Ground motion scales helicorder vs station view numbers

Hi Ian,
My RJAM DIY was OSOP customised to suit Kinemetrics SS-1 Rangers. I have set the helicorder scaling value to 1.1 and currently get an indicated scale of Each Vertical Division = 90.91 microvolts on my helicorder display. When I go to the Station View for RA373_EHZ, the velocity and displacement figures are massive (millions of microvolts/s for velocity). If I download the instrument response file for the instrument from fdsnws, the gain and gainfrequency is set to 1. Is this correct for this instrument? I have noticed on other stations that this gain figure is variable and can be quite large. Am I missing something here?

Hi Peter:

Great to hear from you.

We do not provide a nominal response file for the RJAM universal digitizer. As the RJAM is a universal digitizer that is personalized for every sensor, there are just too many possibilities/ resultant sensitivities for a nominal response to be possible.

In order to make it obvious that the Sensitivity is unknown in the metadata, we set the Sensitivity to 1, resulting in massive velocity and displacement figures as you observed in StationView.

For additional information see here.


Hi Brandon,
Thanks for the prompt reply. I had actually read the Metadata info in the manual before I posted the question. In that case, where would I find (on the shake) the instrument response file or is it actually located at the DMC and I can’t change it.

Hello again Peter!

The instrument response files actually do not live on the Shakes themselves but are automatically built by the Raspberry Shake Community Server and distributed using the RS’s FDSN Web Service (this is where the IRIS DMC gets its copy). So, in this case, it cannot be changed.

For your own purposes, you can determine the Sensitivity and build your own response by editing one of the RESP, dataless or inventory-xml files available here.