Earthquake Extension Specification

• Title: Earthquake
• Identifier: https://stac-extensions.github.io/earthquake/v1.0.0/schema.json
• Field Name Prefix: eq
• Scope: Item, Collection
• Extension Maturity Classification: Proposal
• Owner: @emmanuelmathot @fabricebrito

This document explains the Earthquake Extension to the SpatioTemporal Asset Catalog (STAC) specification. The specification is largely inspired by the existing earthquakes catalogs such as the USGS Earthquake Hazards Program and the European-Mediterranean Seismological Centre.

A specific section gives the translation between the existing data models and the STAC model.

• Examples:
  • Item example: Shows the basic usage of the extension in a STAC Item
  • Collection example: Shows the basic usage of the extension in a STAC Collection
• JSON Schema
• Changelog

Fields

The fields in the table below can be used in these parts of STAC documents:

• Catalogs
• Collections
• Item Properties (incl. Summaries in Collections)
• Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
• Links

Field Name	Type	Description
eq:magnitude	[number]	REQUIRED. The magnitude for the event. See also magnitude_type.
eq:magnitude_type	string	The type of magnitude. Default to mww.
eq:places	[string]	The list of places referencing locations in relation with the event
eq:felt	number	The number of felt reports.
eq:status	string	Indicates whether the event has been reviewed by a human. Possible value: automatic, reviewed, deleted
eq:tsunami	boolean	This flag is set to true for large events in oceanic regions and false otherwise.
eq:sources	[source object]	REQUIRED. A unique identifier for the event. This is the current preferred id for the event, and may change over time, the
eq:depth	number	The depth of the event in kilometers.

Additional Field Information

eq:magnitude_type

The eq:magnitude_type field is a string that describes the type of magnitude. The default value is mww (moment magnitude). The complete list of possible values is available here.

eq:places

The eq:places field is a list of strings that reference locations in relation with the event. It is recommended to use GeoNames dataset to reference populated places that are in close proximity to a seismic event. If there is no nearby city within 300 kilometers (or if the nearby cities database is unavailable for some reason), the Flinn-Engdahl (F-E) seismic and geographical regionalization scheme is used.

eq:sources

The eq:sources field is an object that contains information about the sources that contributed to the event.

Field Name	Type	Description
name	string	REQUIRED. The name identifying a data contributor in the source catalog
code	string	REQUIRED. An identifying code assigned by - and unique from - the corresponding source for the event
catalog	string	The name of the catalog that the source belongs to. See Catalogs for the possible names

The order of the sources in the list is important. The first source is considered the preferred source of information for the event. For each catalog, one or more links should be provided to the related event items (see Relation types).

Catalogs

Several sources are cataloging seismic events. The catalog field may be used to reference the catalog that the source belongs to so that multiple sources can be linked to the same event.

The following table list the catalogs that are currently identified:

Catalog Name	Description
USGS	USGS Earthquake Hazards Program
EMSC	European-Mediterranean Seismological Centre
FDSN	International Federation of Digital Seismograph Networks

Mappings with existing catalogs

USGS Earthquake GeoJSON Summary Feed

The following table gives the mapping between the fields in the USGS Earthquake GeoJSON Summary Feed and the STAC model.

ComCat Field Name	STAC Field Name	Description
title	title	A brief description of the event.
mag	eq:magnitude	The magnitude for the event.
magType	eq:magnitude_type	The type of magnitude.
time	datetime	The time of the event converted from milliseconds since the epoch to ISO8601
updated	updated	The time when the event was last converted transformed to ISO8601
place	eq:places	The list of places referencing locations in relation with the event
url	links	The URL to the event page on the USGS website. The link must have the relationship related and the mime-type text/html
detail	links	The URL to the event detail page on the USGS website. The link must have the relationship related and the mime-type application/json
felt	eq:felt	The number of felt reports.
status	eq:status	Indicates whether the event has been reviewed by a human.
tsunami	eq:tsunami	This flag is set to true for large events in oceanic regions and false otherwise.
net	eq:sources[0].name	The network code of the preferred source of information for the event.
code	eq:sources[0].code	The event code of the preferred source of information for the event.
sources	eq:sources[*].name	The network code of the other sources of information for the event.
ids	eq:sources[*].code	The event code of the other sources of information for the event.

EMSC Earthquake Catalog

The following table gives the mapping between the fields in the EMSC FDSN-EVENT web service and the STAC model.

EMSC Field Name	STAC Field Name	Description

Relation types

The following types should be used as applicable rel types in the Link Object.

Type	Description
source	This link points to a source of information for the event.

Additional fields

Field Name	Type	Description
source	string	The name of the source of information for the event. See eq:sources.name for more information.

Contributing

All contributions are subject to the STAC Specification Code of Conduct. For contributions, please follow the STAC specification contributing guide Instructions for running tests are copied here for convenience.

Running tests

The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid. To run tests locally, you'll need npm, which is a standard part of any node.js installation.

First you'll need to install everything with npm once. Just navigate to the root of this repository and on your command line run:

npm install

Then to check markdown formatting and test the examples against the JSON schema, you can run:

npm test

This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.

If the tests reveal formatting problems with the examples, you can fix them with:

npm run format-examples