at the USGS Andrew J Michael What Is Operational Earthquake Forecasting aka OEF Currently OEF Earthquake Clustering aka Foreshocks and Aftershocks Earthquakes trigger other earthquakes ID: 804409 Download
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Slide1
History and Future of
Operational Earthquake Forecasting
at the USGS
Andrew J. Michael
Slide2What Is Operational Earthquake Forecasting?
a.k.a. OEF
Currently OEF = Earthquake Clustering
a.k.a. Foreshocks and Aftershocks
Earthquakes trigger other earthquakes.
When you have one earthquake,
the probabilities for other earthquakes go up.
Slide3Semantics
When earthquake happens without obvious ancestors, it is a
mainshock
.
If smaller earthquakes follow, they are aftershocks.
If an aftershock occurs that is bigger than the
mainshock
, then we rename all previous events foreshocks, and the biggest aftershock is now the mainshock.If smaller earthquakes follow, they are aftershocks.……
The Physics Fine Print: all earthquakes are the same, we can’t tell foreshocks,
mainshocks
and aftershocks apart.
Slide4Standard Aftershock Warning
Issued after M>=5 Earthquakes in California
PROBABILITY REPORT Published on May 24, 2009 @ 16:58:34 GMT
Version 3: This report supersedes any earlier probability reports about this event.
MAINSHOCK Magnitude : 4.6 Mw (A light quake) Time : 23 May 2009 03:58:32 PM, PDT : 23 May 2009 22:58:32 GMT Coordinates : 36 deg. 25.28 min. N, 117 deg. 46.24 min. W : 36.4213 N, 117.7707 W Depth : 0.0 miles ( 0.1 km) Quality : Fair Location : 7 mi. ( 11 km) SE from Keeler, CA : 20 mi. ( 32 km) SE from Lone Pine, CA Event ID : NC 66099
STRONG AFTERSHOCKS (Magnitude 5 and larger) 
At this time (18 hours after the
mainshock) the probability of a strong and possibly damaging aftershock IN THE NEXT 7 DAYS is less than 10 PERCENTEARTHQUAKES LARGER THAN THE MAINSHOCK Most likely, the recent
mainshock
will be the largest in the sequence. However, there is a small chance (APPROXIMATELY 5 TO 10 PERCENT) of an earthquake equal to or larger than this
mainshock
in the next 7 days.
WEAK AFTERSHOCKS (Magnitude 3 to 5) 
In addition, up to approximately 5 SMALL AFTERSHOCKS are expected in the same 7DAY PERIOD and may be felt locally.
This probability report is based on the statistics of aftershocks typical for California. This is not an exact prediction, but only a rough guide to expected aftershock activity. This probability report may be revised as more information becomes available
.
Slide5Standard Aftershock Warning
Issued after M>=5 Earthquakes in California
Background
Information About Aftershocks
Like most earthquakes, the recent earthquake is expected to be followed by numerous aftershocks. Aftershocks are additional earthquakes that occur after the
mainshock
and in the same geographic area. Usually, aftershocks are smaller than the
mainshock, but occasionally an aftershock may be strong enough to be felt widely throughout the area and may cause additional damage, particularly to structures already weakened in the mainshock. As a rule of thumb, aftershocks of magnitude 5 and larger are considered potentially damaging.Aftershocks are most common immediately after the mainshock; their average number per day decreases rapidly as time passes. Aftershocks are most likely to be felt in the first few days after the mainshock
, but may be felt weeks, months, or even years afterwards. In general, the larger the
mainshock
, the longer its aftershocks will be felt.
Aftershocks tend to occur near the
mainshock
, but the exact geographic pattern of the aftershocks varies from earthquake to earthquake and is not predictable. The larger the
mainshock
, the larger the area of aftershocks. While there is no "hard" cutoff distance beyond which an earthquake is totally incapable of triggering an aftershock, the vast majority of aftershocks are located close to the
mainshock
. As a rule of thumb, a magnitude 6
mainshock
may have aftershocks up to 10 to 20 miles away, while a magnitude 7
mainshock
may have aftershocks as far as 30 to 50 miles away.
