# Output is velocity or acceleration

**URL:** <https://discourse.obspy.org/t/output-is-velocity-or-acceleration/2262>\
**Category:** Usage Questions\
**Created:** [July 17, 2025, 9:06pm UTC](https://discourse.obspy.org/t/output-is-velocity-or-acceleration/2262 "2025-07-17T21:06:37Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Nas94](https://discourse.obspy.org/user_avatar/discourse.obspy.org/nas94/32/838_2.png) [@Nas94](https://discourse.obspy.org/u/Nas94)\
**Post date:** [July 17, 2025, 9:06pm UTC](https://discourse.obspy.org/t/output-is-velocity-or-acceleration/2262/1 "2025-07-17T21:06:37Z")

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I used the following code to retrieve data. If some stations in my study area have been equipped with accelerographs or seismographs, it does affect the output. I wrote “output velocity” because I need velocity data; however, I know that some stations are accelerographs. For example, the below station is an accelerograph, so the output has to be velocity or acceleration?

client = Client(‘NCEDC’)  
t = UTCDateTime(“2010-01-10T00:27:31”)  
st = client.get\_waveforms(“BK”, “JCC”, “”, “\*H?”, t, t + 3 \* 60, attach\_response=True)  
st.detrend(type=“demean”)  
st.detrend(type=“linear”)  
st.detrend(type=“polynomial”, order=2)  
st.remove\_response(output=‘VEL’, water\_level=60)  
st.filter(type=“bandpass”, freqmin=0.1, freqmax=5)  
st.write(“Number17”, format=“TSPAIR”, Units=‘m/s’)  
st.plot()

And how do I determine the type of NHERP(Vs30) of stations ?  
Thanks alot

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**Author:** ![megies](https://discourse.obspy.org/user_avatar/discourse.obspy.org/megies/32/9_2.png) [@megies](https://discourse.obspy.org/u/megies)\
**Post date:** [July 28, 2025, 7:49am UTC](https://discourse.obspy.org/t/output-is-velocity-or-acceleration/2262/2 "2025-07-28T07:49:47Z")

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If you select `output="VEL"` then indeed the result should be ground velocity in m/s.