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rachelmaddie

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Can someone tell me if I’m correct?
320C3776-30BE-4AF6-A359-AF2A6399CFA3.jpeg
The building at Denali can withstand a quake of magnitude 6.7, 70 times as intense.
The building at Rat Islands can withstand a quake of magnitude 7.8, 30 times as intense.
Use the properties of multiplication to solve.
Denali —> 6.7 * 70 = 469
Rat Islands —> 7.8 * 30 = 234

Solution: The building in Denali can withstand a higher magnitude of quake.
 
My first thought is, that problem is very poorly worded. He's designed "a building"; how can they ask "which structure"? They must really mean "he designed one building strong enough ... and another building strong enough ...". But it doesn't say that.

But the bigger question is, how are they measuring how "intense" an earthquake is? I know that you never multiply Richter magnitudes; the whole point is that the scale is logarithmic. You seem to be missing that point.

Please quote what you were told about what the Richter scale means in terms of intensity.

Unfortunately, you will find different things if you look at what math textbooks say about this, and what scientists themselves say. Here is the former (which is probably what your book teaches): http://www.sosmath.com/algebra/logs/log5/log56/log56.html

Here is the latter (which is not nearly as simple): http://www.geo.mtu.edu/UPSeis/intensity.html; https://courses.lumenlearning.com/geo/chapter/reading-magnitude-versus-intensity/ You'll note that the Richter scale isn't really used any more, and intensity is really the wrong word to use.

And even that is wrong: https://pnsn.org/outreach/about-earthquakes/magnitude-intensity

This is why we really need to see what you were taught about this, which you seem to have skipped over.
 
Dr.Peterson said:
My first thought is, that problem is very poorly worded. He's designed "a building"; how can they ask "which structure"? They must really mean "he designed one building strong enough ... and another building strong enough ...". But it doesn't say that.

But the bigger question is, how are they measuring how "intense" an earthquake is? I know that you never multiply Richter magnitudes; the whole point is that the scale is logarithmic. You seem to be missing that point.

Please quote what you were told about what the Richter scale means in terms of intensity.

Unfortunately, you will find different things if you look at what math textbooks say about this, and what scientists themselves say. Here is the former (which is probably what your book teaches): http://www.sosmath.com/algebra/logs/log5/log56/log56.html

Here is the latter (which is not nearly as simple): http://www.geo.mtu.edu/UPSeis/intensity.html; https://courses.lumenlearning.com/geo/chapter/reading-magnitude-versus-intensity/ You'll note that the Richter scale isn't really used any more, and intensity is really the wrong word to use.

And even that is wrong: https://pnsn.org/outreach/about-earthquakes/magnitude-intensity

This is why we really need to see what you were taught about this, which you seem to have skipped over.
Click to expand...
So how would I correctly answer this question?
 
rachelmaddie said:
So how would I correctly answer this question?
Click to expand...
1595192301529.png

An earthquake, 70 times as intense as the Dinali quake - What will be the reading in Richter scale? ...................................[edited - added "times"]

An earthquake, 30 times as intense as the Rat island quake - What will be the reading in Richter scale?...................................[edited - added "times"]
 
Last edited by a moderator:
rachelmaddie said:
I don’t understand?
Click to expand...

Tell us:

The Rat island earthquake was "how many times more intense" compared to the Dinali earthquake?

I had a mistake in the problem statements of response #4. I have corrected it. Do you understand those questions now
 
Subhotosh Khan said:
Tell us:

The Rat island earthquake was "how many times more intense" compared to the Dinali earthquake?

I had a mistake in the problem statements of response #4. I have corrected it. Do you understand those questions now
Click to expand...
Are you saying that I should not have multipled for this? I should just state this “The building is strong enough to withstand an earthquake 70 times as intense as the Denali quake and 30 times as intense as the Rat Islands quake” in the problem?
 
In order to be given this problem, you must have been given some sort of information about the Richter scale, probably similar to what is given in http://www.sosmath.com/algebra/logs/log5/log56/log56.html . I asked to show us what you were told about it. Please do so, so we can use that to explain. (Or else, use my link and apply the ideas there to your problem, especially example 1.)
 
Dr.Peterson said:
In order to be given this problem, you must have been given some sort of information about the Richter scale, probably similar to what is given in http://www.sosmath.com/algebra/logs/log5/log56/log56.html . I asked to show us what you were told about it. Please do so, so we can use that to explain. (Or else, use my link and apply the ideas there to your problem, especially example 1.)
Click to expand...
I did take a look at the link but it is to complex for me to follow. Can you please show me how I would solve this?
 
I will help as soon as you show some evidence of your thinking, so I can tell where you need help. I can't tell what part of it is too complex for you.

Again, are you saying your book never mentioned the Richter scale, or gave any examples, before giving this problem? That should be your first source of help.
 
Dr.Peterson said:
I will help as soon as you show some evidence of your thinking, so I can tell where you need help. I can't tell what part of it is too complex for you.

