- Exact functional form of Ground-motion model is not given but note includes linear and quadratic terms
of magnitude and a geometric spreading term. Coefficients not given but report ratios of σ using different
definitions w.r.t. σ using geometric mean.
- Distribution w.r.t. NEHRP site classes is:
- 8 records
- 37 records
- 358 records
- 534 records
- 11 records
- 1 record
- Use data from Next Generation Attenuation (NGA) database.
- Distribution w.r.t. mechanism is:
- 333 records, 51 earthquakes
- 36 records, 12 earthquakes
- 329 records, 21 earthquakes
- 223 records, 9 earthquakes
- 25 records, 7 earthquakes
- 3 records, 3 earthquakes
- Exclude records from Chi-Chi 1999 earthquake and its aftershocks to avoid bias due to over-representation
of these data (> 50% of 3551 records of NGA databank).
- Exclude records with PGA (defined using geometric mean) < 0.05g to focus on motions of engineering
significance and to avoid problems with resolution of analogue records.
- Exclude records with maximum usable period < 0.5s.
- Exclude records without hypocentral depth estimate since use depth in regression analysis.
- Earthquakes contribute between 1 and 138 accelerograms.
- Note data is from wide range of M, d, mechanism, site class and instrument type.
- State aim was not to derive state-of-the-art Ground-motion models but to derive models with the same
data and regression method for different component definitions.
- Assume ratios of σs from different models fairly insensitive to assumptions made during regression but
that these assumptions affect σ values themselves.
- Find ratios of σs from using different definitions close to 1.
- Note that results should be applied with caution to subduction and stable continental regions since have
not been checked against these data.