The document discusses earthquakes, including the 1960 Valdivia earthquake in Chile that was magnitude 9.5 and caused 6000 casualties and $800 million in damage. It describes how earthquakes are caused by the sudden release of energy along fault lines in the earth. Different types of seismic waves are discussed, as well as the Richter scale and Mercalli intensity scale used to measure earthquake magnitudes and effects. Damage from earthquakes can include physical impacts like landslides as well as structural collapse and loss of life.
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1960 Valdivia Earthquake: 9.5 Quake in Chile
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2. The 1960 Valdivia earthquake or Great Chilean
Earthquake
May 22nd
, 1960
Intensity – 9.5
Casualties : 6000
Damage : 800 million US$
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21. The shaking or trembling caused by the sudden
release of energy
Usually associated with faulting or breaking of rocks
Continuing adjustment of stress results in
aftershocks
Most earthquakes are small and harmless, but rare
much larger ones can cause enormous damage and
loss of lives.
California has dozens of earthquakes every day, so
we need to learn to live safely with them.
22. The Focus and Epicenter of an Earthquake
• The point within the earth
where faulting begins is
the focus, or hypocenter
• The point on the surface of
the earth directly above
the focus is the epicenter
27. Body waves
P or primary waves
▪ fastest waves
▪ travel through solids,
liquids, or gases
▪ compressional wave,
material movement is
in the same direction
as wave movement
S or secondary waves
▪ slower than P waves
▪ travel through solids
only
▪ shear waves - move
material perpendicular
to wave movement
28. Surface Waves
Travel just below or along the ground’s surface
Slower than body waves; rolling and side-to-side
movement
Especially damaging to buildings
29. Seismic wave behavior
P waves arrive first, then S waves, then L and R
Average speeds for all these waves is known
After an earthquake, the difference in arrival times at a
seismograph station can be used to calculate the distance
from the seismograph to the epicenter.
30. Richter Magnitude
Richter scale measures
the total amount of
energy released by an
earthquake;
independent of intensity
Amplitude of the largest
wave produced by an
event is corrected for
distance and assigned a
value on an open-ended
logarithmic scale
For very large
earthquakes, a modified
Richter scale is used
that takes into account
the size of the failure
surface as well as the
amplitude of the seismic
waves
31. Ground Shaking
amplitude, duration, and damage increases in poorly
consolidated rocks
32. The Richter magnitude scale was developed to
assign a single number to quantify the energy
released during an earthquake.
The scale is a base 10 logarithmic scale.
The magnitude is defined as the logarithm of the
ratio of the amplitude of waves measured by a
seismograph to an arbitrary small amplitude.
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34. An earthquake that measures 5.0 on the Richter scale has a
shaking amplitude 10 times larger than one that measures
4.0, and corresponds to a 31.6 times larger release of energy.
Since the mid 20th century, the use of the Richter magnitude
scale has largely been supplanted by the
moment magnitude scale in many countries.
The Richter and MMS scales measure the energy released by
an earthquake; another scale, the Mercalli intensity scale,
classifies earthquakes by their effects, from detectable by
instruments but not noticeable to catastrophic.
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37. Based on location
1. Interplate
2. Intraplate
Based on epicentral distance
1. Local earthquake < 1o
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Regional Earthquake 1 - 10o
3. Teleseismic Earthquake > 10o
Based on Focal depth
1. Shallow depth 0 - 71 km
2. Intermediate depth 71 – 300 km
3. Deep earthquake > 300 km
38. Based on magnitude
1. Micro earthquake < 3
2. Intermediate earthquake 3 - 4
3. Moderate earthquake 5 - 5.9
4. Strong Earthquake 6 - 6.9
5. Major Earthquake 7 - 7.9
6. Great Earthquake > 8