# How many times stronger is a 7.2 earthquake compared to a 4.3 earthquake on the richter scale?

Aug 25, 2009
in
Earthquake Questions

I need to know how to work this question out. I think the richter scale works a base of 10 but that is all I know of this type of problem. If anyone can help, I’d really appreciate it.

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5 comments

ideaquest on August 25, 2009 at 9:35 am

10^(7.2 – 4.3)

= 10^2.9

= 794X

The Richter magnitudes are based on a logarithmic scale (base 10). What this means is that for each whole number you go up on the Richter scale, the amplitude of the ground motion recorded by a seismograph goes up ten times.

Using this scale, a magnitude 5 earthquake would result in ten times the level of ground shaking as a magnitude 4 earthquake (and 32 times as much energy would be released).

To give you an idea how these numbers can add up, think of it in terms of the energy released by explosives: a magnitude 1 seismic wave releases as much energy as blowing up 6 ounces of TNT. A magnitude 8 earthquake releases as much energy as detonating 6 million tons of TNT.

Richter TNT for Seismic Example

Magnitude Energy Yield (approximate)

-1.5 : 6 ounces Breaking a rock on a lab table

1.0 : 30 pounds Large Blast at a Construction Site

1.5 : 320 pounds

2.0 : 1 ton Large Quarry or Mine Blast

2.5 : 4.6 tons

3.0 : 29 tons

3.5 : 73 tons

4.0 : 1,000 tons Small Nuclear Weapon

4.5 : 5,100 tons Average Tornado (total energy)

5.0 : 32,000 tons

5.5 : 80,000 tons Little Skull Mtn., NV Quake, 1992

6.0 : 1 million tons Double Spring Flat, NV Quake, 1994

6.5 : 5 million tons Northridge, CA Quake, 1994

7.0 : 32 million tons Hyogo-Ken Nanbu, Japan Quake, 1995; Largest Thermonuclear Weapon

7.5 : 160 million tons Landers, CA Quake, 1992

8.0 : 1 billion tons San Francisco, CA Quake, 1906

8.5 : 5 billion tons Anchorage, AK Quake, 1964

9.0 : 32 billion tons Chilean Quake, 1960

10.0 : 1 trillion tons (San-Andreas type fault circling Earth)

12.0 : 160 trillion tons (Fault Earth in half through center,

OR Earth’s daily receipt of solar energy)

——————————————————————————–

Earthquake Severity

Richter Earthquake

Magnitudes Effects

Less than 3.5 — Generally not felt, but recorded.

3.5-5.4 — Often felt, but rarely causes damage.

Under 6.0 — At most slight damage to well-designed buildings. Can cause major damage to poorly constructed buildingsover small regions.

6.1-6.9 — Can be destructive in areas up to about 100 kilometers across where people live.

7.0-7.9 — Major earthquake. Can cause serious damage over larger areas.

8 or greater — Great earthquake. Can cause serious damage in areas several hundred kilometers across.

—–

Aaron H on August 25, 2009 at 9:35 am

1*10^2.9 or 900 I think

pockettanx90 on August 25, 2009 at 9:35 am

The numbers on the richter scale mean are the exponets with base 10. so in this case you would compare 10^4.3 and 10^7.2 devide the larger by the smaller and you get the answer.

Steven W on August 25, 2009 at 9:35 am

simple, you minis, example 7.2 – 4.3 = 2.9, 2.9 is your answer, any questions?

zanti3 on August 25, 2009 at 9:35 am

As others have said, the scale is logarithmic, with each unit increase signifying the earthquake is 10 times stronger. So, to compare the 7.2 quake with a 4.3 one, find the number whose logarithm is 2.9. From that you’ll find the 7.2 quake is about 800 times stronger.