JK's+LIGO+Assessment

LIGO Sensitivity Project Assessment


 * 1. Use Google Maps (or Google Earth—your pick) to calculate the distance from the quake’s epicenter to LIGO.**

**-** I used google maps and plugged in the points for each location. 34.5390, 73.5880 for the quake location and 46.455211, -119.407642 for LIGO. Then I used the measurement tool and got **10927.5 km**.

**2. Calculate the seismic wave speed twice, once for each of the LIGO plots shown.**

- Distance/Time = Speed

1. __Using the Seismic Graph Y__: You would use 10927.5 km as your distance, and the time it was picked up at LIGO would be approximately 4:12. The actual inception of the quake was 03:50:40.80 and so the time difference was 21 minutes and 20 seconds or 1,280 seconds.

(10927.5) / (1,280) = 8.54 km/sec.

2. __Using the Seismic Graph Z__: You would use 10927.5 km as your distance, and the time it was picked up at LIGO would be approximately 4:08. The actual inception of the quake was 03:50:40.80 and so the time difference was 17 minutes and 20 seconds or 1,040 seconds.

(10927.5) / (1,040) = 10.51 km/sec. **3. Comment on any difference you see between the LIGO plots, and between the wave speed estimates obtained using each plot.**

Differences between the LIGO plots include the time of arrival for each point. For the first plot the earthquake spike starts at about 4:12, but for the second plot it occurs a bit earlier at approximately 4:08. This indicates different wave speeds. The z graph's spike is also strange, because it spikes, spikes again, and then has a very jagged decline following the quake unlike the clear y graph. This may indicate another earthquake or possibly just intense tremors following the quake. One explanation for the lag in reception for the seismic y graph is that that specific detector may be looking for something different than the z. Possibly a different type of wave which arrived a bit later.

The waves which reached LIGO were definitely P-waves opposed to S-waves. P-waves generally have a travel time of 5-8 km/sec and S-waves are 3-5 km/sec and both of the speeds shown above fall into the P-wave category. This P and S wave simulation found [|here] also helps to show how they travel. The quake occured on practically the other side of the earth and P-waves are able to travel through the core so they were P-waves.