NSTA presentation part 1
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MIQuakes presentation and activity at NSTA Chicago 2015. There are 2 parts to this presentation. Make sure you get both!
NSTA presentation part 1
- 1. MiQuakes Earthquakes in the Classroom Loose Sediments to Hard Core NSTA 2015 Michele Svoboda Mill Creek Middle School Comstock Park, MI Cris DeWolf Chippewa Hills High School Remus, MI
- 8. A major magnitude 7.1 earthquake occurred on the North America Eurasia Plate boundary. The epicenter ( ) was located ~1170km SE of Greenland in the middle of the North Atlantic Ocean. Magnitude 7.1 NORTHERN MID-ATLANTIC RIDGE Friday, February 13, 2015 at 18:59:12 UTC Image courtesy of the US Geological Survey
- 9. Modified Mercalli Intensity Perceived Shaking Extreme Violent Severe Very Strong Strong Moderate Light Weak Not Felt The Modified-Mercalli Intensity scale is a twelve-stage scale, from I to XII, that indicates the severity of ground shaking. Because of the remote location, no one was shaken by this earthquake. Image courtesy of the US Geological Survey USGS Estimated shaking Intensity from M 7.1 Earthquake Magnitude 7.1 NORTHERN MID-ATLANTIC RIDGE Friday, February 13, 2015 at 18:59:12 UTC
- 10. Magnitude 7.1 NORTHERN MID-ATLANTIC RIDGE Friday, February 13, 2015 at 18:59:12 UTC The Mid-Atlantic Ridge is a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. Image courtesy of www.shadedrelief.com
- 11. While the Mid-Atlantic Ridge is a divergent plate boundary, every 50-500 km, this mid- ocean ridge is offset sideways right or left by transform faults. After an earthquake, focal mechanisms are used to describe the deformation in the source region that generates the seismic waves. This focal mechanism is consistent with right-lateral strike-slip faulting on a near-vertical fault. Along with the location, it helps define this earthquake as having occurred as the result of right-lateral strike-slip faulting on a transform fault. USGS Centroid Moment Tensor Solution Magnitude 7.1 NORTHERN MID-ATLANTIC RIDGE Friday, February 13, 2015 at 18:59:12 UTC
- 12. USGS Centroid Moment Tensor Solution The focal mechanism is how seismologists plot the 3-D stress orientations of an earthquake. Shaded areas show quadrants of the focal sphere in which the P-wave first- motions were away from the source, and unshaded areas show quadrants in which the P-wave first-motions were toward the source. Translated to a block diagram, the focal mechanism is illustrating classic strike slip motion with quadrants of compression and extension. In the block diagram, the shaded regions experience compression during fault motion while the unshaded regions experience extension. Magnitude 7.1 NORTHERN MID-ATLANTIC RIDGE Friday, February 13, 2015 at 18:59:12 UTC The offset direction of a strike-slip fault is the direction a feature is displaced when you cross the fault. The road is displaced to the right, so this is a right- lateral strike-slip fault.
- 13. Magnitude 7.1 NORTHERN MID-ATLANTIC RIDGE Friday, February 13, 2015 at 18:59:12 UTC Animation: Exploring Transform Faults
- 14. Based on the location and focal mechanism of this earthquake, it likely occurred as the result of right- lateral strike-slip faulting on or near the Charlie-Gibbs Fracture Zone, a system of two parallel fracture zones that act as a transform fault on the Mid-Atlantic Ridge System between the North American and Eurasian Plates. Magnitude 7.1 NORTHERN MID-ATLANTIC RIDGE Friday, February 13, 2015 at 18:59:12 UTC Image courtesy of the US Geological Survey The rate of spreading of the Mid-Atlantic Ridge near the Charlie-Gibbs Fracture Zone is about 2 cm/year. Image courtesy Wikimedia Commons User:Pimvantend
Editor's Notes
- Shaking intensity scales were developed to standardize the measurements and ease comparison of different earthquakes. The Modified-Mercalli Intensity scale is a twelve-stage scale, from I to XII. Lower numbers represent imperceptible shaking while XII represents total destruction.
- Relevant Animations: Earthquake focal mechanisms? http://www.iris.edu/hq/programs/education_and_outreach/animations/25 (at 2 minutes 22 seconds into the animation there is a good description of how the focal mechanisms in this part of the world are determined) Image Caption: Shaded areas show quadrants of the focal sphere in which the P-wave first-motions were away from the source, and unshaded areas show quadrants in which the P-wave first-motions were toward the source. The black dot shows the axis of maximum compressional strain, called the "P-axis畤, and the white circler shows the axis of maximum extensional strain, called the "T-axis畤.
- Relevant Animations: Earthquake focal mechanisms? http://www.iris.edu/hq/programs/education_and_outreach/animations/25 Image Caption: The black dot shows the axis of maximum compressional strain, called the "P-axis畤, and the white circler shows the axis of maximum extensional strain, called the "T-axis畤.