Colliding black holes effect on the Richter scale

[jerromyjon]

Would it make sense to ask? Is there any other scale for cosmic collisions? What about supernovae? Google is stupid sometimes.

 

[sophiecentaur]

Would it make sense to ask? Is there any other scale for cosmic collisions? What about supernovae?

I have a feeling that the frequencies of the two disturbances would be very different. So perhaps Richter wouldn't apply.

Google is stupid sometimes.

You have to ask it the right questions you know. What do you think we used to do when google didn't exist? You guys have it really easy these days.

 

[davenn]

Colliding black holes effect on the Richter scale.

Would it make sense to ask? Is there any other scale for cosmic collisions? What about supernovae? Google is stupid sometimes.

The Richter scale is totally irrelevant ... it is for earthquakes and quakes specifically recorded by a certain seismometer and for events out to around 200km from the seismometer ( local/regional events). It was also designed for Californian earthquakes.

 

[fresh_42]

The Richter scale is totally irrelevant

IIRC Richter is logarithmic. Well, there is plenty of room until $- \infty$

 

[mfb]

The Richter scale is defined based on amplitudes in a seismometer - colliding black holes don't produce that. There is a relatively robust relation between the Richter scale and the energy released in an earthquake, however: Log(E/J) = 4.8 + 1.5 M where the logarithm has base 10, E is the energy and M is the magnitude.
Based on this formula, a magnitude 0 earthquake has 10^4.8 J, a magnitude 9 earthquake has 10^18.3 J (about 500 MT TNT equivalent) and a magnitude 10 earthquake has 10^19.8 J (~15 GT TNT equivalent). The first observed binary black hole merger released an energy corresponding to three times the mass of the Sun, or 5*10⁴⁷ J. Converting this to the Richter scale would give it a magnitude of 28.6. I'm not sure how meaningful this number is apart from giving an idea how much energy was released there.

We can also look at the gravitational wave energy that passed through Earth: About 30 GJ, which would correspond to 3.8 on the Richter scale. The actual motion of things on Earth was much smaller as most of this energy just passed through the Earth without notable effects.

 

[sophiecentaur]

About 30 GJ, which would correspond to 3.8 on the Richter scale.

You discuss the Richter scale being applicable to a seismometer. There are two issues that I can think of which would be relevant to the suitability of a seismometer.
Firstly, would the frequencies be matched to the sensitivity curve of a seismometer? (Perhaps they would be.)
Then there is the issue of coupling the G wave energy to the Earth's crust and to the seismometer. The wavelength of the gravity waves would be extremely long (more than 3e8 m) so the differential effects on just a few tens of km of Earth and are very small. Seismic waves travel much slower and the wavelengths are of 'geographical' magnitudes.
The G wave detectors are based on having masses, separated by as large a distance as possible and mounted so as to be isolated from the Earth. As a 'probe' that is a much more sensitive arrangement. A seismometer mass is subject to the same G variations as the local ground it stands on so would the change in force be measurable?

 

[jerromyjon]

The Richter scale is totally irrelevant ... it is for earthquakes and quakes specifically recorded by a certain seismometer and for events out to around 200km from the seismometer ( local/regional events). It was also designed for Californian earthquakes.

My wife was watching a show about various faults and the quakes they produce while I was thinking about something else and just got wondering if there were any similarities... I have a basic understanding of plate tectonics and that an event is somehow given a "value" on this scale. Just wondering if anyone has given any thought to a scale for rating cosmic events now that we can detect the ripples in spacetime...

 

[jerromyjon]

You have to ask it the right questions you know.

When you get into deep subjects without much information online you get some pretty far off results, the closest I was able to get was asteroid impacts...

What do you think we used to do when google didn't exist? You guys have it really easy these days.

It would be a lot more difficult to people reliant on google to not have that resource suddenly. It's kind of like those cashiers who can't make change in their head or on paper, if the register breaks they are helpless...

 

[sophiecentaur]

now that we can detect the ripples in spacetime...

Those ripples have been quantified in terms of Energy and that's all (afaik). The Richter Scale deals with much more tangible effects and the damage done by seismic events can be classified according to observable effects (as the Beaufort Scale is applied to the effects of Wind). This link describes how the scale was related to actual measurements and conditions on the West Coast of the USA. In other parts of the World, the correspondence between the Richter scale as measured and the actual effects.

 

[jerromyjon]

the correspondence between the Richter scale as measured and the actual effects.

I keep thinking about different BH dynamics, If one is still and one is charged spinning... Or opposites attracting... There a whole another world out there I'm referring to.

 

[mfb]

You discuss the Richter scale being applicable to a seismometer. There are two issues that I can think of which would be relevant to the suitability of a seismometer.
Firstly, would the frequencies be matched to the sensitivity curve of a seismometer? (Perhaps they would be.)
Then there is the issue of coupling the G wave energy to the Earth's crust and to the seismometer. The wavelength of the gravity waves would be extremely long (more than 3e8 m) so the differential effects on just a few tens of km of Earth and are very small. Seismic waves travel much slower and the wavelengths are of 'geographical' magnitudes.
The G wave detectors are based on having masses, separated by as large a distance as possible and mounted so as to be isolated from the Earth. As a 'probe' that is a much more sensitive arrangement. A seismometer mass is subject to the same G variations as the local ground it stands on so would the change in force be measurable?

LIGO is sensitive to frequencies of about 50 Hz to 1 kHz, higher than typical earthquake waves. The corresponding wave length is 300 km to 6000 km, that is shorter than 3e8 m (which would correspond to 1 Hz).
Gravity waves are something different.

A seismometer doesn't see gravitational waves.

I keep thinking about different BH dynamics, If one is still and one is charged spinning...

Basically all black holes spin.

 

[jerromyjon]

A seismometer doesn't see gravitational waves.

Duh. lol. Or we'd have seen collisions with no earthquake reports to attribute it to...

 

[jerromyjon]

Basically all black holes spin.

And degrees of conflict, I'd imagine? Could black holes merge peacefully? Theoretically speaking.

 

[mfb]

Duh. lol. Or we'd have seen collisions with no earthquake reports to attribute it to...

Sorry, what?
No.

And degrees of conflict, I'd imagine? Could black holes merge peacefully? Theoretically speaking.

Please limit the thread to physics.

 

[davenn]

My wife was watching a show about various faults and the quakes they produce while I was thinking about something else and just got wondering if there were any similarities...

no, no similarities with your thread topic ... colliding black holes or any other cosmological event

I have a basic understanding of plate tectonics and that an event is somehow given a "value" on this scale.

As I commented in my earlier post. The Richter Scale, which was "created" by Charles Richter was for Californian earthquakes out to a certain distance from a specific sensor.
It is VERY unfortunate that the term "Richter Scale" has got extremely misused by the media all around the world since that time and still is miss used to describe all earthquakes that the media report

When you get into deep subjects without much information online you get some pretty far off results, the closest I was able to get was asteroid impacts...

Well that is one thing that will cause earthquakes and for massive impacts like the impact in Mexico around 65 million years ago, it would have been probably felt world wide.Dave

 

[sophiecentaur]

A seismometer doesn't see gravitational waves.

Because it measures the difference in position between the Mass and where it's standing and they both experience the same part of the passing gravitational wave.

 

[alantheastronomer]

Even if it did, it's not sensitive enough to detect gravitational waves. Interesting question, though.