Preliminary Seismic 1 Source Characterization (SSC) Logic ... · Source Characterization (SSC)...

1

PG&E DCPP SSHAC Study

Preliminary Seismic Source Characterization (SSC) Logic Tree Overview

SSC TI Team Evaluation Steve Thompson

Diablo Canyon SSHAC Level 3 PSHA

Workshop #3

Feedback to Technical Integration Team on Preliminary Models

March 25-27, 2014

San Luis Obispo, CA

PG&E DCPP SSHAC Study 2

Overview of the Preliminary SSC Model

SSC Elements:

Key Fault Sources

San Andreas and Other Regional Fault Sources

Background Source


Key Fault Sources Four fault sources contribute most to hazard at DCPP:

Hosgri

Los Osos

San Luis Bay

Shoreline

Characterization of these fault sources with the following goals in mind:

• Capture the CBR of TDI

• Focus on hazard-significant parameters


SSC Elements for Logic Tree

Fault Model

Deformation Model

Rupture Model

Earthquake Rate Model

Recurrence Model



Fault Model

Deformation Model

Rupture Model


Recurrence Model


Fault Models

Alternative fault models:

Describe the geometry and kinematics of how the site vicinity is deforming

Allow for correlated, mechanically consistent fault geometries, slip types, and slip rates

Allow a logical framework for developing rupture scenarios and fault linkages.


Three Fault Models

(1) Outward Vergent

(2) Southwest Vergent

(3) Northeast Vergent


Outward Vergent Model

• Hosgri dips 85°E

• Vertical Shoreline fault

• Irish Hills underlain by:

• Reverse-oblique Los Osos (60° SW)

• Reverse San Luis Bay (75°N)


Southwest-Vergent Model

• Hosgri dips 75°E


• Irish Hills underlain by

• Reverse San Luis Bay (45° N)

• Reverse Los Osos backthrust (80°SW)


Northeast-Vergent Model

• Hosgri dips 90°


• Irish Hills underlain by

• Reverse Los Osos fault (50° SW)

• Reverse San Luis Bay backthrust (70°N)

PG&E DCPP SSHAC Study 11 Fault Models (cont.)

Alternative Fault Models:

Describe the fault geometry for each tectonic model in a correlated way

Dip variability is achieved through the differences between tectonic models

Depths are fixed: 15 km maximum depth for Hosgri; 12 km maximum depth for other faults.

NE Model SW Model OV Model


Fault Models

Logic Tree for Fault Models:

Southwest Vergent

[0.4]

Outward Vergent

Northeast Vergent

[0.3]

[0.3]



Fault Model

Deformation Model

Rupture Model


Recurrence Model


Deformation Model

Describes the long-term rate of motion on the fault sources

Fault slip rates are used to calculate seismic moment release


Deformation Models

Fault slip rates are expressed as cumulative distribution functions (CDFs):

Based on geologic slip rate studies

Evaluated against geodetic data and modeling

Weighted mean, 3-pt, 5-pt distributions may be extracted from CDFs


Example: Oso Terrace Horizontal Slip Rate

Source: Hanson and Lettis (1994)


Example Slip Rate Assessment

Oso Terrace Offset Oso Terrace Age

0.000

0.005

0.010

0.015

0.020

0 200 400 600 800

Pro

ba

bil

ity

Offset (m)

Paleostrandline offset

0.00

0.05

0.10

160 180 200 220 240 260P

rob

ab

ilit

y

Channel Age (ky)

Stage 7 Highstand Age Model

Stage 7 Highstand Age Value (ky)

Min -> 190

Best min -> 195

Best max -> 215

Max -> 220

Lateral Offsets Value (m)

Min -> 150

Best min -> 300

Best max -> 450

Max -> 560


Deformation Models - Example Oso Terrace Slip

Rate CDF Four Hosgri Sites

Slip Rate CDFs

Slip Rate Value

(mm/yr)