Slide6Standard Aftershock Warning
Issued after M>=5 Earthquakes in California
STRONG
AFTERSHOCKS (Magnitude 5 and larger)

At this time (18 hours after the
mainshock
) the probability of a strong and possibly damaging aftershock IN THE NEXT 7 DAYS is less than 10 PERCENTEARTHQUAKES LARGER THAN THE MAINSHOCK Most likely, the recent mainshock will be the largest in the sequence. However, there is a small chance (APPROXIMATELY 5 TO 10 PERCENT) of an earthquake equal to or larger than this mainshock in the next 7 days.WEAK AFTERSHOCKS (Magnitude 3 to 5) 
In addition, up to approximately 5 SMALL AFTERSHOCKS are expected in the same 7DAY PERIOD and may be felt locally
.
Slide7California Advisories
Slide8Haiti
Slide9Haiti
Slide10Mineral, VA
Slide11STEP
Gerstenberger
et al.
Nature, 2005
USGS OFR 2004
Slide12Reasenberg
and Jones, Science, 1989
Probability of earthquakes
during an aftershock sequence
as a function of time and
magnitude.
Initial estimates are based on
parameters for a “generic”
California earthquake sequence.
Sequence specific parameters
are used once they can be
determined.
Slide13Spatial Clustering
Aftershocks occur in the general region of the
mainshock
.
Up to about 1 – 2 fault lengths away.
In the case of a large aftershock at the edge of the zone, the zone will get larger.
The people we are warning, felt the
mainshock or should be aware of it.
Slide14How Many Aftershocks?
Bigger
Mainshocks
Produce More Aftershocks
Magnitude of
Mainshock
Expected number of aftershocks
Magnitude 3 or largerIn
the first week
5
6.7
6
67
7
670
8
6700
Slide15The Sizes of Aftershocks
(including bigger ones)
Minimum
Magnitude
Observed Number
Expected Number
3
310
340
4
42
34
5
6
3.4
6
0
0.34
7
0
0.034
Most Aftershocks Are Smaller
1994 Northridge Earthquake Magnitude 6.7
Number of Aftershocks within 30 km of
Mainshock
In the first week
Slide16The Times of Aftershocks
When
Observed Number
Expected Number
First Day (½ – 1½)
420
733
Tenth Day
44
70
100
th
Day
4
7.1
1000
th
Day
0
0.71
10000
th
Day
? until
2021
0.071
The Rate of Aftershocks Decays at About 1/time
1994 Northridge Earthquake Magnitude 6.7
Number of Aftershocks in 1 day
Magnitude
2
or
larger, within 30 km of
Mainshock
Slide17Forecast After a Magnitude 7
Minimum
Magnitude
Expected Number
Probability
of
1 or more events
3670
>99%
4
67
>99%
5
6.7
99%
6
0.67
50%
7
0.067
6.5%
8
0.0067
0.66%
Magnitude 7
Mainshock
Forecast for the First Week
Slide18Forecast After a Magnitude 5
Minimum
Magnitude
Expected Number
Probability
of
1 or more events
36.7
99%
4
0.67
49%
5
0.067
6.5%
6
0.0067
0.67%
7
0.00067
0.067%
8
0.000067
0.0067%
Magnitude 5
Mainshock
Forecast for the First Week
Wide Range of
Probabilities
Slide19Forecast After a Magnitude 5
Minimum
Magnitude
Expected Number
Probability
of
1 or more events
30.31
27%
4
0.031
3.1%
5
0.0031
0.31%
6
0.00031
0.031%
7
0.000031
0.0031%
8
0.0000031
0.00031%
Magnitude 5
Mainshock
Forecast for the Fifth Week
Slide20The Long Lives of Aftershocks
Aftershocks of the Magnitude 8¼
Nobi
Earthquake of 1891
Slide21Forecasts With Respect to
Urban Planning for Recovery
Stage
Emergency Response
(search and rescue, fire fighting, shelters, damage assessment)
2. Restoration
(restore utilities, debris removal, temporary repairs)
3. Reconstruction
(structures replaced to predisaster levels)
4. Betterment
(major projects improve community to a new standard)
5. LongTerm
(life with a new normal)
Forecast for a Magnitude 7
Mainshock
Slide22Forecasts With Respect to
Urban Planning for Recovery
Stage
Dominant
Time Period
(Kobe, Northridge, Christchurch)
Emergency Response
(search and rescue, fire fighting, shelters, damage assessment)
0
to
14
days
2. Restoration
(restore utilities, debris removal, temporary repairs)
14 days to 1 year
3. Reconstruction
(structures replaced to predisaster levels)
1 to 3 years
4. Betterment
(major projects improve community to a new standard)
3 to 10 years
5. LongTerm
(life with a new normal)
10 to 50 years
Forecast for a Magnitude 7
Mainshock
Slide23Forecasts With Respect to
Urban Planning for Recovery
Stage
Dominant Time Period
(Kobe, Northridge, Christchurch)
Probability of an Aftershock with Magnitude 6 or larger
Emergency Response
(search and rescue, fire fighting, shelters, damage assessment)
0
to
14
days
61%
2. Restoration
(restore utilities, debris removal, temporary repairs)
14 days to 1 year
33%
3. Reconstruction
(structures replaced to predisaster levels)
1 to 3 years
11%
4. Betterment
(major projects improve community to a new standard)
3 to 10 years
11%
5. LongTerm
(life with a new normal)
10 to 50 years
13%
Forecast for a Magnitude 7
Mainshock
Slide24Uncertainties
Variability from sequence to sequence by at least a factor of 10. Our forecasts will adapt to each sequence as we collect data.
