How earthquakes happen…??

When tectonic plates collide, they can cause the Earth’s crust to crack. These cracks called faults, usually run along the edges of the plates. A few are in the middle of the plates. Most faults run deep into the crust. The rocks on both sides of the fault fit tighly together. They bend as stress builds up because of continental drift.

If the stress gets strong enough, the rocks suddenly snap backinto shape. They release shock wave of energy. The shock waves reach the surface of the Earth. The land starts to shake. An earthquake has began.

The focus of the earthquake is the point where the stress releases. The epicenter is the place on the Earth’s surface directly above the focus.

Some place that happened an earthquakes

The San Andreas fault is the best known fault in North America. It runs through California for 800 miles (1,300 km). it was the cause of the great San Fransisco earthquake of 1906. The earthquake caused massive fires and terrible destruction. It was one of the worst natural disasters even to hit the United States.

Many people think of fault lines occuring near the edges of continents. In fact, fault can occur anywhere. If you live in Southern or Midwestern United States, you might live near the New madrid Faults Line.

( Source : Rouke’s World of Science, Encyclopedia Volume 4 – Earth Science, page30-31 )

Bagaimana dengan Tsunami...?

Gempa bumi dapat menyebabkan terjadinya tsunami. Gelombang laut raksasa ini juga dapat ditemukan oleh aktivitas vulkanik, yang dipercaya muncul jika lantai samudera ikut bergoyang atau bergerak akibat gempa bumi. Goyangan itu dapat membangkitkan gelombang pasang yeng bergerak dengan kecepatan mencapai 725-800 km/jam dan menempuh jarak ratusan km. Kecepatannya berkurang ketika mencapai perairan dangkal. Namun, ketinggian gelombang meningkat hingga mencapai 15 meter, bahkan lebih. Lidah-lidah gelombang raksasa tersebut melintasi garis pantai dan menghancurkan apapun yang ada di depannya.