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Conducted for NEXT GENERATION OF ATTENUATION RELATIONSHIPS PROJECT (NGA )

NGA – COSMOS JOINT WORKING GROUP PRELIMINARY REPORT ON EVALUATION OF DATA PROCESSING FOR ELASTIC RESPONSE SPECTRA. Conducted for NEXT GENERATION OF ATTENUATION RELATIONSHIPS PROJECT (NGA ). WORKING GROUP OBJECTIVE.

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Conducted for NEXT GENERATION OF ATTENUATION RELATIONSHIPS PROJECT (NGA )

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  1. NGA – COSMOS JOINT WORKING GROUPPRELIMINARY REPORT ON EVALUATION OF DATA PROCESSING FOR ELASTIC RESPONSE SPECTRA Conducted for NEXT GENERATION OF ATTENUATION RELATIONSHIPS PROJECT (NGA)

  2. WORKING GROUP OBJECTIVE Assess whether PEER records represent a valid interpretation of ground motion for purposes of developing NGA relationships for elastic response spectral values and PGA, PGV, and PGD.

  3. NGA-COSMOS JOINT WORKING GROUP • Norm Abrahamson, PG&E • Dave Boore, USGS • Brian Chiou, Caltrans • Bill Iwan, Caltech • Bob Nigbor, USC • Dan O’Connell, USBR • Maury Power, Geomatrix • Tony Shakal, CSMIP

  4. ISSUES • Causal vs. Acausal Filtering • PEER data set developed using both causal and acausal filtering whereas CSMIP, USGS used acausal filtering. • Filter Corner Frequencies • PEER, CSMIP, USGS used different approaches for selecting the corner frequencies.

  5. CONCLUSIONSCAUSAL VS ACAUSAL FILTERING • Acausal approach preferred (response spectra are less affected by filtering). • On average, there is no systematic difference between response spectra computed using causal and acausal filters. • Need to check effect on PGA, PGV, and PGD. • Working group concluded that PEER response spectra are adequate for NGA needs except for small group of near-source recordings with large residual displacements. • NGA project will reprocess recordings with large residual displacements using acausal filters because differences in response spectra could be larger and records are important for constraining regression analyses for short distances and large magnitudes.

  6. CONCLUSIONSFILTER CORNER FREQUENCIES • Selection of filter corner frequencies has large effect on response spectral values outside the passband and may affect PGA, PGV, and PGD. • Both PEER and CSMIP/USGS filter corner frequencies will be included in the NGA data file. • NGA Developers will select the usable passband of the spectral values. • Dual sets of PGA, PGV, and PGD values will be included in the NGA data file (PEER and CSMIP/USGS values). • NGA project will compare differences in corner frequencies and values of PGA, PGV, and PGD from different organizations for individual records and collectively to obtain overall trends for differences.

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