probabilistic seismic hazard analysis
DESCRIPTION
Probabilistic Seismic Hazard Analysis. Overview. History 1969 - Allin Cornell BSSA paper Rapid development since that time. Probabilistic Seismic Hazard Analysis. Overview. Deterministic (DSHA) Assumes a single “scenario” Select a single magnitude, M Select a single distance, R - PowerPoint PPT PresentationTRANSCRIPT
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisOverview
History1969 - Allin Cornell BSSA paperRapid development since that time
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisOverview
Deterministic (DSHA)Assumes a single “scenario”
Select a single magnitude, MSelect a single distance, RAssume effects due to M, R
Probabilistic (PSHA)Assumes many scenarios
Consider all magnitudesConsider all distancesConsider all effects
Ground motion
parameters
Ground motion
parameters
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisOverview
Probabilistic (PSHA)Assumes many scenarios
Consider all magnitudesConsider all distancesConsider all effects
Ground motion
parameters
Why? Because we don’t know when earthquakes will occur, we don’t know where they will occur, and we don’t know how big they will be
Consists of four primary steps:
1. Identification and characterization of all sources
2. Characterization of seismicity of each source
3. Determination of motions from each source
4. Probabilistic calculations
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
PSHA characterizes uncertainty in location, size, frequency, and effects of earthquakes, and combines all of them to compute probabilities of different levels of ground shaking
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Need to specify distance measureBased on distance measure in attenuation relationship
rhypo
rseis
rrup
rjb
Seismogenicdepth
Vertical Faults
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Need to specify distance measureBased on distance measure in attenuation relationship
Dipping Faults
rhypo
rseis
rrup
rjb=0
rhypo
rseis & rrup
rjb
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Where on fault is rupture most likely to occur?
Source-site distance depends on where rupture occurs
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Where is rupture most likely to occur? We don’t know
Source-site distance depends on where rupture occurs
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Approach:
rmin
rmax
r
fR(r)
rmin rmax
Assume equal likelihood at any pointCharacterize uncertainty probabilistically
pdf for source-site distance
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Two practical ways to determine fR(r)
rmin
rmax
Draw series of concentric circles with equal radius increment
Measure length of fault, Li, between each pair of adjacent circles
Assign weight equal to Li/L to each corresponding distance
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Two practical ways to determine fR(r)
rmin
rmax
Divide entire fault into equal length segments
Compute distance from site to center of each segment
Create histogram of source-site distance. Accuracy increases with increasing number of segments
Linear source
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Areal Source
Divide source into equal area elements
Compute distance from center of each element
Create histogram of source-site distance
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Divide source into equal volume elements
Compute distance from center of each element
Create histogram of source-site distance
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Unequal element areas?
Create histogram using weighting factors - weight according to fraction of total source area
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUncertainty in source-site distance
Quick visualization of pdf?
Use concentric circle approach - lets you “see” basic shape of pdf quickly
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCharacterization of maximum magnitude
Determination of Mmax - same as for DSHA
Empirical correlationsRupture length correlationsRupture area correlationsMaximum surface displacement correlations
“Theoretical” determinationSlip rate correlations
Also need to know distribution of magnitudes
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
Given source can produce different earthquakesLow magnitude - oftenLarge magnitude - rare
Gutenberg-RichterSouthern California earthquake data - many faultsCounted number of earthquakes exceeding different magnitude levels over period of many years
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
M
NM
M
log NM
M
log M
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
Mean annual rateof exceedance
M = NM / T
M
log M
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
Return period(recurrence interval)
TR = 1 /M
0.001 1000 yrs
log TR
0.01 100 yrs
M
log M
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
Gutenberg-RichterRecurrence Law
logM = a - bM log TR0
10a
b
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
Gutenberg-Richter Recurrence Law
log M = a - bM
Implies that earthquake magnitudes are exponentially distributed (exponential pdf)
Can also be written as
ln M = - M
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
Then
M = 10a - bM = exp[ - M]
where = 2.303a and = 2.303b.
For an exponential distribution,
fM(m) = e-m
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
Neglecting events below minimum magnitude, mo
m = exp[ - (m - mo)] m > mo
where = exp[ - mo].
Then,
fM(m) = e-m-mo)
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
For worldwide data (Circumpacific belt),
log m = 7.93 - 0.96M
M = 6 m = 148 /yr TR = 0.0067 yr
M = 7 m = 16.2 TR = 0.062
M = 8 m = 1.78 TR = 0.562
M = 12 m = 0.437 TR = 2.29M > 12 every two years?
