Sky Quakes, Broken Gear, or Something Else.

[ArMaP]

I know, but given the weirdness of these events, it's worth trying to rule items out.

For me it was always ruled out.

[guyfriday]

I just wanted to provide a somewhat update.
As of right now 9/16 00:54 PDT there has been no further negative altitude quakes. Even a couple of places that have had quakes near or at the places that did register these negative altitude quakes are registering them as being below ground again. I'm not sure what this whole mess was about. We should keep an eye out for these things in the future, I guess.

[guyfriday]

I guess I was wrong about this being over.
at 16:18 PDT a 1.7 over Boron California Depth -0.4 Mi
at 12:56 PDT a 1.4 over The Silos Montana depth -1.2 Mi
at 12:01 PDT  a 1.5 over Butte Montana Depth -1.2 Mi
at 14:09 PDT on 9/16 a 1.9 over Enumclaw Washington depth -0.4 Mi
at 12:44 PDT on 9/16 a 1.2 over Home California Depth -0.3 Mi
at 10:20 PDT on 9/16 a 1.9 over Princeton Canada Depth -0.2 Mi


I'm wondering if these are actually seismographic reports of Sonic Booms that are not being cross referenced off the Earthquake charts? A little off the book flights taking place?

[ArMaP]

I guess I was wrong about this being over.
at 16:18 PDT a 1.7 over Boron California Depth -0.4 Mi
at 12:56 PDT a 1.4 over The Silos Montana depth -1.2 Mi
at 12:01 PDT  a 1.5 over Butte Montana Depth -1.2 Mi
at 14:09 PDT on 9/16 a 1.9 over Enumclaw Washington depth -0.4 Mi
at 12:44 PDT on 9/16 a 1.2 over Home California Depth -0.3 Mi
at 10:20 PDT on 9/16 a 1.9 over Princeton Canada Depth -0.2 Mi


I'm wondering if these are actually seismographic reports of Sonic Booms that are not being cross referenced off the Earthquake charts? A little off the book flights taking place?

If an earthquake is reported as being 500 metres above sea level on an area that is 1000 metres above sea level then that means the earthquake was 500 metres below the ground.

If possible, check the altitude of the locations of those earthquakes. If the altitude is greater than the negative depth then the earthquake was underground.
Check the locations. If possible, check the altitude of the locations

[ArMaP]

Now that I have a little more time, I decided to look for more "air quakes", and I found these:

1 - M 1.2 - 16 km WNW of Emery, Utah. Location 38.997°N 111.408°W. Depth -1.3 km
Altitude on Google Earth: 2746 metres, so that earthquake was 2746 - 1300 = 1446 metres below surface.

2 - M 2.1 - 14 km S of Fern Forest, Hawaii. Location 19.337°N 155.143°W. Depth -0.5 km
Altitude on Google Earth: 716 metres. 716 - 500 = 216 metres below surface.

3 - M -0.8 - 63 km ENE of Pedro Bay, Alaska. Location 60.013°N 153.070°W. Depth -0.9 km
Altitude on Google Earth: 2026 metres. 2026 - 900 = 1126 metres below surface.

4 - M -0.5 - 7 km E of Mammoth Lakes, CA. Location 37.650°N 118.897°W. Depth -2.4 km
Altitude on Google Earth: 2340 metres. 2340 - 2400 = -60 metres.
This was the only one that, apparently, was above ground, but the depth uncertainty is 700 metres, so it's inside the error margin.

[guyfriday]

Now that I have a little more time, I decided to look for more "air quakes", and I found these:

1 - M 1.2 - 16 km WNW of Emery, Utah. Location 38.997°N 111.408°W. Depth -1.3 km
Altitude on Google Earth: 2746 metres, so that earthquake was 2746 - 1300 = 1446 metres below surface.

2 - M 2.1 - 14 km S of Fern Forest, Hawaii. Location 19.337°N 155.143°W. Depth -0.5 km
Altitude on Google Earth: 716 metres. 716 - 500 = 216 metres below surface.

3 - M -0.8 - 63 km ENE of Pedro Bay, Alaska. Location 60.013°N 153.070°W. Depth -0.9 km
Altitude on Google Earth: 2026 metres. 2026 - 900 = 1126 metres below surface.

