Earthquakes Part 2 Flashcards
What is seismic wave data?
-Provides information about earthquakes
-Provides information about the structure of the Earth itself
-Enables researchers to identification the location of the epicenter and hypocenter
What is a seismograph?
-Tool that records data about seismic waves
-Tool that measures seismic waves generated by earthquakes
-Tool that detects and records movements of Earth using sensor placed deep in the ground
What is a seismometer?
-Sensor on a seismograph that detects movement. It touches rocks in the ground and can sense vibrations travelling through earth. Seismometer transmits vibrational signals detected up to seismograph
What is a seismograph?
Data generated by seismograph based on vibrations detected by a seismometer
If there are no vibrations on earth what is the line on seismogram?
Straight line
What is amplitude and wavelength
A: max displacement or height of a wave relative to its equilibrium position. (Eq position is the black line)
Wavelength: distance over which wave shape repeats itself, distance between two crests or troughs.
How to determine location of epicenter?
Measure and compare arrival times of seismic waves at different locations/stations monitoring seismic activity.
To determine location of hypocenter?
More complicated, use seismic tomography
What is seismic tomography?
An imaging technique using seismic wave data to create computer generated 3-dimensional images of earth’s interior
Earthquakes release energy that makes ground vibrate. What is intensity of an earthquake?
Intensity: Measure of shaking and damage caused by earthquake
What is magnitude of an earthquake?
-Measured at the earthquakes source
-A single number is reported, most common measure of earthquake size
What is the Richter scale?
-Outdated method for measuring magnitude
-Developed by Charles Richter in 1932
-Hypotheticaly scale has NO upper or lower limit
-Usually from 1-10 (10=most powerful)
Richter scale is logarithmic (for every 1 unit on the scale, magnitude is 10x larger)
True
What magnitude number is needed to destroy communities near epicenter vs which is not even felt by humans?
More than 8= destroy communities near epicenter
Less than 2.5= humans cannot feel it, just detected by seismometers
Calculation of Richter scale magnitude involves:
-Measuring largest signals (greatest amplitudes on seismograph)
-Meausring time difference between arrival of p-waves and s-waves
-Accounting for distance from earthquake source
Why is Richter scale bad?
-IT underestimates energy released by earthquakes with magnitudes > 6.5
What scale is used now to measure earthquakes?
Moment magnitude scale
What are other examples of earthquakes (3)
Volcanic earthquakes (occur parallel with volcanic activity)
Collapse earthquake (smaller caused by subterranean/underground collapse of caves or mines
Explosion earthquakes (caused by explosions of nuclear or chemical devices)
