learning about: the great southern california shakeout november 13, 2008 a teachable moment
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Learning about:The Great Southern California ShakeOut November 13, 2008 A Teachable Moment
What is the ShakeOut?Mw 7.8 earthquakeSouthern San Andreas FaultWhat if Click image above to play animationDownload the animation: http://www.unavco.org/edu_outreach/resources/teachable/scec-shakeout-simulation-rt.wmv
How do we study earthquakes?
GPS DataWest of the San Andreas fault:The Pacific PlateEast of the San Andreas fault:The North American Plate
Velocity VectorsMap from USGSdirection of motionGPS stationlength=rate of motion
Chino Hills Mw 5.4 July, 2008
*Thanks for using UNAVCOs Teachable Moment! Notes are provided beneath each slide to give you more information, resources, and student activities. Feel free to use what you need, and to edit the slides to suit your classroom. Email Celia Schiffman at firstname.lastname@example.org with questions and comments.
To view the simulation of the earthquake, download the animation: http://www.unavco.org/edu_outreach/resources/teachable/scec-shakeout-simulation-rt.wmv and place the file in the same folder as this Power Point.
The Great Southern California ShakeOut is an earthquake drill for a potential M7.8 earthquake on the San Andreas fault. ShakeOut is organized by a variety of partners with the Earthquake Country Alliance (http://www.earthquakecountry.info/alliance.php).See http://www.shakeout.org/organizers.html for more details.*ShakeOut is an earthquake drill on November 13, 2008 at 10 a.m PST if a magnitude 7.8 earthquake occurred on the southern San Andreas FaultAn earthquake of this magnitude will happen in this area, this drill is to test emergency response procedures, and to encourage individuals to be prepared by readying their homes, etc.ShakeOut simulation based on the ShakeOut scenario by the USGS (United States Geological Survey), which includes expected shaking, death, damage, and injuriesMany agencies, including UNAVCO, are treating this as a real event, and acting accordingly.
Movie shows simulated shaking in southern California. Ask students to note areas of the most intense shaking, and to hypothesize why some areas shake longer and harder than others. Answer: most areas of intensified shaking are basins, where looser more hydrated sediments amplify shaking. Notably: east LA and the San Gabriel Valley.
More questions: How do the areas of shaking correlate with population density? What sort of implications does a scenario like that have for earthquake preparedness? What do you think people living in these areas should do to be prepared for an earthquake? Where should you go to find information about preparing for an earthquake (especially if you are currently in an earthquake prone area)?*Ask your students if they know what any of the images represent.Top right is the EarthScope Observatories (PBO, USArray, and SAFOD, see more details below), which is a GPS (Global Positioning System) array, a seismic array, and a borehole through the San Andreas Fault. See http://www.earthscope.org/ for more information.Top left is InSAR (Interferommetric Synthetic Aperature Radar). The colored rings show degree of movement between a before and after picture taken with radar. This scene is from the LA Basin. See http://en.wikipedia.org/wiki/Interferometric_synthetic_aperture_radar for more information on InSARBottom left is LiDAR (Light Distance and Ranging). LiDAR uses radar to make a very detailed 3-d map of topography, and you can see what has changed during an earthquake is you make a picture before and after the earthquake. This picture is of the San Andreas fault in Southern California taken as part of the B4 project (http://www.livescience.com/environment/051207_san_andreas.html). See http://en.wikipedia.org/wiki/Lidar for more information on LiDAR.Bottom center and right: A GPS campaign instrument. After an earthquake, scientists deploy temporary instruments such as GPS and seismometers to record the after effects of the earthquake. The PBO is made up of permanent GPS stations.
The Plate Boundary Observatory (PBO), part of the EarthScope project that is funded by the National Science Foundation, studies the three-dimensional strain field resulting from active plate boundary deformation across the Western United States.Over 1000 high-precision continuously-recording Global Positioning System units. GPS units are anchored to the ground, have cm-scale precision, and are constantly recording position in space. Ask your students if they have a handheld GPS, or a GPS in their/their parents car. These scientific GPS units use the same technology, which is based on using satellites circling the earth fpr location, only these are much more accurate, and are attached to the ground, so they record the movement of the ground from plate tectonics and volcanic activity. Note the density of instrumentation along the San Andreas fault. An earthquake along this fault would be very well instrumentally documented because of the PBO.
