GEOL 108 - Crises of a Planet Lab 2 - Locating Earthquakes
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GEOL 108 - Crises of a Planet Lab 2 - Locating Earthquakes Sept. 9 - 14, 2012 Department of Earth Sciences
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GEOL 108 - Crises of a Planet Lab 2 - Locating Earthquakes . Sept. 9 - 14, 2012. Department of Earth Sciences. LAB 2 - EARTHQUAKES - KEY CONCEPTS Reading seismograms Using travel time curves to triangulate an epicenter Predicting tsunami arrivals. EARTHQUAKES | 2. - PowerPoint PPT Presentation
Transcript of GEOL 108 - Crises of a Planet Lab 2 - Locating Earthquakes
GEOL 108 - Crises of a PlanetLab 2 - Locating Earthquakes
Sept. 9 - 14, 2012
Department of Earth Sciences
Department of Earth Sciences
EARTHQUAKES | 2
LAB 2 - EARTHQUAKES - KEY CONCEPTS
• Reading seismograms
• Using travel time curves to triangulate an epicenter
• Predicting tsunami arrivals
Department of Earth Sciences
EARTHQUAKES | 3
SEISMIC WAVES
• Release of accumulated energy leads to quake• Energy travels in waves of vibration
− Body waves• P-waves - primary• S-waves - secondary
− Surface waves• Love• Rayleigh
• Waves travel at different known velocities
Department of Earth Sciences
EARTHQUAKES | 4
DETERMINING QUAKE EPICENTER
• Step 1: Identify P and S arrival times
2:37:10 2:41:50
Department of Earth Sciences
EARTHQUAKES | 5
DETERMINING QUAKE EPICENTER
• Step 2: Subtract arrival times to get S-P delay
2:37:10 2:41:50
S-P delay = 2:41:50 – 2:37:10S=P delay = 0:04:40(4 minutes, 40 seconds)
Department of Earth Sciences
EARTHQUAKES | 6
DETERMINING QUAKE EPICENTER
• Step 3: Use seismic wave travel time vs. distance chart to determine distance to epicenter
Find where S-wave line minus P-wave line equals the delay you determined
S-P delay = 2:41:50 – 2:37:10S-P delay = 0:04:40(4 minutes, 40 seconds)
Read what distance that delay corresponds to…
~ 3,600 km here
Department of Earth Sciences
EARTHQUAKES | 7
DETERMINING QUAKE EPICENTER
• Repeat steps 1-3 for two other seismic stations
Distance to epicenter (determined from reading seismographs, not shown)Los Angeles: 1800 kmAustin: 3150 kmUrbana: 3400 km
Department of Earth Sciences
EARTHQUAKES | 8
DETERMINING QUAKE EPICENTER
• Step 4: Use a compass to plot all possible epicenter locations. The epicenter is where they intersect.
Distance to epicenter (determined from reading seismographs, not shown)Los Angeles: 1800 kmAustin: 3150 kmUrbana: 3400 km
Department of Earth Sciences
EARTHQUAKES | 9
TSUNAMIS
• http://www.youtube.com/watch?v=2uJN3Z1ryckFukushima Prefecture, Japan. Photograph by Sadatsugu Tomisawa, AP
Department of Earth Sciences
EARTHQUAKES | 10
PREDICTING TSUNAMI ARRIVALS
• Tsunamis are triggered by earthquakes
• Tsunamis travel at 600 km/hr on average
• Given a known epicenter, you can predict the tsunami arrivals elsewhere by rearranging the equation we used last week (velocity = distance / time)
• Assignment will ask you to plot how far a tsunami has traveled in 1, 2, 3 and 4 hours. So what should you solve the above equation for?
