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The files contain phase-velocity maps of Love and Rayleigh waves
derived from USArray data for the period 2006-2015 using
noise-tomography techniques. This set of phase-velocity maps are
referred to as "USANT15".

The data set and the maps are described in the manuscript:
Ekstrom, G., Short-period surface-wave phase velocities across
the conterminous United States,
submitted to Physics of the Earth and Planetary Interiors,
June 2017

There is a separate file for phase velocity at
each period and for each wave type (Love or Rayleigh).

Letter codes in the file name indicate maps related to some
experiment described in the paper.
RAD - Rayleigh wave maps determined from radial-component data
SUM - Maps determined from summer measurements
WIN - Maps determined from winter measurements
NS - Maps determined from N-S paths
EW - Maps determined from E-W paths
NESW - Maps determined from NE-SW paths
NWSE - Maps determined from NW-SE paths
See the paper for details.

Each file contains a line close to the beginning that looks like 
#PVELREF: x.xxxx
This line gives the reference phase velocity for the anomaly
values that follow.

The files contain values of phase velocity for latitude-longitude
pixels. Variations are given in percent. The format of the data is 
latitude, longitude, pixel size in degrees, percent deviation.
The latitude and longitude refer to the center of the pixel.

The pixel map is referenced to geocentric coordinates.  Therefore
the latitude should be corrected to the ellipsoid if maps are 
plotted in geographic coordinates.

Please cite the paper if you make use of these maps.
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GE 2017-06-05
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