GEOS 112 Lecture Topics 2303

1
GEOS 112 Lecture Topics 2/3/03

• Earthquake Basics
• Tectonics and EQ Distribution
• USGS-NEIC website ? real-time EQ info
  (http//wwwneic.cr.usgs.gov)

Read Chapter 16 (Earthquakes) EQ links on
GEOS112 homepage
2
Earthquakes
3
Elastic Rebound Theory of EQs
Figure 16.2
4
Basic Definitions and Concepts
Figure 16.4
5
Types of Seismic Waves
2-3 km/s
Body waves (4-6 km/s)
P and S waves travel through Earths interior ?
info about the mantle and core (density,
composition) Surfaces waves (Love, Rayleigh)
travel through the crust ? info about the crust
6
Body Wave Motions
P-wave (primary)
S-wave (secondary)
vertical shearing motion perpendicular to
direction of wave propagation
compression/expansion in same direction of wave
propagation
Figure 16.5
7
Surface Wave Motions
Love wave
Rayleigh wave
complex, orbital, water wave motion
horizontal shearing motion perpendicular to
direction of wave propagation
Figure 16.5
8
Recording EQs on Seismograms
vertical ground motion
horizontal ground motion
Figure 16.6
9
Recording EQs on Seismograms
analog recording
Figure 16.7
digital recording
10
GEOS 112 Lecture Topics 2/6/03

• Earthquake Basics
• Tectonics and EQ Distribution
• Destructive Effects - Loma Prieta Movie
• USGS-NEIC website ? real-time EQ info
  (http//wwwneic.cr.usgs.gov)

Read Chapter 16 (Earthquakes) EQ links on
GEOS112 homepage
11
Mercalli Intensity Scale

• Numeric scale from I (smallest) to XII (largest)

• Based on amount of damage subjective human
  assesment

• Used primarily for estimate of pre-seismogram
  EQs (before early 1900s)

12
Richter Earthquake Magnitude Scale
1 mm M 5
10 mm M 6

• Richter scale (M -2 to infinity) EQ range from
  2 to 9.5. Largest EQ recorded Chile, 1960, M
  9.5

• Based on maximum amplitude of seismogram recording

• Log10 scale every 1 increment increase on scale
  is 10x the amplitude on the seismogram. (e.g.,
  M 6 is 10x amplitude than M 5).

13
Frequency, Magnitude, and Comparative Energy
Release
14
GEOS 112 Lecture Topics 2/6/03

• Earthquake Basics
• Tectonics and EQ Distribution
• Destructive Effects - Loma Prieta Movie
• USGS-NEIC website ? real-time EQ info
  (http//wwwneic.cr.usgs.gov)

Read Chapter 16 (Earthquakes) EQ links on
GEOS112 homepage
15
EQ Distribution
Figure 16.22
16
Divergent and Transform Boundary EQs
Maximum Magnitudes divergent (M7) transform (M
8)
Depths usually lt25 km
17
Convergent Boundary - Subduction Zone EQs
Maximum Magnitudes (M 9.5) largest on Earth!!
Depth ranges from 0 to 700 km
18
EQ Distribution and Depth
19
Convergent Boundary - Collision Zone EQs
Figure 16.28
Maximum Magnitudes (M 8.0)
Depth usually lt80 km
20
Intraplate EQs
21
Large, Historic EQs in New England
1783 Mfa 5.3 New York City
22
New Jersey Seismicity (1952 1971)
all M lt 3.5
Ramapo Fault
Large, inactive fault related to the initial
rifting of the Atlantic Ocean 200 m.y. ago
23
GEOS 112 Lecture Topics 2/6/03

• Earthquake Basics
• Tectonics and EQ Distribution
• Destructive Effects - Loma Prieta Movie
• USGS-NEIC website ? real-time EQ info
  (http//wwwneic.cr.usgs.gov)

Read Chapter 16 (Earthquakes) EQ links on
GEOS112 homepage
24
Ground Motion (Shaking)
25

• Factors that Affect Amount of Ground Motion
• EQ magnitude
• distance to the EQ focus
• local geology (material amplification)

26
Liquefaction
27
Liquefaction Damage
Great Alaskan EQ (1964 M 9.2)

• National Geophysical Data Center/NOAA

28
Fires
Broken gas lines ignite
Fires burn uncontrolled
29
Landslides
30
Figure 16.19
Tsunami harbor wave in Japanese
31
Fig. 10.34b

• Pacific Tsunami Museum

32
Fig. 10.34a
Figure 16.20

• Cecilio Licos, Yasuki Arakaki Collection/Pacific
  Tsunami Museum

33
Fig. 10.34c

• NOAA

34
Travel Times for Tsunami