Earthquake Data Retrieval Instructions

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Earthquake Data Retrieval Instructions

Get the following information for the earthquake in which you would like to obtain the data for:

Longitude
Latitude
Depth
Date
Time

This information can be found on NEIC (Near Real time Earthquake List) at

http://earthquake.usgs.gov/neis/bulletin/bulletin.html

On the SUN, look for the regional directory for the region in which the earthquake

occurred in. You will find the regional directories in:

/kali/data1/LCSN/Earthquakes

Change into the appropriate regional directory by using the command cd

i.e. — cd (region)

If a regional directory does not exist for the location you want, create a new

directory for that region by using the command mkdir

i.e. — mkdir (region)

Then change into the directory using the cd command.

On the SUN, run the program GetQuake

This program will automatically calculate the travel and arrival times for the

earthquake you are interested in.

For each line, enter the appropriate information asked for by the program.

i.e. — "Enter the latitude: " (input latitude of earthquake)

NOTE — latitude is negative in the south, and longitude is negative in the west

NOTE — the time entered must be in UT time

Once you have entered all the information for the earthquake, the program will ask

you if the information you entered is correct; check and make sure that it is.

When the program is finished, write down the arrival dates and arrival times for the P

and S waves of the earthquake. This information is important because the files we are interested in are named by their arrival times.

On the PC, open the MS-DOS prompt clicking on

Start->Programs->Command Prompt

Run the program

c:/Program Files/gcfutils/gslconv

If you are not familiar with DOS, execute the following commands:

cd program~1

cd gcfutils

gslconv

This program is used to convert the .gcf files saved by Scream on the PC, to the

.sac format that is readable on the SUN

Leaving the MS-DOS prompt open, navigate your way to the E:\temp drive through

My Computer or Windows NT Explorer

In this directory, you will find all of the data files that are saved by Scream every

half-hour.

You will see several directories in the E:\temp folder, but we are only interested in

three:

E:\temp\3630e2 - contains east-west component data of seismic motion

E:\temp\3630n2 - contains north-south component data

E:\temp\3630z2 - contains vertical component data

Begin with the east-west component by going into the E:\temp\3630e2 directory and

finding the file that corresponds to the calculated arrival date and times

The file will be in the following format: (year)(month)(day)_(time)

Once you have located the correct file, copy that file into the E:\temp1 directory

Go into the E:\temp1 directory and highlight the copied file

Then click back on the MS-DOS prompt window and press Enter

This will convert the .gcf file in E:\temp1 to .sac and save it in the E:\temp1

directory

Rename the new file so that it is in date, time, component format.:

(year)(month)(day)_(time)_(e, n, or z)

i.e. — 20000804_1400_e

You can now safely delete the original .gcf file from the E:\temp1 directory and

repeat steps 7 and 8 for the remaining two components by converting the appropriate

.gcf files from the 3630n2 and 3630z2 directories.

NOTE — If the P and S waves arrive at different half-hour increments you must

convert both half-hour interval data files from each component directory.

Using a FTP program, preferably WS_FTP, which is installed on the PC, connect to the SUN. The profile name for the SUN is saved as kali under the pull-down menu in WS_FTP

Upload the converted .sac files that are saved in E:\temp1 to the regional folder
for the earthquake, which is located on the SUN.

Moving to the SUN and if the P and S waves arrive in the same time interval,

continue this step. Otherwise, if they are in different time intervals, skip to step 15 and then come back.

Through the UNIX console, go into the directory that holds the .sac files.

Type the command: "pql —sac (first component file) (second) (third)

*NOTE that no particular order is necessary

i.e. — "pql —sac 20010804_430_E 20010804_430_N 20010804_430_Z"

This will open a window with the seismic record image

Right click on the left hand side and then the right hand side of the time interval for the P and S waves.

Click Select All

Click Magnify

Click Filter

Click Controls

Change the filter settings to High Pass — Num Poles = 4

Cutoff Freq (Hz) = .5

Low Pass- Num Poles = 4

Cutoff Freq (Hz) = 2

Click Screen Dump

Back at the Unix/Kali prompt. Rename the file by using the command:

xpr —dev (the new file created) > (rename it __.ps)

NOTE — Be sure to include the location name, date, and time in the name of the

new postscript file

Now the renamed file is in postscript format.

Using WS_FTP from any other computer that has Adobe Illustrator, download the postscript file from the SUN and edit the file to show the P and S arrival times and add any other description that you like.

Save the postscript file as a .jpg so that it can easily be posted on the web.

If the P and S waves arrive at different times, the two files from each component need to be merged so they can be viewed together.

Convert each of the six .sac files to the .ah format. Use the command:

sac2ah (original file) (new file ___.ah)

The two .ah files for each component must now be merged. Begin with the east-west component and use the command:

ahconadd5 —p —n (second interval file) (first interval file) (renamed __.ah)

Repeat step 15 for the remaining two components and their pairs of files.

Go back to step 13, but when using the pql command use the —ah switch instead of the —sac switch.