Ground-motion model is not given here since it requires evaluation of a matrix equation that cannot be
summarised. Derive model using feed-forward artifical neural network (1 5-neuron hidden layer; 1 neuron
for each independent parameter considered: Mw, log(rjb), log(Vs,30), focal depth and mechanism class)
with a procedure similar to random-effects approach to compute inter- and intra-event σ. Because provide
the matrices and functional form to evaluate model it is included in this section rather than simply
being listed. Authors provide spreadsheet to evaluate model. Standard deviations (in terms of common
logarithms): τ = 0.155 (inter-event), ϕ = 0.267 (intra-event) and σ = 0.309.
Use Vs,30 to characterise sites. Only 6.9% of sites have Vs,30> 800m∕s. Italian sites have higher average
Vs,30 (496m∕s) than Turkish sites (389m∕s).
Use 3 mechanisms (classified using plunge and rake angles):
Most (76%) Italian events are normal and most (57%) Turkish events are strike-slip.
Select records from events with focal depth ≤ 25km and measured values of Vs,30.
Most data from Turkey and Italy. Most Turkish data from rjb> 30km and larger magnitude range than
Data roughly uniformly distributed w.r.t. Mw and rjb for Mw≤ 6. Few larger events.
Find increasing the number of hidden layers would risk the problem of over-determination without a
significant decrease in σ. Find that including depth and mechanism leads to marginal decrease in σ but are
included to aid comparisons with other models. Undertake various tests to find most appropriate model.
Note that despite not imposing a functional form the model is physically sound and suggests nonlinear
magnitude, distance and Vs,30 scaling.
Examine inter-event residuals w.r.t. Mw and intra-event residuals w.r.t. rjb and Vs,30 grouped by principal
country of origin (Italy, Turkey or other). Compute mean residuals by bins and generally find no
evidence for bias by country or significant trends. Find bias for Italian intra-event residuals in range
400 ≤ Vs,30≤ 600m∕s, which may indicate that Vs,30 is not a universal proxy for site amplification (the
sites might include those with shallow soft soil overlying hard bedrock).
Recommend that model is never used outside these ranges of applicability: 4 ≤ Mw≤ 7, 5 ≤ rjb≤ 200km,
200 ≤ Vs,30≤ 800m∕s and 0.01 ≤PGA≤ 10m∕s. Also recommend model is not used for reverse-faulting
events because lack of data.