Wills Map

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Comparison of Wills Map 2006 versus 2015

Wills Map 2006
Wills Map 2015


Vs30 Map based on UCVM Etree for 2006
Wills Map 2015

Description of Wills Digital Map


 2015 is the latest version that I am aware of. The supplementary data of the paper provides the map as a GIS shapfile (http://www.seismosoc.org/Publications/BSSA_html/bssa_105-6/2015105-esupp/index.html). I then rasterized it to a binary floating point file (which similar to the 2006 file, except with floats instead of short ints) using the gdal_rasterize command (http://www.gdal.org/gdal_rasterize.html).

The original and rasterized data is stored here on opensha.usc.edu:

/export/opensha-00/data/siteData/wills_2015

I suggest you use raster_0.00025.flt, which is rasterized with 0.00025 degree spacing (~25 meters). The raster_0.00025.hdr file contains the necessary coordinates for georeferencing it, but I'll summarize here:

The first location in the file is at:

x/longitude/ULXMAP = -124.406528862058
y/latitude/ULYMAP = 42.0090923024621

This is the upper left (northwest) point in the map.

numX/numLon/NCOLS = 41104
numY/numLat/NROWS = 37900

Grid spacing (both X and Y): 0.00025 degrees

Data type: 4-byte/32-bit little-endian floating point numbers

Mesh ordering: fast XY, so the first few points are:

    Index 0 (at byte 0): -124.406528862058, 42.0090923024621
    Index 1 (at byte 4): -124.406528862058+0.00025, 42.0090923024621 = -124.406278862058, 42.0090923024621
    Index 2 (at byte 8): -124.406528862058+0.0005, 42.0090923024621 = -124.406028862058, 42.0090923024621
    ...

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