(03-11-2025, 10:14 AM)TomK Wrote: Just asking for clarification..
Ok, I've been hosed with the demands of my 'day job' the last so long and am sorry for the delay in responding.. but here I'll give it one more try..
We have a machine, we call it a tilt meter, that records tilt (just like a carpenter’s level does) at the point it is deployed. Tilt meters as they are used in Hawaii by HVO are explained here..
https://www.usgs.gov/programs/VHP/tiltme...-volcanoes
It is a simple matter of recording a point, a “bubble” as explained in the referenced article, and then plotting its changes on a graph. The machine itself has no contact with, and in no way is directly tied to, the magma that is assumed to be the driving force of the larger ground changes being seen, recorded, by the meter. Just as we place tilt meters where they can record ground tilt they can be installed on any structure, for instance they are installed in dams to record the deformation caused by the force of the water being held back by the structure, as explained here..
https://jewellinstruments.com/wp-content...meters.pdf
In Hawaii we employ tilt meters to record ground motion, often called deformation, that is associated with magmatic processes adjacent to the deployed instrument. I say adjacent to because if an instrument were placed directly above a source and all that happened was the ground moved vertically then there would be no tilt to record. Though you will note there is also a network of GPS stations which don’t have the same limitations as a tilt meter.
So we have an instrument, a meter, in an environment that is both deep enough in the ground to get a clean reading of its motion without being overwhelmed by interference, noise, from the surface, and yet is not deep enough to avoid being influenced by the heating and cooling of the surrounding rock due to atmospheric changes. And, I am talking about, pointing out, the effects of the atmosphere, as recorded by the tilt meter, and seen superimposed over the larger changes being driven by the magmatic processes when plotted, as is the case in the HVO sourced graphics I have included in my earlier posts.
If that does not get through, as I said, if you’re really interested maybe find someone in your own personal hui that knows this kind of stuff to explain it to you. Isn’t there still a TO or two up there that are alumni of HVO?
Btw.. anyone having followed my posts here over the years knows that I often, regularly, cite the tilt as my source of whatever I am going on about. In fact, the day in 2018 when during a storm that would not let up for three days to come so as to let us in and able to see what happened, when the magma column under Puu Oo collapsed (which lead to the onset of the Leilani eruption) I said as much right here on PW. Tilt meters are cool. And omg are they sensitive.. and the digital ones employed now are fantastic. Online all the time streaming, as kalianna pointed out, the life’s rhythms of Mother Nature. To me, this is one of the most enriching parts of life..
As to that noise.. there’s all kinds. The steady daily heating and cooling which I am sure is a big concern to the astronomy community as well as just a passing fancy here in this discussion. And, please, do not confuse my use of the term noise to say it degrades the data, it's just a part of it. The nuances that are so important to know to understand what's actually being 'seen'.
And then there’s the random events like waves crashing against the shore of the island that create their own wave forms. More noise. I assume you see them with your telescopes. Are you now able to digitally identify them and cancel them out of your final products like you do the more predictable twinkling of starlight? Btw, years ago, a whole lot of years ago, I did a bunch of remodeling in the basement of the CFHT for the very purpose of limiting how much of that kind of “noise" got to the inner ring of their foundation.
Simple stuff.. definitely not rocket science.
And, since you mention in your model the magma is deep within the volcano, keep in mind that during pauses in the surface eruptions the magma comes to within feet of the surface, and is technically erupting, and the surrounding rock can itself be effected by the daily changes in the atmosphere. More on the way HVO thinks of this eruption can be read in this recent Volcano Watch..
https://www.usgs.gov/observatories/hvo/n...ay-beneath