- Ground-motion model is:
- Response parameter is acceleration for 5% damping.
- Use data from 377 sites with V s,30 > 500m∕s.
- Use data from the Trinet broadband high and low gain channels (BH and HL). BH are STS-1 and STS-2
instruments and HL are mainly FBA-23 instruments. Use BH data when not clipped and otherwise HL
- Eliminate DC offset for each record. Convert ground motions into acceleration while applying a high-pass
filter with cut-off of 40s. Display recovered acceleration, velocity and displacement time-histories from a
ML5.1 earthquake from the BH and HL data. Note that they are similar and hence that reliable ground
motion can be recovered from these data.
- Display the signal and noise Fourier amplitude spectra for one record and find that the signal-to-noise
ratio is higher in the BH channel than in the HL channel. State that the signal-to-noise ratio is still > 1
for periods of 20s for both types of data.
- Compute acceleration and relative displacement response spectra for both channels. Find that for periods
> 0.3s the response spectra from the two channels are very close. State that the difference for short periods
is due to the low sampling rate (20sps) for the BH channel and the higher (80 or 100sps) sampling rate
for HL channel.
- Conclude that reliable ground motions up to 20s can be recovered from these data.
- Use a two-stage regression method where first determine c4 and c5 and then the other coefficients.
- Most data from digital instruments from M ≤ 5.5 and R < 300km. Most data from analogue instruments
from 6.0 ≤ M ≤ 7.0 and 10 < R < 100km.
- Use data from analogue instruments for short-period range (0.04–3s) and data from Trinet instruments for
long-period range (1–20s). Connect the two sets of coefficients at 1.5s after confirming that the predictions
match at this period.
- Do not give coefficients only predictions.