Modified Mercalli Shaking Intensity Scale

 Modified Mercalli Shaking Intensity Scale

In the early days of earthquake investigations, seismologist used earthquake intensities as the applicable yardstick to estimate the size of an earthquake. Intensities are measured by means of the degree of damage to structures, the amount of disturbance to the ground surface, and the extent of human and animal reactions to the shaking.

A scale developed by the Italian seismologist and volcanologist G. Mercalli in 1902 has 12 values for describing an earthquake. The scale was later modified to better fit modern conditions.

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How Often do Earthquakes Occur?

How often do earthquakes occur?

To most people’s surprise, significant worldwide earthquake activity happens at a phenomenal rate. The number of worldwide earthquakes registering M4.0 or stronger ranges between 100 – 500 events per week; activity in the M5+ range happens between 5 – 70 times per week; and it is unusual when a M6+ quake does not happen somewhere on the planet during a week.

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Why do Earthquakes Happen ?

What causes earthquakes?

Just below Earth’s surface, the crust layer is divided up into several “plates”, which are always moving slightly. Between these plates are fault lines, which is where the plates come together. At these fault lines, the plates are constantly rubbing and sliding against each other, but sometimes due to irregularities and high friction, the plates become locked and stop moving.

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What is a Tsunami?

 What are Tsunamis?

On Boxing Day 2004 a horrific wave swept across the Indian Ocean killing over two hundred and thirty thousand people. After receiving massive media coverage, the topic of Tsunamis became widely discussed for a time before dying down. However, this topic of discussion returned abruptly in March 2011 when a Tsunami devastated the Japanese East Coast. But what are Tsunamis? What causes them?

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Earthquakes in Japan

 Earthquakes and Tsunamis in Japan

When the blocks of earth slip past each other on a fault line on land it is called an earthquake. When the blocks of earth skip past one another on a fault line in the ocean it is still considered an earthquake, but this type of earthquake can cause a Tsunami. In March of 2011 a giant earthquake hit Japan and then created a Tsunami that killed thousands of people and cause billions of dollars in property damage.

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