Earthquake forecasting using earthquake catalogs

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Earthquake forecasting using earthquake catalogs
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• Since my first attachment to seismology, I have
  had a horror of predictions and of predictors.
  Journalists and the general public rush to any
  suggestion of earthquake prediction like hogs
  toward a full trough.
• - Charles Richter (1977)

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Whoever wishes to foresee the future must consult
the past

• Turn to you partner and discuss this statement
• What does it mean?
• Provide an example where it applies
• Could this statement connect to earthquakes? How?

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• Earthquake Prediction
• vs.
• Earthquake Forecasting
• Earthquake Prediction a short-term (hours to
  days) statement that an earthquake of a specified
  size will occur at a given location.
• Earthquake Forecast a long term (years to
  decades) statement of the probability of an
  earthquake in a region (or the probability of one
  or more earthquakes in a region).

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IRIS Earthquake Browser - www.iris.edu gtFor
Educators
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Looking for seismicity patternsSteps

• Select a region of the world that is of interest
  to you
• Interrogate the EQ catalogue to determine the
  number of various sized events that occur in a 25
  year period for your region. (Start at min 9.0
  and use M 0.5 intervals)
• Make a 3 column table of
• Magnitude
• total number of earthquakes greater than or equal
  to a specified magnitude
• number/year
• Plot this information on the graph provided (or
  use Excel)

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IRIS Earthquake Browser - www.iris.edu gtFor
Educators
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Looking for seismicity patternsSteps

• Select a region of the world that is of interest
  to you
• Interrogate the EQ catalogue to determine the
  number of various sized events that occur in a 25
  year period for your region. (Start at min 9.0
  and use M 0.5 intervals)
• Make a 3 column table of
• Magnitude
• total number of earthquakes greater than or equal
  to a specified magnitude
• number/year
• Plot this information on the graph provided (or
  use Excel)
• How might this information help to forecast
  future earthquakes?

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Questions to discuss with your partner

• Do you see any patterns or trends in earthquake
  occurrence in the 2 regions?
• What is the likelihood that an earthquake of
  magnitude 7.0 or greater (which can cause severe
  damage) will occur in the next year in the 2
  regions?
• How might this information be useful to society?
• Is there a risk for forecasting earthquake
  likelihood using a data set that only goes back
  to 1973?

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Earthquakes, Magnitude gt3.5, 1973-2007
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Earthquakes, Magnitude gt3.5, 1973-2007
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Questions

• What is the likelihood that an earthquake of
  magnitude 7.0 or greater will occur in the next
  year in the 2 regions?
• How might this information be useful to society?
• Is there a risk for forecasting earthquake
  likelihood using a data set that only goes back
  to 1973?

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What is the probability of an M6 event next year?
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What is the probability of an M7 event next year?
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Are the numbers of earthquakes in the smallest
and largest ranges consistent with the trends in
the other regions? Can you think of any reasons
why the trend is flat for small and also large
magnitudes?
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1973-2007
10-3
10-4
10-5
N
10-6
10-7
10-8
10-9
Magnitude
N earthquakes per km2 per yr
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Ground shaking from a magnitude 6 earthquake in
the east is approximately equivalent to that of a
magnitude 7 earthquake in the west.
http//pasadena.wr.usgs.gov/office/hough/east-vs-w
est.jpg
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2002 National Seismic Hazard Map
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Although we cant predict earthquakes (in the
sense of predicting a specific time, location and
magnitude) Earthquake Hazard Analysis
Global Seismic Hazard Map
We can estimate the probability that a given
amount of ground shaking will occur during a
given period of time at some location.
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Japanese Folklore Earthquakes caused by giant
Namazu.
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Following the 1755 Lisbon earthquake on All
Saints Day, the Spanish Inquisition burned
people at the stake to atone for the citys sins.
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Earthquake Prediction Precursory Events Ex/
1989 Loma Prieta Earthquake
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Also Resistivity, water pressure and well
levels, geyser activity, changes in seismicity
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Earthquake Prediction Animal Behavior??
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The exception Feb 4, 1974 Haicheng, China
Almost no details are known of this.
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Another Approach Forecasting
Seismic Gap Hypothesis
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OLD Map of Seismic Gap Predictions
Parkfield was in correct place, but very
late. Northridge, Landers, Joshua Tree and Big
Bear Earthquakes were not even on this map!!! ?
New York City Bear Gap Hypothesis
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Parkfield, California, showed evidence of the
recurrence of similar-sized (M 6.0) earthquakes
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In 1985 a 6.0 Parkfield earthquake was predicted
with 95 confidence to occur by 1993. Mean
(1966-1857)/5 22 years Expected date 1988
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Didnt occur until 2004 (16 years late!) Was it
a success? Right size, right location, wrong date.
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Paleoseismology
Sieh et al., 1989
Extend earthquake history with geologic record
M gt7 mean 132 yr s 105 yr Estimated
probability in 30 yrs 7-51
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However, even earthquake recurrence along plate
boundaries is highly variable probabilities hard
to assess

• Mgt7 mean 132 yr s 105 yr
• Estimated probability of next earthquake in 30
  yrs is 7-51
• Random!

Elastic Rebound (Seismic Gap) Theory? NY City
Bear Gap Hypothesis?
Sieh et al., 1989
Random seismicity simulation