- Ground-motion model is:
where Y is in cm∕s2, a = 3.287, b = 0.503, c = -0.079, d = -1.1177, e = 0.141, f = 0.331, h = 14.82km
and σ = 0.260.
- Use three site classes:
G1 = 0, G2 = 0
- A: shear-wave velocity > 750m∕s, 4 records, and B: shear-wave velocity 360–750m∕s, 20 records.
G1 = 1, G2 = 0
- C: shear-wave velocity 180–360m∕s, 35 records.
G1 = 0, G2 = 1
- D: shear-wave velocity < 180m∕s, 136 records.
Originally A and B were separate but combine due to lack of data for site class A.
- Focal depths between 5.4 and 25.0km.
- Use Mw for M > 6 to avoid saturation effects.
- Assume ML = Mw for M ≤ 6.
- Select records from earthquakes with M ≥ 5.0.
- Most (15 earthquakes, 146 records) data from earthquakes with M ≤ 5.8.
- Only use data from the Earthquake Research Department of General Directorate of Disaster Affairs from
df ≤ 100km.
- Exclude record from Bolu because of possible instrument error.
- Use mixed effects model to account for both inter-event and intra-event variability.
- Find that the mixed effects model yields σs lower than fixed effects model.
- Compare predictions with observed data from the Kocaeli and Düzce earthquakes and find reasonable fit.
- Plot coefficients and σs against frequency and find dependence on frequency.
- Plot inter-event and intra-event residuals against distance and magnitude and find not systematic trends.
- Find intra-event residuals are significantly larger than inter-event residuals. Suggest that this is because
any individual event’s recordings used to develop model follow similar trends with associated parameters.
- Recommend that equations are only used for ground-motion estimation in NW Turkey.