Exploring Earth’s structure using Occam’s Razor

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