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Seismic Waves NOTES.notebook
1
January 05, 2016
Dec 108:10 AM
Seismic Waves
Dec 108:10 AM
Earthquake
Earthquake: Release of the built‐up stress in the ________________
once the ____________ __________ is passed
Release of this energy is called ___________ ____________
Most earthquakes occur along a ____________
__________: crack in the Earth’s crust where _____________can occur.
Energy is released at a _________ in the form of
_____________ ____________.
lithosphereelastic limit
elastic rebound
faultFault movement
faultseismic waves
Dec 108:10 AM
Earthquake
________________ ______________ originate at the ___________
of the earthquake.
_____________________: the location on Earth’s surface directly
above the ______________.
Seismic waves focus
focusEpicenter
Dec 108:10 AM
Seismic Waves
Move in _________ directions from the ___________.
Carry the energy of an earthquake away from the focus,
through the Earth’s ____________, and across its ____________.
all focus
interior surface
Dec 108:10 AM
Seismic Waves
Felt the ___________________ at the epicenter.
Two categories of seismic waves:
1. ________________________________
2. ________________________________
strongest
Body wavesSurface waves
Dec 108:10 AM
Body Waves
Travel through the ground in __________ directions.
______________ Waves (P‐Waves)
First waves to arrive
Produce __________________ waves
Travel from one end to the other and back in astraight line
all
Primary
compression
Seismic Waves NOTES.notebook
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January 05, 2016
Dec 108:10 AM
P‐Waves
Series of ___________________ & ___________________ waves
Also known as “ _________ ‐ _________” waves
Travel through _____________, ______________, and __________
expanding contracting
Push Pullsolids liquids gases
Dec 108:10 AM
Body Waves
______________________ Waves (S‐Waves)
Second waves to arrive
Produce ________________ waves
Move ________ and ___________
Travel through _________________ only
Secondary
shearup down
solids
Dec 108:10 AM
Body Waves
Primary Waves Secondary Waves
Fast, Arrive 1st Slow, Arrive 2nd
Push - Pull Wave(Compression) Shear Wave
Solids ONLYSolids, Liquids & Gases
Dec 108:10 AM
Surface Waves
Travel along ____________________ only
_________________ than body waves
While P and S‐waves are generated by the ____________________,
surface waves are made by _______________________.
surface
Slower
earthquake (focus)
P-Waves
Dec 108:10 AM
Surface Waves
Produce the____________ ________________ ground movements.
____________ wave actions at the same time:
_________________ waves: causes ground to _________ like ocean waves
_________________ waves: shake ground from _________
to __________
most severe
TwoRayleigh roll
Love sideside
Dec 108:10 AM
Surface Waves
Rayleigh
Love
Seismic Waves NOTES.notebook
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January 05, 2016
Dec 108:10 AM
Earthquake Strength
Seismograph: Records __________________ movements
caused by _______________ ______________ .
groundseismic waves
Dec 108:10 AM
Earthquake Strength
Richter Scale: Measure of earthquake _____________________ (released energy from earthquake)
Logarithm of the maximum wave amplitude
No _________________ limit
Reported using ________________ numbers
2.0 – 3.0 : Felt by people (minor) 6.0 : Strong4.0 : Light 7.0 : Major (18/yr)5.0 : Moderate (800/yr) 8.0 – 9.0: Great 10.0+ : Epic (Never)
MAGNITUDE
upper
decimal
Dec 108:10 AM
Earthquake Strength
Moment Magnitude Scale: _________________ version of the Richter scale.
In addition to the amplitude of the seismic waves, it also considers:
1. Amount of _______________ ________________ along the fault
2. Strength of ____________ that were broken
(Also uses _________________ numbers)
Modern
surface movement
rocksdecimal
Dec 108:10 AM
Earthquake Strength
Mercalli Scale: Measure of _____________________
Not a precise measurement using instruments, but based
on __________________ _____________________
Scale of 1 to 12 using _____________ numerals:
_______ to ________
INTENSITY
human observationsroman
I XII
Dec 108:10 AM
Earthquake Strength
Dec 108:10 AM
Determining Distance to Epicenter
Seismograph records the arrival of P and S‐waves on a24‐hour clock using Greenwich Mean Time (GMT)
May also be called Universal Coordinated Time (UTC)
The prime meridian runs through Greenwich, England
Greenwich, England is 5 hours ahead of New York State.
Seismic Waves NOTES.notebook
4
January 05, 2016
Dec 108:10 AM
Determining Distance to Epicenter
Seismograph records the arrival of P and S‐waves on a24‐hour clock using Greenwich Mean Time (GMT)
May also be called Universal Coordinated Time (UTC)
The prime meridian runs through Greenwich, England
Greenwich, England is 5 hours ahead of New York State.
Dec 108:10 AM
Determining Distance to Epicenter
Seismograph records the arrival of P and S‐waves on a24‐hour clock using Greenwich Mean Time (GMT)
Times reported as hh:mm:ss (uses a 'military time' format)
Ex: 09:14:32
14:52:17
9:14:32 in the morning
2:52:17 in the afternoon
Dec 1012:29 PM
New York is GMT -5 (UTC -5):
If it is 4:00:00 pm in New York, whatis GMT?
4:00:00 pm + 5 hours = 9:00:00 pm
or, 21:00:00 GMT
Dec 1012:29 PM
If it is 4:00:00 pm in New York, whatis the time in Chicago (central time zone)?
3:00:00 pm
Dec 1012:29 PM
Chicago is GMT -6 (UTC -6):
If it is 3:00:00 pm in Chicago, whatis GMT?
