ANNOUNCEMENTS

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ANNOUNCEMENTS

• Generally speaking, you have to give it a week to
  get your exams back If you are wildly curious,
  email me any time after the weekend and hopefully
  Ill have yours graded!
• Between one thing and another I have nearly
  everyones PIN now, but if you havent sent it
  yet, you cant take the next exam (whenever that
  is)

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TODAY

• The earthquake cycle (elastic rebound)
• Kinds of earthquake waves
• The relation between depth and intensity

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• Clickers please

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• Overall, how was the exam?
• Too easy
• Easy enough
• Hard, but challenging, so okay
• Too hard

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Please click whichever is correct for you

1. True -- I got the 2 points of extra credit for
   reading the directions and putting in my initials
   in the space
2. False -- what 2 points?
3. False -- Im moderately bad about reading
   directions

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The earthquake cycle, usually called elastic
rebound -- how stress is applied to rocks until
they break
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What happens when rocks break?remember the
little radio tower with the waves coming out in
all directions
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I. waves INSIDE the earth
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I. waves ON the SURFACE of the earth
(put these two motions together)
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Clickers
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Seismologists tell us the outer core is molten.
What aspect of earthquake waves supports this
hypothesis?

1. P waves going through the center of the earth
   arrive faster on the exact opposite side
2. P waves vanish when going through the center of
   the earth
3. S waves going through the center of the earth
   arrive faster on the exact opposite side
4. S waves vanish when going through the center of
   the earth

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What probably happens to wave speed in the
asthenosphere?

1. They all slow down
2. They all speed up
3. Only P waves slow down
4. Only P waves speed up
5. Only S waves are affected

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Creep
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Clickers
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What kind of fault is creeping in this picture?

1. A normal fault
2. A reverse fault
3. A left-lateral strike-slip fault
4. A right-lateral strike-slip fault

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How to predict an earthquake

• (how to try to predict an earthquake)

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Ground deformation the Palmdale Bulge
Located some 35 miles north of downtown Los
Angeles at the edge of the Mojave Desert,
Palmdale (pop. 13,500), Calif., is a sleepy town
where the loudest sounds are usually the
whistling of desert winds and the popping noise
of exhausts as teen-age dragsters race their
cars. But Palmdale has been lifted, quite
literally, out of obscurity. Scientists have
recently discovered that it is in the center of a
120-mile-long, kidney-shaped area of land that
rose as much as ten inches in the early 1960s.
The phenomenon has earned the desert town a
dubious notoriety. The Palmdale bulge, as the
uplift is called, could be an early warning
signal of a majorand potentially disastrous
earthquake. Recent studies have shown that the
ground rose noticeably before the 1971 San
Fernando quake that killed 58 people in
California's last major trembler. Before a 1964
quake that destroyed much of Niigata, Japan, the
ground lifted two inches, and the Chinese
discovered an elevation of the land in Liaoning
province before the Manchurian earthquake of
February 1975.
TIME magazine, April, 1976
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SAN ANDREAS FAULT
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Ground deformation the Palmdale Bulge
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The results land to the NE of the fault
subsides, but nothing necessarily associated with
the earthquake
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Foreshocks (or the earthquake itself?)Water
wellsAnimals