-waves – also called primary waves, or compressional waves – P-waves travel faster – They always reach the seismic stations first – P-waves cause particles to vibrate back and forth in the direction that a P-wave moves (← →) – P-waves can travel through solids, liquids, and gases Earthquake Waves • S-waves – also called secondary waves, or shear waves. – S-waves travel slower than P-waves and reach seismic stations second. – S-waves cause particles to vibrate at right angles (up and down motion) to the direction that S-waves move. (↑↓) – S-waves can only travel through solids NEVER through liquids Shadow zones are created due to secondary waves cannot pass through the liquid outer core. These are areas where no seismic recording occurs. Notice the vertical axis This represents TIME (in minutes!) Let’s enlarge a small section Between each minute, we notice that there are 3 segments. If there are 60 seconds in a minute, each one of these segments must be ________seconds. What would this time be? Notice the horizontal axis This represents DISTANCE (in thousands of Kilometers!) Let’s enlarge a small section There are also two curves on this chart that display the way different earthquake waves behave. This chart can be used for answering many different questions! How long does it take an S-Wave to travel 5,000km? The recording station tells us it took 6 minutes and 20 seconds for the P-Wave to reach them. How far away from the epicenter of the earthquake must they be? I know that there was a 7 minute difference in the arrival of my P and S waves. How far away from the epicenter must I be? Slide your scrap paper up until the tick marks match up with the curves… Mark off 7 minutes on scrap paper…