ML041490247

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5/27/04, Diablo Canyon - Presentation Slides - Summary of Meeting with Diablo Canyon to Discuss Pg&E'S Response to the San Simeon Earthquake and Related Licensing Basis Issues
ML041490247
Person / Time
Site: Diablo Canyon  Pacific Gas & Electric icon.png
Issue date: 05/27/2004
From:
Pacific Gas & Electric Co
To:
Office of Nuclear Reactor Regulation
Shukla G, NRR/DLPM/LPDIV-2/415-8439
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ML041620324 List:
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Download: ML041490247 (65)
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I Diablo Canyon -San a Simeon Earthquake HI L.I - ..

Meleting May 27, 2004, Rockville, MD 1

Introduction

  • Decision not to shut down was appropriate
  • San Simeon excursion from DE vertical response spectra at top of containment was to be expected
  • DCPP DE licensing/design basis provides adequate margin for OBE function
  • San Simeon earthquake was consistent with the tectonic framework developed in the LTSP 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 2

Why DCPP Did Not Shutdown on December 22, 2003

  • Maximum ground acceleration (<0.05g) less than DE value of 0.2g
  • All plant systems continued to operate
  • Plant inspection (walkdown per CP M-4) did not identify any damage or system leakage 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 3

Subsequent Evaluation of No Shutdown Decision The San Simeon Earthquake was significantly less than the Design Earthquake and did not have the potential to cause damage to DCPP c5/2-6/2-IJU-1 r' Pr PIn nA Iarrlf

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San Simeon Free Field Response I

Spectra less than DE Mar 2.5 2.0 0) a, 1.5 0

Ir-0 1 .0

-a L.

cn 0.5 0.0 1.00 1 0.00 100.00 Frequency (Hz)

Free Field Ground Motion - Plant North-South Direction CO 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 5

OBE Exceedance Check icperRl6

  • The OBE is exceeded only when both of the following ground motion parameters are exceeded for one of the three directional components:
  • Response Spectrum Check
  • Damage Potential Check U 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 6 U

l l OBE Exceedance Check per RG 1.166 (cont.)

  • Response Spectrum Check Computed response spectrum for the recorded free field ground motion less than the OBE spectrum for frequencies < 10 Hz.

San Simeon Earthquake

-0.35 < 1.0 Design Earthquake

  • Therefore, there was no OBE exceedance.

I 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 7

OBE Exceedance Check 1-per RG 1.166 (cont.)

m Damage Potential Check Cumulative absolute velocity (CAV) less than 0.16 g-sec.

San Simeon Earthquake

= 0.51 < 1.0 RG 1.166 Limit

. Therefore, there was no OBE exceedance.

I 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 8

DE Response Spectra Excursion I

at Top of Containment (TOC) 0.5 0.4 0)

I-(U0.

M 0_

a) 0)

O U

E 0.2 L..

n U) 0.

C,)

0.1 0.0 &-

1.00 10.00 100.00 Frequency (Hz)

Top of Containment - Vertical Direction 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 9

I DE Response Spectra Excursion

-I at TOC (cont.)

N m DE spectra excursion at the top of the containment resulted from two factors:

  • Large structures were considered to be rigid vertically, consistent with industry practice at the time. Thus, vertical amplification was not considered in the DE analyses.
  • Top of Containment acted as a diaphragm to amplify vertical motion (with a resonant frequency of approx. 13 Hz). Vertical amplification was considered in the HE and LTSP analyses.

5/26/2004 7:31 PM May 27, 2004, Rockville, MD 10

DE Vertical Response Spectra I Com pared to HE at TOC 7.0 6.0

-5.0 0

AS 0 4.0 U

3'.0 Z 3

.- 0 0.

