Signal processing device and signal processing method

A signal processing device includes a propagation speed calculating means for calculating strength and a direction of vibration in an underground structure region using a calculation model including data of a vibration propagation speed; a simulated propagation speed calculating means for inputting seismic source information to a calculation model and calculating the strength and the direction of the vibration in the underground structure region using the calculation model; and an update amount calculating means for calculating an update amount to update the calculation model, on the basis of propagation speed distribution information and simulated propagation speed distribution information. The calculation model is a solid model, the propagation speed calculating means calculates strength and a direction of first vibration using a first measurement signal input to the calculation model and calculates strength and a direction of second vibration using a second measurement signal input to the calculation model.