edited 2020-07-08: refined code and updated quake
Hi Timo,
Welcome to the community forum! Using Python you can easily convert from counts to acceleration (this is also called “removing the instrument response”) by installing obspy and running the following two pieces of code:
from obspy.clients.fdsn import Client
from obspy.core import UTCDateTime, Stream
rs = Client('RASPISHAKE')
# set the station name and download the response information
stn = 'R24FA' ### <<< replace this with your station name ###
inv = rs.get_stations(network='AM', station=stn, level='RESP')
# set data start/end times
start = UTCDateTime(2020, 3, 7, 2, 40, 45) # (YYYY, m, d, H, M, S)
end = UTCDateTime(2020, 3, 7, 2, 42, 0) # (YYYY, m, d, H, M, S)
# set the FDSN server location and channel names
channels = ['EHZ', 'ENE', 'ENN', 'ENZ'] # ENx = accelerometer channels; EHx or SHZ = geophone channels
# get waveforms and put them all into one Stream
stream = Stream()
for ch in channels:
trace = rs.get_waveforms('AM', stn, '00', ch, start, end)
stream += trace
# here you will plot raw counts for all four channels
stream.plot()
Plot of raw data in counts:
# attach the response info
stream.attach_response(inv)
# remove the response and plot
resp_removed = stream.remove_response(output='ACC') # convert to acceleration in M/S
# now plot all channels in acceleration units (m/s/s)
resp_removed.plot()
Plot of acceleration in m/s2:
Note that the ground motion for this quake near my house in Panama is just barely enough to register on the accelerometers—since the accelerometer channels are not very sensitive to weak motion—so they are more noisy. Keep in mind that most of the time, when the ground is not moving enough for humans to feel, the accelerometer channels will be too noisy to get anything good out of.
There are other ways to do it, but as far as I am aware, Python/obspy this is the most reliable (free) way. Others may be able to comment on how to do it in MATLAB or R. I think it is also possible in SWARM, but only if the server provides metadata for the station (not all servers do).
Ian