C) 2.0 nL 1.0 0.0 i-1.00 10.00 100.00 Frequency (Hz)

Top of Containment - Vertical Direction 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 11

I Conc usion o DE Vertica A_ I Response Spectra Excursion-TOC

  • Vertical peak frequency matched HE, as expected, confirming models used for HE and LTSP analyses
  • Amplitude of vertical acceleration was very low relative to HE
  • HE design ensures the protection of public health and safety 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 12

Seismic Licensing/Design qF~ Hsor/

  • Plant designed to DE/DDE (late '60s)
  • DE(vertical) = 2/3 x DE (horizontal) static
  • No vertical amplification
  • SC I SSCs were re-analyzed to Hosgri spectra (late '70s)
  • HE spectra include vertical amplification
  • Significant field modifications made 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 13

I lSeismic Licensing/Design I History (cont.)

U Independent Design Verification Program re-analyzed all SC I SSCs (1982-1984)

  • Updated models for key SC I structures
  • Additional field modifications made Long Term Seismic Program (1985-1991)
  • Served as a useful check on the adequacy of the seismic margins
  • Commitment to continue to evaluate new seismic information with respect to impact on DCPP 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 14

Purpose of Engineering Study Validate the adequacy of the DE/DDE seismic design of safety related structures, systems and components, considering amplified vertical ground motion 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 15

Study DE Differences from I Licensing Basis DE

'JR

  • Vertical Amplification

. RG 1.61 Damping Frequency up to 33 Hz I

5/26/2004 7:31 PM May 27, 2004, Rockville, MD 16

Engineering Study t Ove ra I co pe mStructures

  • Systems

. Piping

  • Electrical Raceways

. Components 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 17

Engineering Study Scope Selection SSCs in rigid areas (no amplification)

. Reactor

  • Items supported by crane wall
  • Containment cylinder below 140'
  • ESF pump rooms (including AFW)

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I_ I- Engineering Study

-Scope Sel ection (cont.)

  • SSCs on grade (no amplification)

Diesel generators

. ASW pumps/piping

  • CCW heat exchangers mEmergency water tanks 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 19

Engineering Study

.1

_ Scope Selection (cont.)

. SSCs on flexible slabs, but shake table tested

  • 480v switchgear

. Batteries/inverters

  • 4kv switchgear
  • Cable spreading room equipment
  • Control room equipment I 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 20

Engineering Study eScope Selection (cont.)

mTop of Containment - Studied

  • 140' Auxiliary Bldg - Studied d slabs 5 and 11 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 21

Engineering Study Scope 777% L Equipment LI ~

. Electrical

  • Battery chargers, vital MCCs, 4kV switchgear, relays, fuses, etc.

n Instruments & Controls

  • Switches, transmitters, mechanical panels, main control boards, air regulators, cabinets, etc.

. Mechanical

  • Pumps/motors, heat exchangers, containment fan coolers, etc.
  • HVAC UFans/motors, thermostats, condensers, etc.

5/26/2004 17:31 PM May 27, 2004, Rockville, MD 22

Engineering Study Assumptions!

-Methodologies - Equipment

- Equipment qualification for DCPP was done by:

. Shake table testing,

. Analysis, or

. Shake table testing and Analysis 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 23

Engineering Study Assumptions/

Methodologies - Equipment Qualified by Shake Table Testing

  • To meet OBE provisions of IEEE-344, equipment was tested/qualified to 50%-66% of the HE
  • NSSS components by Westinghouse
  • To meet SSE provisions of IEEE-344, equipment tested/qualified to HE C/lIoT I~AnnA 7.01 rltA RA 7 MAMA D1-7^;IIA RAM A may L/I /-UUt, KULKV111t, VIU /If ble-612-UU-1 /.jjL PI-I

Engineering Study Assumptions/

Methodologies - Equipment Qualified by I Shake Table Testing (cont.)

0.75 .

On o 0.50 a) a)

I-C.)

L..

<v 0.25 0e Co 0.00 L-1.000 10.000 100.000 Frequency (Hz)

Free Field Input Response Spectra - Vertical Direction C oL-Ij&

5/26/2004 7:31 PM May 27, 2004, Rockville, MD 25

Engineering Study Assumptions/

Methodologies -

Equipment Qualified by Analysis Evaluation for Slabs 5 & 11

  • Evaluated for HE
  • Compared demand vertical amplified spectra at 2% damping (for DE equipment) with HE vertical (4% damping)
  • Compared allowable stress for HE vs. DE to identify the governing case 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 26

Engineering Study Assumptions/

Methodologies

. Equipment Qualified by Analysis (cont.)

