Lesson 10 Seismology

Seismology is the study of what is under the surface of the Earth by measuring vibrations on the Earth's surface. A person who does this is called a seismologist. It is part of the science of geophysics, which studies the physics of the processes that formed the Earth and other planets. Seismology is done by seismologists and geophysicists using devices called geophones, hydrophones or seismometers to pick up the vibrations. Seismology can either be passive, just listening to vibrations caused by earthquakes and volcanic activity, or active, using small explosive charges to send vibrations into the ground. Seismic detectors come in two types, one which measures up and down vibrations, and one which measures side to side vibrations. Both types use an arrangement of a magnet and a coil of wire which will convert the vibrations into an electrical signal which can be stored in a computer for analysis. Seismologists can find the location of earthquakes by plotting received vibrations on a map. They can also pick up underground nuclear tests, and this is what many of the seismic recording stations were set up for. They can also examine the crust in a seismic survey to find information about layers of rock, locate oil or gas fields and to get information about the internal structure of volcanoes.

Memorize the words:

to measure – вимірювати device – пристрій, прилад to pick up – відбирати, добирати explosive – вибуховий charge – заряд coil – котушка wire – дріт, провід to convert – перетворювати to store – накопичувати, зберігати to plot – накреслювати план to receive – одержувати, отримувати nuclear – ядерний to record – записувати, реєструвати to set up – встановлювати, розміщувати survey – огляд, обслідування to locate – визначати місцезнаходження

Answer the questions:

1. What devices do seismologists and geophysicists use? What for?

2. What is passive seismology?

3. How does active seismology work?

4. What are the two types of seismic detectors?

5. How do seismic detectors work?

6. What can seismologists do?

Lesson 11

Earthquakes

A replica of (78–139 AD) seismometer. It employed a pendulum sensitive to ground tremors; placed in Luoyang in 133, it detected an earthquake 400 to500 km away in Gansu.

Damage from the San Francisco, California earthquake in 1906.

An earthquake (also known as a quake or tremor) is a violent movement of the rocks in the Earth's crust. Earthquakes are usually quite brief, but may repeat over a long period of time. They are the result of a sudden release of energy in the Earth's crust. This creates seismic waves, waves of energy that travel through the Earth.

There are large earthquakes and small earthquakes. Big earthquakes can take down buildings and cause death and injury. The study of earthquakes is called seismology. Seismology studies the frequency, type and size of earthquakes over a period of time.

When the earth moves offshore in the ocean, it can cause a tsunami. A tsunami can cause just as much death and destruction as an earthquake. Landslides can happen, too. This is an important part of the Earth's cycle.

Earthquakes are measured using observations from seismometers. The magnitude of an earthquake, and the intensity of shaking, is measured on a numerical scale. On the scale, 3 or less is scarcely noticeable, and magnitude 7 (or more) causes damage over a wide area.

The ancient Chinese also used a device that looked like a jar with dragons on the top surrounded by frogs with their mouths open. When an earthquake occurred, a ball fitted into each dragon's mouth would drop out of the dragon's mouth into the frog's. The position of the frog which received a ball indicated the direction of the earthquake.

Memorize the words:

earthquake – землетрус replica – точна копія to employ – наймати на роботу, використовувати pendulum – маятник sensitive – чутливий, сприйнятливий tremor, quake – тремтіння, дрижання to detect – виявляти,викривати brief – короткий sudden – раптовий, несподіваний release – вивільнення, звільнення wave – хвиля frequency – частота, частотність offshore – у відкритому морі magnitude – величина, розмір numerical – числовий, цифровий scale – шкала scarcely – ледве noticeable – помітний, гідний уваги jar – глечик to fit in – пристосовувати

Answer the questions:

1. What is an earthquake? 2. What is the cause of earthquakes? 3. What creates seismic waves? 4. What does seismology study? 5. What do earthquakes offshore create? 6. How is magnitude of earthquakes measured? 7. How did the seismometer of the ancient Chinese work?