Thread: Dynamic Data request

Started: 2019-02-22 00:59:16
Last activity: 2019-02-22 02:12:34
Lucas Sawade
2019-02-22 00:59:16
To whom it may concern,

I have been looking into different ways of downloading/requesting data from IRIS, among them the obspy fdsn massdownloader and SOD (Standing Order for Data). As of now the SOD approach seems to be best suited for me, but since I want to scale my application in the long run, I thought it would be best to ask instead of just going with the one I found best till now. So, here is my case:

The page globalcmt creates Centroid Moment Tensor solutions for new earthquakes every day. I am always downloading the newest one and then request data for that specific event. As of now, what I’m doing is, windowing the event location, origin time and magnitude such that I only get one event. Then, I request the time series data using that found event using its parameters. Is that the best way of going about it? I am especially unsure about the whole windowing thing since it seems to me that for certain events it might be prone to errors (two very similar locations).

Maybe, I was just not able to find the right webpage/source, it would be nice if you could just point me to something!

Thank You!

Cheers,

Lucas



  • Nick Falco
    2019-02-22 02:12:34
    Hi Lucas,

    The ObsPy massdownloader seems like a reasonable way to request data assuming that you are using Python. Otherwise there are simpler ways to request data that don’t require this large of a dependency. I have not personally used SOD before, but after reading through some of the SOD documentation it looks like it may have to be run continuously and could be overkill for your use case.

    The most direct way to download data from the DMC is to make requests to the IRIS fdsnws-dataselect web service https://service.iris.edu/fdsnws/dataselect/1/ directly. You can make requests to the service directly using a Unix command line utility like wget or curl, as described in the examples at https://service.iris.edu/fdsnws/dataselect/docs/1/help/#dataselection. FetchData https://seiscode.iris.washington.edu/projects/ws-fetch-scripts/wiki, a command line utility designed to make FDSN web service data requests, could also be used.

    I think the solution that is best for you will largely depend on your software development background. SOD may provide an out of the box solution, but you could pretty easily write a more streamlined script by directly using the web services as I’ve indicated above.

    An additional optimization would be to use of the IRIS availability web service https://service.iris.edu/irisws/availability/1/. You could check your time windows against the stations that you are requesting data from in order to ensure that the data you are requesting is actually available. This would help you to avoid making requests that result in no data being returned.

    Lastly, we are currently developing a new command line client for robust data retrieval from the IRIS DMC, called ROVER. This tool is not yet available and undergoing internal beta testing, but will be released in the near future. By using the IRIS DMC's availability web service, it verifies that all data that can be retrieved has been retrieved. It is also restartable in case of a failure. This will be another option to consider once it is released.

    Let me know if you have any questions.

    Thanks,

    Nick
    --
    Nick Falco
    Web & Apps Developer
    IRIS Data Management Center
    nick<at>iris.washington.edu

    On Feb 21, 2019, at 9:31 AM, Lucas Sawade <lsawade<at>princeton.edu> wrote:

    To whom it may concern,

    I have been looking into different ways of downloading/requesting data from IRIS, among them the obspy fdsn massdownloader and SOD (Standing Order for Data). As of now the SOD approach seems to be best suited for me, but since I want to scale my application in the long run, I thought it would be best to ask instead of just going with the one I found best till now. So, here is my case:

    The page globalcmt creates Centroid Moment Tensor solutions for new earthquakes every day. I am always downloading the newest one and then request data for that specific event. As of now, what I’m doing is, windowing the event location, origin time and magnitude such that I only get one event. Then, I request the time series data using that found event using its parameters. Is that the best way of going about it? I am especially unsure about the whole windowing thing since it seems to me that for certain events it might be prone to errors (two very similar locations).

    Maybe, I was just not able to find the right webpage/source, it would be nice if you could just point me to something!

    Thank You!

    Cheers,

    Lucas



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23:07:15 v.22510d55