# How to Plotting Waveforms Relative to Earthquake Origin Time?

Hello everyone,

I am trying to plot waveforms from different stations with respect to their epicentral distance. Currently, my plot starts at the waveform’s start time, but I would like the waveforms to start at the earthquake’s origin time. How can I modify my code to achieve this?

Here is my current code:

import glob
import matplotlib.pyplot as plt
from matplotlib.transforms import blended_transform_factory

all_z_data = glob.glob(“H?Z.SAC”)

stream = Stream()
for trdata in all_z_data:
#tr[0].detrend(“spline”, order=3, dspline=500)
#tr[0].filter(“bandpass”, freqmin = 1/40, freqmax = 1/5, corners=1, zerophase=True)
tr[0].stats[‘distance’] = tr[0].stats.sac.dist*1000
stream +=tr[0]

stream.plot(outfile=‘recordSection1.png’,type=‘section’,offset_max=900*1000, scale=15, orientation=‘horizontal’, linewidth=0.8)

plt.xlim(-20, 500) # Set y-axis limit from 0 to 800 km

# Set axis labels

plt.ylabel(‘Epicentral Distance (km)’)
plt.xlabel(‘Time (s)’)

# Show the plot

plt.show()

Check the docs for `Stream.plot()`. It’s quite long but if you scroll down there is a part `Section parameters` and you can see `reftime` being mentioned there.

Also, please have a look at the pinned “Read this first” post for formatting (the python code blocks).

https://docs.obspy.org/master/packages/autogen/obspy.core.stream.Stream.plot.html#obspy.core.stream.Stream.plot

Thanks Megies, It is really helpful for me.