Transcript EARTHQUAKES !!!

EARTHQUAKES !!!
1) Earthquakes (EQ) are a shaking of
the ground
2) Caused MAINLY by the breaking of rock due to
moving tectonic plates.
3) EQ occur Mainly on plate boundaries &
volcanoes
3) EQ CAN occur anywhere at any time.
4) EQ occur at least 1 per minute somewhere in the
world. Approximately 20 Earthquakes have
occurred while you have written this.
• http://nationalatlas.gov/mapmaker
EQ around the world
RISK map…
• http://nationalatlas.gov/mapmaker
• http://earthquake.usgs.gov/earthquakes/state
s/virginia/hazards.php
http://earthquake.usgs.gov/eqcent
er/recenteqsanim/world.php
• Recent EQ
Fault lines
4) Faults are breaks or cracks in the
Crust
5) Formed by forces/stress in the rocks
as the plates move.
6) Types of Forces, Faults, & Plate
Boundaries
• Type 1
A. Caused by
COMPRESSION
(squeezing)
B. Causes REVERSE or
THRUST FAULTS (the
hanging wall moves
up!)
6) Types of Forces, Faults, & Plate
Boundaries
C. Forms at CONVERGENT
BOUNDARIES (plates
that move together)
D. Landforms: Plateaus –
high flat areas.
(ex: Colorado Plateau)
Mountains. (ex:
Appalachians, Blue
Ridge, etc…)
6) Types of Forces, Faults, & Plate
Boundaries
• Type 2
A. Caused by Tension
(pulling)
B. Causes Normal FAULTS
(the hanging wall
moves down, but the
footwall moves up!)
6) Types of Forces, Faults, & Plate
Boundaries
C. Forms at DIVERGENT
BOUNDARIES (plates
that move apart)
D. Landforms: Rift valleys.
(ex: The GREAT RIFT
VALLEY in Africa)
<the Horn of Africa is
literally tearing away
from Africa>
7&9) Types of Forces, Faults, & Plate
Boundaries
• Type 1
A. Caused by Shearing
(ripping sideways)
B. Causes STRIKE-SLIP
FAULTS (both walls
moves sideways!)
6 cont’d) Types of Forces, Faults, &
Plate Boundaries
C. Forms at TRANSFORM
BOUNDARIES (plates
that move sideways or
laterally)
D. Landforms: Mostly just
Earthquakes & visible
fault lines.
(ex: San Andreas Fault
in CA)
7) There are 2 sides of a fault line
• Footwall (or Footblock)
Hanging wall (or Hang block)
Fault lines
9) FOCUS – the Origin of the EQ (underground!)
10) EPICENTER – the Origin of the EQ (above
ground…like ‘X’ marks the spot on a map)
11) Fault- labeled picture
SEISMIC
WAVES
12) Damages of Earthquake
TSUNAMI – caused by EQ on Ocean floor.
Water is pushed up & moves fast towards
shore.
Tsunami-Sri Lanka
12) Damages of Earthquake
• LIQUEFACTION- EQ
shakes wet ground,
causing buildings to
sink.
13) Strength of Earthquakemeasured by damage done.
3 SCALES TO Measured :
1) RICHTER SCALE- measures
EQ strength.
2) MERCALLI SCALE measures EQ damage
3) MOMENT MAGNITUDE
**The highest numbers in the
scale mean the worst
Earthquakes!!
Measured by:
1) Tiltmeter- vertical
movements by
water changes
Measured by:
2) CreepmeterHorizontal
movements by
wire
Measured by:
3) Laser guidance- horizontal
movements by Laser
Measured by:
4) GPS- satellites
measure ground
changes
Measured by:
5) SeismographGround shakes,
records strength.
1) MERCALLI Scale– measures total
damage
• http://www.dnr.sc.gov/geology/images/Equak
e%20intens2-pg.pdf
2) RICHTER – magnitude (strength) &
the earthquake (EQ) waves. Good for ONLY
nearby EQ
3) MOMENT MAGNITUDE SCALE –
measures TOTAL energy. Good for ALL EQ.
• 4) Highest # on ANY scale is the WORST EQ.
