What I found interesting was that a pendulum, with a reasonably high Q, could acquire energy from the seismic disturbance to shift its phase. Now a 10Kg pendulum would require a significant amount of energy, and it can only absorb energy of a very narrow bandwidth, which is calculable from its Q. The energy can be calculated, I think, from the phase shift and the amplitude of the swing. The total amount of energy over the whole spectrum must have been quite high. Cheers, Neville Michie
> On 2 Dec 2018, at 12:45, Tom Van Baak <[email protected]> wrote: > > "Paul Bicknell" -- >> Any chance of a picture of your Synchronome pendulum clock and associated >> timing / logging equipment > > Yes, I'll update that page with more info and photos at some point. > Meanwhile there are some links to follow at the end of the page: > http://leapsecond.com/pend/synchronome/quake.htm > > ---- > > "Didier Juges" -- >> Tom, >> I suspect something so sensitive gives you significant "false positives" >> when a delivery truck goes by. I assume you try to correlate your data with >> other enthusiasts nearby to resolve those discrepancies the way we do with >> our clocks? > > The pendulum is directly bolted to large thick basement corner wall. Local > door slams or delivery trucks have no effect that I've ever seen. But a 7.0 > earthquake is truly massive and it creates ground motion at the many microns > to mm levels even 1500 miles away. A precision pendulum clock is affected by > this level of vibration, especially when it persists for many minutes. > > Yes, the pendulum data correlates in time with professional seismometer > stations here and around the northwest. > > ---- > > "Hal Murray", "Poul-Henning Kamp" -- >> And can you reverse-engineer the local ground movement from the >> pendulum measurements ? > > For quartz, rubidium, and pendulum clocks, it is possible to partially > reverse-engineer effects of temperature, pressure, and humidity. These are > scaler quantities and very slow moving processes. > > Seismic effects on pendulums are a whole different problem. It's a 3D vector > quantity. They are very dynamic (rapidly changing), with a complex power > spectrum. And the interaction of ground acceleration with a swinging pendulum > is extremely dependent on angles and on the instantaneous pendulum phase vs. > seismic power relationship, which is changing every millisecond and lasts for > minutes. Plus the pendulum reaction to some of these changes is non-linear. > As Bob would say, lot's of fun. > > In theory if you had several pendulums arranged around a circle, and used > ultra wide band seismometers (or super high resolution accelerometers), and > took measurements at 10 to 100 Hz, then I suspect computer simulations might > be able to make some predictions out of the data. Which you could then back > out. > > /tvb > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
