Geotechnical Engineering 101 and more…

Building firm foundations

Earthquake in Japan

Posted by Kshitija Nadgouda on July 18, 2007

A 6.8 Magnitude earthquake hit Japan on Monday, July 16, 2007. Considering the high magnitude, the loss of life was small – seven persons dead and hundreds injured. So what exactly is an earthquake?

Japan quake July 2007
(Image Courtesy: Environment News Service and Japan Meteorological Agency)

Wikipedia defines earthquakes as “the result from the sudden release of stored energy in the Earth’s crust that creates seismic waves”. I will try and explain that in simple words.

The earth is not a stationary, passive body. In fact, it is a very active and changes are continuously taking place inside it. The “solid” earth is actually made of four parts: the inner core which is solid, the outer core which is liquid, the mantle and the crust which are solid too.The crust is the thinnest layer and being relatively cold, it is brittle. The upper part of the mantle and the crust together make up the “lithosphere”.

Earth Core
(Image Courtesy: Nevada Seismological Laboratory)

The lithosphere is not contiguous, it is made up of several pieces like a jigsaw puzzle. However, these pieces – called tectonic plates – are continuously moving around, sliding past each other, colliding or moving away from one another. When these plates that are touching each other, get locked at the plate boundaries (while the rest of the plate is trying to move), it causes frictional stress. When this stress is exceeded beyond a certain value, these plates get unlocked and suddenly move relative to one another. This violent displacement is called an earthquake.

Here are some pictures that show devastation caused by earthquakes.

Collapse of the Hanshin Expressway Bridge in the Kobe, Japan earthquake of 1995.
Hanshin Expressway Collapse
(Image courtesy: University of Washington)

The 1906 earthquake damage in San Francisco, USA.

(Image courtesy: Science Photo Library)

The earthquake in Bhuj, India in 2001

Bhuj Quake
(Image courtesy: International Federation of Red Cross and Red Crescent Societies)

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Copyright Kshitija Nadgouda.


6 Responses to “Earthquake in Japan”

  1. devindra singh said

    Can I hear how and why earthquakes occur

  2. I have given a brief description about it in this article. If you want more, I will certainly try and write about it in detail.

  3. khalila said

    hi…can you help me?i need article about earthquake in bengkulu. do you have it?

  4. Nicely written!! not that complicated to understand for a person without any technical education. One question tough, have the techniques of predicting earthquakes advanced sufficiently to minimize the damage or loss? Because these techniques, if well developed, i think will have positive socio economic repercussions.

  5. Hi Aseem,
    Humans cannot predict earthquakes as yet. There has been tremendous research and attempts at it, but to no avail! However, by monitoring the tectonic movements and vibrations felt on the surface of the earth, we can get a few minutes or a couple of hours lead into knowing when the earthquake will reach us. That is usually sufficient for saving lives, but we can do nothing about the property/road or structural damage in general. The only way to minimize that – is to build structures that can withstand these vibrations.

    You have given me a topic to write about. Thanks! And check back for more in a day or two.

  6. Fishily said

    Somehow i missed the point. Probably lost in translation đŸ™‚ Anyway … nice blog to visit.

    cheers, Fishily.

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