1) calculate S-P time:
MPH 14:05:17 - S -14:05:07 - P 10 seconds |
UALR 14:05:52 - S -14:05:27 - P 25 seconds |
SLM 14:06:18 - S -14:05:40 - P 38 seconds |
2) Take this time difference for each station and multiply by 8. The p waves travel at roughly 8 kilometers per second. This will give the distance in kilometers the quake occurred from each station.
MPH: | 10 x 8 = 80 kilometers |
UALR: | 25 x 8 = 200 km |
SLM: | 38 x 8 = 304 km |
3) To plot the location, refer to the station location map, map.pdf. Using the above distances as radii, you can draw the arc of a circle around each station. The map scale indicates 100 kilometers = 2.5 centimeters. Calibrate the compass and measure from each station point on the map. Where the arcs intersect is the earthquake location. |
If you want to determine the "Origin Time" (actual time the earthquake occurred at the source), take the s-p times above and multiply by 1.37. Take this time and subtract that from the P arrival time to get the approximate origin time.
For example:
MPH: s-p = 10 secondsFor the location information and map for a comparison, refer to the website:
10 x 1.37 = 13.7
P wave arrival time is 14:05:07
subtract 13.7 seconds from 14:05:07 to give
origin time of 14:04:53.3 UTC
http://www.eas.slu.edu/Earthquake_Center/NEW/localmaps.html