> ## Documentation Index
> Fetch the complete documentation index at: https://data.avert.ldeo.columbia.edu/llms.txt
> Use this file to discover all available pages before exploring further.

# Instruments

> Seismic data

We are using Trillium Compact (120s post-hole) seismometers manufactured by Nanometrics. For more information, please see the [Nanometrics webpage](https://nanometrics.ca/instrumentation/products/seismometers/trillium-compact-posthole). The voltage signals output by the analogue seismometers are digitised using the 24-bit Nanometrics Centaur datalogger, which we also use to digitise the signals from our analogue fluxgate magnetometers.

<AccordionGroup>
  <Accordion title="Okmok">
    Seismicity captures caldera unrest cycles and eruption precursors.
  </Accordion>

  {" "}

  <Accordion title="Cleveland">
    Seismic monitoring supports eruption detection at one of the Aleutians’ most
    active volcanoes.
  </Accordion>

  <Accordion title="Poás">
    Seismic records capture both volcanic and hydrothermal system activity.
  </Accordion>
</AccordionGroup>

## Example data plots

An example of a drumplot (/helicorder) showing a day of seismic data.

<Frame caption="Drum plot showing seismic data at AV.CLNE, an AVO site on Cleveland volcano.">
  <img src="https://avert-legacy.ldeo.columbia.edu/seismology/static/img/AV.CLNE_2023.074-2023.075_seismic-highpass-helicorder.png" alt="Drum plot showing seismic data at AV.CLNE, an AVO site on Cleveland volcano." height="400" className="rounded-lg" />
</Frame>