How big can an earthquake get?

Answer 1

According to several US news agencies (c.g. CBSNEWS), the USGS provided a comparison to help people gain perspective of Japan's recent earthquake.

It was cited that

"USGS compared Japan's earthquake with two well known quakes: last year's earthquake in Haiti and the historic 1906 San Francisco quake.

The USGS calculated the magnitude 8.9 earthquake in Japan [on March 11, 2011] to be 700 times stronger than Haiti's recent magnitude 7.0 earthquake, which devastated Port-au-Prince and killed more than 300,000 people.

When comparing to the San Francisco magnitude 7.9 earthquake in 1906, the USGS has figured that Japan's earthquake is equivalent to 30 times stronger."

Answer 2

There is no theoretical limit, however in practice the largest earthquake ever recorded has had a magnitude of 9.5.

Answer 3

Earthquakes have three different levels in terms of how deep they are. These are:

Shallow: 0-70 km deep

Intermediate: 70-350 km deep

Deep: 350-670 km deep

Answer 4

The Richter scale

For every increase of one there is a tenfold increase in the power.

Answer 5

It was measured as 7.0 on the Richter scale. Aftershocks were measured much lower.

Answer 6

That earthquake measured 7.0 mw on the Richter scale, making it extremely big.

Answer 7

7.0 on the Richter scale