Distinctive FILE FORMATS Used in this Archive

By Peter Bird, UCLA, 2025.09.19

.DIG format	DIGitized data, consisting of points and/or polylines in either Cartesian (x, y) or spherical-planet (longitude, latitude) coordinates. Labels and/or other metadata optional but recommended.
.GRD format	GRiDed data, with 2 introductory lines that define the (x, y) or (longitude, latitude) grid, followed by a listing of real or integer data numbers in text order; i.e., Eastward within each grid row, with grid rows listed North-to-South.  (Note that line-breaks in this section have no significance).
.GPS format	Interseismic horizontal velocities of geodetic benchmarks measured using the Global Positioning System.  Uncertainty ellipses provided at each benchmark. Note that .GPS format does not include correlations between uncertainties at different benchmarks; for that, a supplemental .GP2 file is recommended.
.GP2 format	Format for listing either the upper-triangle or the lower-triangle excerpt from the symmetrical matrix of covariances between interseismic horizontal velocity components at all benchmarks described by an accompanying .GPS file.
.EQC format	EarthQuake Catalog format, consisting of single-line summaries of hypocenter (or hypocentroid), time, magnitude, and focal mechanism [when available] of any number of earthquakes.

Note: All file formats described here can be opened and read with ordinary ASCII text editors.  Files with .DIG and .GPS and .EQC formats can be edited in such an ASCII text editor by simply deleting or adding lines.  However, the very dense structures of .GRD and .GP2 formats make hand-editing difficult and inadvisable.