Revised Probabilistic Seismic Hazard Map of Turkey and Its Implications in Seismic Design

Transcription

1 New Generation Seismic Codes and New Technologies in Earthquake Engineering Februray 2015 Ankara, Turkey Revised Probabilistic Seismic Hazard Map of Turkey and Its Implications in Seismic Design Boğaziçi University Kandilli Observatory and Earthquake Research Institute Çengelköy İstanbul

2 Outline Revised Turkish seismic hazard map Observations for design ground-motion definition Comparisons of old and new design spectral ordinates Damping scaling factors Long-period spectral corner period (T L ) Vertical-to-horizontal spectral ratios Near-fault effects

3 Revision of Turkish seismic hazard map project S. Akkar, T. Eroğlu Azak, T. Çan, U. Çeken, M.B. Demircioğlu, T. Duman, S. Ergintav, T.F. Kadirioğlu, D. Kalafat, Ö. Kale, R.F. Kartal, T. Kılıç, S. Özalp, K. Şeşetyan, S. Tekin, A. Yakut, M.T. Yılmaz, M. Utkucu, Ö. Zülfikar A multi-institutional project funded by the Disaster and Emergency Management Presidency (AFAD) and Turkish Catastrophe Insurance Pool (TCIP)

4 Revise seismic hazard maps at the national level based on the recent state-of-the-art developments and findings in this field (Turkey and worldwide) Provide spectral ordinates (PGA, SA at T = 0.2s and 1.0s) for return periods of 43 years (69%/50 years), 72 years (50%/50 years), 475 years (10%/50 years) and 2475 years (2%/50 years) for their use in the definition of updated code spectra and insurance premiums Provide additional information on vertical-tohorizontal spectral ordinate ratios, long-period corner period, damping scaling factors and forward directivity effects

5 Earthquake Catalog Compilation of instrumental catalog (12674 earthquakes) is based on national / international catalogs Historical catalog (512 earthquakes) is compiled from the recently finished GEM-Historical Catalog, SHARE and EMME projects Minimum magnitude bound is 4 Homogenized magnitudes (M w ) through empirical conversion equations developed from the compiled catalog Declustering and completness analyses

6 Seismic Sources Active faults in mainland Turkey Area sources in and around mainland Turkey 553 fault segments Active faults around mainland Turkey 200 km buffer zone Literature review, already finished national and international projects, earthquake catalogs, GIS maps to determine active fault segments, area sources, maximum magnitudes, slip rates, geometries, style-of-faulting, depth distribution etc.

7 SOURCE CHARACTERIZATION AREA SOURCE (AS) FAULT + BACKGROUND (FS)

8 GROUND-MOTION CHARACTERIZATION SHALLOW ACTIVE CRUSTAL SEISMICITY INTERFACE AND INSLAB SEISMICITY Akkar et al. (2014) 0.3 Akkar and Çağnan (2014) 0.3 Chiou and Youngs (2008) 0.3 Zhao et al. (2006) 0.1 Zhao et al. (2006) 0.4 Lin and Lee (2008) 0.2 Atkinson and Boore (2003) 0.2 Youngs et al. (2006) 0.2

9 Compute hazard for each seismic source model considering the GMPEs and seismic source logic-trees. Combine the results with alternative source model weights SA at PGA 1.0s 0.2s 475 yrs yrs (10% in in yrs)

10 Current Turkish design spectrum Proposed Turkish design spectrum Site Classes T A T B Design: 10% probability of exceedance in 50 years (T R = 475 yrs) SA = A 0 S(T) = 8s Earthquake Zone For T R = 475 yrs (10%/50) Increase by 50% for T R = 2475 yrs (2%/50). Reduce by 50% for T R = 72 yrs (50%/50) Immediate Occupancy, Life Safety and Collapse Prevention performances: 50% to 2% probability of exceedance in 50 years

11 Comparisons of design ground motion TEC %/50yrs TEC %/50yrs TEC07-2%/50yrs 120 TEC07-2%/50yrs New New New Map Map Map %/50yrs New New Map Map %/50yrs New Map New New Map Map - - 2%/50yrs 2%/50yrs 100 New New Map Map - - 2%/50yrs demands Spectral shape provided in TEC Spectral Acceleration (g) Spectral Acceleration (g) Ataşehir - İstanbul Bursa İzmir Period Period (s) (s) (s) Spectral Displacement (cm) Spectral Displacement (cm) Ataşehir - İstanbul Bursa İzmir New maps generally yield smaller seismic results in large differences in the longperiod Period (s) (s) range Period (s) (s) Ad-hoc 1.5 Maslak factor -Eskişehir İstanbul Antalya to scale 2475-year Maslak -Eskişehir İstanbul Antalya TEC07 TEC %/50yrs TEC07 10%/50yrs TEC %/50yrs TEC TEC TEC07-2%/50yrs 120 spectrum from New Map year spectrum New Map -- is not TEC07-2%/50yrs New Map - 10%/50yrs New New Map Map %/50yrs New Map - 10%/50yrs New New Map Map %/50yrs 2%/50yrs realistic. Scaling between 2475-year and year spectra depends on the seismic Spectral Acceleration (g) (g) Spectral Acceleration (g) Spectral Displacement (cm) Spectral Displacement (cm) activity of the region Period Period (s) (s) (s)

