Paper Geologia

Education & & Outreach Education Outreach SeriesSeries

No. 5

Exploring the Earth Using Seismology
Earthquakes create seismic waves that travel through the Earth. By analyzing these seismicwaves, seismologists can explore the Earthʼs deep interior.
IRIS is a university research consortium dedicated to monitoring the Earth and exploring its interior through the collection and distributionof geophysical data.

On January 17, 1994 a magnitude 6.9 earthquake near Northridge, California released energy equivalent to almost 2 billion kilograms of high explosive. The earthquake killed 51people, caused over $20 billion in damage, and raised the Santa Susana Mountains north of Los Angeles by 70 centimeters. It also created seismic waves that ricocheted throughout the Earthʼs interiorand were recorded at geophysical observatories around the world. The paths of some of those seismic waves and the ground motion that they caused are shown below. On the right, the horizontal traces ofground motion (seismograms recorded at various locations around
Earthquake Epicenter 0˚ Northridge, California
PFO SRR TEIG HKT
P wave, S wave

30

Pw

˚

PAYG

JTS SDV

Su ave , S wrfa ave ce

0 minutes 0˚
DISTANCE

10 minutes

20 minutes

30 minutes

BOCO RPN

Pw av

30˚

av W

˚ 60 es

e, S

IRIS programs contribute to scholarly research, education,earthquake hazard mitigation, and the verification of the Comprehensive Test Ban Treaty.

NNA LPAZ LVC

PTGA SAML

wa ve

PLCA

S

OU

TH

AM

ER

IC

A

60˚

su

Pw

SS

rface

from

a ve

w

av e

wa ve

P

S

w

av w

PK Pw

S e, av

earthquake

e

TRQA

CPUP

BDFB

INNER CORE

w

av

e

90˚

90˚

ave

PP

PP w a ve, S S w ave

ve wa

EFI EFI

HOPE ASCN

OUTER CORE CRUST

Sha

dow

Zon

e 120˚

(1˚ =111

12 0˚

PKP

SUR BOSA LBTB

SHEL

150˚

e wav

km)

A F R I C A
LSZ...