- Ground-motion model is: where y is in g, C′1 = -1.48, C2 = 0.266, C4 = -0.922, CA = 0.117, CS = 0.124, h0 = 3.5 and σ = 0.25.
- Use four site conditions but retain three (because only three records from very soft (L) soil which combine with
soft (S) soil category):
- Rock: V s > 750m∕s, ⇒ SA = 0,SS = 0, 106 records.
- Stiff soil: 360 < V s ≤ 750m∕s, ⇒ SA = 1,SS = 0, 226 records.
- Soft soil: 180 < V s ≤ 360m∕s, ⇒ SA = 0,SS = 1, 81 records.
- Very soft soil: V s ≤ 180m∕s, ⇒ SA = 0,SS = 1, 3 records.
- Lower limit of Ms = 4.0 because smaller earthquakes are generally not of engineering significance.
- Focal depths less than 30km, 81% between 5 and 15km.
- Note for some records distances have uncertainty of about 10km.
- Most records from distances less than about 40km.
- For some small events need to estimate Ms from other magnitude scales.
- Most records from free-field stations although some from basements or ground floors of relatively small
structures, and tunnel portals. Do not exclude records from instruments beyond cutoff distance because
of limited knowledge about triggered level.
- All uncorrected records plotted, checked and corrected for spurious points and baseline shifts.
- Uniform correction procedure was applied for all records. For short records (< 5s) a parabolic adjustment
was made, for long records (> 10s) filtering was performed with pass band 0.20 to 25Hz and for intermediate
records both parabolic and filtering performed and the most realistic record was chosen. Instrument
correction not applied due to limited knowledge of instrument characteristics.
- Also analyze using one-stage method, note results comparable.