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Is it possible for an earthquake to generate such a design in a sand pendulum during an earthquake? I saw an article online describing the story of a shop owner finding one of his pendulums had created this image during an earthquake.

I researched seismographs and they all seem to be in a linear fashion. Obviously a pendulum is not a scientific seismograph which raises the question: is this possible?

I could not find any research debunking this concept nor confirming. All the articles I read were different news groups reiterating the same story.

This image is of a sand pendulum design that a shop owner claims was created during the 45 second earthquake in Olympia, WA in 2001

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    $\begingroup$ It seem possible to me, but note that the main symmetrical pattern is what sand pendulums usually do, the Earthquake can indeed be an explanation for the irregularities in the innermost part of the pattern. $\endgroup$
    – Camilo Rada
    Jan 29, 2019 at 19:56
  • $\begingroup$ In Chile there is a room in a museum (Museo Interactivo Mirador mim.cl/index.php/es/162-filtrado-de-modulos/sala-tierra/…) that emulates the February 2010 earthquake in Chile. You can take a sand pendulum there (or a similar installation) and see what comes out. $\endgroup$
    – Camilo Rada
    Jan 29, 2019 at 19:59
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    $\begingroup$ I remember in the '89 earthquake in the San Francisco Bay Area my TV, which sat on a stand with casters, did a figure eight in my living room; it did not move in a linear fashion. $\endgroup$
    – BillDOe
    Jan 29, 2019 at 21:37

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Interesting images, thanks for sharing them.

I think its quite likely that a sand pendulum would act as a type of seismograph. I'm more in geochemistry than geophysics side of things but this kind of pattern does not seem at all inconsistent with seismic shaking. The linear nature of a recording seismograph is because it is designed to record against a time scale which is perpendicular to the "movement" scale. Even if movement had a stronger direction in the ground, the table and building this sand pendulum is in would translate the shaking movement into additional directions. There were multiple movements to make the pattern shown. It defiantly looks like more than just a truck or subway going by!

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