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Exploring Earth’s structure using Occam’s Razor. Adapted from Braile, 2000 & DLESE Teaching Boxes, 2008. Prepared by Michael Hubenthal, IRIS Consortium. What is inside ?. How do you know what is inside?. What is inside here?. How do you know what is inside?. Think, Write, Pair, Share. - PowerPoint PPT Presentation
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Exploring Earth’s structure using Occam’s Razor
Prepared byMichael Hubenthal, IRIS Consortium
Adapted from Braile, 2000 & DLESE Teaching Boxes, 2008
How do you know what is inside?
What is inside ?
What is inside here?
Think, Write, Pair, Share
How do you know what is inside?
How do you know?
Occam’s Razor - All other things being equal, the simplest solution is the best
Based on your “evidence” what is beneath our feet?
Cal
vin
and
Hob
bes
by B
ill W
atte
rson
Why
are
mod
el im
port
ant i
n sc
ienc
e?
Could this help us test our model?
Theoreticians
Seismologist
Theoreticians
Seismologist
Earth’s surface
Center of the Earth
Scale model of a homogeneous Earth
140°
Seismologists
Theoreticians
Creating a travel-time plot
•Work in teams of ~ 2•Each pair calculates 3 travel times
•Each team makes 1 travel time plot, 0-180 degrees•Discuss results
Use velocity=11 km/sec, distance scale 320 km/cm
103040507080100115130150
Earthquake Wave First Arrivals
Distance From Epicenter (Deg)
Time (Min)
What is the cause of model and observations mismatch?
Shadow zone
Something changes beyond ~110 deg.
Combine results from multiple earthquakes
Assumptions?
?
What has your data established so far?
Have we found any layers?
1st: 1 deg - .5 min2nd: 16 deg - 3.5 min
First Arrivals
http://rev.seis.sc.edu/
Earth’s Interior Structure - Seismic Travel Times in a Constant Velocity Sphere
(L. Braile , December, 2000)
:http// . . . /~web ics purdue edu braile
R = 6371 km
Δ
/ 2
S / 2
Raypath
(chord of length S)
R = 6371 km
Earth’s
Surface
Source
Receiver
Copyright 2000. L. Braile. Permission granted for reproduction for non-commercial uses.
http://rev.seis.sc.edu/ > DLESE Teaching Boxes!
Updated Version