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
Every source has some maximum magnitude
Distribution must be modified to account for Mmax
Bounded G-R recurrence law
)](exp[1)](exp[)](exp[
max
max
mmmmmm
o
oom
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
Every source has some maximum magnitude
Distribution must be modified to account for Mmax
Bounded G-R recurrence law
)](exp[1)](exp[)](exp[
max
max
mmmmmm
o
oom
MMmax
log m Bounded G-RRecurrence Law
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
Characteristic Earthquake Recurrence Law
Paleoseismic investigationsShow similar displacements in each earthquakeInividual faults produce characteristic earthquakesCharacteristic earthquake occur at or near Mmax
Could be caused by geologic constraintsMore research, field observations needed
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDistribution of earthquake magnitudes
MMmax
log m
Seismicity data
Geologic data
CharacteristicEarthquakeRecurrence Law
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisPredictive relationships
MMmax
log m
log R
ln Y
M = M*
R = R*
ln YY = Y*
P[Y > Y*| M=M*, R=R*]
Standard error - use to evaluate conditional probability
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisPredictive relationships
M
log R
ln Y
M = M*
R = R*
ln YY = Y*
P[Y > Y*| M=M*, R=R*]
Standard error - use to evaluate conditional probability
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisTemporal uncertainty
Poisson process - describes number of occurrences of an event during a given time interval or spatial region.
1. The number of occurrences in one time interval are independent of the number that occur in any other time interval.2. Probability of occurrence in a very short time interval is proportional to length of interval.3. Probability of more than one occurrence in a very short time interval is negligible.
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisTemporal uncertainty
Poisson process
!][
nenNP
n
where n is the number of occurrences and m is the average number of occurrences in the time interval of interest.
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisTemporal uncertainty
Poisson process
Letting = t
!)(][n
etnNPtn
Then][...]3[]2[]1[]0[ nPNPNPNPNP
]0[1 NP
e t1
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisTemporal uncertainty
Poisson process
eP t1
Consider an event that occurs, on average, every 1,000 yrs. What is the probability it will occur at least once in a 100 yr period?
= 1/1000 = 0.001
P = 1 - exp[-(0.001)(100)] = 0.0952
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisTemporal uncertainty
What is the probability it will occur at least once in a 1,000 yr period?
P = 1 - exp[-(0.001)(1000)] = 0.632
Solving for ,
tp)1ln(
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisTemporal uncertainty
Then, the annual rate of exceedance for an event with a 10% probability of exceedance in 50 yrs is
0021.050
)1.01ln(
The corresponding return period is TR = 1/ = 475 yrs.
For 2% in 50 yrs, = 0.000404/yr TR = 2475 yrs
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisSummary of uncertainties
Location
Size
Effects
Timing
fR(r)
fM(m)
P[Y > Y*| M=M*, R=R*]
P = 1 - e-t
Source-site distance pdf
Magnitude pdf
Attenuation relationship including standard error
Poisson model
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
P[A] =
P[A] = P[A|B1]P[B1] + P[A|B2]P[B2] + … + P[A|BN]P[BN]
B1 B2B3
B4B5
A
U
P[A B1] +
U
P[A B2] + … +
U
P[A BN]
TotalProbabilityTheorem
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
dxfyYPPyYPyYP X )(]|*[][]|*[*][ XXXX
Applying total probability theorem,
where X is a vector of parameters.
We assume that M and R are the most important parameters and that they are independent. Then,
dmdrrfmfrmyYPyYP RM )()(],|*[*][
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
Above equation gives the probability that y* will be exceeded if an earthquake occurs. Can convert probability to annual rate of exceedance by multiplying probability by annual rate of occurrence of earthquakes.
dmdrrfmfrmyYPyYP RM )()(],|*[*][
dmdrrfmfrmyYP RMy )()(],|*[*
where = exp[ - mo]
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
If the site of interest is subjected to shaking from more than one site (say Ns sites), then
dmdrrfmfrmyYP RiMiN
iiy
s)()(],|*[
1*
For realistic cases, pdfs for M and R are too complicated to integrate analytically. Therefore, we do it numerically.
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
Dividing the range of possible magnitudes and distances into NM and NR increments, respectively
rmrfmfrmyYP kRijMikjiN
k
N
j
N
iy
RMS)()(],|*[
111*
This expression can be written, equivalently, as
][][],|*[111
* rRPmMPrmyYP kjkjiN
k
N
j
N
iy
RMS
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
][][],|*[111
* rRPmMPrmyYP kjkjiN
k
N
j
N
iy
RMS
What does it mean?