Again, are you saying your book never mentioned the Richter scale, or gave any examples, before giving this problem? That should be your first source of help.
Click to expand...
i asked my teacher to reword the problem and this is what she said, “Use the formula M = log I, where M is the magnitude and I is the intensity.”
 
rachelmaddie said:
i asked my teacher to reword the problem and this is what she said, “Use the formula M = log I, where M is the magnitude and I is the intensity.”
Click to expand...
I would have said:

MRichter = k * Log10(I)

But those are similar. You know how to manipulate "Log" functions.

So now show us how would you use the equation given by your teacher.
 
rachelmaddie said:
i asked my teacher to reword the problem and this is what she said, “Use the formula M = log I, where M is the magnitude and I is the intensity.”
Click to expand...
Yes, that is the first equation in the link I gave you, if we consider intensity to be measured in units such that the "standard intensity" S is 1. Presumably this is what your textbook told you.

So example 1 in the link shows how to apply it to a problem like yours.
 
Dr.Peterson said:
Yes, that is the first equation in the link I gave you, if we consider intensity to be measured in units such that the "standard intensity" S is 1. Presumably this is what your textbook told you.

So example 1 in the link shows how to apply it to a problem like yours.
Click to expand...
Using the formula, M = log I, where M is the magnitude and I is the intensity.

M= log I is the same as I = 10^M
Denali is 10^6.7 = 350831063.539
And Rat Islands is 10^7.8 * 30 = 1892872033.44
Then work out the magnitudes of each to compare what the structures would withstand using M = log I with each intensity answer
Compare 70 x I for D and 30 x I for RI
70 * 350831063.539 = 24558174447.7
and 30 *1892872033.44 = 56786161003.2
The building in Rat Islands can withstand a higher magnitude of quake.

How is this?
 
rachelmaddie said:
M= log I is the same as I = 10^M
Denali is 10^6.7 = 350831063.539
And Rat Islands is 10^7.8 * 30 = 1892872033.44
Then work out the magnitudes of each to compare what the structures would withstand using M = log I with each intensity answer
Compare 70 x I for D and 30 x I for RI
70 * 350831063.539 = 24558174447.7
and 30 *1892872033.44 = 56786161003.2
The building in Rat Islands can withstand a higher magnitude of quake.

How is this?
Click to expand...

That's the right idea, but 10^6.7 is NOT 350831063.539, and you should know that based on the number of digits. How did you calculate that? You may be using the wrong calculator button.
 
Dr.Peterson said:
That's the right idea, but 10^6.7 is NOT 350831063.539, and you should know that based on the number of digits. How did you calculate that? You may be using the wrong calculator button.
Click to expand...
Is this better?
The building at Denali can withstand a quake of magnitude 6.7.
The building at Rat Islands can withstand a quake of magnitude 7.8.
The building is strong enough to withstand an earthquake 70 times as intense as the Denali quake and 30 times as intense as the Rat Islands quake.
Using the formula, M = log I, where M is the magnitude and I is the intensity.
M= log I is the same as I = 10^M
Denali intensity is 10^6.7 = 5011872.33627
Multiplying Denali’s intensity by 70 we get 70 * 5 million or 350831063.539 for the intensity of the new Denali bridge.
And Rat Islands intensity is 10^7.8 = 63095734.448
Multiplying Rat Islands intensity by 30 for the new bridge we get 10^7.8 * 30 = 1892872033.44
So the intensity of the new Rat Islands bridge is greater than the intensity of the new Denali bridge.


Then work out the magnitudes of each to compare what the structures would withstand using M = log I with each intensity answer

Compare 70 x I for D and 30 x I for RI
70 * 350831063.539 = 24558174447.7
30 *1892872033.44 = 56786161003.2

Solution: The building in Rat Islands can withstand a higher magnitude of quake.
 
rachelmaddie said:
Is this better?
The building at Denali can withstand a quake of magnitude 6.7.
The building at Rat Islands can withstand a quake of magnitude 7.8.
The building is strong enough to withstand an earthquake 70 times as intense as the Denali quake and 30 times as intense as the Rat Islands quake.
Using the formula, M = log I, where M is the magnitude and I is the intensity.
M= log I is the same as I = 10^M
Denali intensity is 10^6.7 = 5011872.33627
Multiplying Denali’s intensity by 70 we get 70 * 5 million or 350831063.539 for the intensity of the new Denali bridge.
And Rat Islands intensity is 10^7.8 = 63095734.448
Multiplying Rat Islands intensity by 30 for the new bridge we get 10^7.8 * 30 = 1892872033.44
So the intensity of the new Rat Islands bridge is greater than the intensity of the new Denali bridge.


Then work out the magnitudes of each to compare what the structures would withstand using M = log I with each intensity answer

Compare 70 x I for D and 30 x I for RI
70 * 350831063.539 = 24558174447.7
30 *1892872033.44 = 56786161003.2

Solution: The building in Rat Islands can withstand a higher magnitude of quake.
Click to expand...
You say:

So the intensity of the new Rat Islands bridge is greater than the intensity of the new Denali bridge.​

What is - intensity of a bridge?
 
It's not the intensity of the bridge, but of the strongest earthquake the bridge can withstand. Just a matter of wording.
 
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