3:00:00 pm + 6 hours = 9:00:00 pm
or, 21:00:00 GMT
Jan 52:26 PM
If a seismograph location records the arrival of a P-wave at 10:21:30 am (hours : minutes : seconds) ...and the earthquake occurred 8,000 km away, what time did the earthquake originate?
Seismic Waves NOTES.notebook
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January 05, 2016
Dec 147:25 AM Dec 147:25 AM
Dec 147:25 AM Dec 108:10 AM
Determining Distance to Epicenter
Must determine the difference between the P and S‐wave arrival times, then use ESRT (Page 11) to determine the distance.
Determine the Difference to get the Distance
between P and S-Wavearrival times
to the Epicenter
Dec 108:10 AM
Determining Distance to Epicenter
Say what?
Dec 108:10 AM
Determining Distance to Epicenter
In class example:
P(arrival) = 17:43:32 GMT
S(arrival) = 17:45:21 GMT
Seismic Waves NOTES.notebook
6
January 05, 2016
Dec 108:10 AM
Determining Distance to Epicenter
Step 1: Determine the Difference between the P and S-Wave arrival times.
Subract the P-Wave arrival (the lower number) from the S-Wave arrival
17:45:2117:43:3200:
Dec 108:10 AM
Determining Distance to Epicenter
Step 1: Determine the Difference between the P and S-Wave arrival times.
Subract the P-Wave arrival (the lower number) from the S-Wave arrival
17:45:2117:43:3200: 02:
Dec 108:10 AM
Determining Distance to Epicenter
Step 1: Determine the Difference between the P and S-Wave arrival times.
Subract the P-Wave arrival (the lower number) from the S-Wave arrival
17:45:2117:43:3200:02: -11
The negative value means we need to borrow 60 seconds (one minute) from the minutes.
Dec 108:10 AM
Determining Distance to Epicenter
Subract the P-Wave arrival (the lower number) from the S-Wave arrival
17:45:2117:43:3200: -1102:
Reduce the minutes by 1 minute and then subtract the negative value from 60 seconds:
17:45:2117:43:3200: (60-11)01:
Dec 108:10 AM
Determining Distance to Epicenter
Subract the P-Wave arrival (the lower number) from the S-Wave arrival
17:45:2117:43:3200: -1102:
Reduce the minutes by 1 minute and then subtract the negative value from 60 seconds:
17:45:2117:43:3200: (60-11)01: = 00:01:49
Dec 167:46 AM
Find the difference between the following P and S-wave arrival times:
1. Parrival: 07:30:24 GMT Sarrival: 07:35:42 GMT
2. PA: 19:24:46 UTC SA: 19:27:02 UTC
Use some paper to supplement your notes:
Seismic Waves NOTES.notebook
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January 05, 2016
Dec 167:54 AM Dec 167:54 AM
Dec 167:54 AM Dec 167:55 AM
Dec 167:55 AM Dec 167:55 AM
Seismic Waves NOTES.notebook
8
January 05, 2016
Dec 167:55 AM Dec 167:55 AM
Dec 108:10 AM
Determining Distance to Epicenter
Now what?
Dec 108:10 AM
Determining Distance to Epicenter
Now what?Take a piece of scrap paper (with a straight edge) and make a 'tic' mark at one minute and 49 seconds as read against the y-axis
Dec 108:10 AM
Determining Distance to Epicenter
Now what?Take a piece of scrap paper (with a straight edge) and make a 'tic' mark at one minute and 49 seconds as read against the y-axis
Dec 108:10 AM
Determining Distance to Epicenter
Now what?Take a piece of scrap paper (with a straight edge) and make a 'tic' mark at one minute and 49 seconds as read against the y-axis
one minute
Seismic Waves NOTES.notebook
9
January 05, 2016
Dec 108:10 AM
Determining Distance to Epicenter
Now what?Take a piece of scrap paper (with a straight edge) and make a 'tic' mark at one minute and 49 seconds as read against the y-axis
one minute;20 seconds
Dec 108:10 AM
Determining Distance to Epicenter
Now what?Take a piece of scrap paper (with a straight edge) and make a 'tic' mark at one minute and 49 seconds as read against the y-axis
one minute;40 seconds
Dec 108:10 AM
Determining Distance to Epicenter
Now what?Take a piece of scrap paper (with a straight edge) and make a 'tic' mark at one minute and 49 seconds as read against the y-axis
one minute;49 seconds
Dec 108:10 AM
Determining Distance to Epicenter
Now what?Take a piece of scrap paper (with a straight edge) and make a 'tic' mark at one minute and 49 seconds as read against the y-axis
one minute;49 seconds
'tic' mark
Dec 108:10 AM
Determining Distance to Epicenter
Step 2: Determine the Distance to the Epicenter.
Use the ESRT (page 11) and the
"Slip and Slide" method
Dec 108:10 AM
Determining Distance to Epicenter
Use the ESRT (page 11) and the
"Slip and Slide" method:Slide the scrap paper with the 'tic' mark on it up and between the "P" and "S" curves (keeping it verticle) until the bottom of the paper is touching the "P" curve at the same time the "S" curve is touching the 'tic' mark.
Seismic Waves NOTES.notebook
10
January 05, 2016
Dec 108:10 AM
Determining Distance to Epicenter'tic' mark
Slip andSlide toget the distance
Epicenter Distance (x103 km)
Dec 108:10 AM
Determining Distance to Epicenter
The greaterthe difference between the P and S-Wave arrival, the greater the distance to the Epicenter
Dec 1010:35 AM
What is the time difference between these arrival times?
Dec 1010:35 AM
What is the distance to the epicenter?
Jan 58:51 AM
Let's Practice......