Transcript File - We All Love Science

Unit 5: Earthquakes
Mr. Ross Brown
Brooklyn School for Law and
Technology
What causes earthquakes?
• 22 November 2016
• Do now: A ____ fault forms as a result of
horizontal compression.
a)
b)
c)
d)
Blind
Normal
Strike-slip
Reverse
What causes earthquakes?
• The San Andreas Fault, a result of horizontal
shear, is a ____ fault.
a)
b)
c)
d)
Blind
Normal
Strike-slip
Reverse
In this unit we will learn about:
• The relationship between plate tectonics and
earthquakes
• How scientists locate and measure
earthquakes
• The ways earthquakes produce so much
damage
What causes earthquakes?
• 22 November 2016
• Based on our earlier lessons, what causes
earthquakes?
What causes earthquakes?
• Vibrations in the Earth’s crust
• Elastic Rebound Theory: as forces at the fault
build up, stress increases. Rocks fracture 
earthquake; rocks spring back to original
shape
Homework
• 22 November 2016
• Test corrections
• Also, be sure to check my website for a new
Science in the News assignment to be
completed over the Thanksgiving break.
What causes earthquakes?
• 23 November 2016
• Do now: What is the relationship between the
velocity of compressional waves (P-waves) and
the velocity of shear waves (S-waves) as they
travel through the same material?
a) P-waves have a greater velocity.
b) S-waves have a greater velocity.
c) P-waves and S-waves have the same velocity.
What causes earthquakes?
• 23 November 2016
• This question may require the use of the Earth
Science Reference Tables. Approximately how long
does an earthquake P-wave take to travel the first
6500 kilometers after the earthquake occurs?
a)
b)
c)
d)
6.5 minutes
8 minutes
10 minutes
18.5 minutes
What causes earthquakes?
• Energy radiates outward in seismic waves
• These stress other rocks which fracture and
result in aftershocks
• The area where slippage begins is the focus
• The point on the surface directly above the
focus is the epicenter
What causes earthquakes?
How does Focus Location
Determine Earthquake Strength?
• 90% of earthquakes are Shallow-focus
– Within 70 km of surface
– Result in the most damage
• Intermediate (70-300 km deep)
• Deep (300-650 km deep)
Earthquake Focus Location
Homework
• 23 November 2016
• Science in the News
– www.rossbrownscience.com
How does location on the planet
relate to likelihood of earthquakes?
• 28 November 2016
• DO NOT MOVE STOOLS; we are moving to assigned
seats today
• Do now: Seismograph station D is 7,700 kilometers
from the epicenter. If the P-wave arrived at this
station at 2:15 p.m., at approximately what time did
2:15 PM – 11 min = ?2:04 PM
the earthquake occur?
a)
b)
c)
d)
1:56 PM
2:00 PM
2:04 PM
2:08 PM
Think, Pair, Share
• Turn to page 5 in Reference Tables
• Do now: There have been recent earthquakes in
Nepal, Chile, and Haiti. Based on what we’ve
learned and the chart, how can we compare these
locations?
Haiti
Chile
Nepal
How does location on the planet
relate to likelihood of earthquakes?
What are Major Earthquake Zones?
• Pacific Ring of Fire
• Mid–Ocean Ridges
• Eurasian-Melanesian Belt
– European and African/ Indian plates colliding
How Likely Is A Major Earthquake
In Brooklyn?
What Causes Fault Zones?
• Fault Zone: groups of interconnected faults
• Typically, at plate boundaries due to stresses
when plates:
– Subduct
– Collide
– Separate or Rift
– Slide past each other or Strike Slip or Shearing
• San Andreas Fault
Homework #4
• 28 November 2016
• Explain the Elastic Rebound Theory
• What are the four types of plate movements
that can cause earthquakes? Explain each,
being sure to use complete sentences.
How do we Detect and Record
Earthquakes?
• 29 November 2016
• Do now: Seismograph station B recorded the arrival of Pwaves at 2:10 p.m. and the arrival of S-waves at 2:15 p.m.
Approximately how far is station B from the earthquake
epicenter?
a)
b)
c)
d)
1400 km
2400 km
3400 km
4400 km
2:15 – 2:10 = ?5 min
How do we Detect and Record
Earthquakes?
• Seismograph
– Records vertical motion of the ground
– Records horizontal in east-west and north-south
• Records as waves on paper or electronically
How do we Detect and Record
Earthquakes?
• P (primary) waves and S (secondary) waves
– P waves are compression waves, rock moves in
the direction of the wave; fastest
– S waves are shear waves, rock moves
perpendicularly to the wave; slower
• When these reach the surface, they can be
converted to Surface Waves.
– Slow moving, like ocean waves on the surface
– Rise and fall; VERY destructive
Earthquake Waves
Earthquake Waves
Earthquake Waves
Homework
• 23 November 2015
• If a seismograph station measures P waves but
no S waves, what can you conclude about the
location of the earthquake?
How can we locate an earthquake’s
epicenter?
• 30 November 2016
• Do now: Four seismograph stations receive data from the
same earthquake. The table below shows the differences in
travel times for the P- and S-waves recorded at each station.
Which station is the closest to the epicenter of the
earthquake?




