where A is in g, a1= -1.43, a2= 0.31, a3= -0.62 and a4= -0.0026 (σ not given).
Note equation only for hard rock sites.
Equation from a composite of two separate regressions: one using data from 6 earthquakes, 4.7 ≤ M ≤ 6.4
and d primarily between 40 and 820km and one using the same data supplemented with data from 2
earthquakes with M = 1.8 and M = 3.2 and d ≤ 20km to extend results to smaller M and d. Give no
details of this composite regression.
Note regressions are preliminary and should be tested against more data.
Note careful assessment of uncertainties is required.