All possible magnitudes are considered - contribution of each is weighted by its probability of occurrence
All sites areconsidered
All possible distances are considered - contribution of each is weighted by its probability of occurrence
All possible effects are considered - each weighted by its conditional probability of occurrence
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
NM x NR possible combinationsEach produces some probability of exceeding y*Must compute P[Y > y*|M=mj,R=rk] for all mj, rk
m1 m2
r1
m3 mNM
rNR
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
Compute conditional probability for each element on gridEnter in matrix (spreadsheet cell)
log R
ln Y M=m2
r1
ln YY = y*
P[Y > y*| M=m2, R=r2]
r2
r3
rN
P[Y > y*| M=m2, R=r1]
P[Y > y*| M=m2, R=r3]
Combining uncertainties - probability computations
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
m1 m2
r1
m3 mNM
rNR
P[Y > y*| M=m2, R=r1]
P[Y > y*| M=m2, R=r3]
P[Y > y*| M=m2, R=r2]
“Build” hazard by:computing conditional probability for each elementmultiplying conditional probability by P[mj], P[rk], i
Repeat for each source - place values in same cells
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
m1 m2
r1
m3 mNM
rNR
P[Y > y*| M=m2, R=r1]
P[Y > y*| M=m2, R=r3]
P[Y > y*| M=m2, R=r2]
When complete (all cells filled for all sources),
Sum all -values for that value of y* y*
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
m1 m2
r1
m3 mNM
rNR
P[Y > y*| M=m2, R=r1]
P[Y > y*| M=m2, R=r3]
P[Y > y*| M=m2, R=r2]
Choose new value of y*Repeat entire processDevelop pairs of (y*, y*) points Plot
y*
log TRlo
g y
*
SeismicHazardCurve
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisCombining uncertainties - probability computations
y*
log TRlo
g y
*
amax
log TRlo
g a
max
Seismic hazard curve shows the mean annual rate of exceedance of a particular ground motion parameter. A seismic hazard curve is the ultimate result of a PSHA.
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisUsing seismic hazard curves
amax=0.30g
log TRlo
g a
max
0.001
Probability of exceeding amax = 0.30g in a 50 yr period?
P = 1 - e-t
= 1 - exp[-(0.001)(50)] = 0.049 = 4.9%
In a 500 yr period?
P = 0.393 = 39.3%
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
amax=0.21g
log TRlo
g a
max
0.0021
What peak acceleration has a 10% probability of being exceeded in a 50 yr period?
10% in 50 yrs: = 0.0021or
TR = 475 yrs
Use seismic hazard curve to find amax value corresponding to = 0.0021
Using seismic hazard curves
475 yrs
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
amax
log TRlo
g a
max
Contribution of sources
Can break -values down into contributions from each sourcePlot seismic hazard curves for each source and total seismic hazard curve (equal to sum of source curves)Curves may not be parallel, may crossShows which source(s) most important
Using seismic hazard curves
Total
12
3
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
Can develop seismic hazard curves for different ground motion parameters
Peak accelerationSpectral accelerationsOther
Choose desired -valueRead corresponding parameter values from seismic hazard curves
Using seismic hazard curves
amax, Sa
log TRlo
g a
max
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
Can develop seismic hazard curves for different ground motion parameters
Peak accelerationSpectral accelerationsOther
Choose desired -valueRead corresponding parameter values from seismic hazard curves
Using seismic hazard curves
amax, Sa
log TRlo
g a
max
amax
0.1
0.01
0.001
0.0001
Crustal
Intraplate
Interplate
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
2% in 50 yrs
Peak acceleration
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
2% in 50 yrs
Sa(T = 3 sec)
amax
0.1
0.01
0.001
0.0001
Crustal
Intraplate
Interplate
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
Find spectral acceleration values for different periods at constant All Sa values have same -value same probability of exceedance
Uniform hazard spectrum (UHS)
Sa
T
UniformHazardSpectrum
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
Common question:
What magnitude & distance does that amax value correspond to?
Disaggregation (De-aggregation)
5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5
25 km
75 km
100 km
125 km
150 km
175 km
200 km
50 km
0.01 0.01 0.02 0.03 0.03 0.02 0.01 0.01
0.030.02 0.04 0.04 0.05 0.04 0.03 0.02
0.000.00 0.00 0.00 0.01 0.00 0.00 0.00
0.030.03 0.05 0.06 0.09 0.06 0.05 0.02
0.030.03 0.05 0.05 0.08 0.05 0.05 0.02
0.020.02 0.03 0.04 0.05 0.03 0.02 0.01
0.010.01 0.02 0.03 0.05 0.02 0.01 0.00
0.000.00 0.01 0.01 0.03 0.01 0.01 0.00
Total hazard includes contributions from all combinations of M & R.