Comparison of Slab 11 Node 85 Vertical Spoctra 112 Hosgrl Earthquake vs. Amplified Design Earthquake 3.0000- -. - --

-__ 1Q2 HE (Newmark, 4% Damping)

-E2%Damping) 2.5000 *.*---4..

2.0000 --  ;- -- - _- --

0*

1.0000 _ _ _ _ - - - - -

0.0000 _____- -- iL:J"zziii 1.000 1.00 10.00 100.00 1000.00 Frequency (Hz)l 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 27

Engineering Study Assumptions/

Methodologies I Equipment Qualified by Analysis (cont.)

Comparison of Slab 5 Node 200 Vertical Spectra 1/2 Hosgrl Earthquake vs. Amplified Design Earthquake

_ I I LL ILII Y.UUU

_ _ _*DE (2% Damping) 8.000

_-112 HE (Newmark, 4% Damping) 7.000 8.000 C

0 5.000 1!

4.000

=== X- - . __ _ _ _ 1 1 - -

3.000 2.000 1.000 0.000 1.1000 10.000 100.000 1000.000 Frequency (Hz) 1& 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 28

Engineering Study Results Equipment Qualified by Analysis

  • The HE vertical demand load (spectra) governs over study DE

. The vertical seismic spectra for HE is > 2 x Study DE (amplified vertical spectra)

  • The HE stress allowables are < 2 x DE stress allowables
  • Based on the review of approximately 40 calculations, it was judged that amplified vertical DE would not have an adverse impact on the conclusions of the calculation, primarily due to significantly higher HE loads as well as high horizontal loads 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 29

Engineering Study Conclusions -

Equipment

  • Shake table tested equipment is qualified for DE with vertical amplification
  • Vertical component of seismic is a relatively small portion of the demand load on equipment and is not a governing case for qualification by analysis 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 30

Engineering Study Scope -

Piping System s P

Analyses for 5 piping systems rigidly connected to structures addressed in study mTwo Containment Spray header piping systems connected to the containment dome structure mTwo analyses in Auxiliary Building connected to "Slab 11" (Elev. 140 ft.)

. One analysis in Auxiliary Building B. connected to "Slab 5" (Elev. 140 ft.)

5/26/2004 7:31 PM May 27, 2004, Rockville, MD 31

Engineering Study Assumptions!

-774i- I L

Methodolog ies - Piping Systems

. The piping stress analysis study used the following parameters:

Pipingi Study Licensing Basis DE Vertical Damping 1 0/0 0.5 0/0 DDE Vertical 2 O/0 0.5 0/0 Damping DE / DDE Horizontal 0.5 0/0 0.5 0/0 Damping DE / DDE Modal 33 Hz. 20 Hz.

Freq. Cut off I : May 27, 2004, Rockville, MD 32 5/26/2004 7:31 PM

Engineering Study Results FPiping Systems Existing Study Allowable Study Analysis # Seismic (Licensing) (psi) (psi)

Stress Ratio Case (psi) 2-112 DE 13676 13680 18000 0.76 (Slab 11)

DDE 21903 27000 21965 0.81 8-118 14861 14977 22320 0.67 (Slab 11) DE DDE 22413 22496 33480 0.67 8-301 DE 6112 9569 22440 0.43 (Slab 5)

DDE 10824 10969 33660 0.33 5-106 DE 17518 17988 22320 0.81 (Ct. Dome)

DDE 32675 24774 33480 0.74 t '

5-107 DE 16085 16552 22320 0.74 (Ct. Dome)

DDE 30310 24806 33480 0.74

.Ii I IMI

. i .

5/26/2004 7:31 PM May 27, 2004, Rockville, MD 33

Engineering Study Conclusions Piping Systems

  • The piping stresses remained well within the DE/DDE code design allowables for the study case (with vertical DE/DDE spectra modified to include amplification)
  • Pipe support loads remained within design allowables 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 34

r-- --

Engineering Study Scope i

-Structures

  • Containment Structure (Exterior Shell) mAuxiliary Building Roof Slabs at Elev.

