Perspective: a graphical comparison of earthquake energy release

[kristopher]

[Control-Z]

1. Seriously mind blowing!

Having experienced a few of California's big earthquakes, I really cannot comprehend how much worse they could have been.

[OKIsItJustMe]

3. Log scales are like that, they sneak up on you

http://earthquake.usgs.gov/learn/topics/richter.php

[font face=Serif][font size=5]The Richter Magnitude Scale[/font]

[font size=3]…

The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value.

…[/font][/font]

(Emphasis added by me.)

[Link Speed]

2. Good catch nt

[AtheistCrusader]

4. That one is good, but this one will scare the shit out of you.

http://www.youtube.com/watch?feature=player_detailpage&v=NSBjEvPH2j4

Especially if you turn the sound up so you can clearly hear the blipping before the main fault cuts loose.

[kristopher]

5. OUCH! I turned up the volume wearing earphones

Not recommended.

I'd seen that video, but I don't think I had the sound on at all. Every time I see it I become religious long enough to thank TFSM that I wasn't there when it happened. Earthquakes are scary as hell.

[AtheistCrusader]

6. I was in a 7.2 once, but it wasn't listed on this chart.

On the 'temporarily religious' metaphysical or anthropomorphizing front, for a few minutes I couldn't shake the feeling that the very planet itself was trying to kill me.

Sorry about the sound volume. I think mine must have some sort of limiting feature.

[kristopher]

7. "the very planet itself was trying to kill me"

I can relate. I usually describe the feeling of being in a strong earthquake as " being betrayed by the ground itself". The largest I experienced was about a 6, and that was plenty. I can't imagine a 7.2 and I have absolutely no desire to obtain the experience that would improve my ability to relate.

Where were you?

[AtheistCrusader]

8. I was about halfway between Tacoma and Enumclaw when this hit.

http://en.wikipedia.org/wiki/2001_Nisqually_earthquake

I could have sworn it was a 7.2, maybe it was initially reported as that, and later corrected. I have problems with the first data I am exposed to sticking in my mind forever, even if I am made aware later of a correction.

[kristopher]

9. It could be that or it could possibly be the scale used

ML (local magnitude (or Richter - k)) was not designed to be applied to data with distances to the hypocenter of the earthquake greater than 600 km (373 mi). For national and local seismological observatories the standard magnitude scale is today still ML. Unfortunately this scale saturates at around ML = 7, because the high frequency waves recorded locally have wavelengths shorter than the rupture lengths of large earthquakes.

To express the size of earthquakes around the globe, Gutenberg and Richter later developed a magnitude scale based on surface waves, surface wave magnitude Ms; and another based on body waves, body wave magnitude mb. These are types of waves that are recorded at teleseismic distances. The two scales were adjusted such that they were consistent with the ML scale. This succeeded better with the Ms scale than with the mb scale. Both of these scales saturate when the earthquake is bigger than magnitude 8 and therefore the moment magnitude scale, Mw, was invented.

http://en.wikipedia.org/wiki/Richter_magnitude_scale


The table at the bottom of this page shows 3 out of 9 instances where the Richter rating was higher than the moment magnitude scale. http://en.wikipedia.org/wiki/Moment_magnitude_scale#Comparison_with_Richter_scale

Together with early reporting uncertainty this could explain the discrepancy without having to question the quality of your recollections.

When we returned from Japan, we were both attracted to the Pacific NW but ruled it out early because of the quakes. Having been on the East Coast and away from quakes for a while now, though, we are presently reconsidering that decision; but it still figures in our thinking.

[AtheistCrusader]

13. Very interesting. I didn't know about that.

An aside on another topic that we have discussed in the past, when that quake hit, not long after I thought to myself;

Good thing they never completed the reactors at SATSOP.

[OKIsItJustMe]

11. There had been a previous quake which measured in at 7.1

Perhaps you heard that mentioned? (Sometimes, when there is too little information about current events, reports will deal with past events.)

http://www.dnr.wa.gov/ResearchScience/Topics/GeologicHazardsMapping/Pages/nisqually_eq.aspx

At 10:54 A.M. Pacific Standard Time on Wednesday, February 28, 2001, a magnitude 6.8 Benioff zone earthquake shook southern Puget Sound. The Nisqually earthquake was centered at latitude 47.1525N, longitude 122.7197W at a depth of 52.4 km. The epicenter, located adjacent to the Nisqually River delta, was at the same location as the magnitude 7.1 earthquake on April 29, 1945. The state capital, Olympia, is located 18 km (11 mi) southwest of the epicenter. Aftershocks followed on March 1st, with a 3.4 magnitude earthquake at 1:10 a.m. followed by a 2.7 magnitude earthquake at 6:23 a.m.

…

[AtheistCrusader]

12. I or a second hand piece of information may have

flipped the bits on that follow-up mag 2.7 also.
The brain reconstructs memories in weird ways.

[truebrit71]

10. I know that feeling...I went through the Northridge quake in 1994..

...and I was convinced that the someone was picking up and slamming the house on the ground until it broke...

I had been through many other slightly smaller quakes living in So. Cal, but those were 'rollers'...Northridge was a violent "I'm going to kick your ass' quake...