Andrija Mohorovicic discovered that seismic wave speed _____________ abruptly at about 30 km beneath the surface of continents.
What is increases?
100
This causes buildings to either sway or collapse during a bad earthquake.
What is the type of ground they are on?
100
If you are indoors during an earthquake, it is important to protect yourself from falling debris and do this.
What is stand in a doorway or crouch under a desk?
100
The location within Earth along a fault at which the first motion of an earthquake occurs is called this.
What is the focus?
200
Body waves that are known as primary or compression waves which are the fastest seismic waves, so they are first to be detected.
What are P waves?
200
The three main layers of Earth's interior are the crust, mantle and core. The five mechanical layers are: lithosphere, ___________, outer core and ______________.
What are asthenosphere and inner core?
200
Vibrations in the ground can be detected and recorded by using this instrument.
What is a seismograph?
200
If you are in a car during an earthquake you should do this.
What is stop in a place away from tall buildings, tunnels, power lines or bridges?
200
Earth's surface directly above the focus is called this.
What is the epicenter?
300
Body waves that are known as secondary waves or shear waves and are the second fastest waves to arrive at detection sites.
What are S waves?
300
These are locations on Earth's surface where no body waves from a particular earthquake can be detected.
What are shadow zones?
300
A tracing of earthquake motion that is recorded by a seismograph is called this.
What is a seismogram?
300
Mostly, scientists study these to predict where future earthquakes are most likely to occur.
What is past earthquakes?
300
This is the sudden return of elastically deformed rock to its undeformed shape.
What is elastic rebound?
400
Surface waves that cause rock to move side to side and perpendicular to the direction in which the waves are traveling.
What are love waves?
400
S waves cannot reach S-wave shadow zones because they cannot pass through this layer.
What is the liquid outer core?
400
To determine the distance to an epicenter, scientists analyze these.
What are arrival times of P and S waves?
400
This is an area along a fault where relatively few earthquakes have occurred recently but where strong earthquakes occurred in the past.
What is a seismic gap?
400
At some plate boundaries, there are regions of numerous, closely spaced faults called this.
What is fault zones?
500
Surface waves that cause the ground to move with an elliptical, rolling motion.
What are rayleigh waves?
500
Since the mantle is denser than the crust, the speed of seismic waves ___________ when it reaches it.
What is increases?
500
The strength of an earthquake is called _________ and the effects of an earthquake is called __________.
What are magnitude and intensity?
500
Some earthquakes are preceded by little earthquakes called this.
What is foreshocks?
500
An earthquake whose epicenter is on the ocean floor may cause a giant ocean wave called this.