Min -> 0.7

Max -> 2.9

Mean -> 1.8

0

0.2

0.4

0.6

0.8

1

0.5 1.0 1.5 2.0 2.5 3.0

Cu

mu

lati

ve

Pro

ba

bil

ity

Slip Rate (m/ky)

0

0.2

0.4

0.6

0.8

1

0 1 2 3 4 5C

um

ula

tive

Pro

ba

bil

ity

Slip Rate, mm/yr

San Simeon / OsoTerrace

Pt. Estero Cross-Hosgri slope

Estero Bay SubmarineChannel

Pt. Sal Channel F

Weighting

Scheme San

Simeon Pt.

Estero Estero

Bay Pt. Sal

Near-Equal 0.3 0.3 0.2 0.2

Inverse-Age 0.27 0.50 0.07 0.16

Inverse-Distance 0.13 0.22 0.38 0.27


Deformation Models - Example 5-pt distribution for Hosgri fault, Near-Equal weighting:

[0.101]

Weighted mean slip rate: 1.8 mm/yr

2.5 mm/yr

[0.244]

[0.244]

[0.101]

1.7 mm/yr

1.1 mm/yr

0.6 mm/yr

3.3 mm/yr

[0.309]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5

Cu

mu

lati

ve

Pro

ba

bil

ity

Slip Rate, mm/yr

Near-Equal Weighting

Age-Weighted

Distance-Weighted

CDFs for Hosgri fault, alternative weighting schemes:


Deformation Models - Example

Hosgri slip rate:

Center: 1.8 mm/yr (wtd mean)

Body: 0.6 to 3.4 (95%)

Range: 0.26 min; 4.7 max

0

0.2

0.4

0.6

0.8

1

0 1 2 3 4 5

Slip Rate, mm/yr

Hosgri fault slip rate CDFs Other constraints:

1) GPS plate boundary: 0.5 to 4 mm/yr

2) USGS Block modeling: 0.5 to ~3 mm/yr

3) UCERF3 Targets (mm/yr): Zeng: 1.0-1.4; Bird: 1.2; ABM: 1.64; Geologic: 2.15;

4) UCERF3 Solution (mm/yr): 1.4 to 1.5 mean


Deformation Models - Summary

Hosgri slip rate:


Body: 0.6 to 3.4 (95%)


0

0.2

0.4

0.6

0.8

1

0 1 2 3 4 5

Cu

mu

lati

ve

Pro

ba

bil

ity

Slip Rate (mm/yr)

Hosgri fault slip rate CDF

0

0.2

0.4

0.6

0.8

1

0.0 0.1 0.2 0.3 0.4 0.5C

um

ula

tive

Pro

ba

bil

ity

Slip Rate (mm/yr)

Shoreline fault slip rate CDF

Shoreline slip rate:


Body: 0.08 to 0.30 (95%)



Deformation Models - Summary

Los Osos slip rate (mm/yr):

Center(s): 0.27, 0.20, 0.44

Body: 0.2 to 0.6


Los Osos fault slip rate CDFs

San Luis Bay fault slip rate CDFs

0

0.2

0.4

0.6

0.8

1

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Cu

mu

lati

ve

Pro

ba

bil

ity

Slip Rate (m/ky)

Outward

SW Model

NE Model

San Luis Bay slip rate (mm/yr):

Center(s): 0.17, 0.23, 0.17

Body: 0.1 to 0.35


0

0.2

0.4

0.6

0.8

1

0.0 0.1 0.2 0.3 0.4 0.5

Cu

mu

lati

ve P

rob

ab

ilit

y

Slip Rate (m/ky)

Outward

SW Model

NE Model



Fault Model

Deformation Model

Rupture Model


Recurrence Model


Rupture Model

Describes the combinations of fault sections that may rupture together

Single faults may be involved in multiple Rupture Sources

The Rupture Sources can be characterized in the SSC as discrete “fault sources” with a specified geometry and logic tree branches and weights for slip rate, magnitude PDF, and recurrence rate


Example of Rupture Model

(Outward Vergent Fault Model)

Consider ways Los Osos fault may rupture with adjacent faults


Rupture Model OV-15


Rupture Model OV-12


Rupture Model OV-17


Rupture Model OV-17 (cont.)


