Global Vs30 Map Server

This data release provides the global mosaic of the time-averaged shear-wave velocity in the upper 30 m (Vs30) described by Heath and others (2020a). This map uses the Wald and Allen (2007) slope-based Vs30 as the basemap, and regional maps take precedence where they are available.

This is an update to the Heath and others (2020b) data release. Changes include updates to the data sources that are included in the mosaic, the use of a more accurate coastline for masking water bodies, more comprehensive treatment of surface ice, bug fixes to the code that combines the different Vs30 sources, and conversion to the Cloud-Optimized GeoTiff format.

A modeling process produces maps of Vs30. The result is an estimate of Vs30, which includes uncertainty. To represent this uncertainty, Vs30 is modeled with a lognormal distribution with two parameters: the median and the logarithmic standard deviation. 

Data Description 

vs30_mosaic_median_30c.tif

Median of the Vs30 distribution.
Cloud-Optimized GeoTiff format.
Resolution: 30 arcseconds, ~900 m.
Units: m/s.
Values of 600 indicate oceans.
Values of 601 indicate ice.
Values of 602 indicate glaciers. 
Values of 603 indicate lakes.

vs30_mosaic_sd_30c.tif

Logarithmic standard deviation of the Vs30 distribution.
Cloud-Optimized GeoTiff format.
Resolution: 30 arcseconds, ~900 m.
Units: m/s.
Values of 600 indicate oceans.
Values of 601 indicate ice.
Values of 602 indicate glaciers. 
Values of 603 indicate lakes.

version.json

File for specifying version information.
This is a JSON file format with the following keys:

title: Title of the data.
description: Description of the data.
map_version: Version number.
generated: The date these data were generated. 
extent: Extent of the map (minimum longitude, minimum latitude, maximum longitude, maximum latitude).

color_palette.csv

Suggested color palette for shading Vs30 values on plots.
Each Vs30 range has a defined color in terms of red, green, and blue values.  
Comma-separated value (CSV) format.

References 

Heath, D.C., Wald, D.J., Worden, C.B., Thompson, E.M., and Smoczyk, G.M., 2020a, A global hybrid Vs30 map with a topographic slope–based default and regional map insets: Earthquake Spectra, 36(3), pp.1570-1584, doi: 10.1177/8755293020911137.
Heath, D.C., Wald, D.J., Worden, C.B., Thompson, E.M., and Smoczyk, G.M., 2020b, A Global Hybrid Vs30 Map with a Topographic-Slope-Based Default and Regional Map Insets: U.S. Geological Survey data release, doi: 10.5066/P96HFVXM.

Wald, D.J. and Allen, T.I., 2007, Topographic slope as a proxy for seismic site conditions and amplification: Bulletin of the Seismological Society of America, 97(5), pp.1379-1395, doi: 10.1785/0120060267.