- Ground-motion model is (Type A):
where PGA is in g, a = -1.434 ± 0.339, b = 0.209 ± 0.036, c = 0.00297 ± 0.00093, d = -0.449 ± 0.186 and
σ = 0.276.
- Find that ground motions in previous earthquakes were significantly higher than the motions predicted by
equations derived from W. N. America data.
- Only include records from earthquakes for which Mw is known because of poor correlation between ML
and Mw in New Zealand.
- Focal depths, he ≤ 122km.
- 140 records from reverse faulting earthquakes.
- Divide records into crustal and deep earthquakes.
- Only use records for which reliable event information is available, regardless of their distances with respect
to untriggered instruments.
- Only use records which triggered on the P-wave.
- Also derive separate equations for shallow, upper crustal earthquakes (he ≤ 20km, 102 records, 5.1 ≤
Mw ≤ 7.3, 13 ≤ r ≤ 274km) and crustal earthquakes (he ≤ 50km, 169 records, 5.1 ≤ Mw ≤ 7.3,
13 ≤ r ≤ 274km).
- Also try equations of form: log 10PGA = a+bMw-dlog 10r (Type B) and log 10PGA = a+bMw-cr-log 10r
(Type C) because of large standard errors and highly correlated estimates for some of the coefficients
(particularly c and d). Find Type B usually gives much reduced standard errors for d than Type A model
and have lowest correlation between coefficients, but are sceptical of extrapolating to distance ranges
shorter and longer than the range of data. Type C usually has similar standard deviations to Type A.
Find that usually all three models give similar predictions over distance range of most of the data, but
sometimes considerably different values at other distances.
- Derive separate equations for reverse faulting earthquakes only and usually find similar results to the
- Find deep earthquakes produce significantly higher PGAs than shallow earthquakes for similar r.