Local earthquake tomography with flexible gridding
In local earthquake tomography (LET) problems, the spatial resolution of velocity structure varies significantly in a model due to the naturally heterogeneous distribution of earthquake sources. We present a flexible gridding strategy for tailoring the velocity model parameterization to the dataset being analyzed. The strategy combines regular gridding with two forms of node 'linking' to allow for finer-scale resolution where warranted by the data, to provide improved model stability where resolution is relatively poor and to allow for the incorporation of a priori information on structure, for example the location of significant discontinuities. Flexible gridding has been incorporated into a widely-used LET inversion algorithm. The inversion approach is documented along with a discussion of other recent advances and improvements to the algorithm. We discuss various situations in which flexible gridding can be useful. An example application of flexible gridding to a dataset from the San Andreas fault in central California illustrates how the approach can yield a sharper image of the fault while at the same time improving the overall quality of the model and the fit to the data. (C) 1999 Elsevier Science Ltd. All rights reserved.
local earthquakes gridding inversion seismic tomography