Example: Rupture Model Table

OV model Scenario Primary fault Other faults Rupture

Category MFD Type

Slip

Sense

OV-01 Hosgri Central to MTJ Hosgri Central link Maximum ss

OV-02 Hosgri West to MTJ Hosgri West link Maximum ss

OV-03 Hosgri East to MTJ Hosgri East link Maximum ss

OV-04 South Hosgri to Piedras Blancas Hosgri Central Piedras Blancas Anticlinorium complex Maximum ss,rev

OV-05 Shoreline full Shoreline char Characteristic ss

OV-06 Shoreline and Hosgri north Shoreline Hosgri North link Maximum ss

OV-07 Shoreline and full Hosgri Shoreline Hosgri Central splay Maximum ss

OV-08 Shoreline N and San Luis Bay Shoreline San Luis Bay complex Characteristic ss,rev

OV-09 Shoreline N, Hosgri, and SLB Shoreline Hosgri, San Luis Bay complex Maximum ss,rev

OV-10 San Miguelito, and SWBZ Wilmar, SWBZ San Miguelito complex Maximum ss,rev

OV-11 San Luis Bay, Mallagh to Shoreline San Luis Bay char Characteristic rev

OV-12 SLB with Los Osos backthrust San Luis Bay Los Osos full splay Characteristic rev

OV-13 Oceano and SWBZ Oceano Foxen Canyon, Little Pine link Characteristic rev-obl

OV-14 Wilmar Avenue proper Wilmar Avenue char Characteristic rev

OV-15 Los Osos full Los Osos char Characteristic ss-obl

OV-16 Los Osos east and Edna Los Osos East Edna link Characteristic ss-obl

OV-17 Los Osos West and Hosgri Los Osos Hosgri complex Maximum ss-obl,ss


Rupture Model

Each Fault Model has ~15 distinct Rupture Sources that involve the key faults

The total fault slip rate is partitioned among the Rupture Sources. The partitioning is based on TI Team judgment about the relative likelihood of each rupture source

The methods to evaluate this forward model approach may include inspection of “participation MFDs”


Slip Rate Allocation


Example: Rupture Model Rate Allocation Target Percent Allocation Mean Fault Slip Rates (mm/yr)

OV model Hosgri Shoreline Los

Osos-

Irish Hills

San Luis

Bay Mean Rupture

Rate (mm/yr) Hosgri Shoreline

Los

Osos-

Irish Hills

San Luis

Bay

OV-01 41% 0.75 0.75

OV-02 38% 0.7 0.7

OV-03 8% 0.15 0.15

OV-04 11% 0.2 0.2

OV-05 31% 0.05 0.05

OV-06 19% 0.03 0.03

OV-07 1% 13% 0.02 0.02 0.02

OV-08 19% 18% 0.03 0.03 0.03

OV-09 19% 18% 0.03 0.03 0.03

OV-10 0.05

OV-11 35% 0.06 0.06

OV-12 19% 29% 0.05 0.05 0.05

OV-13 0.15

OV-14 0.16

OV-15 52% 0.14 0.14

OV-16 0.05

OV-17 30% 0.08 0.08

100% 100% 100% 100% Sum: 1.82 0.16 0.27 0.17

Target: 1.82 0.16 0.27 0.17

P[S] 100% 100% 100% 100%


Example Rupture Model Rate CDF

0

0.2

0.4

0.6

0.8

1

0.001 0.01 0.1 1 10

Cu

mu

lati

ve P

rob

ab

ilit

y

Slip Rate (mm/yr)

