Step 2: Measuring arrival times
To be able to determine a more accurate estimate of the earthquake's location you will use the information of multiple stations. For this, you will measure P wave arrival times at 11 seismic stations distributed around the world. Then, in step 3, you will use a Matlab program to determine the actual location.
1. Make a working directory in which you will store the
measurements and from which you will execute the program in Step
3. e.g. "U:\eqlocation" (U: is your personal drive on the
university network).
2. Create a simple data file that contains the station
locations and P arrival times. Use a simple text editor, such as
Notepad++, to create this data file. (Do note use Word as text
editor because it adds unwanted layout information to the file
that is not readable by Matlab.)
The file will consist of 11 lines with each 5 numbers:
stlat stlon hrP mnP secP
where:
| stlat = | geographic latitude of station |
| stlon = | longitude of station |
| hrP = | hour of arrival time of P (0-24, only integers) |
| mnP = | minutes of arrival time of P (0-60, only integers) |
| secP = | seconds of arrival time of P (0-60, real) |
Measure the arrival times of the P waves from the vertical
component
of the ground displacement as recorded by the 11 stations listed
below.
Pick the P onset as precisely as possible and save the data in the
file.
2. Why is it important to pick the onset and not, for
example, the first peak, if you want to determine the earthquake's
hypocenter?
3. Estimate the precision with which you can determine the
onset (= measurement error).
August 17, 1999, near Izmit, Turkey
| Station | Lat (N) | Lon(E) | Vertical |
| ASCN | -7.93 | -14.36 |
|
| BTDF | 1.36 | 103.77 |
|
| COLA | 64.87 | -147.85 |
|
| FFC | 54.73 | -101.98 |
|
| HIA | 49.27 | 119.74 |
|
| KEV | 69.76 | 27.01 |
|
| KMBO | -1.13 | 37.25 |
|
| KONO | 59.65 | 9.60 |
|
| MAJO | 36.54 | 138.21 |
|
| PAB | 39.55 | -4.35 |
|
| TSUM | -19.20 | 17.58 |
|
Instructions