1. Teaching earth science content with iPods, laptops and other portable accelerometers
Jesse Lawrance, Stanford University
Michael Hubenthal, IRIS Consortium
John Taber, IRIS Consortium

2. Peak acceleration of about 1g at base

3. Peak ground accelerations in region were 0.8g
1995 Kobe earthquake M 6.9
Peak ground accelerations in region were 0.8g

4. How much energy was released?
Could you calculate the amount?
Kinetic energy KE = ½ mv2
Distance traveled D = ½ gt2
Landing velocity Vf = gt
KE = mass X Distance X gravity constant

5. For example If I jump off a table 1 meter high
KE ~ 100 kg X 1 m X 10 m/s2
= 1000 joules

6. Does the amount of energy released change as the source is moved horizontally?
How does the amplitude recorded by the sensor change as the source is moved further away?
How could you modify the experiment to increased the recorded amplitude at each position?
We determined that
KE = mass X Distance X gravity constant

7. If you add energy to the impact, is this equivalent to changing earthquake magnitude or intensity?
Magnitude – energy released
Intensity – amount of shaking at a point

8. Energy release in an earthquake
Seismic Moment
Mo = fault length
x fault width
x displacement
x rigidity
Can also be determined from seismograms

9. Moment Magnitude = Mw = log Mo/1.5 – 10.7
Energy release in an earthquake
Seismic Moment
Mo = fault length
x fault width
x displacement
x rigidity
Moment Magnitude = Mw = log Mo/1.5 – 10.7

10. Moment Magnitude of my jump
Moment Magnitude = Mw = log Mo/1.5 – 10.7
1000 joules = 1010 ergs
Mjump = - 4

12. Relationship between Magnitude and Shaking:
The relationship between magnitude and shaking (acceleration)
a =13*(e0.67*M)*(D+25) -1.6
Where a is acceleration (in units of m/s/s), M is magnitude, and D is distance (in km) (From Donovan, 1973)

13. Correlated Acceleration and MMI
Modified Mercalli Intensity
Acceleration (g) I II
III IV V VI
VII
VIII IX X+
Above 1.24
Trifunac and Brady (1975) and Wald et al. (1999 a, b)

14. ShakeMaps M8.8 at 3:34 AM on Saturday February 27
One of the 5 largest earthquakes ever recorded
577 killed, 12,000 injured and 800,000 displaced
Earthquake caused trans-Pacific tsunami

15. ShakeMaps M 7.0 at 4:53 PM on Tuesday January 12, 2010
15 miles WSW of Port au Prince, Haiti
222,570 killed, 300,000 injured and 1.3 million displaced
Worst natural disaster since Indian Ocean Tsunami of 2004

16. ShakeMaps
M7.0 located 30 m W of Christchurch at 4:36 AM on Saturday September 4
No fatalities (2 serious injuries)
Contrast with Haiti earthquake
Good buildings and preparedness paid off!

17. Did You Feel it? Vs. ShakeMap

18. Did You Feel it? Intensity Vs. Distance

19. QCN Rapid Detection Maps

20. QCN Rapid Detections