"Jim and Connie Lehman"  writes:

> Steinar---I am not sure what arithmetic would come out at 2cm motion!!!

My mistake.  I misread my quake table and looked up 39° as the
distance, while the correct distance is about 74°.  39° is my
direction.  Then it gives about 7 mm, which is consistent with Audun's
measurements.

-Steinar

> If so you would be heading for open space rather than watching your
> pendulum.  Yes. your whole system was moving about, especially the
> vertical member supporting the mass--and you may well have seen motion
> on the boom.
>
> Jim
> ----- Original Message ----- 
> From: "Steinar Midtskogen" 
> To: 
> Sent: Sunday, March 13, 2011 2:35 AM
> Subject: Re: Lehman seismometer movement
>
>
>> "Jim and Connie Lehman"  writes:
>>
>>> Steinar--an interesting observation at 8200 km--Let's chalk it up to
>>> half plausible, and half imagination.  This event is a powerful
>>> exhibit of energy, and it will be interesting to see reports of motion
>>> exhibited or detected by conditions other than seismographs.
>>
>> By extrapolating http://jclahr.com/science/psn/magnitude.html we
>> should expect about 2 cm (!) ground movement at this distance, but I
>> expect that this would be longer periods than what my Lehman was
>> designed for.
>>
>> While my observation might be plausible I'm actually more impressed
>> with what I saw on my 4.5 Hz geophones.  Here's what I get if I apply
>> a 1 Hz lowpass filter to the N-S geophone:
>>
>> http://voksenlia.net/nytt/2011/jordskjelv-20110311.jpg
>>
>> And here's the raw unfiltered seismometer plot:
>>
>> http://voksenlia.net/nytt/2011/jordskjelv-20110311b.jpg
>>
>> It's badly clipped, so it's less useful to study.
>>
>> -- 
>> Steinar
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