earthquakes 2 Flashcards
what does seismic wave data provide?
✓ provides information about EARTHQUAKES
✓ provides information about the structure of Earth itself (as previously seen).
✓ enables researchers to identify location of
EPICENTER and HYPOCENTER.
what is the hypocenter also referred to as?
the FOCUS of an EARTHQUAKE
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 seismometer?
sensor on a SEISMOGRAPH that detects
movements.
SEISMOMETER touches rocks in the ground and can therefore sense/detect any vibrations travelling through Earth SEISMOMETER transmits vibrational signals detected up to SEISMOGRAPH
what is a seismogram?
Data generated by SEISMOGRAPH;
SEISMOGRAM is data generated by SEISMOGRAPH based on vibrations detected by SEISMOMETER.
If no vibrations in Earth, see straight line on SEISMOGRAM.
If have vibrations, see “jumps” (increased AMPLITUDE) on SEISMOGRAM.
what is an amplitude of a wave?
maximum displacement or height of a wave relative to its equilibrium position (here equilibrium position is the black line).
what is a wavelength?
✓ distance over which wave shape repeats.
✓ distance between two CRESTS (i.e., peaks)
or two TROUGHS on a wave.
how do you determine the location of the epicenter?
measure and compare arrival times of SEISMIC WAVES at different locations/stations monitoring SEISMIC ACTIVITY.
how do you determine the location of the hypocenter?
more complicated
(must analyze SEISMIC WAVE patterns -use SEISMIC TOMOGRAPHY (SEISMIC TOMOGRAPHY also provides information about Earth’s composition)
what is intensity?
measure of shaking and damage caused by EARTHQUAKE INTENSITY will vary from LOCATION to LOCATION.
what is magnitude?
Largest recorded EARTHQUAKES have had a magnitude of approximately 9. But what does that mean?
what are some characteristics of magnitude?
✓ most common measure of EARTHQUAKE’s size
✓ measured at EARTHQUAKE’s source
✓ a single number is reported (no matter where we are relative to EARTHQUAKE and what we feel)
what is the Richter scale?
✓ outdated method for measuring magnitude
✓ developed by Charles Richter in 1932
✓ hypothetically scale has NO upper or lower limit
✓ Practically scale ranges from 1 to 10 (with 10 being most powerful EARTHQUAKE)
what type of scale is the Richter scale?
LOGARITHMIC!
In other words: Each time scale value goes up by 1 unit (e.g., from 1 to 2 or 5 to 6), MAGNITUDE of EARTHQUAKE is 10x bigger!
Based on this:
MAGNITUDE 2 is 10x BIGGER than MAGNITUDE 1
MAGNITUDE 3 is 10x10 or 100x BIGGER than MAGNITUDE 1
MAGNITUDE 4 is 10x10x10 or 1000x BIGGER than MAGNITUDE 1
MAGNITUDE 5 is 10x10x10x10 or 10,000x BIGGER than MAGNITUDE 1
etc…
If MAGNITUDE ≥ 8, dealing with a huge EARTHQUAKE that can destroy communities near EPICENTER.
If MAGNITUDE ≤ 2.5, EARTHQUAKE usually not even felt by humans, just detected by SEISMOMETERS.
what does the calculation of pitcher scale magnitude involve?
✓ measuring largest signals (greatest
AMPLITUDES) on SEISMOGRAM
✓ measuring time difference between arrival of
p-WAVES and s-WAVES
✓ accounting for distance from EARTHQUAKE
source
what are some negative go the Richter scale magnitude?
✓ underestimates energy released by EARTHQUAKES with MAGNITUDES > 6.5.
✓ unknown to many, it has now been largely replaced by the MOMENT MAGNITUDE SCALE.
what are some other types other than tectonic earthquakes we also encounter?
VOLCANIC EARTHQUAKES: Earthquakes that occur in parallel with volcanic activity.
COLLAPSE EARTHQUAKES: Smaller earthquakes caused by subterranean/underground collapse
of caves or mines.
EXPLOSION EARTHQUAKES: Earthquakes caused by explosions of nuclear or chemical devices (e.g., bombs).
