Efficient calculation of complete differential seismograms for laterally homogeneous earth models

Differential seismograms, the sensitivity of the seismogram to perturbations of parameters of the earth model, are essential for waveform modelling with iterative non-linear optimization techniques. The growing number of broad-band high-dynamic-range fixed and portable stations provide a rich data set of regional distance events with accurate locations and source mechanisms that are ideal for modelling lithospheric structure. An efficient technique for calculating differential seismograms for complete synthetic seismograms in laterally homogeneous earth models will significantly decrease the computational burden of seismic-waveform inverse modelling. The technique we present here is equivalent to computing three synthetic seismograms in multilayered models, contrasted with N+ 1 seismograms for a typical brute-force approach, which reduces the work to 3/(N+ 1) or about a 90 per cent saving for 30 layers. The lateral-homogeneity requirement will yield path-averaged structures which may form the basis for later tomographic studies to resolve lateral variations.