Hosgri Total


Example Rupture Model Rate CDF

0

0.2

0.4

0.6

0.8

1

0.001 0.01 0.1 1 10

Cu

mu

lati

ve P

rob

ab

ilit

y

Slip Rate (mm/yr)

Hosgri Total

OV-01

OV-02

OV-03

OV-04

OV-07

(41%)

(38%)

(8%)

(11%)

(1%)


Example Rupture Source Slip Rate Logic Trees

[0.101]

2.5 mm/yr

[0.244]

[0.244]

[0.101]

1.7 mm/yr

1.1 mm/yr

0.6 mm/yr

[0.309]

3.3 mm/yr

Branch Slip Rate

(mm/yr) Weight

OV-01 (41%)

0.11 0.248

0.63 0.504

1.65 0.248

OV-02 (38%)

0.10 0.248

0.59 0.504

1.54 0.248

OV-03 (8%)

0.02 0.248

0.13 0.504

0.33 0.248

OV-04 (11%)

0.03 0.248

0.17 0.504

0.43 0.248

OV-07 (1%)

0.003 0.248

0.02 0.504

0.04 0.248

Hosgri Rupture Sources Hosgri Fault Source


Rupture Model

Iteration with Hazard Analyst is expected, and basis for the rate allocation will be an important part of documentation.

Hazard sensitivity will be important to show the degree to which this approach is hazard sensitive and how it may compare to more traditional, epistemic-minded approaches.



Fault Model

Deformation Model

Rupture Model


Recurrence Model



Describes the size distribution of earthquakes (ruptures) that occur on the rupture sources.

Includes the functional form of the magnitude PDF

Includes the selection of magnitudes (Mmax, Mchar) that help define the magnitude PDF


Earthquake Rate Model – Two Rupture Model Categories

“Maximum” Rupture Sources “Characteristic” Rupture Sources

Rupture Model OV-15

Rupture Model OV-17


Magnitude PDF alternatives

Exponential

Characteristic (YC85)

0.0001

0.001

0.01

0.1

5 5.5 6 6.5 7 7.5 8

An

nu

al

Ra

te (

yr-

1)

Magnitude

GR

YC85


Magnitude PDF alternatives

Modified YC85 (WACY):

Exponential

Characteristic

Tail


Earthquake Rate Model: Logic Tree for Maximum-Type Sources

Magnitude PDF

[0.9]

Modified YC85

(WACY)

Exponential

(G-R)

[0.1]

Char Magnitude Max Magnitude

N/A Mmax 2

Mmax 3

Mmax 1

Mmax 2

Mmax 3

Mmax 1

Mchar 2

Mchar 3

Mchar 1


Earthquake Rate Model: Logic Tree for Characteristic-Type Sources

Magnitude PDF

[1.0]

Characteristic

(YC85)

Char Magnitude Max Magnitude

Mchar 2

Mchar 3

Mchar 1

Mchar 2 + 0.25

Mchar 3 + 0.25

Mchar 1 + 0.25


Earthquake Rate Model – Selection of Magnitudes

Mmax and Mchar estimates are based on length scales observed along the faults and estimated fault widths based on dip and seismogenic thickness

The length scales represent alternative hypotheses of “characteristic” earthquake sizes

Segmentation criteria are applied for the length scales following concepts such as:

Slip rate changes

Fault bends and stepovers

Changes in rake

Fault intersections


Earthquake Rate Model – Selection of Magnitudes (cont.)

