Transcript 2007 NSTA: St. Louis, Missouri Earthquake Prediction and Forecasting: A Case Study of the San Andreas and New Madrid Faults Sponsored by: IRIS (Incorporated Research.

2007 NSTA: St. Louis, Missouri
Earthquake Prediction and Forecasting:
A Case Study of the San Andreas and
New Madrid Faults
Sponsored by:
IRIS (Incorporated Research Institutions for Seismology)
NSF (National Science Foundation)
Presented by:
John Taber, IRIS
Michael Wysession, Department of Earth and Planetary
Sciences, Washington University, St. Louis, Missouri
For all IRIS NSTA activities
www.iris.edu/joomla
Go to: NSTA 2007
Earthquake
Prediction:
Precursory Events
Ex/ 1989 Loma
Prieta Earthquake
Also: Resistivity, water pressure and well levels, geyser
activity, changes in seismicity
Earthquake Prediction: Animal Behavior??
The exception: Feb 4, 1974: Haicheng, China
* Almost no details are known of this.
Another Approach: Forecasting
Seismic “Gap” Hypothesis
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
Parkfield, California,
showed evidence of
the recurrence of
similar-sized (M 6.0)
earthquakes
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
Didn’t occur until
2004
(16 years late!)
Was it a success?
Right size, right
location, wrong date.
Paleoseismology
Extend earthquake
history with geologic
record
Sieh et al., 1989
M >7 mean = 132 yr s = 105 yr
Estimated probability in 30 yrs 7-51%
The NMFZ (New
Madrid Fault
Zone) is a region
of elevated
seismicity at the
intersection of
Missouri,
Arkansas,
Tennessee,
Kentucky, and
Illinois
The NMFZ is
associated with
the Reelfoot Rift –
a failed rift zone
that was active 750
million years ago,
as the
supercontinent
Rodinia began to
break up.
The Reelfoot Rift is a region of lower elevation
(which is why the Mississippi River flows
down through it!).
In 1811-1812,
swarm of
earthquakes
occurred. The
largest were:
12/16/1811: M7.2
1/23/1812: M7.0
2/07/1812: M7.4
[Hough et al., 2000]
A Magnitude 8 (M8)
earthquake is much
bigger than a M7
earthquake:
Roughly 10x greater
displacements
Roughly 30x more
energy released
“the big one”
NMSZ FREQUENCY-MAGNITUDE RELATIONSHIP
For New Madrid,
combine instrumental
seismology with earlier
data to explore large
earthquake recurrence
?
Large
paleoearthquakes
occurred at
~ 1450 and 900 AD
(Magnitudes unknown)
Gives a M7 every
few thousand years.
 Might NEVER get a
M8 earthquake
Stein & Newman, 2004
“Seismologists have predicted a 40-60%
chance of a devastating earthquake in the
New Madrid seismic zone in the next ten
years. Those odds jump to 90% over the
next 50 years. The potential magnitude of a
catastrophic New Madrid quake dictates
that we approach the preparedness on a
regional basis"
 Unjustified given geologic evidence
Are the seismic hazards as great in NMSZ as
California? Of course not.
2% chance of shaking within 50 years:
= seismic hazard within next 2500 years
More reasonable assessment, based upon actual seismicity
The Global Seismic Hazard Assessment Program (GSHAP), with the support
of the International Council of Scientific Unions (ICSU), and endorsed as a
demonstration program in the framework of the United Nations International
Decade for Natural Disaster Reduction (UN/IDNDR).
Earthquakes occur where earthquakes occur
Earthquakes occur where seismometers exist
Earthquakes occur where earthquakes occur
Earthquakes occur where seismometers exist
Almost no
seismometers!!
Notice all the
earthquakes EAST of
the NMSZ!
The NMSZ might be
finished (for now?).
It might be time for
a different failed rift
to undergo some
continental
creaking.
o Historical
o Instrumental
GPS SITE MOTIONS:
Vertical show glacial rebound
Horizontal show no pattern
GPS site motions within their
ellipse of uncertainty - no
motion!
DON’T SEE MOTION
AT NEW MADRID OR
ELSEWHERE IN
EASTERN US:
If you don’t bend it,
you can’t break it
No significant or coherent
intraplate deformation visible
GPS CONSTRAINTS ON LARGE EARTHQUAKE
MAGNITUDE & RECURRENCE
GPS data show little
or no (< 2 mm/yr)
motion
Newman et al, 1999
Little - or none accumulating for
future earthquakes
Intersection of
Paleoseismology
and GPS evidence
suggests low M7
earthquakes, but
larger events would
have VERY long
recurrence times.
GPS
Will we ever
have a real-time
warning system
for St. Louis?
Not likely. Not
much you can do
with 25 seconds!
25 s !!