4. 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="nds.gwosc.org",
)
llo = TimeSeriesDict.get(
    [c.format(ifo="L1") for c in channels],
    "Jan 16 2020 8:00", "Jan 16 2020 14:00",
    host="nds.gwosc.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)

../../../_images/blrms-5.png

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