Knowledge Base Question

Wilber3 - Question About Downloaded Time Series Data

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Webmaster  staff  Aug. 5, 2014, 9:59 a.m.

I am working with strong motion data downloaded from the IRIS website via Wilber3. I have a question about the data that I downloaded.

I have searched Wilber3 and I was able to successfully download time series data for events that occurred in the US Northeast.

I am not familiar with the SEED format and hence did not use it. I downloaded the data as ASCII TSPAIR in two column format.

The metadata in the file says that the second column is an Integer and is in Counts. Is there a way to convert the data that is in Counts to Acceleration units like g’s or cm/ sec 2, etc. Or is there any way to download the data in Acceleration units rather than in Counts?

Can you suggest any reference available at the IRIS website that lets me convert the downloaded time series data to units of acceleration? Here is a sample file that I downloaded:

TIMESERIES LD_ODNJ__BHE_M, 50640 samples, 40 sps, 2013-06-23T15:53:40.019500, TSPAIR, INTEGER, Counts
2013-06-23T15:53:40.019500  545
2013-06-23T15:53:40.044500  561
2013-06-23T15:53:40.069500  565
2013-06-23T15:53:40.094500  575
2013-06-23T15:53:40.119500  573
2013-06-23T15:53:40.144500  556
2013-06-23T15:53:40.169500  570
2013-06-23T15:53:40.194500  590
2013-06-23T15:53:40.219500  578
2013-06-23T15:53:40.244500  561
2013-06-23T15:53:40.269500  569
2013-06-23T15:53:40.294500  588
2013-06-23T15:53:40.319500  582
2013-06-23T15:53:40.344500  574
2013-06-23T15:53:40.369500  590
2013-06-23T15:53:40.394500  587
2013-06-23T15:53:40.419500  575
2013-06-23T15:53:40.444500  586
2013-06-23T15:53:40.469500  584
2013-06-23T15:53:40.494500  569
2013-06-23T15:53:40.519500  574
2013-06-23T15:53:40.544500  574
2013-06-23T15:53:40.569500  568
2013-06-23T15:53:40.594500  576
2013-06-23T15:53:40.619500  573
---- cut here for brevity ----

IRIS Webmaster gravatar

IRIS Webmaster  accepted answer  poster  staff  Aug. 5, 2014, 10:12 a.m.

The recommended method is to download the data through our Time Series Web Service. You can use the URL Builder application to simply insert the query values in form fields and clicking the link in the yellow box at the foot of the form.

You will have to re-initiate the request for each seismogram but the Web Service will do the conversion to units of ground motion and convert velocity to displacement, etc.

Below is a screenshot of how to do it for the first time series in your emaill below. The units of the data for that station are velocity so I have selected differentiate to get it to acceleration.

Figure 1
Figure 1: Screenshot of the IRIS Time Series Web Service URL builder.

Full resolution view of the URL Builder

Figure 2
Figure 2: Screenshot of the waveform image created by the IRIS Time Series Web Service URL Builder. Click the image for a larger view.

Full resolution view of the resulting waveform