Hello Esteemed Gentlemen,

Many of us were wondering why recently most of the Yellowstone Webicorder displays were calibrated down to such a low sensitivity. Rather than speculate, it would be nice to know why, if either of you would be so kind as to enlighten us. Thanks much!

We are happy to answer your inquiry.

I presume you are asking about the amplification scale of our Yellowstone webicorders. In which case their amplifications have not been changed. The amplification value depends on multiple factors including the sensitivity and amplification of the seismometers, amplification of the telemetry and recording systems, ground noise including geothermal, human and wind induced noise, etc. that all lead to what we call the system sensitivity and related magnification. And on occasion station signals are lost due various technical glitches that we fix as soon as possible.

The Yellowstone area as you may expect has a high level of natural noise related to ground shaking from the widespread geothermal features. Thus each station is tuned, like an AM/FM radio station, to show the best signal keeping in mind that we want provide images of small and larger earthquakes that do not go off scale on the recording system.

In more detail, calibrations of display systems depend the amplification levels set on the preamp, seismometers, etc., that depend on natural ground noise conditions. Then the amplification levels are set on the webicorders for optimum viewing and implicitly take into account the system calibration. This means that each station webicorder is tuned to its own condition.

An example of our seismic station metadata with sensor information can be seen from:

www.quake.utah.edu...

Station metadata and quality information including calibration response can be accessed in a station by station mode at:

www.quake.utah.edu...

This information is required to manage the network in terms of calibration data for all stations and display of such data, but it is in technical seismology terminology.

The bottom line is that if we turn up a station magnification it may cause loss or over saturation of a signal from larger the daily earthquakes. Thus our staff works at keeping the webicorder at optimum levels for best fidelity over the average daily magnitude range expected for a specific station.

Hope that helps.