Global CMT Catalog

What you can build

• Attach the mechanism to an incident record

  After a felt earthquake near a site, the operator drafts the incident with the quick CMT event name, depth, Mw, and nodal planes, then updates the draft when the final solution arrives.

  With Incident Draft

• Explain a step change months later

  When a metric shifted on a date that matches a catalogue event, the operator proposes an annotation carrying the CMT event name and scalar moment instead of leaving the change unexplained.

  With Change Annotation

• Keep source parameters for insurers

  The operator files the ndk lines for each qualifying event with your claim or audit pack, so the source parameters come from the publisher rather than from memory.

  With Compliance Evidence

Requirements

• A magnitude threshold; the catalogue holds moderate to large earthquakes only
• A rule for replacing a quick CMT with the final solution, which follows three to four months later
• Site coordinates for a latitude and longitude box in the search, or a filter on the ndk hypocenter line
• Citation of Dziewonski, Chou and Woodhouse (1981) and Ekström, Nettles and Dziewonski (2012) in anything you publish

Authentication

No key or account. The ndk files are plain downloads from www.ldeo.columbia.edu and the search form at globalcmt.org is open.

Limits

• The main catalogue runs from January 1976 to about six months before the present; quick CMTs cover the gap
• Final solutions are computed for M>5 and quick CMTs for M>5.5, so smaller events are absent
• There is no JSON API or event feed; you poll the ndk directories or submit the search form

Questions and answers

How soon after an earthquake does a Global CMT solution appear?

Quick CMTs for earthquakes above M5.5 are produced rapidly and posted under NEW_QUICK. Final solutions for earthquakes above M5 are determined systematically with a three-to-four-month delay, and the main catalogue ends about six months before the present.

What is in an ndk record?

Five 80-character lines. Line one is the hypocenter from the reference catalogue such as PDE. Line two is the CMT event name and the data used. Line three holds the centroid time, location, and depth with errors. Line four holds the six moment-tensor elements. Line five gives principal axes, scalar moment, and nodal planes.

How is moment magnitude computed in the search?

The search form uses the Kanamori (1977) formula, MW = (2/3)*(log M0 - 16.1). The project asks users to cite Dziewonski, Chou and Woodhouse (1981) and Ekström, Nettles and Dziewonski (2012) in published articles.