# How to Plotting Waveforms Relative to Earthquake Origin Time?

**URL:** https://discourse.obspy.org/t/how-to-plotting-waveforms-relative-to-earthquake-origin-time/1964
**Category:** Usage Questions
**Created:** [June 14, 2024, 8:35am UTC](https://discourse.obspy.org/t/how-to-plotting-waveforms-relative-to-earthquake-origin-time/1964 "2024-06-14T08:35:41Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![moly](https://discourse.obspy.org/user_avatar/discourse.obspy.org/moly/32/1094_2.png) [@moly](https://discourse.obspy.org/u/moly)
#### Post date: [June 14, 2024, 8:35am UTC](https://discourse.obspy.org/t/how-to-plotting-waveforms-relative-to-earthquake-origin-time/1964/1 "2024-06-14T08:35:41Z")

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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:

from obspy import read, Stream  
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 = read(trdata)  
#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)

# Adjust y-axis limit

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()

 ![download](https://discourse.obspy.org/uploads/default/original/1X/375435feaa71645308bff71c4e43f198401cadc6.png)

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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: [June 14, 2024, 9:56am UTC](https://discourse.obspy.org/t/how-to-plotting-waveforms-relative-to-earthquake-origin-time/1964/2 "2024-06-14T09:56:20Z")

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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).

> **[obspy.core.stream.Stream.plot — ObsPy...](https://docs.obspy.org/master/packages/autogen/obspy.core.stream.Stream.plot.html#obspy.core.stream.Stream.plot)**

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### Author: ![moly](https://discourse.obspy.org/user_avatar/discourse.obspy.org/moly/32/1094_2.png) [@moly](https://discourse.obspy.org/u/moly)
#### Post date: [June 17, 2024, 3:37am UTC](https://discourse.obspy.org/t/how-to-plotting-waveforms-relative-to-earthquake-origin-time/1964/3 "2024-06-17T03:37:30Z")

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Thanks Megies, It is really helpful for me.