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
Common question:
What magnitude & distance does that amax value correspond to?
Disaggregation (De-aggregation)
5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5
25 km
75 km
100 km
125 km
150 km
175 km
200 km
50 km
0.01 0.01 0.02 0.03 0.03 0.02 0.01 0.01
0.030.02 0.04 0.04 0.05 0.04 0.03 0.02
0.000.00 0.00 0.00 0.01 0.00 0.00 0.00
0.030.03 0.05 0.06 0.09 0.06 0.05 0.02
0.030.03 0.05 0.05 0.08 0.05 0.05 0.02
0.020.02 0.03 0.04 0.05 0.03 0.02 0.01
0.010.01 0.02 0.03 0.05 0.02 0.01 0.00
0.000.00 0.01 0.01 0.03 0.01 0.01 0.00
Total hazard includes contributions from all combinations of M & R.
Break hazard down into contributions to “see where hazard is coming from.”
M=7.0 at R=75 km
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
USGS disaggregations
Disaggregation (De-aggregation)
Seattle, WA
2% in 50 yrs (TR = 2475 yrs)
Sa(T = 0.2 sec)
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
USGS disaggregations
Disaggregation (De-aggregation)
Olympia, WA
2% in 50 yrs (TR = 2475 yrs)
Sa(T = 0.2 sec)
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard Analysis
USGS disaggregations
Disaggregation (De-aggregation)
Olympia, WA
2% in 50 yrs (TR = 2475 yrs)
Sa(T = 1.0 sec)
log R
ln Y M=m2
r1
ln Y Y = y*
r2r3
rN
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisDisaggregation (De-aggregation)
Another disaggregation parameter
y
yy
ln
ln*ln
= -1.6
= -0.8
= 1.2 = 2.2
For low y*, most values will be negative
For high y*, most values will be positive and large
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisLogic tree methods
Not all uncertainty can be described by probability distributions
Most appropriate model may not be clear• Attenuation relationship• Magnitude distribution• etc.
Experts may disagree on model parameters• Fault segmentation• Maximum magnitude• etc.
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisLogic tree methods
AttenuationModel
MagnitudeDistribution Mmax
BJF(0.5)
A & S(0.5)
G-R(0.7)
Char.(0.3)
G-R(0.7)
Char.(0.3)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisLogic tree methods
AttenuationModel
MagnitudeDistribution Mmax
BJF(0.5)
A & S(0.5)
G-R(0.7)
Char.(0.3)
G-R(0.7)
Char.(0.3)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
Sum of weighting factors coming out of each node must equal 1.0
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisLogic tree methods
AttenuationModel
MagnitudeDistribution Mmax
BJF(0.5)
A & S(0.5)
G-R(0.7)
Char.(0.3)
G-R(0.7)
Char.(0.3)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
0.5x0.7x0.2 = 0.07
Final value of Y is obtained as weighted average of all values given by terminal branches of logic tree
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisLogic tree methods
AttenuationModel
MagnitudeDistribution Mmax
BJF(0.5)
A & S(0.5)
G-R(0.7)
Char.(0.3)
G-R(0.7)
Char.(0.3)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
7.0 (0.2)7.2 (0.6)7.5 (0.2)
0.070.210.07
0.030.090.03
0.070.210.07
0.030.090.03
w
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisLogic tree methods
Recent PSHA logic tree included:
Cascadia interplate2 attenuation relationships2 updip boundaries3 downdip boundaries2 return periods4 segmentation models2 maximum magnitude approaches
192 terminal branches
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisLogic tree methods
Recent PSHA logic tree included:
Cascadia intraplate2 intraslab geometries3 maximum magnitudes2 a-values2 b-values
24 terminal branches
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisLogic tree methods
Recent PSHA logic tree included:
Seattle Fault and Puget Sound Fault2 attenuation relationships3 activity states3 maximum magnitudes2 recurrence models2 slip rates
72 terminal branches for Seattle Fault 72 terminal branches for Puget Sound Fault
Probabilistic Seismic Hazard AnalysisProbabilistic Seismic Hazard AnalysisLogic tree methods
Recent PSHA logic tree included:
Crustal areal source zones7 source zones2 attenuation relationships3 maximum magnitudes2 recurrence models3 source depths
252 terminal branches
Total PSHA required analysis of 612 combinations