Seismology based strong ground motion attenuation relationship for

national zoning map

TAO Zhengru

Institute of Engineering Mechanics, China Earthquake Administration

2011.11.25-11.30, HIT·Harbin

1

• Empirical method• For regions with enough data (e.g. western US and Japan)• For most countries or regions?

• More and more strong motion observationinstruments are installed…

• Space• Time

2

Background

3

National strong motion observation network system (Li et al., 2008)

How to establish relationships for regions with few or without strong

ground motion records?

Background• In China, strong ground motion records

are not enough now.• Mapping method (Hu, 1980s):

This method assumes that, for region A of enoughacceleration observation data and a region B of few suchdata, earthquake pairs (MA, RA; MB, RB) exist in theintensity attenuation curves IA(MA, RA) of region A andIB(MB, RB) of region B, so that they give the sameintensity I and ground motion Y.

Region A:

Region B:

]0461log[7231566.0297.1)log(5.0 AM

AAA eRMY

)10log(014.200659.0500.1514.0 AAAA RRMI

)24lg(136.44461019.5 BBB RMI

]700.1log[902.1548.0027.2)log(425.0 BM

BBB eRMY

China Earthquake Data Center

FrameworkTarget region

Data from digital seismic network

Data from strong motion networkEmpirical relations

∆σ, Q0 and η

µGA

Strong ground motion attenuation

relationship

Stochastic Method

Comparison

Methodology

8

Assuming the accelerations, on the far-field and an elas ichalf space, are band-limited, finite-duration, white Gaussiannoise, and based on Brune ω2 model, he source Fourierspectra FA(M0, f, R) on a site can be described as

fIfPfAfRDRGfMSCRfMFA ,,,, 00

where, C is proportion factor; S(M0, f) is source spectrum for a specifiedseismic moment; G(R) is geometric spreading function; D(R, f) isanelastic attenuation function; A(f) is the amplification factor of nearsurface amplitude; P(f) is a high-cut filter that rapidly reduces amplitudesat high frequencies; I(f) is spectrum shape parameter, used to shape thespectrum to correspond to the particular ground-motion measure ofinterest.

130130

70

1

1307070

1

701

)(

RR

R

RR

RG

( , ) expfRD R f

Q

0Q Q f

1/28

max

( ) 1 fP ff

( ) (2 )zI f f

6 1/30 04 9 10 ( / )f M

9

2

0

00

1

),(

ff

MfMS

304 ssRFVR

C

Following Hanks (1979), we estimate the arms using Parseval’s theorem. The estimation is valid for a time window equal to the faulting duration Tdbeginning with the direct shear arrival; in Hanks (1979), Td =1/fo. In terms of spectral parameters, Ω0 and fo, the result is

1 2

0ms

d

maT

According to the relation between Fourier spectrum and power spectrum and the definition of spectral moment, the latter can be calculated by the following numerical integration,

22 ( )kkm f FA f df

0

dfefdffFAmf

f

Q

fRf

f

max

0

max

0

2

200

2

0 )2(2)(2

The peak factor γm, which describes the ratio of peak to rms motion, is calculated by the following numerical integration,

PGA= γm * arms

0

2exp112 dzz eNm

2140

2

mmm

NN

e

z TfN ezez ,, 2 21022

1 mmf z

21242

1 mmfe

11

CASE OF SENDAI AREA

12

13

1996.1-2011.4

12 F-net stations632 earthquakes

14

Distribution of hypocentral distance with Mw

15

Distribution of focal depth with Mw

6

Δσ Qo η

40~100 bars 100~300 0.6~1

Δσ Qo η

45.17 bars 124.91 0.61

Inversion ranges

Inversion results

17

PGA attenuation relations Strong motion data from K-NET

• 4256 strong motion data (Mw≥4.5 and focal depth≤30 km)

• 88 K-NET bedrock stations (TG<0.2s)

Empirical relations• Tatsuo Kanno, et al., (2006)

• Hongjun Si, et al., (2000)

• Yoshimitsu Fukushima, et al., (1990)

19

370260)1000550log(00310560)log( 5.0 wMw XXMPGA

30.10034.0)10032.0(log41.0)log( 41.010 RRMPGA sM

s

eqeqw XXDMPGA 0030log28012000390580)log(

21

N

i valuepredicted

valueobserved

Nresidual

110 )(log

1

PGA relations Mw=5 Mw=6 Mw=7

Fukushima (1990) -0 2970 -0.0613 0.0887

Kanno (2006) -0.4168 -0.3503 -0.3591

Si(2000), D=10 -0 2003 -0.1698 -0.2407

Si(2000), D=20 -0 2393 -0.2088 -0.2797

Si(2000), D=30 -0 2783 -0.2478 -0.3187

This study -0 5093 -0.3894 -0.2520

22

Case of Southwestern China

23

Yunnan Province

2001-2007

26 seismic stations162 earthquakes863 records

Sichuan Province

2001-2007

29 seismic stations48 earthquakes147 records

Distribution of hypocentral distance with Mw

24

25

Distribution of focal depth with Mw

Inversion ranges (Ye, 2001; Su, 2009)

Δσ Qo η

40~200 bars 90~400 0.15~0.8

Inversion results

Δσ Qo η

105.14 bars 92.41 0.21

PGA attenuation relations

27

Strong ground motion data

• 66 strong motion data (Mw≥4.5 and D≤30 km)• 36 strong motion station (bedrock)

28

Empirical relations• Yanxiang YU and Suyun WANG (Western China, 2006)

• Jiancheng LEI, et al. (Sichuan basin, 2007)

• Jiancheng LEI, et al. (southwestern region, 2007)

• Jianwen CUI, et a . (Yunnan 2006)

• Jianguang XIANG and Dong GAO (Yunnan, 1992)

29

)018.2(log954.1532.0206.2)(log 06.0

00sM

ss eRMMPGA

)5292.2(log1920.20665.0380713349.0)(log 333.0

02

10sM

ss eRMMPGA

)340.0(log441.1501.00101)(log521.0

010sM

ss eRMMPGA

)0617.1(log8499.10715.04539.15206.1)(log385.0

0

2

10sM

ss eRMMPGA

)8691.0(log639210845.05408.182441)(log38.0

0

2

10sM

ss eRMMPGA

)4022.0(log3846.10812.04860.11376.2)(log56.0

10

2

0sM

ss eRMMPGA

)13(log)0889.07317.2(2881.05549.3)(log 1010 RMMPGA ss

5785.15275.0)15(071291 RePGA sM

30

N

i valuepredicted

valueobserved

Nresidual

110 )(log

1

31

Relations Mw =5 Mw =6 Mw =7

Xiang, et al. (1992) -0.1524 -0 0895 0.1381

Cui, et al. (2006) 0 3242 0.1188 0 2376

Yu, et al. (2006)-0 0907 -0 2262 -0.1191

0.1957 0 0306 0 0524

Lei, et al. (2007)0 2543 -0 0437 0.1091 0.4792 0.1359 0 2108

Lei, et al. (2007)0 2997 0 0083 0.1130

0 3395 0 0646 0.1222

This study 0.2092 0.1053 -0.1217

The endThanks

32