Thread: magnitudetype in FDSN Event

Hi Philip,

Ah, the troubles with magnitudes types. I think a pragmatic partial
solution is to simply search magnitude types case insensitively, which is
exactly what the DMC's service does. We would support such a proposal to
FDSN Working Group III.

Your concept of searching for *-style magnitudes is interesting. The
example with MW works, there might be some dark corners with other types
but I cannot think of any offhand. I like the addition of wildcards as a
way to specify a pattern versus an exact search best. Might also be worth
pitching to WG III.

At the DMC we are getting out of the event information distribution
business. With NEIC and ISC catalogs, representing the bulk of event
parameters we distribute, both available via fdsnws-event services from
their respective producers, we can exit stage left so to speak.

Chad

On Jun 29, 2015, at 7:35 AM, Philip Crotwell <crotwell<at>seis.sc.edu> wrote:


Hi

I have had quite a few SOD users report trouble that ends up being related
to how the magnitudetype parameter is used by the FDSN Event web services
at IRIS and elsewhere. The trouble is both that the acceptable values of
this are unspecified in the FDSN documentation and that specific
implementations often differ from common seismic usage. For example,
suppose a user wants events with a moment magnitude (Mw) >=6. There is an
event on 2015-01-07 that satisfies this (I think) in the IRIS web service:


http://service.iris.edu/fdsnws/event/1/query?nodata=404&includeallmagnitudes=true&minmagnitude=6&starttime=2015-01-07T05:00:00&endtime=2015-01-17T06:00:00

The catch is that the preferred magnitude has type MWW and the list of
magnitude types for this event are MWB, MWC, MWW, MWP, MI, MO. So a user
searching for events with type MW and mag >=6 would get get no events
returned. Moreover, there is no way in the FDSN spec to get a list of known
magnitude types from the service.


http://service.iris.edu/fdsnws/event/1/query?nodata=404&includeallmagnitudes=true&minmagnitude=6&starttime=2015-01-07T05:00:00&endtime=2015-01-17T06:00:00&magnitudetype=MW

I understand that magnitude types are really up to the catalog, but it
would be really nice if there was a way for the service to help translate
from common magnitude type nomenclature to catalog specific. We have, for
example, a way to query for known catalogs and contributors, so it would be
might be helpful to query for known magnitude types. In addition, if the
service internally had a list of known/valid magnitude types, then it could
return a "unknown magnitude type" error instead of simple "no events
found", which would help users understand why they were not getting any
events.Even better would be for each instance to document the list of
magnitude types used and what they mean.

The optimum solution, I think, would be for the magnitudetype parameter to
support both exact matches, so users can search for MWW if that is what
they really want, and a way to search for "MW-style magnitudes" that would
be an alias for all of the various magnitudes that are subtypes of the
moment magnitude. Perhaps this could be accomplished if the given type
matched the start of the magnitude type, so MW would match MW and MWW or
perhaps MW* could be used as a type.

It would also be helpful for ease of interacting with various data centers
if the fdsn specification denoted whether the magnitudetype parameter
should be case sensitive or not.

thanks,
Philip



----------------------
DMC Web Service Developer (
http://ds.iris.edu/message-center/topic/dmc-web-service-developer/)

Sent via IRIS Message Center (http://ds.iris.edu/message-center/)
Update subscription preferences at http://ds.iris.edu/account/profile/




----------------------
DMC Web Service Developer (
http://ds.iris.edu/message-center/topic/dmc-web-service-developer/)

Sent via IRIS Message Center (http://ds.iris.edu/message-center/)
Update subscription preferences at http://ds.iris.edu/account/profile/