Seismographs
Instruments located at or near the surface of the Earth that record seismic waves.
When the waves reach a seismograph, the seismograph creates a
seismogram
the point on Earth's surface directly above an earthquake's starting point
epicenter
the point inside the earth where an earthquake begins
focus
Seismologists also use ________ to find an earthquake's epicenter.
seismograms
Seismologists find an earthquake's start time by comparing _________ and noticing the differences in arrival times of_____________________
Seismograms, P waves and S waves
The simplest method by which seismologists find an earthquake's epicenter
The S-P time method
Seismograms can be used not only to determine and earthquake's epicenter and its start time, but also to find out an earthquake's ________
strength
A measure of the strength of an earthquake
magnitude
measures the ground motion from an earthquake and adjusts for distance to find its strength.
The Richter Scale
Each time the magnitude increases by one unit, the measured ground motion becomes ____ times larger.
10
Each time the magnitude increases by one unit, the measured ground motion becomes 10 times larger.
The Richter Scale
A measure of the degree to which an earthquake is felt by people and the amount of damage caused by the earthquake.
intensity.
Seismologists in the U.S. use this to measure earthquake intensity
Modified Mercalli Intensity Scale
The scale is a numerical scale that uses Roman numerals from I to XII to describe increasing increasing earthquake intensity levels.
Modified Mercalli Intensity Scale
a measurement of how likely an area is to have damaging earthquakes in the future
Earthquake hazard
An areas earthquake-hazard level is determined by...
past and present seismic activity
a hypothesis that sates that sections of active faults that have had relatively few earthquakes are likely to be the sites of strong earthquakes in the future
Gap hypothesis
The areas along a fault where relatively few earthquakes have occured
seismic gaps
The greater the seismic activity, the higher the __________________
earthquake-hazard level
Explain the difference between the Richter Scale and the Mercalli Modified Intensity Scale?
There are many differences between the Mercalli Scale and the Richter Scale. The Richter Scale measures the ground motion from an earthquake and adjusts for distance to find its strength. The data is collected using a logarithmic formula using high-freque