Southern California Earthquake Center -...
Transcript of Southern California Earthquake Center -...
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Southern California Earthquake Center• Operates 1991 – present, $3 - $5 million per year• NSF Science and Technology Center at first• Mission: Provide scientific basis for seismic hazard
assessment.• Involves Seismology, Geology, Geodesy• One year + in consensus building,
– 4 100 20 participants• Management plan: “Center without walls,” led by Prof.
Kei Aki, member of NAS• Funding from NSF, USGS, CGS, USC• High profile seismic hazard reports from 1993• Community data bases –faults, earthquakes, 3-D
seismic velocity
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Backgroundseismicity
Type-A Faults Type-B Faults
Type-C Sources
Quake rates on known faults
Quake rates
elsewhere
Putting it all together …
Uniform California Earthquake Rupture ForecastUCERF2 Earthquake Rate Model 2008
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UCERF2 Recipe for Type A Faults:(from WGCEP (2002 & 2007)
Possible Ruptures
Northern San Andreas Fault (NSAF)
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New Approach: 2014 versionSystem of Equations
Dsrr =1
R
∑ fr = vs
Gsrr=1
R
∑ Prpaleo fr = fs
paleo
fr = fra−priori
fr − fr+1 = 0
Frequency (rate) of the rth rupture - what we’re solving for
Mmrg
r =1
R
∑ fr ≤ GRmg
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A stochastic forecast of California earthquakes based on fault
slip and smoothed seismicity
S. Hiemer, ETHZ, D.D. Jackson, Q. Wang,Y. Y. Kagan, UCLAJ. Woessner, J. D. Zechar, S. Wiemer ETHZ
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Approach• Start with the answer! Include physics only
as it is expressed in observable distributions• Synthesize (in this order)
– Magnitude– Location wrt faults and prior earthquakes– Focal mechanism– Fault dimesions– Fault orientation
• Weighted average of earthquake and fault info
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Tapered GR magnitude distribution based on global analysis of transform boundaries; corner magnitude 8.1
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Southern California earthquakes, mostly located using precise waveform correlation. Typical horizontal location uncertainty “tens of meters.”From Shearer et al., BSSA 2005
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Conclusions• Model fits observed distributions
– Magnitude, – Inter-event distance– Epicenter-fault distance– Pair-wise focal mechanism rotations– Fault-focal mechanism rotations?
• Largest earthquakes occur very near faults– Implies b-value variation
• Expect Surprises