4 - M -0.5 - 7 km E of Mammoth Lakes, CA. Location 37.650°N 118.897°W. Depth -2.4 km
Altitude on Google Earth: 2340 metres. 2340 - 2400 = -60 metres.
This was the only one that, apparently, was above ground, but the depth uncertainty is 700 metres, so it's inside the error margin.

This is a reasonable, with the exception of Mammoth Lake, explanation for most of these negative altitude quakes.

[ArMaP]

This is a reasonable, with the exception of Mammoth Lake, explanation for most of these negative altitude quakes.

Why is it not reasonable for the Mammoth Lake earthquake?
With such an error margin of 700 metres, 60 metres is less than 10% of the error margin.

[Maxmars]

I just thought I would pop this article in since it seems to present a similar (above sea level) seismic signature...

From ArsTechnica: Bizarre, nine-day seismic signal caused by epic landslide in Greenland

Earthquake scientists detected an unusual signal on monitoring stations used to detect seismic activity during September 2023. We saw it on sensors everywhere, from the Arctic to Antarctica.

We were baffled—the signal was unlike any previously recorded. Instead of the frequency-rich rumble typical of earthquakes, this was a monotonous hum, containing only a single vibration frequency. Even more puzzling was that the signal kept going for nine days.

Initially classified as a “USO”—an unidentified seismic object—the source of the signal was eventually traced back to a massive landslide in Greenland’s remote Dickson Fjord. A staggering volume of rock and ice, enough to fill 10,000 Olympic-sized swimming pools, plunged into the fjord, triggering a 200-meter-high mega-tsunami and a phenomenon known as a seiche: a wave in the icy fjord that continued to slosh back and forth, some 10,000 times over nine days.

To put the tsunami in context, that 200-meter wave was double the height of the tower that houses Big Ben in London and many times higher than anything recorded after massive undersea earthquakes in Indonesia in 2004 (the Boxing Day tsunami) or Japan in 2011 (the tsunami which hit Fukushima nuclear plant). It was perhaps the tallest wave anywhere on Earth since 1980.

I know this doesn't exactly line up with the thread topic... but it occurred to me that seismic data doesn't always relate to earthquakes... and maybe sometimes those negative values might fall into other categories of events, like this one.

[guyfriday]

Not an update or anything, but there have been more negative altitude Earthquakes lately. This was posted today about skyquakes.

Terrifying 'skyquakes' are being heard around the world including the US - and scientists don't know what they are | Daily Mail Online

Mysterious 'skyquakes' have been heard around the world for more than 200 years, but scientists have yet to uncover the cause and origin of the bizarre noises.
The sounds could be mistaken for a gunshot or a car backfiring, and have been heard in areas ranging from Belgium and Japan to the Finger Lakes region in New York.
Scientists have tried to uncover where the resounding booms are coming, proposing theories like a meteor exploding in the atmosphere, military exercises, quarry blasts and distant storms or earthquakes.

ok the meat of the story, for me anyway.

It wasn't until 2020 that scientists started using seismic data obtained from the EarthScope Transportable Array (ESTA) since 2013. 
 
ESTA is a network of more than 400 seismic stations across the US that detects earthquakes, volcanoes and landslides. 
 
A team of researchers at the University of North Carolina at Chapel Hill cross-referenced ESTA's data with news articles to determine if the noises were caused by earthquakes.
 
'Generally speaking, we believe this is an atmospheric phenomenon – we don't think it's coming from seismic activity,' Eli Bird who, a researcher who was involved in the study told Live Science at the time.
 
'We're assuming it's propagating through the atmosphere rather than the ground.'
 
The researchers speculated that another possibility could be bolides - which are space rocks that explode when they hit the Earth's atmosphere.
Bird said another possibility could be oceanic events like large waves crashing offshore or thunder cracking over the ocean.
 
'The atmospheric conditions could be such that that gets amplified in a particular direction, or is primarily affecting this localized area,' he told Live Science.
 
However, despite their efforts, seismologists have still been unable to definitively pinpoint where the skyquakes are coming from.
 
Residents in 15 Alabama counties were shocked by a boom in November 2017, prompting them to call 911 operators in fear.
 
The National Weather Service in Birmingham informed people that they couldn't clearly explain the noise and satellite imagery and radar scans didn't show signs of an explosion in the region.

So as for now these Skyquakes will remain a mystery, but the negative altitude earthquakes might have been solved to some degree here in this thread.