Lacking fault-specific behavioral activity, and acknowledging that segmentation criteria are problematic to defend rigorously based on empirical data:

1. Adding Epistemic uncertainty casts a broad range

2. Aleatory variability is added through the rupture model concept

0

10

20

30

40

50

60

5.9 6.1 6.3 6.5 6.7 6.9 7.1 7.3 7.5 7.7 7.9 8.1 8.3 8.5

Co

un

t

Magnitude

OV Model, All Magnitudes, Branch Weighted

Mchar

Mmax


Earthquake Rate Model – Magnitude Distribution

0

10

20

30

40

50

60

5.9 6.1 6.3 6.5 6.7 6.9 7.1 7.3 7.5 7.7 7.9 8.1 8.3 8.5

Co

un

t

Magnitude

OV-Model, All Magnitudes, Branch Weighted

Mchar

Mmax

0

20

40

60

80

100

120

5.9 6.1 6.3 6.5 6.7 6.9 7.1 7.3 7.5 7.7 7.9 8.1 8.3 8.5

Co

un

t

Magnitude

OV-Model, All Magnitudes, Branch Weighted, Boxcar Smoothed

Mchar

Epistemic

+

Rupture Model

aleatory

+

Boxcar aleatory



Fault Model

Deformation Model

Rupture Model


Recurrence Model


Recurrence Model

Describes the rate of earthquakes expected over a specified time interval.

Typical PSHA assumes time independence (random in time)

Theory and paleoseismic study of crustal faults suggests earthquake recurrence is not random in time, but follows a renewal process


Recurrence Model (cont.)

Challenge is how to incorporate uncertainty in recurrence behavior for faults with little direct information on past events

Approach is to explore a lognormal distribution as a proxy functional form for faults that rupture according to a renewal process


Recurrence Model

Recurrence Coefficient of Variation (CV) is a key parameter

Considering Paleoseismic data from California and NZ, lower limit appears to be ~0.4; more common is ~0.6 to 0.8

Assuming lognormal functional form, CVs of 0.4 to 0.8 result in Poisson-equivalent rates of ~0.2 to 2.2

More Thursday!


Recurrence Model Logic Tree Recurrence

CV Renewal Process?

Form of Process

2.2 [0.5]

[0.4]

0.8

0.4

Poisson-Equivalent

Rate

Yes

No

[1.0]

[0]

Hosgri

[0.1]

Type of Fault

Exponential

Lognormal

[0.9]

0.6

[0.4]

[0.2]

[1.0]

1.0

0.2 [0.5]

1.8 [0.5]

0.4 [0.5]

1.4 [0.5]

0.6 [0.5]

1.0 [1.0]


Recurrence Model Logic Tree Recurrence

CV Renewal Process?

Form of Process

1.8 [0.5]

[0.3]

1.0

0.6

Poisson-Equivalent

Rate

Yes

[1.0]

Other

[0.4]

Type of Fault

Exponential

Lognormal

[0.6]

0.8

[0.3]

[0.2]

[1.0]

1.0

0.4 [0.5]

1.4 [0.5]

0.6 [0.5]

1.3 [0.5]

0.9 [0.5]

1.0 [1.0]

1.3 [0.5]

0.9 [0.5]

1.2

[0.2]


San Andreas and Other Fault Sources

San Andreas Fault Other 200-Mile Site Region Faults

Goal:

Capture maximum

contribution of SAF

Goals:

Complete SSC within 200-mi

Site Region

Confirm past results about contribution of Other faults


San Andreas Fault

Approach:

Approximate UCERF3 Characterization

Ten Sections in 200-mi

Matched a composite “Participation MFD”

Overestimates UCERF3 Solution


“Other” Faults

Other Faults within the 200-Mile Site Region

UCERF3.3, Fault model 3.2

Additional offshore faults from LTSP


Background source

Poorly resolved sources of seismicity

Undefined faults

Goals:

Complete SSC within 200-mi Site Region

Confirm past results about contribution of Background source


Background source

Approach:

Use historical seismicity rate, G-R distribution

Be conservative – include seismicity associated with on fault sources

Consider alternative characterizations:

UCERF2 gridded seismicity


PG&E catalog, areal zonation

Felser catalog, areal zonation


Background source


Mmax ~7.0

60

PG&E DCPP SSHAC Study

Diablo Canyon SSHAC Level 3 Study

Thank You

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