Determine the Difference to get the Distance Say what? In class

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Determine the Difference to get the Distance Say what? In class
Determining Distance to Epicenter
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.
Say what?
Determine the
Difference
to get the
Distance
between P and S-Wave
arrival times
to the Epicenter
Dec 10­8:10 AM
Determining Distance to Epicenter
In class example:
Dec 10­8:10 AM
Determining Distance to Epicenter
Step 1: Determine the Difference between
the P and S-Wave arrival times.
P(arrival) = 17:43:32 GMT
Subract the S-Wave arrival (the higher number) from the P-Wave arrival
S(arrival) = 17:45:21 GMT
17:45:21
17:43:32
00:
Dec 10­8:10 AM
Determining Distance to Epicenter
Dec 10­8:10 AM
Determining Distance to Epicenter
Step 1: Determine the Difference between
the P and S-Wave arrival times.
Step 1: Determine the Difference between
the P and S-Wave arrival times.
Subract the S-Wave arrival (the higher number) from the P-Wave arrival
Subract the S-Wave arrival (the higher number) from the P-Wave arrival
17:45:21
17:43:32
17:45:21
17:43:32
00: 02:
00: 02: -11
The negative value means we need to borrow 60
seconds (one minute) from the minutes.
Dec 10­8:10 AM
Dec 10­8:10 AM
1
Determining Distance to Epicenter
Subract the S-Wave arrival (the higher number) from the P-Wave arrival
Determining Distance to Epicenter
Subract the S-Wave arrival (the higher number) from the P-Wave arrival
17:45:21
17:43:32
17:45:21
17:43:32
00: 02: -11
00: 02: -11
Reduce the minutes by 1 minute and then subtract the
negative value from 60 seconds:
Reduce the minutes by 1 minute and then subtract the
negative value from 60 seconds:
17:45:21
17:43:32
17:45:21
17:43:32
00: 01: (60-11)
00: 01: (60-11)
Dec 10­8:10 AM
= 00:01:49
Dec 10­8:10 AM
Determining Distance to Epicenter
Determining Distance to Epicenter
Now what?
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
Dec 10­8:10 AM
Determining Distance to Epicenter
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
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
Dec 10­8:10 AM
2
Determining Distance to Epicenter
Now what?
one minute;
20 seconds
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
Determining Distance to Epicenter
Dec 10­8:10 AM
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
Step 2: Determine the Distance to the
Epicenter.
Use the ESRT (page 11) and the
"Slip and Slide" method
Dec 10­8:10 AM
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
one minute;
49 seconds
Now what?
one minute;
40 seconds
Determining Distance to Epicenter
one minute;
49 seconds
'tic' mark
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
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.
Dec 10­8:10 AM
3
Determining Distance to Epicenter
'tic' mark
Determining Distance to Epicenter
The greater
the difference
between the P
and S-Wave
arrival, the
greater the
distance to the
Epicenter
Slip and
Slide to
get the
distance
Epicenter Distance (x103 km)
Dec 10­8:10 AM
Dec 10­8:10 AM
4

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