TAO Zhengru ( 陶正如 ) , Sendai, Japan 1

Transcription

1 TAO Zhengru ( 陶正如 ) Institute of Engineering Mechanics, China Earthquake Administration , Sendai, Japan 1

2 Contents Background Methodology Demonstration region Sichuan-Yunnan region

3 Data of paleo-eq Data of historical EQs Instrumental dataa of EQs Active fault data Tectonic data s G eophysical dataa Strong ground motion observatio Intensity survey n Potential source area delineation Seismic fortification level l Seismicity parameters of seismic zones Geometrical parameters in potential seismic source zones PSHA on sites Seismic zonation Attenuation ti relation 3

4 How to establish relationships for regions with few or without strong ground motion records? 4

5 In China, strong ground motion records are not enough now. Mapping method (Hu, 1980s): This method assumes that, for region A of enough acceleration observation data and a region B of few such data, earthquake pairs (M A, R A ; M B, R B ) exist in the intensity attenuation curves I A (M A, R A ) of region A and I B (M B, R B ) of region B, so that they give the same intensity I and ground motion Y. 5

6 Western US: I = M R.014 log( R + 10), σ = 0.74, R < 300 km 0.451M log( PGA) = M 1.73log[ R e ], σ = 0.40 Eastern China: I I a b = M = M lg( R + 4), lg( R + 9) σ = Western China: I a = M lg( R + 6), I b = M.943lg( R + 8) σ = 0.63 Eastern China: log( PGA) log( PGA ) Western China: a b = M 1.90 log[ R + = M log[ R e 0.381e log( PGA ) a = M log[ R +.018e log( PGA ) b = M log[ R e 0.45M 0.55M M 0.51 M ], ] ], ] σ = σ =

7 It is easier to obtain observed data in small earthquakes. More and more digital seismic stations are b ilt up. built China Earthquake Data Center 7

8 Methodology Source Fourier spectrum of ground motion FA(M 0, f, R) from a point source can be described as FA( ( M f, R ) = C S ( M, f ) G ( R ) D ( R, f ) A ( f ) P ( f ) I ( f ) 0, 0 where, C is proportion factor; S(M 0, f) is source spectrum for a specified seismic moment; G(R) ( ) is geometric spreading function; D(R, (, f) ) is anelastic attenuation function; A(f) is the amplification factor of near surface amplitude; P(f) is a high-cut filter that rapidly reduces amplitudes at high frequencies; I(f) is spectrum shape parameter, used to shape the spectrum to correspond to the particular ground-motion measure of interest. 8

9 C = R S( M = f FV θφ 3 4πR 0ρsβs 0, f ) M 0 f + f 1 0 = β( Δσ / M ) 6 1/ R R 1 R 1 G( R ) = R1 < R < R R1 1 R R R 1 R π fr DR (, f) = exp Qβ Q = Q f η 0 f P( f) = 1+ f max I ( f ) = ( π f ) z 8 1/ R No available values 9

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11 33 events, 50 stations, 59 records - CENC 11

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14 Inversion strategy μga is developed from GA, the main procedure is similar. In μga, there still retain selection and crossover, but no variation, at the same time, it retains the optimal individual. Objective function Fitness φ j = [ FA0 ( m, n ) FA j ( m, n )] F j = m e n βφ j 14

15 Inversion ranges σ (bars) Q o η R 1 (km) R (km) 1~00 00~700 0.~0.6 50~ ~150 Inversion results σ (bars) Q o η R 1 (km) R (km)

16 Time-domain simulation Combined with random phase spectra, the Fourier spectra can be transformed into the time domain. In time-domain i simulations, these time series are windowed d by f ( t ) = ( t ) t 1, 0 t t 1 1.0, t1 < t t c ( t t ) e, t < t where, t 1 and t are the starting point and finishing point of the stable section, c is the attenuation rate. ß An envelop curve on bedrock (Huo and Hu, 1991) is adopted. lg t1 = lg( R + 10) lgt = M w lg( R + 10) lg c = M w lg( R + 10) 16

17 The windowed time histories are transformed into the frequency domain. Complex spectra are transformed back to the time domain. Attenuation curves, which show mean levels, can be constructed after mean PGAs from 50 different random phase spectra are calculated. 17

18 Strong motion data from CSMNC events 1 stations Mw=5.0, 33 records Mw=6.0, 5 records Mw=7.0, 1 record 18

19 Empirical i relations Seven sets of relations-empirical Western China, Loess region of China Zoning map, Western China (001) ln( PGA) = M.846 ln( R e 0.451M ) ln( PGA) = M ln( R e 0.451M ) Model 1 (01) log 10 log M ( PGA ) = M M.0707 log ( R e ) ( PGA) = M XIAO Liang (010) log M ( PGA) = M 1.98 log log 10 ( R + 10 ( R e 0.55 e 0.451M ) 0.57M ) 19

20 YU Yanxiang and WANG Suyun (Western China, 006) log log ( PGA) ( PGA) = = M M log log ( R + ( R e e 0.406M 0.51M ) ) DING Boyang, TIAN Shaobo and LEI Zhongsheng (Loess region of China, 1991). Circle model, IR and IM l( ln( PGA ) = M.01 l( ln( R + 17) ( R + 17) ln( PGA) = M 1.50 ln( R + 17) DING Boyang, LEI Zhongsheng and FANG Shulan (Loess region of China, 1989). Circle model ln( PGA) = M ln R R 0

21 RUAN Aiguo and SUN Congshao, A study on attenuation law of seismic ground motion in the loess region of the Northwest China, 1989 ln( PGA ) = M ln R R + 36 ln( PGA ) = M ln R R

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25 Application in PSHA R M

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27 Conclusions In the demonstration region of this project, five regional parameters are inversed from small earthquakes by μga. Strong ground motion attenuation relationship is constructed from small earthquake records by China Earthquake Network. The relation is expressed as a D table and is adopted in PSHA. The seismic zoning map of the demonstration is compared with the national map to prove the validation. 7

28 Thanks 8