Strength of EQ
13) Determined by
amount of damage
14 &15) Epicenter of EQ
found by using the
intersection of at
least 3
seismograph
locations.
Seismograph & Seismogram
16) Seismograph –
machine that records the
arrival of all 3 seismic
waves & strength
17) Seismogram – the
written sketch of the EQ
19) Seismograms: 3 basic types
• No EQ recorded
• Low-Intensity EQ
• High-Intensity EQ
20) Seismic Wave – Vibrations
caused by the breaking of rock.
SEISMIC
WAVES
21)
3 types of Seismic Waves
a. Type 1: PRIMARY WAVE
•
•
•
•
a.k.a. ‘P-Wave’
The first wave to arrive
The fastest wave
Moves as a
‘COMPRESSION’ WAVE
• Travels through the
entire Earth.
3 types of Seismic Waves
b. Type 2: Secondary Wave
• a.k.a. ‘S-Wave’
• The second wave to
arrive
• Speed = ½ of the Pwave
• Moves as a ‘ROLLING’
WAVE
• Travels through all of
Earth EXCEPT LIQUID
IRON****
3 types of Seismic Waves
c. Type 3: Surface Waves
• a.k.a. L-Wave (‘Love’
•
•
•
•
•
Waves)
Last wave to arrive
Slowest of all waves
Most damaging (all of
energy is at surface)
Motion is chaotic
(Rolling, backwards &
side-side)
Moves only at surface.
SPEED of P-waves & S-waves
P wave speed
S wave Speed
400 mph
200 mph
600 mph
300 mph
1200 mph
600 mph
300 mph
150 mph
22)
No EQ
P-Wave
S-Wave
L-Wave
23) Why Study Seismic waves? To learn the
composition of the Inner Earth
Mohorovicic Discontinuity!!
24) Located between CRUST and UPPER
MANTLE.
25) It is a boundary where SEISMIC WAVES
SPEED UP.
26) The Shadow Zone!! – a region
of Earth without EQ
• Reasons: Seismic waves SLOW DOWN & BEND
as they travel through Earth.
• The S- Wave does not travel through the outer
core(liquid iron).
• This produces a region without EQ. Hence,
the SHADOW ZONE!
27) Shadow Zone image
28) Virginia receives EQ MAINLY due to the
SETTLING OF BEDROCK. This doesn’t usually
cause bad damage
30) CONVERGENT boundary
29) Features &
Plate
31) COMPRESSION forces
boundaries
32) REVERSE Faults
PLATEAU 
33) ex: COLORADO PLATEAU
34) CONVERGENT Boundary
29) Features &
Plate
35) COMPRESSION Forces
boundaries
36) REVERSE faults
FOLDED
MOUNTAINS 37) ex: APPALACHIANS
38) DIVERGENT Boundary
29) Features &
Plate
39) TENSION Forces
boundaries
40) NORMAL faults
FAULT BLOCK
MOUNTAINS 41) ex: GREAT BASIN,
OTHERS
42) CONVERGENT Boundary
29) Features &
Plate
43) COMPRESSION Forces
boundaries
44) REVERSE faults
UP WARPED
MOUNTAINS 45) ex: ROCKIES
46) VOLCANOES AT
CONVERGENT, DIVERGENT
29) Features &
Boundary and
Plate
HOT SPOTS
boundaries
47) COMPRESSION /TENSION
Forces
VOLCANIC
48) REVERSE /NORMAL faults
MOUNTAINS
49) ex: MT. ST. HELENS,
MAUNA KEA (HAWAII),
ICELAND, ETC…
Features & Plate boundaries
50) Transform boundaries form NO mountains
51) Most mountains made by CONVERGENT
boundaries and COMPRESSION forces
52) Volcanoes forma at CONVERGENT boundary,
DIVERGENT BOUNDARIES, AND HOT SPOTS
(WEAK PLACES IN CRUST WHERE LAVA COMES
OUT. OCCUR ANYWHERE.)
PREDICTION- Can’t predict because
1)
2)
3)
4)
Energy not always released
Equipment doesn’t always work
Low understanding
Other reasons…
Safety Design of buildings based on
• 1) ABSORPTION OF ENERGY
• 2) REINFORCEMENT
• 3) FIRE PREVENTION