- Ground-motion model is:
where A is in cm∕s2, using just soil records a = 0.430, b = 0.428, c = -0.764, d = -0.00480 and σ = 0.271.
- Use records from aftershocks of Tangshan earthquake.
- Focal depths between 5.7 and 12.9km.
- Note Ms values used may have some systematic deviation from other regions and errors, which decrease
with increasing magnitude, can reach ±0.5.
- Errors in epicentral locations not less than 2km. Reject 3 records because have R < 2km, if include then
find standard deviation increases and c obtained is unreasonable.
- Fit equation to all data (both rock and soil) but note that only for reference. Also fit equation to soil data
only (2.1 ≤ R ≤ 41.3km, 3.7 ≤ Ms ≤ 4.9, 33 records from 6 earthquakes).
- Remove all four earthquakes with Ms < 4.0, for which error in magnitude determination is large, and fit
equation to soil data only (2.8 ≤ R ≤ 41.1km, 4.5 ≤ Ms ≤ 4.9, 13 records from 2 earthquakes). Find
- Also fit data to log A = a + bMs - clog(R + R0); find similar results.
- Also use resultant of both horizontal components; find similar results to using larger component.
- Also fit eastern North America data (3.9 ≤ R ≤ 61.6km, 2.3 ≤ Ms ≤ 3.8, 7 records from 3 earthquakes);
find similar attenuation characteristics.
- All equations pass F-tests.