EL's+LIGO

=Earthquake from the near Central Coast of Peru= =Aug 15 2007 23:47:57 GMT Magnitude 8.0=



1. Analysis on graphs
• The earthquakes occurred on 15 Aug 2007 23:30:47 GMT in local area, but the time that wave reached at Hanford Center was approximately 16 Aug 2007 00:18:00 GMT. • The time that the strongest wave reached is various according to the observation locations. (such as x, y, z-axis, VAULT, Corner Station, etc) • The maximum values on y-axis are various. (Hence, the value on y-axis may be different on each graph.) • Sudden strong wave appeared on the particular point of time.

2. Subquestion
• What is the expected S-wave and P-wave onset difference, and what does that tell us about the distance of the quake from LIGO? - **P-Waves** are compressional waves, particles travel along the path of propagation. - **S-Waves** are shear waves, particles travel perpendicular to the direction of propagation. - Both P and S waves have own speeds because of different reaching time on the graph.
 * We can estimate P-wave is recorded through seismic y, S-wave is recorded through seismic x. It conveys that P-wave is faster than S-wave and does not oscillate vertically like S-wave does. We can see 2 relative maxima on seismic x graph while only 1 maximum appears on seismic y graph.

3. Conclusion

 * 1 maximum appears on seismic y graph.
 * 1) 5km/sec -> the speed of P-wave, 3km/sec -> the speed of S-wave
 * 2) A distance between Hanford Observation center and Central Coast of Peru is about 7600km.
 * 3) How long does P-wave take to get LIGO center from Central Peru?

7600/5 = 1520 seconds 1520/60 = 25.3 minutes ∴ The time P-wave reaches at LIGO center is 16 Aug 2007 00:06:00 GMT.

4. How long does S-wave take to get LIGO center from Central Peru? 7600/3 = 2533.333 seconds 2533.333/60 = 42 minutes ∴ The time S-wave reaches at LIGO center is 16 Aug 2007 00:22:00 GMT.

∴ **The LIGO observation by using Bluestone analysis tool identifies the earthquake of Central Coast of Peru on the certain time between Aug 15 2007 20:00:00 GMT and Aug 16 04:00:00 GMT.**

4. Bibilography
• **http://www.discoverourearth.org/student/earthquakes/index.html** • [|**http://en.wikipedia.org/wiki/Shear_wave**]

**5. Question by EL**
(Each graph has different values, even negative value.At least, I can assume that the y-value does not indicate the amount, or negative sign just symbolize the opposite direction from the origin.)
 * 1. What can be the values on the y-axis?**

(Unlike x-axis and y-axis, z-axis measure the wave occuring in vertical motion. In this case, vertical wave does not mean the motion of P-wave which moves up and down on 2-dimension plane, but something moves along the height line on 3-dimension plane. -- It's really hard to explain! But you might have vague idea of what z-axis represents.)
 * 2. How can Z-axis have the values?**