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README.md

Active Faults of Central America and the Caribbean

Central America and the Caribbean contain both rapidly-slipping faults and a large pulation, leading to great seismic hazard and risk. As part of the [CCARA] project, and to fill in a critical gap in the [GEM Global Active Faults][gaf] project, we have made a database of active faults in the region for use in seismic hazard analysis, earth science research, and education.

The database is a collection of fault traces in GIS vector formats, with associated metadata (attributes) for each structure describing the fault's geometry, kinematics, slip rates and other pertinent characteristics. The individual structures are mapped anew for this project based on interpretations of the literature and other datasets (e.g., digital topography data, earthquake catalogs, and GPS velocities). References for each structure are contained in the metadata, and a list of all references used is given in the repository.

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 are for textual data.

File Formats

The fault database is provided in a variety of GIS vector file formats. The version of record is the GeoJSON file, as changes in this file are tracked with git. The other versions are produced from this file via a script. QGIS users may use the GeoJSON file with the least friction; the GMT and KML formats work well in the GMT and Google Earth platforms, respectively, though metadata may be lost. The ShapeFile format suffers from truncation of attribute names and possibly text fields. ESRI users are suggested to use the GeoPackage format.

Other information

This project is funded by USAID as part of the CCARA project. A publication describing the work is forthcoming.

User reviews and revisions, and any additional feedback, are highly encouraged. Ideally contributions can be made by editing the GeoJSON file (hopefully in QGIS for maximum compatibility) and submitting a pull request. However we can work to accommodate most types of revision or addition. Please make an issue or email Richard Styron (richard dot h dot styron at gmail dot com).