Slide25Agnew and Jones, JGR, 1991:
“But it ought to be possible to do better:
Should we say the same thing
after every event?
the probability of a very large earthquake should be higher if the candidate foreshock were to occur near a fault capable of producing that
mainshock
than if it were located in an area where we believe such a
mainshock to be unlikely.Moreover, the chance of a candidate earthquake actually being a foreshock should be higher if the rate of background (nonforeshock) activity were low.”
Foreshock Model
to a
Specific
Mainshock
Slide26M4.8 Event At Bombay Beach On March 24, 2009
Could It Be A Foreshock To A Larger Earthquake In The Next 3 Days?
Slide27Mainshock
:
SAF, Coachella
Seg
.
UCERF2:
Length = 69 km
M 75yr Prob. = 5%3day Prob.= 0.009%M4.8 Event At Bombay Beach On March 24, 2009Could It Be A Foreshock To A Larger Earthquake In The Next 3 Days?
Slide28Mainshock
:
SAF, Coachella
Seg
.
UCERF2:
Length = 69 km
M 75yr Prob. = 5%3day Prob.= 0.009%Reasenberg &Jones, 1989:Probabilityof M4.8 beingfollowed by
an M≥7 event
PF = 0.05%
M4.8 Event At Bombay Beach On March 24, 2009
Could It Be A Foreshock To A Larger Earthquake In The Next 3 Days?
Slide29Mainshock
:
SAF, Coachella
Seg
.
UCERF2:
Length = 69 km
M 75yr Prob. = 5%3day Prob.= 0.009%R&J 1991:PF= 0.05%Agnew and
Jones, 1991:
PF = 4%
M4.8 Event At Bombay Beach On March 24, 2009
Could It Be A Foreshock To A Larger Earthquake In The Next 3 Days?
Slide30Past Efforts 
Parkfield
Slide31Past Efforts 
Parkfield
Alert versus
Status
Slide32Forecast After a Magnitude 5
Minimum
Magnitude
Probability
of
1 or more events
Probability
of 1 or more events if M≥7 occur 100xmore frequently
3
>99%
>99%
4
49%
52%
5
6.5%
12%
6
0.67%
7%
7
0.067%
6.4%
Magnitude 5
Mainshock
Forecast for the First Week
Integrated Aftershock
and Foreshock Forecast
Slide34Uncertainties
The probabilities for the largest events could be underestimated by a factor of 10 to 100.
Slide35Future USGS Plans
Expand the standard aftershock warnings nationally and internationally (for internal government use) with updated messaging. This will start as a
Reasenberg
and Jones calculation.
Develop the UCERF3 clustering model and associated products. This will combine
Reasenberg
and Jones type calculations with Agnew and Jones type calculations.
1year hazard assessments for induced seismicity.Test models and products, develop new methods.
Slide36Are these statements worth saying?
They are
true, everyone
knows
it, and they will ask.
New Zealand and Italy
experiences
When probabilities are high enough then public warnings have been issued in conjunction with the State of California. "During the August 8, 1989 advisory, all our departments ran drills to prepare for an imminent earthquake. This made a tremendous difference in the city's response when the earthquake struck," said Henry Renteria, Emergency Services Manager, Oakland, California"The probability of aftershocks given by the U.S. Geological Survey was one of the factors we used in deciding how many firefighters to keep on duty after the 1989 San Francisco Bay area earthquake," said Greg Abell
, Battalion Chief in the San Francisco Fire Department
.
The
important thing is what you want to do with them.
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