140 ft.

. Slab No. 5 (Areas I & K)

. Slab No. 11(Area GE) 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 35

Engineering Study Assumptions!

- I

  • Methodologies Structures

- Iv.

Study Licensing Basis Vertical Input Dynamic Rigid, no Motion amplification amplification Vertical DE/DDE Response spectral Static Load Application analysis Damping Ratios Containment Containment (for vertical DE = 4% DE = 2%

analyses) DDE = 7% DDE = 5%

Auxiliary Building Auxiliary Building DE = 4% DE = 5%

DDE = 7% DDE = 5%

1: 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 36

--1 Engineering Study Assumptions/

Methodologies - Structures (cont.)

Study Licensing Basis Foundation Fixed base Soil structure Conditions (vertical) interaction (horizontal only)

Spatial SRSS combination Absolute sum Combination of vertical and two combination of horizontal vertical and one horizontal Vertical Response Per RG 1.122 None Spectra 33 Hz. cut-off Development 15%

broadening Frequency Cut-off Frequency > 33 Hz. Frequency > 20 Hz.

I%  ; 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 37

Engineering Study Results -

Containment Structure I

bL E Evaluated for the following loads (1) 1.05 Dead + 1.5 Pressure + Thermal (2) 1.05 Dead + 1.25 Pressure + Thermal + 1.25 DE (3) 1.05 Dead + 1.00 Pressure + Thermal + 1.00 DDE (4) 1.05 Dead + 1.00 Pressure + Thermal + 1.00 HE

  • Interaction ratios (demand/capacity) for center of dome for critical structural components:

Component Load Case Design Basis Study Rebar (1) 0.75 (2) 0.68 0.68 (3) 0.56 0.57 (4) 0.53 Liner Plate (1) 0.30 (2) 0.26 0.27 (3) 0.22 0.23 I (4) 0.23 F79. 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 38

Engineering Study Conclusion 71-

-Containment Structure

  • The Design Basis evaluation demonstrated that the design is governed by Load Case (1) due to the large multiplier on the internal pressure mAdding vertical amplification does not impact this conclusion 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 39

Engineering Study Results -

I -Auxiliary Building Slab Nos. 5 & 11 m Evaluated for the following load cases:

(1) Dead + Live + DE (Working Stress Design)

(2) Dead + Live + DDE (Ultimate Strength Design)

(3) Dead + Live + HE (Ultimate Strength Design)

. Load Case (1) governs I795/26/2004 7:31 PM May 27, 2004, Rockville, MD 40

Engineering Study Results I

.Auxiliary Building Slab 5 & 11 (cont.)

- Interaction ratios (demand/capacity) and seismic margin factors for critical region of slab no. 5:

Interaction Ratio Seismic Margin Factor -

Load Component Design Basis Study Study Moment 0.92 0.93 2.8 Shear 0.92 0.93 2.7 Interaction ratios and seismic margin factors for critical region of slab no. 11:

Interaction Ratio Seismic Margin Factor -

Load Component Design Basis Study Study Moment 0.89 0.90 3.2 Shear 0.93 0.94 2.2 IM 1 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 41

Engineering Study Conclusion Auxiliary Building Slab Nos. 5 & 11

  • The Design Basis evaluation is governed by Load Case (1) due to the acceptance criteria based on working stress design and the dominance of dead and live loads
  • The results of the Engineering Study indicate that the slabs satisfy DE code allowables when the amplification of vertical seismic motion is considered F i 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 42

Engineering Study Conclusion -

Structures Containment Structure and Auxiliary Building slabs at elev. 140' satisfy DE/DDE code allowables when the amplification of vertical seismic motion is considered 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 43

Engineering Study Scope -

Other Components i

  • Plant Vent
  • HVAC Ducts and Supports
  • Electrical Raceways and Supports Ia 5/26/2004 7:31 PM May 27, 2004, Roc .kville, MD 44

Engineering Study Assumptions!

