RM's+LIGO+Post-Activity+Assessment

SJHSRC LIGO SSP Home

The distance, from 34.5390, 73.5880 to Hanford Observatory equals about 11, 053.3 km, according to Google Maps.

Thus, the time it took for the seismic waves to reach LIGO's Hanford Observatory is explained below:

11, 053.3 km/ (5km/sec) = 2210.66 sec 2210.66 sec/ 60 sec x 1 min. = 36.84433 min.
 * P-Waves**

11, 053.3 km/ (8km/sec) = 1381.6625 sec 1381.6625 sec/ 60 sec x 1 min. = 23.028 min.

Time Frame: 23.028 - 36.844 min., which fits the data.

But, calculating it from the graphs, the time it took for the earthquake to reach LIGO was 25 minutes. Accordingly,

11, 053.3 km/25 min = 442.132 km/min x 1min/60 sec = around 7.37 km/sec, which is approximately the speed of the P-Waves on the first graph. 11, 053.3 km/18 min = around 614.07 km/min x 1 min/60 sec = around 10.23 km/sec, which shows the approximate speed of the P-Waves on the second graph.

11, 053.3 km/ (3km/sec) = 3684.433 sec 3684.433 sec/ 60 sec x 1 min. = 61.407 min. 61.407 min./ 60 min. = 1.023 hr.
 * S-Waves**

11, 053.3 km/ (5km/sec) = 2210.66 sec 2210.66 sec/ 60 sec x 1 min. = 36.844 min.

Time Frame: 36.844 min. - 1.023 hr., which also fits the data, but seems rather too slow.

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3) Based on the data, I can rule out a few possibilities for the difference in graphs. First, S-Waves cannot account for the difference because they are much slower than P-Waves, and the difference between the two graphs occurs at the beginnings of the graphs. Next, it seems unlikely that P-Waves accounted for the difference because the P-Waves would have to travel much faster than 8km/sec, which is the fastest average rate of travel.

Therefore, I almost believe that the difference between the two graphs occurred from an external force. The only problem is that the two detectors are located very close to one another, so it seems strange that one should record the earthquake sooner than the other. My other thought was that, as the two detectors measure the seismic waves in different planes (in the case, in the y and z planes), I thought the dfiference might have occurred due to a higher impact/faster impact from the waves traveling in a perpendicular motion to the direction of wave propogation. However, with this, too, am I unsure because S-Waves would be the waves that would be recorded in the z-plane because they travel in a perpendicular motion to the propagation of the wave.

Also, very interestingly, every peak of the graph in the seismic y graph has a trough at the corresponding time on the seismic z graph. So, in other words, when there is a high point on the seismic y graph, this is a low point on the seismic z graph, and vice versa. Also, the degree of intensity is much greater on the seismic z graph than the seismic y graph.