Japanese Earthquake: How Did it Happen?

While St. Norbert College kicked off its spring break, Japan was rocked by a 9.0 magnitude earthquake-the largest to ever hit the country. Shortly afterward a tsunami swept through the northern part of Japan, tearing up cities and farmland.The media quickly jumped on this phenomenon of a story describing in detail the tremendously large earthquake and the affects it had not only on the people of Japan, but changes world economic partners, such as the United States, would endure in the years to come.

The media focus a great deal of their attention on humanitarian aspects, but it is also necessary to focus on scientific features in order to understand the gravity of the situation in order to make accurate and conscientious decisions.

It may be hard to believe, but earthquakes occur daily by the thousands throughout the world. Granted most of these earthquakes are minor trembles, but some can cause an enormous amount of damage.

The earth is enveloped within an upper layer known as the crust. This crust consists of gigantic rock slabs, known as tectonic plates, which occasionally slide past each other or collide. Many of these contacts are unnoticeable to the surface, but when tensions build up, the stress may be released quickly in the form of seismic waves. These vibrations caused by the seismic waves push their way to the surface through hundreds of miles of rock.

According to Tim Flood, professor of geology at St. Norbert College, the situation was not one where the plates were sliding past one another, but rather one of the plates (under Japan) collided with another plate and fell below it at a somewhat diagonal angle. This inequality in the sea floor eventually caused the tsunami.

Interestingly enough, Flood says that earthquakes are absolutely nothing new to our planet. These have been occurring for millions of years and they have developed the sort of physical world we live in today.

For instance, climbers who have traveled to the top of the Himalayas have reported shell sightings on the mountains. Now how did sea shells get to the top of such an extremely high mountain peak? Well, research has proven that an estimated half a million earthquakes at a high frequency for millions of years allowed such a displacement of objects (like seashells) from the Tibetan Plateau to the Himalayas.

Now comparing the enormity of the recent 9.0 Japanese earthquake to the 8.3 earthquake in Chile last year, the severity intensified greatly. Flood said that when measuring via Richter scale, each gap between two consecutive numbers is multiplied by 33.

"Let's say I have some firecrackers and one of these firecrackers represents the number eight on the Richter scale," Flood said. "Now let's say we move up to number nine. Here I would light 33 fire crackers at one time in order to show the [major] difference between an 8.0 earthquake and a 9.0 earthquake."

The largest earthquake ever recorded was 9.5 that occurred in Chile in 1960. According to USGS, the recent Japanese earthquake near the east shore of Honshu is tied with the 1952 earthquake that occurred in Kamchatka.