Figure 4 shows a compilation of S-wave splitting results across North America. Results from much of the elevated western US, however, are complex and must represent small-scale, poorly understood deformation processes beneath this currently active area. The transportable array would allow us to map anisotropy uniformly across the continent. S-wave splits from the U.S. and southern Canada compiled from several different studies and publications. Green lines indicate the fast direction and split time of split SKS arrivals.
Red lines indicate the backazimuths of null arrivals in areas where null arrivals are common.
The emphasis would be on high-quality data and efficient data distribution. In addition, some tomography experiments benefit from the accumulation of many observations at a single site, since this allows for a better separation of local and distant wave propagation effects. These considerations suggest that an initial goal for the permanent component of USArray should be uniform coverage. The map on the left shows the location and focal mechanism of the earthquake, with triangles indicating the locations of stations used in the CMT analysis. The seismograms are dominated by fundamental mode Love and Rayleigh waves.