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README.md

README.md

GEM Global Active Faults

DOI

Please note this is a work in progress; version 1 should be complete by the end of 2018.

The GEM Foundation's Global Active Faults project (GEM-GAF) is building a comprehensive, global dataset of active fault traces of seismogenic concern. The dataset comprises GIS files hosted here of fault traces and small amount of relevant attributes or metadata (fault geometry, kinematics, slip rate, etc.) useful for seismic hazard modeling and other tectonic applications. The dataset is being assembled primarily as a part of GEM's global Probabilistic Seismic Hazard Modeling efforts, although we hope that the data find wide use in research, education and general interest among many users.

The dataset is freely and publicly available here, under a Creative Commons attribution license.

The dataset currently covers most of the deforming continental regions on earth with the exceptions of, the Malay Archipelago, Madagascar, Canada, and a few other regions. These are to be added progressively through 2018.

The data is viewable in an interactive map here.

Data Format

Data Table

Attribute Data Type Description Example
dip tuple Dip (40,30,50)
dip_dir string Dip direction W
downthrown_side_id string direction of downthrown side NE
average_rake tuple Slip rake of fault (45,25,55)
slip_type string Kinematic type Sinistral
strike_slip_rate tuple Strike slip rate on fault (1.5,0.5,2.5)
dip_slip_rate tuple Dip slip rate (1.5,0.5,2.5)
vert_slip_rate tuple Vertial slip rate (1.5,0.5,2.5)
shortening_rate tuple Horizontal shortening rate (1.5,0.5,2.5)
accuracy integer Denominator of map scale 40000
activity_confidence integer Certainty of neotectonic activity 1
exposure_quality integer How well exposed (visible) fault is 2
epistemic_quality integer Certainty that fault exists here 1
last_movement string Date of last earthquake 1865
name string Name of fault zone Polochic
fz_name string Name of fault zone Motagua-Polochic
reference string Paper used Rogers and Mann, 2007
notes string Any relevant info May be creeping
ogc_fid integer ID used by GIS 8
catalog_id string Global ID CCARA_8

Data Types

There are three main data types used in the GAF attribute table, tuple, integer and string.

A tuple is a 3-tuple of real (floating-point or integer) numbers representing continuous random variables such as slip rate. The tuple has the format (most-likely, min, max). In some instances where there is no estimated uncertainty in the parameter of interest, the tuple may be simply given as (most-likely,,); this is most common for the dip of purely strike-slip faults. In typed databases it is actually represented by a string, so the parentheses and commas will be preserved. Rake is in Aki-Richards convention. All slip rate fields except shortening_rate describe the slip rate or component on the actual fault, and are in magnitudes, i.e. are always positive. shortening_rate describes the horizontal contraction rate (heave) of a fault (such as a GPS measurement); this is not the dip slip rate. Extension across a fault is negative.

An Integer is used as a categorical variable in this database, typically to denote the relative epistemic uncertainty in a parameter. 1 is most certain, 2 is moderately uncertain, and 3 is highly uncertain. The other uses of Integer types are for table indices in many constituent datasets, and in the accuracy attribute which denotes the denominator of the map scale during fault mapping and digitization; for example, a fault that was mapped in GIS at a 1/40,000 (or 1:40,000) scale will have an accuracy of 40000.

Strings for fields with words.

File Formats

The database is currently available in 3 formats, GeoJSON, GeoPackage, and ESRI ShapeFile. Which file format is most appropriate depends on the software package that is being used. QGIS users and anyone making webmaps or an API will find the GeoJSON format most useful. This is also the version of record as it is tracked best with version control. However, ESRI does not seem to provide acceptable GeoJSON support; ArcGIS users should be able to use the GeoPackage format (note that we have no access to ArcGIS and are unable to test these files for compatibility). ESRI's legacy ShapeFile format is also provided but this is not a good choice as that format truncates both column names and longer text fields such as Notes.

Additional file formats will be provided once the Version 1 of the database is complete; if you have specific needs, please contact richard dot styron at globalquakemodel.org.