About the focal mechanism search

Use this search to produce a list of focal mechanism solutions, within the ISC Bulletin - this includes important datasets such as the Global Centroid Moment Tensor (GCMT) Project. Returned data includes event ids, scalar moments, moment tensor components, nodal planes, principal axes and the hypocentre/centroid parameters for each focal mechanism solution.

Database

• Reviewed ISC Bulletin:

A subset of the ISC Bulletin that has been manually reviewed by ISC analysts. This includes all events that have been relocated by the ISC. For more information on the Reviewed ISC Bulletin, see here.

• ISC Bulletin:

The entire ISC Bulletin from both reviewed and unreviewed events. This includes the most recent events, which have yet to be reviewed.

Output format

• CSV formatted focal mechanisms:

A fixed format, comma separated output, with one line per focal mechanism solution. For a full explanation of each field, see the csv focal mechanism output page.

• QuakeML:

QuakeML is an XML representation of seismological data. Data are output as an XML stream using the QuakeML XML Schema, version 1.2. Similar to the CSV output, only the origin for which there are focal mechanism solutions are output for each event (i.e. the prime hypocentre will not be output if there is no focal mechanism solution). This output is not designed for use in a browser and will cause browsers to crash for large queries. For a complete explanation of the schema, please view the documentation on the QuakeML site.

Search region

There are four possible methods for defining a search region (rectangular, circular, global, Flinn-Engdahl region). Leaving fields blank, will automatically default to a global search. To interactively define a search region, using customised shapes, please use the interactive search page. The defined region is used to check only the prime hypocentre - secondary hypocentres within a search region will not influence the results.

Time period

This is the start and end date to search for events. Only the prime hypocentre will be searched to match events - i.e. origin times for secondary hypocentres will not influence the results.

Unknown depths

As some events have no determined depth, you may optionally choose to include events with unknown depths in the search. This will return events which match any selected depth constraint you enter as well as events with no depth.

Unknown magnitudes

As some events have no determined magnitude, you may optionally choose to include events with unknown magnitude values in the search. This will return events which match any selected magnitude constraint you enter as well as events with no magnitude value.

Magnitude type

Limit events by magnitude for specific magnitude types. Due to the large number of magnitude types and the various notation used, the selected type will search all magnitudes of that type. E.g. MB will match all body-wave magnitudes: mb, mB, MB, mb1mx, etc.

Magnitude author

Limit events by magnitude values determined by a specific author. ISC, NEIC, GCMT/HRVD, JMA, amongst others are considered reliable magnitude authors. The default uses the prime author - these are magnitudes directly associated with the prime hypocentre (and usually the same author) - i.e. for events with an ISC authored prime hypocentre, selecting 'Prime author', will only return events with magnitudes (matching any selected min/max value) determined by the ISC. For more information on any of these agencies, please visit the contributing agencies page.

E.g. To search for events with MW >= 6, you may want to specify the magnitude author to be GCMT as there may be few events where the 'prime author' has computed a moment magnitude.

Please note: selecting either GCMT or HRVD, will return results from both agencies, as GCMT is a continuation of HRVD.

Focal mechanism author

Limit focal mechanism solutions computed by a specific author. The drop-down list is a complete list of agencies that have contributed focal mechanism solutions to the ISC Bulletin. Selecting from this list will give access to specfic data sets such as the GCMT project data or NEIC moment tensors. For more information on any of these agencies, please visit the contributing agencies page.

Please note: selecting either GCMT or HRVD, will return results from both agencies, as GCMT is a continuation of HRVD.

Output links

This provides links for each event to the full Bulletin listing. There are also links for each author to provide the full agency details.