Background Information on the Sichuan Earthquake

On 12th May 2008, at 2:28pm, the Szechuan earthquake, which measured 8.0 on the Richter scale, shook the entire Szechuan Province, a mountainous region in Western China. The quake's epicentre was located within Wenchuan Country, 80 kilometres west-northwest of Chengdu, the capital of Szechuan, with a depth of 19 kilometres. The surrounding area, such as Shanxi province, Gansu province and Chongqing city were also adversely affected by the large magnitude quake. Since the Great Szechuan Earthquake is often labelled as "China's deadliest natural disaster in a generation" (Dessianing, 2008), it has definitely garnered much media coverage throughout the world.

Effects of the Sichuan Earthquake

Casualties: 68,712

Missing: 17,921

Injured: 374,643

Left almost 5 million people homeless

Beichuan - an estimated 80% of buildings in the old town and 60% in the new town have been destroyed

More than 7,000 collapsed schoolrooms

420,000 homes destroyed in Qingchuan County, Sichuan, following two aftershocks on Thesday May 27

Rescue methods (Local)

Rescue response was rapid

- China's Health Ministry said that it had sent ten emergency medical teams to Wen chuan County in southwest China's Sichuan Province. On the same day. China's Chengdu Military Area Command dispatched 50,000 troops and armed police to help with disaster relief work in Wenchuan County.

(Rough terrain and close proximity of the quake's epicenter, the soliers found it very difficult to get help to the rural regions of the province)

- Red Cross Society of China provided tents medical supplies, drinking water and food, and cash (donated by interational efforts)

Links for video showing damage of earthquake:

http://www.youtube.com/watch?v=suC0G2XbHmA

http://www.youtube.com/watch?v=l-_KGrcYlw4

Kobe earthquake

Occurred on January 17, 1995.

Magnitude: 7.2 on Richter scale

Hit South-Central Japan

Caused by liquefaction that led to ground shaking and thus, collapsing of buildings.

Effects:

· 4000 over deaths

· One in five of the buildings in the worst-hit area were completely destroyed (or rendered uninhabitable).

· About 22% of the offices in the central business district were rendered unusable and over half of the houses in that area were deemed unfit to live in.

· damage to highways and subways

· Most railways in the region were also damaged

· Port damaged therefore, business lost. Impact on economy.

Mitigation:

· water, electricity, gas, telephone services were fully working by July 1995

· The railways were back in service by August 1995

· A year after the earthquake, 80% of the port was working but the Hanshin Expressway was still closed.

· By January 1999, 134,000 housing units had been constructed but some people were still having to live in temporary accommodation.

- New laws were passed to make buildings and transport structures even more earthquake proof.

-More instruments were installed in the area to monitor earthquake movements.

http://www.georesources.co.uk/kobehigh.htm

Concept Map for Earthquake

Click on the C-map for better view!

Introduction to Earthquake

What is an Earthquake?

Earthquakes occur because of a sudden release of stored energy. This energy has built up over long periods of time as a result of tectonic forces within the earth. This sudden motion causes shock waves (seismic waves) to radiate from their point of origin called the focus and travel through the earth.

It is these seismic waves that can produce ground motion which people call an earthquake. Each year there are thousands of earthquakes that can be felt by people and over one million that are strong enough to be recorded by instruments. Strong seismic waves can cause great local damage and they can travel large distances.

What are Earthquake (seismic) waves

A seismic wave is simply a means of transferring energy from one spot to another within the earth. Although seismologists recognize different types of waves, we are interested in only two types:

P (primary) waves (similar to sound waves)

S (secondary) waves (shear wave)

Within the earth, P waves can travel through solids and liquids, whereas S waves can only travel through solids.

The speed of an earthquake wave is not constant but varies with many factors.
Speed changes mostly with depth and rock type. P waves travel between 6 and 13 km/sec. S waves are slower and travel between 3.5 and 7.5 km/sec.

Types of tectonic Earthquakes

There are three main plate tectonic environments: extensional (divergent), transform, and compressional (convergent). Plate boundaries in different localities are subject to different inter-plate stresses, producing these three types of earthquakes. Each type has its own special hazards.

Earthquakes at divergent plate boundaries

Credit: The Why Files

During an earthquake at a divergent fault line, tectonic plates separate. In many cases, magma rises from the mantle to fill in the gap or one plate slide down to fill in the space. These types of earthquakes usually occur in ocean.

Earthquakes at Convergent plate boundaries

An Earthquake occurs at a convergent fault line when tectonic plates collide. Typically, at such a collision, subduction zones form as a result of a denser, older plate sliding under the other. A trench, sometimes 70 miles wide, is found at a subduction site, the result of the older plate descending into the earth.

Credit: The Why Files

Earthquakes at transform plate boundaries

In an earthquake at a transform fault line, energy stored in tectonic plates is released. This release of energy causes the two plates to rub against each other.