Paul Spudich coauthored a description of rupture directivity based on arrival-time contours across a finite earthquake source. If a rupture advances toward a receiver, seismic waves from successively rupturing patches can arrive over a compressed interval; retreating rupture spreads those arrivals out. The formulation makes this directional pulse concentration depend on source geometry and rupture timing, supplying a physical measure for interpreting strong ground motion.[ref]
A formulation of directivity for earthquake sources using isochrone theory by Paul Spudich and others. 2004 report, finite-source isochrone formulation and directivity interpretation
Geophysicist and author of primary studies of earthquake ground motion and rupture directivity. His authorship and USGS affiliation are documented on the 2004 report: pubs.usgs.gov/of/2004/1268/ .
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