Name_________________________________________Date_________________________________Period_______ The Earthquake Problem
Earthquakes are usually caused when rock underground suddenly breaks along a fault. This
sudden release of energy causes the seismic waves that make the ground shake. The release of
energy of an earthquake has such a large range (it can be really small or really big) that it spans
several orders of magnitude (i.e. powers of 10). The most powerful earthquake recorded in
recent history was a magnitude 9.0 quake off the coast of Japan in 2011. The earthquake caused
a massive tsunami and was one of the biggest crises in Japanese history. The earthquake shifted
the Earth on its axis by 3.9
Richter
Frequency
Description of Destruction
inches.
Magnitude
Around World
<2.0
Micro-earthquakes; not felt
Continually
2.0-2.9
Recorded, but generally not felt
3,500 per day
The Richter scale system
3.0-3.9
Often felt, but not damaging
130,000 per year
assigns a magnitude number
4.0-4.9
Like vibrations from a train
13,000 per year
to quantify the energy
5.0-5.9
Strong enough to wake sleepers
130 per year
released by an earthquake
6.0-6.9
Very strong; walls crack, injuries
130 per year
The formula for the Richter
7.0-7.9
Ruinous;
ground
cracks,
houses
fall
15 per year
scale magnitude of an
8.0-8.9
Disastrous; few buildings survive
1 per year
earthquake is:
9.0-9.9
Devastation reaches 4,000+ miles
1 per 10 years
! E $
2
10.0+
Epic disaster; never recorded
Extremely rare
M = log # 11.8 & ,
3
" 10
%
where E is the energy released (in ergs) and M is the magnitude.
1. In terms of ergs, how much energy was released by the 2011 Japan earthquake? Show all
steps in solving the equation.
2. On October 17, 1989, a 6.9 magnitude earthquake struck the San Francisco Bay Area at
5:04pm local time, during the warm up for Game 3 of the 1989 World Series between the San
Francisco Giants and the Oakland Athletics. The earthquake left up to 12,000 people homeless
and delayed the World Series by 10 days. How much less energy was released by this
earthquake than the 2011 Japan earthquake?
Name_________________________________________Date_________________________________Period_______ 3. The atomic bomb dropped on Hiroshima contained a massive amount of energy that equates to
about 63 TJ. A terajoule, TJ, is one trillion or (1012) joules. In terms of atomic bombs, how much
energy did the 2011 Japan earthquake release? (That is, the earthquake is equal to about how
many atomic bombs?) NOTE: 1 joule = 10,000,000 ergs.
4. The strongest Richter magnitude ever recorded was 9.5 – the Great Chilean Earthquake of
1960. The earthquake produced tsunumi waves that reached the shores of 5 different continents.
Which ones? You may want to look at a map for this one.
5. How many times more energy did Great Chilean Earthquake release than the 2011 Japan
earthquake?
6. True or false: A magnitude 4.0 earthquake releases twice as much energy as a magnitude 2.0
earthquake. Justify your response.
7. What is the purpose for making the Richter scale a logarithmic scale? Answer in complete
sentences.