Earth Science Test 7

Fault

A fracture in Earth's crust where blocks of rock move past each other

Where are faults found?

Sometimes but not always on a tectonic plat boundaries

Stress

Force caused when pieces of crust push on or pull on each other at a fault

Earthquake

Shaking of the ground caused by sudden movement of rock along a fault

Where are most of the earthquakes on Earth?

Around or on the Pacific Tectonic Plate (Ring of Fire)

Seismic Waves

Vibrations caused by an earthquake

Focus

The point underground where rocks first begin to move at an earthquake

Epicenter

The point of Earth's surface directly above the focus

Seismograph

An instrument that constantly records ground movement over time

Seismogram

the record of ground movement made by a seismograph

Seismologists

Scientists who study earthquakes

Magnitude

The strength of the energy released during an earthquake

Richter Scale

A number range indicating the energy released during an earthquake

How does the Richter Scale work?

1. It uses seismograph readings to calculate the energy released by an earthquake

2. Each number increase on the scale represents a 10 fold increase in energy released

Primary Waves

Fastest seismic waves that travel through both liquids and solids

Secondary Waves

Slower seismic waves that travel only through solids

Surface Waves

The slowest seismic waves that only move along Earth's surface

Aftershock

A smaller earthquake following a powerful earthquake in the same area

Liquefaction

A process in which shaking of the ground causes soil to act like liquid leading to landslides and sinkholes

Tsunami

A water wave triggered by an earthquake, volcanic, eruption, or landslide

Why do tsunami waves get bigger when they are closer to land?

The waves energy has less room to spread out so directedco

Cross - Bracing

Diagonal steel beams that strengthen building walls

Base Isolators

Shock absorbers that absorb tremors and shaking during an earthquake

Shear Walls

Concrete walls with steel bars in them which reduce rocking of the wall

How do you read a Seismogram?

1. Seismogram s can be read from left to right, showing primary waves, then secondary waves, and finally surface waves

2. The X axis shows the passage of time in seconds or minutes

3. The Y axis shows the strength of the earthquake shaking