PEER Jonathan P. Stewart University of California, Los Angeles Graduate Students: Yoojoong Choi and Andrew Liu January 18, PEER Annual Meeting Site Categories and Amplification Factors

2002 PEER Annual Meeting Context Conventional PSHA (Cornell, 1968): Attenuation Relationship Derived from PDF f(IM|m,r,…) Described by: - median - standard deviation

2002 PEER Annual Meeting Attenuation Relations Tectonic regime m, r Focal mechanism Site condition Factors affecting attenuation of S a : - Broad site categories

2002 PEER Annual Meeting Amplification Factors Used to adjust moments of attenuation relation Reference site approach –e.g.: Idriss, 1990; Borcherdt and Glassmoyer, 1994; Borcherdt, 2002 –Azimuth and distance corrections –Derived error term

2002 PEER Annual Meeting Amplification Factors Non-reference site approach –Amplification taken as residual from attenuation relation –e.g.: Sokolov, SCEC, this study –Azimuth corrections, event terms –Direct error terms

2002 PEER Annual Meeting Classification Schemes Surface geology

2002 PEER Annual Meeting Classification Schemes NEHRP/V S-30 Reference: Martin (1994)

2002 PEER Annual Meeting Classification Schemes Geotechnical data Reference: Rodriguez- Marek et al. (2001)

2002 PEER Annual Meeting This Study Large strong motion database Leverage new geologic data sources –CDMG mapping –Borehole and geophysical data (e.g., ROSRINE) Reference motions from Abrahamson and Silva (1997) rock attenuation –Directivity correction –Event term correction

2002 PEER Annual Meeting Data Resources Strong motion data –PEER data set (1032 recordings from 51 eqks), up to 1999 Duzce, Turkey event Site classifications –Surface geology 460 age only 240 age + depositional environment 168 age + material texture –NEHRP, 185 sites –Geotechnical data, 183 sites

2002 PEER Annual Meeting Interpretation of Results Data Regression Evidence of nonlinearity –Hypothesis testing –b-value departs from zero by more than its estimation error Distinction between categories –F-test Holocene (all)

2002 PEER Annual Meeting HolocenePleistocene

2002 PEER Annual Meeting Discussion of Results Effect of period Distinct categories for each scheme Comparison to previous studies Inter-category error –Measure of relative effectiveness of classification schemes

2002 PEER Annual Meeting Effect of Period Holocene Age-only

2002 PEER Annual Meeting Surface Geology Holocene lacustrine/marineQuaternary alluvium Tertiary Mesozoic + Igneous Age + Depositional Environment

2002 PEER Annual Meeting Surface Geology Holocene CoarseHolocene Fine Age + Material Texture

2002 PEER Annual Meeting NEHRP B CD

2002 PEER Annual Meeting Geotechnical Data B C DE

2002 PEER Annual Meeting Comparison C D

2002 PEER Annual Meeting Comparison

2002 PEER Annual Meeting Inter-Category Error Terms Individual residual Category residual Scheme residual Inter-category error

2002 PEER Annual Meeting Results: “Soil” Categories

2002 PEER Annual Meeting Final Remarks Desired features of classification schemes: –Minimize dispersion (detailed geology) –Categories have distinct amplification levels (NEHRP) Amplification factors smaller than design standards Further improvements require consideration of basin geometry