unit6earthquake

unit6earthquake内容摘要：

rface. • The world39。 s deadliest recorded earthquake occurred in 1556 in central China. It struck a region where most people lived in caves carved from soft rock. These dwellings collapsed during the earthquake, killing an estimated 830,000 people. In 1976 another deadly earthquake struck in Tangshan, China, where more than 250,000 people were killed. Unit 6 Earthquake • The earliest recorded evidence of an earthquake has been traced back to 1831 BC in the Shandong province of China, but there is a fairly plete record starting in 780 BC during the Zhou Dynasty in China. • The cause of earthquakes was stated correctly in 1760 by British engineer John Michell, one of the first fathers of seismology, in a memoir[memwa:]论文集 where he wrote that earthquakes and the waves of energy that they make are caused by shifting masses of rock miles below the surface. Unit 6 Earthquake • Most earthquake waves have a frequency of less than 20 Hz, so the waves themselves are usually not heard. Most of the rumbling noise heard during an earthquake is the building and its contents moving. • The majority of the earthquakes and volcanic eruptions occur along plate boundaries such as the boundary between the Pacific Plate and the North American plate. One of the most active plate boundaries where earthquakes and eruptions are frequent, for example, is around the massive Pacific Plate monly referred to as the Pacific Ring of Fire. Unit 6 Earthquake • Common myths about earthquakes • 1. Head for the doorway • An enduring earthquake image of California is a collapsed adobe house(土砖房屋 )with the door frame as the only standing part. From this came our belief that a doorway is the safest place to be during an earthquake. Trueif you live in an old, unreinforced adobe home. In modern houses, doorways are no stronger than any other part of the house and usually have doors that will swing and can injure you. You are safer under a table. Unit 6 Earthquake Adobe house: a house made by bricks and drymud. Unit 6 Earthquake • 2. It39。 s hot and dry earthquake weather! • Many people believe that earthquakes are more mon in certain kinds of weather. In fact, no correlation with weather has been found. Earthquakes begin many kilometers below the regi。