-I~ Methodologies - Plant Vent Study Licensing Basis Vertical Input Dynamic Rigid, no Motion amplification amplification Damping Ratios DE = 2% DE = 2%

(for vertical DDE = 4% DDE = 4%

analyses)

Spatial SRSS combination Absolute sum Combination of vertical and two combination of horizontal vertical and one horizontal Frequency Cut-off Frequency > 33 Hz. Frequency > 20 Hz.

'I15/26/2004 7:31 PM May 27, 2004, Rockville, MD 45

Engineering Study Results -

Pant Vent

  • Evaluated for the following load cases:

(1) Dead + Live + Operating Pressure + DE (Working Stress Design)

(2) Dead + Live + Accident Pressure + DDE (Plastic Design)

(3) Dead + Live + Accident Pressure + HE (Plastic Design)

. Results:

  • The design basis evaluation of critical components (support frames and anchorage to Containment Structure) enveloped all load cases and compared them to working stress design allowables.
  • Study DE acceleration (0.48g) is less than HE (1.5g).

9 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 46

Engineering Study Conclusions - Plant Vent The Engineering Study demonstrates that the Plant Vent satisfies DE/DDE code allowables when the amplification of vertical seismic motion is considered 5/26/2004 7:31 PM May 27, 2004, Rockville, MD I.7

Engineering Study Assumptions/

Methodologies Kr HVAC and Electrical Raceways

-_I it Study Licensing Basis Vertical Input Motion Dynamic amplification Rigid, no amplification Damping Ratios HVAC HVAC (for vertical analyses) DDE = 4% DDE = 2%

Electrical Raceways Electrical Raceways DDE = 7% DDE = 7%

Spatial Combination HVAC HVAC SRSS combination of Absolute sum comb. of vertical and two horiz. vertical and one horiz.

Electrical Raceways Electrical Raceways Same as Licensing Absolute sum comb. of Basis vertical and one horiz.

Frequency Cut-off Frequency > 33 Hz. Frequency > 20 Hz.

I&i 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 48

Engineering Study Results HVAC and Electrical Raceways

  • Engineering Study addressed raceways and HVAC duct supports
  • Supports evaluated for following load cases:

(1) Dead + DDE (2) Dead + HE

  • Acceptance criteria is identical for both load cases
  • DDE loads increase due to vertical amplification, but since Engineering Study uses same damping ratios for DDE as are used for HE, load case (2)

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Engineering Study Conclusions -

HVAC and Electrical Raceways The Engineering Study demonstrates that HVAC and electrical raceways satisfy the licensing basis acceptance criteria when amplification of vertical seismic input motion is considered 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 50

Engineering Study to Confirm Adequate Margin Overall Conclusions When vertical amplification is considered, the studied SSCs meet all acceptance criteria:

  • All equipment tested by shake-table is qualified
  • For equipment qualified by analysis, the vertical seismic component is not significant
  • Piping and supports meet DE/DDE code allowables
  • Containment structure and two auxiliary building slabs meet DE/DDE code allowables
  • Plant vent meets DE/DDE code allowables
  • HVAC and electrical raceways meet acceptance criteria 5/26/2004 7:31 PM May. 27,. 2004,. Rockville,. MD 51

`7 7 %

, Conclusions U M- Decision not to shut down was appropriate

  • San Simeon Earthquake ground motion was much less than OBE/DE
  • No damage to DCPP structures, systems and components m San Simeon excursion above DE vertical response spectra at top of containment was to be expected
  • DCPP DE licensing/design basis provides adequate margin for OBE function ir 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 52

