Response parameter is acceleration for 5% damping.
Use three site classes
Shallow soil (depth to rock < 20m). ZSS= 1, ZIS= 0 and ZDS= 0.
Intermediate soil (depth to rock between 20 and 100m). Very limited data. ZIS= 1, ZSS= 0 and
Deep soil (depth to rock more than 100m). ZDS= 1, ZSS= 0 and ZIS= 0.
Cannot also examine effect of rock type (hard crystalline; hard sedimentary; softer, weathered; soft over
hard) because of lack of data from non-crystalline sites in SS and IS classes.
Collect all data from strong-motion instruments in eastern North America (ENA) and all seismographic
network data from mb≥ 5.0 at ≤ 500km. Also include some data from Eastern Canadian Telemetered
Most data from M < 5 and > 10km.
Roughly half the data from aftershocks or secondary earthquakes in sequences.
Limit analysis to M ≥ 4 because focus is on ground motions of engineering interest.
Use geometric mean to avoid having to account for correlation between two components.
Note the large error bars on C3, C5 shows that data does not provide tight constraints on magnitude
scaling and attenuation parameters.
Do not provide actual coefficients only graphs of coefficients and their error bars.
Find smaller inter-event standard deviations when using mLg than when using Mw.
Examine effect on standard deviation of not including site terms. Compute the statistical significance of
the reduction using the likelihood ratio test. Conclude that the hypothesis that the site terms are zero
cannot be rejected at any period.
Split data by region: the Gulf Coast (no records), the rest of ENA or a subregion of ENA that may have
marginally different attenuation characteristics. Add dummy variable to account for site location in one of
the two zones with data and another dummy variable for earthquake and site in different zones. Neither
variable is statistically significant due to the limited and scattered data.
Try fitting a bilinear geometric spreading term but find that the reduction in standard deviation is minimal.