Imaging the Earth

A review by

Paul G. RichardsLamont-Doherty Earth Observatory,

Columbia University, New York 10964, USA

with help from

Tanya Atwater, Roger Bilham, Steve Grand,Rob van der Hilst, Jian Zhang

CTBT: Synergies with Science, 1996-2006 and Beyond; August 31, 2006

Fluid Outer Core

Solid InnerCore

MantleCrust

The major features of planet Earth’s interior,

crust, mantle, fluid core,

have been known for more than 100 years; the

solid inner core was discovered in 1936.

These discoveries were based on observations of

magnetismgravity, Earth’s shape (geodesy)slow movements (tides, precession)fast movements (seismic waves)heat flow

“Imaging the Earth” – classicallyis the work of refining our knowledge ofthe Earth’s internal structure.

“Imaging the Earth” – more generallyconcerns learning about the dynamicprocesses taking place in our planet, thatdetermine its character.

By studying the Earth’s interior today, wecan understand these processes better.

Evidence for the Farallon Plate

shown at three different depths

,

120°W 100°W 80°W 60°W 40°W

40°N

20°N

from P-waves

from S-wavesFARALLON SLAB

2700 km depth

2770 km depth

There is a long list of processes taking place in theEarth’s interior, which we can study today withvarious monitoring technologies.

Scientific study of these processes give insightinto how our planet was formed & how it changes.

Some of these processes influence life on ourplanet — and the location of fossil fuels and ofcommercially valuable minerals.

Two examples:(1) plate convergence and seismic hazard

(biggest earthquakes);(2) inner core rotation.

AlaskaSeismographic

Network

Earthquake inSouth Sandwich

Islands

North-South axis

South Pole

AB

BC

DF

65 ∞ N

60 ∞ N

130∞ W

140∞ W 150∞ W

160∞ W

170 ∞ W

70 ∞ N

ALASKA

∆=150o∆=152o∆=154o

CANADATT01

DAWY

INK

-1 0123-10

123

Constant ∆

IMS

USAEDS

ASN

Eielsonarray

Beaver Creekarray

Burnt Mountainarray

Indian Mountainarray

COL&

COLA

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10 channels at Eielson array (IL01-IL10).

10 channels at Eielson array (IL11-IL19, and IL31).

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1900

1996

“Imaging the Earth” – more generallyconcerns learning about the dynamicprocesses taking place in our planet.

“Imaging the Earth” – more generallyconcerns learning about the dynamicprocesses taking place in our planet.

They made it what it is today.They will shape its future — and ours.

Tomorrow we’ll have a longer discussion:

• how the Earth is imagedat different scales

• how we can model the ground shakingassociated with a large earthquake

• how we can do a better job ofmonitoring earthquakes

and we’ll describe some recentlydiscovered new phenomena.

Final Comments: The need to verify compliance with the ComprehensiveNuclear-Test-Ban Treaty is with us for the long-term.

Sixty years ago, science was called“the endless frontier”

and became widely recognized as the basis for economicprogress and an improved standard of living.

Final Comments: The need to verify compliance with the ComprehensiveNuclear-Test-Ban Treaty is with us for the long-term.

Sixty years ago, science was called“the endless frontier”

and became widely recognized as the basis for economicprogress and an improved standard of living.

There are many ways in which scientific research onplanet Earth can benefit from interactions with the workof CTBT verification – and vice versa.