A
B
C
D
S wave arrival – P wave arrival  distance from epicenter
How can we locate an earthquake’s
epicenter?
How can we locate an earthquake’s
epicenter?
How can we locate an earthquake’s
epicenter?
How can we locate an earthquake’s
epicenter?
How can we locate an earthquake’s
epicenter?
B
Epicenter
A
C
How can we locate an earthquake’s
epicenter?
• Subtract P wave arrival time from S wave
arrival time
• Find that difference on the Reference Table
How does location on the planet
relate to likelihood of earthquakes?
• 1 December 2016
• Do now: please come up to my low desk and take a
copy of Lab #5.
• Begin. Please work in pairs. Put both names on each
copy of the lab & staple together when you’ve
finished.
How can we plot location of
earthquake epicenter?
• 7 December 2016
• Do now: please come up to my low desk and
take a copy of Lab #6.
• You will be working in pairs. One of you must
come see me to sign out a compass.
• I will be meeting with some of you to discuss
missing assignments  failing grades
• We are having an exam this Friday
How do we Measure an
Earthquake’s Severity?
•
•
8 December 2016
Do now: DIRECTIONS: Base your answers to questions 2-6 on your knowledge of earth
science, the Earth Science Reference Tables, and the diagram below. The diagram represents
a cross section of the Earth showing the paths of earthquake waves from a single earthquake
source. Seismograph stations are located on the Earth's surface at points A through F, and
they are all located in the same time zone.
•
a)
b)
c)
d)
4. What explanation do scientists give for the reason that station F did not receive S-waves?
The Earth's inner core is so dense that S-waves cannot pass through.
The Earth's outer core is liquid, which does not allow S-waves to pass.
S-waves do not have enough energy to pass completely through the Earth.
S-waves become absorbed by the Earth's crust.
How do Earthquakes Cause
Damage?
• Damage to buildings
– Looser soil results in more damage
• Tsunamis
– Epicenter on ocean floor
– Faultingrise or fall of ocean floordisturbs
water
– Could trigger underwater landslides
How do we Measure an
Earthquake’s Severity?
World's largest
earthquake tsunami map: The
Chilean earthquake
produced a
powerful tsunami
that traveled at a
speed of about 200
miles per hour
across the Pacific
Ocean. The wave
killed 61 people in
Hawaii, 138 in
Japan, and 32 in
the Philippines.
The star marks the
location of the
epicenter, and the
numbers on the
contour lines are
travel times in
hours for the wave
front. Image by
NOAA.
How do we Measure an
Earthquake’s Severity?
Largest earthquake tsunami damage:
An aerial view of damage
caused along the coast of
Chile by the tsunamis. This
scene shows part of a
coastal community where
homes were torn from their
foundations and tossed
about by the waves.
Damage was near total in
these areas. NOAA image
by Pierre St. Amand.
How do we Measure an
Earthquake’s Severity?
Earthquake damage at
Valdivia: Photograph of
buildings in Valdivia, Chile
damaged by the
earthquake. This photo
shows houses located on
an area underlain by fill.
They slid downhill when
the waterlogged soil
beneath them failed.
NOAA image by Pierre St.
Amand.
How do we Measure an
Earthquake’s Severity?
How do we Measure an
Earthquake’s Severity?
• Magnitude
– The measure of energy released or the amount of
ground motion
– We used to use the Richter scale, now we use
Moment Magnitude or Mercalli Scale
– Largest ever: 9.5 (in Chile in 1960)
– Major is 7 or above
– An earthquake <2.5 unlikely to be felt
•
•
Base your answers to questions 72 through 76 on the modified Mercalli scale of
earthquake intensity below, on the map of Japan in your answer booklet, and on
your knowledge of Earth science. The modified Mercalli scale classifies earthquake
intensity based on observations made during an earthquake. The map indicates
the modified Mercalli scale intensity values recorded at several locations in Japan
during the March 11, 2011 earthquake, which triggered destructive tsunamis in
the Pacific Ocean.
72) On the map in your answer booklet, a line has been drawn to separate regions
with Mercalli values of V from regions with Mercalli values of VI. Draw another line
to separate regions with Mercalli values of VI from regions with Mercalli values of
VII. [1]
•
73) Your answer booklet lists some observations that might be made during an
earthquake according to the modified Mercalli scale. In your answer booklet, place
a check mark (√) in the box if that observation most likely was recorded at
Yamagata during the March 11, 2011 earthquake. More than one box may be
checked. [1]
•
74) The epicenter of this earthquake was located at 38° N 142° E. Identify the type
of tectonic plate boundary that is located nearest to the epicenter of this
earthquake. [1]
75) Describe one way the P-waves and S-waves recorded on seismograms at
Ishinomaki and Nagano were used to indicate that Ishinomaki was closer to the
earthquake epicenter than was Nagano. [1]
76) A 25-foot high tsunami hit the Japanese city of Ishinomaki. Describe a
precaution the city could take now to protect citizens from tsunamis in future
years. [1]
•
•
Homework
• 17 November 2015
• Compare the damage resulting from
earthquakes caused by slippage at 300 km to
earthquakes caused by slippage at 50 km.
Which results in more damage? Why?
• Use complete sentences. Treat this like an
essay on the Regents exam.