5. Comparing seismic trends between LIGO sites¶

On Jan 16 2020 there was a series of earthquakes, that should have had an impact on LIGO operations, I’d like to find out.

First: we import the objects we need, one for getting the data:

from gwpy.timeseries import TimeSeriesDict

and one for plotting the data:

from gwpy.plot import Plot

Next we define the channels we want, namely the 0.03Hz-1Hz ground motion band-limited RMS channels (1-second average trends). We do this using string-replacement so we can substitute the interferometer prefix easily when we need to:

channels = [
'{ifo}:ISI-GND_STS_ITMY_Z_BLRMS_30M_100M',
]

At last we can get() 6 hours of data for each interferometer:

lho = TimeSeriesDict.get([c.format(ifo='H1') for c in channels],
'Jan 16 2020 8:00', 'Jan 16 2020 14:00',
host='losc-nds.ligo.org')
llo = TimeSeriesDict.get([c.format(ifo='L1') for c in channels],
'Jan 16 2020 8:00', 'Jan 16 2020 14:00',
host='losc-nds.ligo.org')

Next we can plot the data, with a separate Axes for each instrument:

plot = Plot(lho, llo, figsize=(12, 6), sharex=True, yscale='log')
ax1, ax2 = plot.axes
for ifo, ax in zip(('Hanford', 'Livingston'), (ax1, ax2)):
ax.legend(['ground motion in the Z-direction'])
ax.text(1.01, 0.5, ifo, ha='left', va='center', transform=ax.transAxes,
fontsize=18)
ax1.set_ylabel(r'\$1-3\$\,Hz motion [nm/s]', y=-0.1)
ax2.set_ylabel('')
ax1.set_title('Impact of earthquakes on LIGO')
plot.show()

(png)

As we can see, the earthquake had a huge impact on the LIGO observatories, severly imparing operations for several hours.