Transcript Earthquake lecture 2

Chapter 12 Section 3
Earthquakes and Society
Discuss the relationship between earthquakes and
tsunamis.
Describe two possible effects of a major earthquake
on buildings.
List three safety techniques to prevent injury caused
by earthquake activity.
Identify four methods scientists use to forecast
earthquake risks.
TSUNAMI - Harbor wave
Caused by underwater earthquakes
that cause:
A drop or rise in the ocean floor OR
A landslide
§ or
§ Seismic Eruption
Savage Earth Animation Tsunami Attack.swf
Savage Earth Animation Tsunami Attack2.swf
Deformations
§ bent, broken, squeezed, folded, or stretched
rocks
l
http://www.seismo.ber
keley.edu/seismo/hayw
ard/hay_eq.gif
l
http://www.seismo.ber
keley.edu/seismo/hayw
ard/hay_faults.gif
Faulting
§ break or crack along which rocks move (6
types)
Normal fault
§ tension
Reverse fault
§ compression
Lateral
§ Shear stress
Which type of fault is this?
Reverse fault
What type of fault is this?
Normal Fault
How about this one?
Lateral Fault
Which type of fault is this?
Which type of fault is this?
Which type of fault is this?
Thrust fault
§ advanced reversal fault
§ Fault block valley
l
tension
§ Fault block mountains
l
compression
Folding
§ a bend in the rock
Anticlines
§ upfold
Synclines
§ downfold
§ www.indiana.edu/~g103/G103/week9/wk9.
html
Much Safer To Be Out In The
Open
§ Most injuries result
from the collapse of
buildings, falling
objects, and flying
glass.
STRUCTURAL DAMAGE
Kobe Earthquake
Other Dangers Include
§ Landslides
§ Fires
§ Explosions (broken electric and gas lines)
§ Floods (from collapsing dams)
KOBE SEISMOGRAPH
Left - Station on solid ground
Right - Station on water
saturated,
soft ground
FIRES
Kobe
Quake Duration
§ A long duration moderate earthquake can
cause more damage than a short one at a
higher magnitude.
Destruction of Buildings and
Property
§ Tall buildings can sway and collapse.
§ Those with weak wall can completely
collapse.
STRUCTURAL DAMAGE
Kobe earthquake
LIQUEFACTION
Kobe
Ground Type Is Important
§ Loose soil and rock
can vibrate like
Jello.
KOBE SEISMOGRAPH
Left - Station on solid ground
Right - Station on water saturated,
soft ground
CHILE - 1960
ALASKA
MAJOR TSUNAMIS
Processes That Shape The
Earth’s Surface
Chapter 13
http://www.ruf.rice.edu/~feegi/index.html
Earthquakes
Topic 1
http://www.ruf.rice.edu/~feegi/calend.html
STRUCTURE OF THE EARTH
§ http://www.seismo.unr
.edu/ftp/pub/louie/clas
s/100/earth-layers.GIF
Crust
§ the very thin outside
layer of the
lithosphere
§ 5-60 km thick
§ least dense layer
§ next
§ http://metolab3.umd.e
du/EARTHCAST/eart
h_jpl_small.gif
How do we know what the
interior of the earth is like?
Using indirect methods:
§ studding earthquake
waves
§ http://www.seismo.unr
.edu/ftp/pub/louie/clas
s/100/earth-rays.GIF
Mantle
§ a very thick layer reaching to 2,900km
beneath the crust.
§ 1,000oC to 3,700oC
§ 80% of volume
§ 2/3 mass
§ Plastic like
Dunite
§ The only exposed
sample of the earth's
mantle
§ http://volcano.und.nod
ak.edu/vwdocs/Parks/
hawaii/picture4.gif
Possible Ray Paths for Seismic
Waves Penetrating the Earth
• In the mantle and inner core, the
velocities increase with depth, so
the ray bend away from the normal
• At the mantle-outer core (fluid)
boundary the decrease in velocity
causes those rays refracted into the
core to bend towards the normal
• What is mode conversion?
GEO 468K GEOPHYS FOR GEOSC
MAJORS
Seismogram Example
P wave
S wave
Pick two seismic phases and measure the time interval
GEO 468K GEOPHYS FOR GEOSC
MAJORS
GEO 468K GEOPHYS FOR GEOSC
MAJORS
Core
§ the center of the earth
§ 1/3 of earth mass
§ made of Ni+Fe
§ divided into two parts
Outer core
§ 2,190km radius
§ liquid
Inner core
§ 1,380km radius
§ solid
Assignment
§ The Earth’s Layers
§ “Looking into the Earth
Assignment
Worksheet on Faults
Use the following
Color Code
Top Surface - Brown
Top Layer - Red