Study of low-frequency seismic activity at Hanford and Livingston

Alistair Hayden alistair@umich.edu)

This website contains graphs of data from the Livingston and Hanford H1 LIGO observatories. It is a result of a project to ascertain the effects of low-frequency (0.03-0.1Hz) Seismic Activity on the 4-km interferometer sensitivities (Effective Range). All the graphs, found at the links located below, therefore contain some combination of the Effective Ranges, Seismic Activity in the X-arm direction, and Seismic Activity in the Y-arm direction.

Three arbitrary seismic noise thresholds (Medium; Large; Highest) were selected by looking at the Livingston Scatter Plot of all the data and choosing three boundaries (150,000; 350,000; 550,000) where data distribution seemed to change. These boundaries were applied to the Hanford data as well by applying a Streckheisen->Guralp conversion factor (17^2 gives boundaries 519; 1,211; 1,903).

'Scatter Plots' contain Effective Range vs. Seismic Activity plots. The data occurs in separate graphs for each month and a graph of all the data from the run.
'Histograms' contain histograms of the number of Effective Ranges that fall above a given threshold.
'Files' contain downloadable, comma-delimited files of GPS times where the Seismic Activity falls above each threshold. There are also similar files for GPS times where data has been discarded (click the link for more info).

As you look at the graphs, there are a couple things to keep in mind:
- Data was sampled at one-minute intervals, therefore there are either 40320, 43200, 44640 points for each month, depending on how many days there are. Many months, especially from Livingston contain gaps in the data. These were filled in with the non-value placeholder -100.
- Seismic Activity is in the lowest measured frequency band, 0.03-0.1 Hz
- High activity in this band is usually caused by earthquakes, leading to interferometer lock loss and insprial ranges of zero in these graphs.

Livingston Graphs Hanford Graphs
Scatter Plots: The Effective Range vs. X Seismic Activity plots The Effective Range vs. X Seismic Activity plots
The Effective Range vs. Y Seismic Activity plots The Effective Range vs. Y Seismic Activity plots
Histograms: Histograms of Boxed Effective Range Histograms of Boxed Effective Range
The Effective Range in All X Seismic Activity Histograms The Effective Range in All X Seismic Activity Histograms
The Effective Range in X Seismic Activity above Medium Histograms The Effective Range in X Seismic Activity above Medium Histograms
The Effective Range in X Seismic Activity above Large Histograms The Effective Range in X Seismic Activity above Large Histograms
The Effective Range in the Highest X Seismic Activity Histograms The Effective Range in the Highest X Seismic Activity Histograms
The Effective Range in All Y Seismic Activity Histograms The Effective Range in All Y Seismic Activity Histograms
The Effective Range in Y Seismic Activity above Medium Histograms The Effective Range in Y Seismic Activity above Medium Histograms
The Effective Range in Y Seismic Activity above Large Histograms The Effective Range in Y Seismic Activity above Large Histograms
The Effective Range in the Highest Y Seismic Activity Histograms The Effective Range in the Highest Y Seismic Activity Histograms
Files: Text Files of GPS Times for each Seismic Activity Range Text Files of GPS Times for each Seismic Activity Range


M-Files that were used

The following is a table of the data channels used to get the data:
Livingston Hanford
Effective Range L1:DMT-SNSM_EFFECTIVE_RANGE_MPC H1:DMT-SNSM_EFFECTIVE_RANGE_MPC
X Seismic
Activity		 L1:DMT-BRMS_SEI_ETMX_STS2_X_0p03-0p1Hz H0:DMT-BRMS_PEM_EX_SEISX_0.03-01Hz
Y Seismic
Activity		 L1:DMT-BRMS_SEI_ETMY_STS2_Y_0p03-0p1Hz H0:DMT-BRMS_PEM_EY_SEISY_0.03-01Hz