12 Spectral ratio distribution between 2475year and 475-year spectral ordinates TR475 /TR475 PGA TR2475 /TR Spectral ratio between 2475-year and 475-year spectral ordinates varies between 1.6 and 3.5. It increases towards seismically less active regions

13 For collapse prevention performance assessment: Buildings located in highly seismic regions will be subjected to lesser seismic demands than those located in low-seismicity regions with respect to their design strength capacities. Dependency of SA 2475 /SA 475 on seismic activity may indicate Performance assessment for collapse prevention: [(Seismic Demand) 2475 /(Seismic Demand) 475 ] high seismicity < [(Seismic Demand) 2475 /(Seismic Demand) 475 ] low seismicity

14 Moreover The exceedance probabilities of ground motions (spectral accelerations) do not consider the uncertainties in the seismic behavior of structures (structural capacity). Thus, the next step in code-based work should be the definition of design ground motions for a uniform risk according to the performance objective: risk-targeted adjustment of ground motions f capacity (c) = capacity probability density function P(SA > c) = annual probability of SA > c Risk Fragility Hazard

15 Damping scaling factors (DSFs) currently expressed as predictive models in terms of magnitude, source-to-site distance, site conditions, faulting style etc) Requires simplifications for their effective use in the codes

16 DSFs for x = 1% for different magnitudes and distances DSF M7.5, M6.5, M5.5, V S30 = 255 m/s, SS, x = 1% Period (s) 7.5, 5.5, 6.5, 1, , 5.5, 6.5, 5, , 6.5, 5.5, 10, , 5.5, 6.5, 20, , 5.5, 6.5, 30, , 6.5, 5.5, 40, , 5.5, 6.5, 50, , 5.5, 6.5, 75, , 6.5, 5.5, 100, 255 No significant differences in DSF variation for different distances Magnitude dependency of DSFs can also be averaged out for their implementation to the codes DSF Period (s) M5.5 M6.5 M7.5 Average x = 1%

17 Period (s) x = 1% x = 3% x = 7% x = 10% x = 20% x = 30% x = 50% DSF Period (s) x = 1% x = 3% x = 7% x = 10% x = 20% x = 30% x = 50% 20% 30% 50% 10% 7% 3% 1%

18 Horizontal-to-vertical spectrum ratio Vertical spectrum should be consistent with the horizontal spectrum Develop the vertical spectrum from the already defined horizontal spectrum Behavior of vertical spectrum is different than the horizontal spectrum: The vertical constant acceleration plateau is shorter than its horizontal counterpart Short-period corner period as well as the decaying branch is sensitive to the variations in the short-period vertical spectral ordinates and long-period horizontal spectral ordinates

19 SA vertical,max (g) Sa v,0.1s (g) Compute Sa v,0.1s and Sa v,1.0s from Sa h,0.2s and Sa h,1.0s : SA horizontal,max Sa h,0.2s (g) -1-1 SA vertical,t1s (g) Sa v,1.0s (g) SA Sa horizontal,t1s (g) h,1.0s (g) Empirical expressions developed from many earthquake scenarios SAv=a*SAh b T=0.2s T=1s -1 a b Define C v and C L from computed Sa v,0.1s and Sa v,1.0s as well as from Sa h,0.2s : Vertical DS T 0V T SV n C L describes the width of const. acc. plateau and slope of decaying branch in vertical spectrum C L C L < C L < C L < C L < C L <

20 Long-period spectral corner period Spectral Spektral Acceleration ivme Acc. Vel. Disp. T A 0 T SB T L T L Important for long-period structures that are more sensitive to deformation demands Important remark: Large magnitude events are richer in long-period groundmotion components. Thus, T L is sensitive to magnitude: T L Magnitude

21 Near-fault (forward directivity) Rupture velocity Particle shear wave velocity Most of the seismic energy arrives in a short-duration waveform with a large amplitude single pulse Long-duration waveform with low amplitudes

22 Implementation to design-based spectra 475 years Prob. dist. of S a considering the occurrence and non-occurrence of pulse-like ground motion 30 5 km Prob. dist. of m, r, t p Pattern used to investigate the influence of forward directivity on code-based design spectrum Fault with different rupture lengths and slip rates to mimic seismic activity

23 Implementation to design-based spectra 2475 years In terms of period, slip rate and M char Amp 2475 /Amp 475 regions Determine the regions where simplified factors apply Factor 3 R y /L Simplification Factor 2 Factor 1 R x /L Spectra with NF effects

24 Success of the proposed model for NF effects

25 Conclusive remarks Revision of Turkish seismic hazard map project will be the basis of new design spectrum The project helped to do many important observations and findings for engineering use Many more can be done These observations can be elaborated further for their use in the definition of design ground motion in the new Turkish code

26 Thank you