Do Now:

1
Do Now

• How are P and S waves affected by the medium
  through which they travel?
• How is the difference in arrival times for p and
  s waves changed by distance from the earthquake
  epicenter? (ESRT p 11)
• Name the instrument used to record the arrival of
  p and s waves.

2
1. How are P and S waves affected by the medium
through which they travel?

• Waves travel faster through denser material
• As speed changes bending (refraction) will occur
• S waves can not travel through liquid

3
2. How is the difference in arrival times for p
and s waves changed by distance from the
earthquake epicenter? (ESRT p 11)

• As the distance increases the difference in
  arrival times increases

4
3. Name the instrument used to record the arrival
of p and s waves.

• Seismograph
• Seismogram

5
Aim How do seismic waves behave as they travel
through the earths interior ?

• Objective
• Refraction of seismic waves
• Shadow zones
• Read the ESRT page 10

6
I. Seismic Wave Behavior

• Refraction of Seismic Waves
• Shadow Zones

7
A. Refraction of Seismic Waves
8
B. P-wave Shadow Zone

• 105o ? 140o from the epicenter
• Location on the earths surface that does not
  record p or s waves

9
S-wave Shadow zone
10
II. Inferred Properties of earths interior

• ESRT page 1O
• State the relationship between the following
  variables
• a. depth density
• b. depth pressure
• c. depth temperature

11
a. As depth increases, the density increases
b. As depth increases, the pressure increases
c. As depth increases, the temperature increases
12
Answer the following based on the ESRT page 10

• Describe the outer core. (density, pressure,
  temperature, composition and phase of matter)
• Provide the temperature and pressure at 3,600 km.
• Name the zone of the earths interior that is
  1,000 km below the surface of the earth.

13
III. Calculating Time Origin

• Time origin time at which the earthquake
  occurred
• Calculate the distance from the epicenter for a
  station recording seismic waves
• Record the arrival time of the p wave
• Calculate the time required to travel the
  distance noted above
• Subtract this time from the arrival time
• p wave - p wave origin time
• arrival travel time

14
Summary

• Give 3 examples of information that is inferred
  through the analysis of seismic waves.
• An earthquake occurs somewhere in the pacific
  ocean. The island of Hawaii receives p wave at
  91510 AM, followed closely by S waves at
  91730 AM.
• Calculate the distance from the earthquake
• Calculate the origin time for this earthquake
• Can you locate the epicenter? If not, why?
• Why should residents of Hawaii be concerned?