The USArray is a dense network of portable and permanent seismic instruments across the United States. The seismographs record the energy released by the hundred of earthquakes that occur around the world everyday. See http://www.iris.edu/USArray / for more details. SAFOD, or the San Andreas Fault Observatory at Depth, is a 3 km deep hole across the San Andreas Fault. See http://earthquake.usgs.gov/research/parkfield/safod_pbo.php for more information. The San Andreas is a right lateral fault: the western side of the fault moves to the north with the Pacific plate, and the eastern side moves to the south with the North American plate. Ask students what the GPS data might show if there was an earthquake along the San Andreas fault? What would the relative motion look like, depending on which side of the fault you were standing on during the earthquake?Have your students think about the movie they just watched on the previous slide. How would that shaking look like as GPS data, and how would it differ based on location (e.g. downtown LA versus San Diego)
*These maps were generated using data for educators: http://www.unavco.org/edu_outreach/data.htmlThese maps are showing GPS stations in the Plate Boundary Observatory in Southern California. The graphs are showing distance to the north (y-axis) versus time (x-axis) at an individual station, or a time-series plot showing position versus time.These two figures are showing the northward component of motion since 2004 to November of 2008 (you cant actually see time on the x-axis) on either side of the San Andreas fault (so over almost 5 years). Have your students do a rough estimate of how many millimeters per year each station has moved.UNAVCO offers free educational materials on using GPS data. See http://www.unavco.org:8080/cws/modules/readingGPStimeseries for our resources on reading time series plots.For VDCY near downtown LA: about 160 mm over about 5 years, so about 32 mm or 1.25 inches per year.For WOMT near Victorville: about 55 mm over about 5 years, so about 11 mm or 0.4 inches per year.You can have your students act this out to demonstrate the right-lateral shear on the San Andreas fault. Have one student be a GPS unit on the pacific plate, and one student be a GPS unit on the north american plate. Over ten years, the Pacific plate will move about 5 ft, while the North American plate will move about 2 ft (you can also have your students make this calculation). Have the plates hold hands with an imaginary San Andreas fault running between them.Have the Pacific plate step forward 5 ft, and the North American plate step forward 2 ft.The Pacific plate is always moving faster than the North American plate, therefore creating the right lateral shear and slip on the San Andreas fault.Again, have your students try to guess what the data would look like if there were an earthquake on the San Andreas fault. Although the amount the earths surface moves in an earthquake is highly variable (depending on the type of earthquake, the depth, rock type, etc.), generally in a magnitude 7.8 earthquake you could get from 5 to 10 meters of motion at the surface (Wells and Coppersmith, 1994). *Image taken using Google Earth with velocity vectors from Plate Boundary Observatory GPS stations plotted. View is tilted and looking north. The longer a vector, the faster that spot is moving. Each vector represents one individual station, which would be located at the base of the arrow (yellow dots on the map). A vector has a direction (the way the arrow is pointing) and a speed (the longer the arrow, the faster its moving) Now we are demonstrating the idea from the previous slide, but with many more stations, and not just the northward component of motion. All the stations on the Pacific plate are moving much faster than those on the North American plate. Ask students, what happens as you move from west to east? Can they tell where the San Andreas fault is by looking at the vector data? Clicking again will show the map of the San Andreas fault for comparison.If you have internet access, you can load the velocity vectors into Google Earth. Put this address into a web browser to download the KMZ file: http://pboweb.unavco.org/python/PyGEVelocity/create_kml_outline.py/handlerOpen Google Earth, and the double-click on the .kmz file to load the velocity vectors. *This is an actual shake map from the magnitude 5.4 earthquake that occurred earlier this year in southern California. A shake map shows the distribution of acceleration recorded by geophysical instruments in the area. A magnitude 7.8 earthquake is 5000 times larger than that!