NGA Project Review and Status
Norm Abrahamson
NGA Workshop #5
March, 2004
Developer Scope
• Ground Motion Model (median, standard dev)
– Ground Motion Parameters:
• Horizontal components (Ave Horiz, FN, and FP)
• PGA, PGV, PGD
• Pseudo spectral acc at 5% damping: 0-10 sec
– Applicable Magnitude Range:
• 5.0 - 8.5 (SS)
• 5.0 - 8.0 (RV)
– Applicable Distance Range:
• 0 - 200 km
– Fault Types
• Strike-slip, Reverse, Normal
– Site Classification Scheme
• Developers select their preferred classification scheme
• Need not include soft-soil
Developer Scope (cont)
• Ground Motion Data Set
– Common data set provided to developers
– Each developer selects applicable subset of data
• Justify the exclusion of earthquakes and recording sites
• Document any modification of independent parameters from
PEER recommended values
• Ground motion values are not modified (e.g. common set used
by all developers), but developers select applicable period
range of each recording
– Final selected data to be listed in report
Developer Scope (cont)
• Evaluate new predictive parameters
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Directivity parameters
Hanging wall / foot wall
Static stress-drop
Asperity depth
Depth to bedrock (or Vs)
Basin parameters
• Each developer decides if new predictive parameter is to
be included in their model
– Justify the selection or rejection of each parameter evaluated
Developer Scope (cont)
• Spectral Periods
– 112 periods provide (from 0.01 to 10 sec
– Minimum set of 20 periods required for model:
• 0.02, 0.03, 0.05, 0.075, 0.10, 0.15, 0.20, 0.25, 0.30,
0.40, 0.50, 0.75, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 7.5, 10
Developer Scope (cont)
• Magnitude definition
– All developers use moment magnitude
• Distance definition
– Developers select appropriate distance metric
• Site classification
– Developers select site classification
• Clear definition of site classes
– Provide a translation scheme to NERHP categories
Tasks to Support NGA Developers
1.
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8.
Empirical database development
1-D rock simulations
Evaluation of source-path predictor variables
Evaluation of site classification and site effects
Site response simulations
Statistical approaches
3-D basin response simulations
Compilation of seismic network ground motion
data for M5 at large distances
Working Groups
1.
2.
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4.
5.
6.
Data Processing
Ground Motion Database
Validation of 1-D Rock Motion Simul
Source/Path Effects
Site Classification & Site Effects
Statistical Modeling of Data
NGA Tasks and Associated WGs
Task
Working Group
1. Database development
WG#1 data proc
WG#2 Database
WG#4 Source/Path
WG#5 Site Classification
2. 1-D rock Simulation
WG#3 Valid of 1-D simulations
WG#4 Source/Path
3. Evaluation source/Path Effects
WG#4 Source/Path
4. Evaluation of site classification
WG#5 Site Classification
5. Site Response Simulations
WG#5 Site Classification
6. Statistical Approaches
WG#6 Statistical Modeling
7. 3-D basin Simulations
WG#4 Source/Path
WG#5 Site Classification
8. Network Data
WG#4 Source/Path
Task 1
Empirical Database Development
• Metadata
– Version 1 released in November
• Source and path parameters review by Somerville
(complete)
• Site parameters review by Wells (not complete)
– Modifications
• Incorporate review comments
• Next version due April 23
• Includes rotations to FN and FP
Task 1 (cont)
Empirical Database Development
• Ground Motion Values
– Evaluation of adequacy of processing in progress
(comparison of PEER Sa values with CSMIP and
USGS Sa values) – WG #1
• Meeting held March 17
• Summary to be given by Abrahamson
– Evaluation of treatment of permanent displacements
(fling step) – WG#1
• Update to be given by Graves
Task 2
1-D Rock Motion Simulation
• Validations
– URS, Silva, Zeng (not complete)
– Update to be presented
• Simulations
– Strike-slip scenarios
• URS complete, Zeng nearly complete (missing SJ)
• Silva results preliminary (to be updated)
– Reverse-slip scenarios
• URS complete, Zeng (7 events complete)
• Silva results due March 31
Task 3 Evaluation of
Source-Path Predictor Variables
• Review of Metadata by WG#4
– Source and travel path parameters
• Review completed (Somerville)
• WG#4
– 1-D rock simulations
• Updated scaling results to be shown (Abrahamson)
• Directivity model using Isochrons
– Spudich working on model refinements
– 3-D basin simulations(mtg held Mar 5)
• Scale factors to be discussed by Steve Day
Task 4 Evaluation of Site
Classification and Site Effects
• Review of Metadata (WG#5)
– Recording site classification
– Structure (building) classification
– Review by Wells to be completed April 2
• Review alternative site classification schemes and
functional forms for site effects (WG#5)
– Evaluate site response simulations and empirical data
• Develop method for translations among different
site classification schemes (WG#5)
– Not started
Task 5
Site Response Simulations
• Simulation method
– RASCALS with soil randomization
• Simulations
– Previous PEER-LL and NEHRP studies (Silva)
– Augment previous simulations
• Identify additional cases needed (April 5)
• Results in May
• Sensitivity analysis
– Comparisons with RASCAL, SHAKE, and Non-linear
models
• Completed. To be shown by Sun
Task 6 Statistical Approaches
• Issues (WG#6)
– Review of alternative methods
• Weights, two-step, random effects, …
– Spatial correlation of ground motion
– Correlation of spectra at different frequencies
– Standard deviation
• Dependence on magnitude, distance, and soil type
– Incorporating measurement errors in predictor variables
– Missing predictor variables
– Censored data (non-triggered stations)
– Combining empirical and simulated data in regression analyses (NGA-H)
• WG#6 held initial meeting
– Scope of work identified
• WG#6 recommendations in May
Task 7
3-D Bain Simulations
• Program verification completed
• Simulations completed
• Evaluation of results
– Will be presented Thursday
Task 8
Network Data Evaluation
• Evaluation of attenuation at large distances
using network data
– Complete
– Presented by Boatwright in WS#4
Revised Schedule
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March 24-25 Workshop #5
April 20
Draft summary of supporting task reports
May 6-7
Developer interaction meeting
June 24-25 NGA workshop #6,
– Developers present preliminary model
– Developers explain
July 12
Draft report due
– Describe approach and preliminary model
– For circulation to other developers
July 19-26? Developer interaction meeting
Sep 17
Final models due
Sep 30
Final report due
Oct 14-15
Final workshop
– Compare models (other developer’s models and past models)
– Examine impacts on hazard
NGA Reports
• Data Report
– Documentation of data set in flat file
• Resource Report
– Documentation of results from supporting tasks
and working groups
• NGA Ground Motion Report
– Documentation of the developers models
• Summary, Overview, and Impacts
Data Report
• Metadata
– Documentation of magnitudes, source geometries, site
conditions, distances, directivity parameters, HW/FW,
etc
• Ground motion processing
– Causal vs acausal
– Filter corners
– Fling step removal
• QA Efforts
– Reviews of metadata and response spectra
Resource Report
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Working Group Activities
Scaling factors based on 1-D rock simulations
Basin scaling factors based on 3-D simulations
Directivity functional form based on Isochron
Site response amplification factors
Attenuation rates from network data
Statistical approaches
NGA Ground Motion Model
Report
• Synthesis of developer’s models
• Model report from each developer
• Fling step model
– (for adding fling back into ground motion)
Summary and Impacts
• General report summarizing NGA project
• Focus on impacts of new models
– How do the new models effects the design
ground motions for future projects?