Fig. 4

Structure of the neural networks for PGA, PGV and PSA [0.01 to 4 s] prediction, for one site proxy (top) and two site proxies (bottom). The \( w_{ij}^{h} \) is the synaptic weight between the ith neuron of the input layer and the jth neuron in the hidden layer, \( b_{j}^{h} \) the bias of the jth neuron in the hidden layer. Also the \( w_{jk}^{0} \) is the synaptic weight between the jth neuron of the hidden layer and the kth neuron in the output layer, \( b_{k}^{0} \) the bias of the kth neuron in the output layer