ATTENUATION RELATIONS OF STRONG ATTENUATION RELATIONS OF STRONG MOTION IN JAPAN MOTION IN JAPAN

USING SITE CLASSIFICATION BASED ON USING SITE CLASSIFICATION BASED ON PREDOMINANT PERIODPREDOMINANT PERIOD

Toshimasa TakahashiAkihiro AsanoTaketoshi Saiki

Hidenobu OkadaKojiro IrikuraJohn X. ZhaoJian Zhang

Hong K. ThioPaul G. Somerville

Yasuhiro FukushimaYoshimitsu Fukushima

2002 OECD/NEA Istanbul

Bridge between Seismology and Engineering

2003 IEAE Vienna

Semi-empirical Green’s function estimation of kinematical-base was applied to seismic evaluation of an existing nuclear facility.

Current from empirical estimation to physical modeling

2004 OECD/NEA Tsukuba

Empirical estimation based on observation can be still useful.

Estimation of strong ground motionDynamics

Theoretical

Dislocation in elastic medium simulating by

kinematics

1

10

100

1000

10000

1 10 100 1000’ f‘ w‚ ©‚ ç‚ Ì‹ ——£ (km)

�ő

å‰Á‘

¬“x(c

m/s

/s)

SoilRock

Rock� |ƒ Ð

Soil� {ƒ Ð

Semi-empirical Empirical

Large motion is synthesized using

small records.

Attenuation relation is determined by

regression analysis of SMDB.

2003 Bam, Iran earthquake

Closest distance from fault (km)

Peak

Gro

und

Acc

eler

atio

n (c

m/s

/s)

ModelingAcquisition of accurate parameters is required.Dynamic

Kinematics

Semi-empirical Green’s function

Attenuation relation

Reflecting characteristics of observed strong motion

Confirmation of derived result

Stress3-D geologyetc.Hybrid

Physical knowledgeEmpirical

Large amount of data exists already.

(NIED etc.)

Dataset used in the present studyDataset used in the present study

Total 4726 data (average of 2 horizontal) from 270 events

Functional form of the attenuation Functional form of the attenuation relationrelation used in the present studyused in the present study

The functional form of attenuation models

i – earthquake numberj – station numberM – magnitudex – source distance h – focal depthhc – depth constantδh – dummy variable

)iexp(dMc +ji,xji,r =

η + ξ + S +S +S +S +δ )h(he + ) log( -x b -Ma = (T)]Y[(log iji,kSIRhcji,ji,iji, r −

SR – reverse fault term for crustal eventsSI – interface event termSS – Slab event termξ – intra-event error η – inter-event errorSk – site term

Site class definitions used in the present Site class definitions used in the present study and the approximately study and the approximately

corresponding NEHRP site classes corresponding NEHRP site classes

Site class Site natural period (s)

Average shear-wave velocity

NEHRP class

SC I: (Rock/stiff soil) TG < 0.2s V30 > 600 m/s A+BSC II: ( Hard soil) 0.2s £ TG < 0.4s 300 m/s < V30 £ 600 m/s CSC III: (Medium soil) 0.4s £ TG < 0.6s 200 m/s < V30 £ 300 m/s DSC IV: (Soft soil) TG ³ 0.6s V30 £ 200 m/s E

Site natural period - four times the S wave travel time (1-D)

Mean H/V ratios and standard errors Mean H/V ratios and standard errors from a subset of Kfrom a subset of K--net stationsnet stations

Mean H/V ratios for four site classes

Individual site terms divided by SCI

Intra-event residuals distribution

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

ln(Vs/700)

Intr

a-ev

ent r

esid

uals

1.0s1.5s2.0s� üŒ ̀(1.0s)� üŒ ̀(1.5s)� üŒ (̀2.0s)

Intra-event residuals of hard rock site, Vs over 1000m/s

1

10

100

1000

0.01 0.1 1 10Period (s)

Pseu

do-V

eloc

ity (c

m/s

)

NS 1715 cm/s2

EW 849 cm/s2

Comparison between observed and predicted spectra of main shock on 23 October. NIG021, reverse type and 15.5km from 3rd GSI fault model

Comparison between observed and predicted spectra of main shock on 23 October. NIG019, reverse type and 7.6km from 3rd GSI fault model

NS 1146 cm/s2

EW 1309 cm/s2

1

10

100

1000

0.01 0.1 1 10Period (s)

Pseu

do-V

eloc

ity (c

m/s

)

J MA EW

Energy is released from surface.

Energy propagated in sediment.

Surface break Blind

conclusions

• Empirical attenuation relation can be used to evaluate strong motion level with known uncertainty and to confirm physical models.

• Predominant period corresponding to site geology such H/V is an effective classification parameter.

• Source type segregating improves prediction of strong ground motion.