PSN-L Email List Message
Subject: Re: Relevelling
From: Steinar Midtskogen steinar@.............
Date: Tue, 29 Jul 2008 22:43:48 +0200
> In a message dated 2008/07/29, steinar@............. writes:
> I've had a SEP seismometer running for a month or so and everything
> has been fine. However, a couple of days ago while we were away on
> vacation it began reporting no activity. When I got back home I found
> that the mass had moved all the way to the side, so I had to change
> the tilt a little so it would move back to the centre again.
> Has there been any rain while you have been away? This is a
> common cause of real ground tilts. Did you switch off the heating
> while you were away?
No rain. Hardly a cloud.
No changes to the heating. There is no heating in that room and the
temperature there is extremely stable. I have a temperature sensor
there and for the day it happened I logged a maximum of 21.33C and a
minimum of 21.04C. I don't think one can get a more stable
temperature than that. Humidity ranged from 38.7% to 43.9%.
The only thing out of the ordinary is that the outside temperature
during the past days reached a high of 29.4C which is a new record for
the 5 years I've been recording the weather. The ground temperature
is very high as well, 18C as deep as 50 cm, something which I don't
think I've recorded before.
> Have you fitted metal ground plates under the adjustment screws?
Yes, but they're not bolted or otherways attached to the floor.
> I use about 8 cm square x 2.5 mm thick SS.
They're around 3x3 cm and 1-2 mm thick.
> Something has happened in your absense. The only question is
> what and can you avoid it happening again?
True. I guess I might have to wait for it to happen again and see if
that offers more hints.
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