Re: OT: Seismographs

On Jul 29, 9:00 pm, "Paul Hovnanian P.E." <p...@xxxxxxxxxxxxx> wrote:
I've got a question about the state of the art in seismographs
[after seeing drum recorder on the California quake, and
accelerometer readings in old Indonesian quake footage]

Seismometers come in short-period and long-period variants,
and resonance is an important part of the signal/noise
equation: accelerometers pick up lots of out-of-band noise.
A simple accelerometer with millisecond output has to be
a short-period seismometer, suitable for local monitoring only.

The drum recorder is just a visual aid and is maintained as
a photo-opportunity model or as a teaching/display model.
The real recordings, nowadays, are digital for the central office
units, and FM encoded onto analog tape for field units (battery
power for an analog tape drive is ... favorable).
.