Earthquakes Considered Post F_

I 7 EMMML -

LTSP Earthquake Magnitude Style of Faulting 1989 Loma Prieta, CA 7.1 Complex buried strike-slip/Oblique 1992 Landers, CA 7.3 Complex strike-slip 1994 Northridge, CA 6.8 Buried complex thrust 1995 Kobe, Japan 6.9 Complex strike-slip 1999 Kocaeli, Turkey 7.4 Simple strike-slip 1999 Duzce, Turkey 7.1 Simple strike-slip 1999 Chi-Chi, Taiwan 7.6 Complex reverse 1999 Hector Mine, CA 7.1 Complex strike-slip 2001 Kunlun, Tibet 8.1 Complex strike-slip/normal/reverse 2002 Denali, Alaska 7.9 Complex strike-slip/reverse/normal 103 San Simeon, CA I 6.5 I Complex buried reverse 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 53

LTSP Source Characteristics and Ground Motion Attenuation

  • Source zone configurations and geometries
  • Probability of activity assigned to faults and source zones
  • Appropriateness of attenuation relationships to estimate ground motions
  • Considerations given to thrust faulting on F7q Hosgri fault 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 54

Geosciences Summary

  • . Maximum magnitudes assigned to earthquake sources
  • Rupture Dimension of San Simeon: 35km x 14 km
  • M6.5 of San Simeon earthquake is smaller than the expected magnitude based on LTSP M(Length) and M(area) models for reverse faults (M6.8-M7.2)
  • No need to increase maximum magnitudes Source zone configurations and geometries
  • San Simeon earthquake hypocentral depth of 11-12 km is consistent with through-going high angle fault model used in LTSP.
  • No need to revise source geometries based on San Simeon earthquake
  • Additional work on depth distributions needed to reach WE consensus with USGS researchers 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 55

-121.2 -121.1 -121 -120.9 -120.8 35.8 35.8 I

35.7 35.7 San Simeon 35.6 35.6 Aftershocks 35,5 35.5 121.2 -121.1 -121 -120.9 -120.8 MAGNITUDES 12=2212003-/1 8/2004 1222J2003W1 212004

  • 3.0-3.99 . 0.0-0.96

. 1.0-1.99

  • 4.0-4.99 0 2.0-299
  • 3.0-3.99 C(gi
  • 4.0-4.99 5/26/2004 7:31 PM May d/, zUU4, RocKviIle, ML) 56

I Oceanic Nacimiento B BI E

D1-1 1

0 5 10 15 Distance (km) 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 57

Geosciences Summary

. Occurrence of single earthquake sequence does not have a significant effect on recurrence rates (for PSHA)

  • Probability of activity assigned to faults and source zones
  • Oceanic fault considered active reverse fault in LTSP (and by CDMG)
  • Occurrence of San Simeon earthquake does not affect probability of activity assessments F:9 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 58

121 I

35 (from PGE LTSP 1988, Fig 2-8)

Sal- Si..I.o.- PG&L Coa 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 59

I From Jennings, 1994 Figure 2-1. Active faults in south-central California (from Jennings, 1994).

co6 i 1`1it 5/26/2004 7:31 PM San Simoon PG&[ 60

Geosciences Summary Appropriateness of attenuation relationships to estimate ground motions

  • Free-field ground motions recorded at DCPP from the San Simeon earthquake were much smaller than expected
  • Lower ground motions may reflect effects of hard rock conditions at DCPP (as compared to generic "rock" used in ground motion models)
  • Ongoing NGA project is developing new attenuation relations that incorporates new strong motion data from recent large magnitude earthquakes 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 61

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,it;1,081; 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 62

r~ Geosciences Summary Considerations given to thrust faulting on Hosgri fault

  • LTSP considered alternative style-of-faulting for Hosgri
  • 65% strike-slip
  • 30% reverse/oblique
  • 5/ reverse
  • (NRC combined reverse/oblique and reverse)
  • Focal mechanisms from recent seismicity show mainly strike-slip mechanisms along the Hosgri fault
  • No basis for increasing weight of reverse style-of-faulting on the Hosgri 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 63

Focal mechanisms 1987-1997 30 121 30 120 Ragged oint eartliqua~k 30 -

20 km - '-

35c-NAx v1 F it-IIrt- 1 1

i~ Fuure Actions

  • Geoscience Reports

. Supplemental Report mFinal Report 5/26/2004 7:31 PM May 27, 2004, Rockville, MD 65

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