Question

PLEASE HELP! This is all the info that I am given. My lab has been moved to online class due to COVA-19

QUESTION 23: The coast of western Sumatra in Indonesia is a very seismically active area. In 2004, a magnitude 9.2 earthquake struck the region and generated a tsunami wave that caused massive destruction. In 2010, a magnitude 7.7 earthquake occurred in the same region, also generating a tsunami, albeit with less destruction than the one in 2004. Both the 2010 and 2004 earthquakes occurred on the same fault, but resulted in earthquakes of different magnitudes. Give one reason why this might be the case.

Question 14: No earthquake with magnitude 7.0-7.9 has occurred in the San Francisco or Los Angeles areas over the 30-year study period.

a.     Do you think this probability is high enough to warrant concern in either or both cities? Why or why not? (2 pts.)

Answer 1

Question 23        The coast of western Sumatra in Indonesia……………….

When comparing the Earthquakes of 2004 and 2010, both were triggered in the same fault area. Yet the magnitude of the earth quake and Tsunami triggered were different. As far as data’s are concerned, the Earthquake of 2004 was much higher in magnitude as it was measured to be equivalent to 9.2 on RS. The Quake that happened on 2010 had a magnitude of 7.7 on the RS.

Even if there was difference in magnitudes, still both types had triggered Tsunami that caused major devastation in that region. He difference in the magnitude of the Earthquake must have been in the region within the fault’s that acts as the triggering point for the Quake.

Generally the Surface of the Earth is made up of what is termed as the Floating tectonic plates. These are the plates that are aligned with each other just like a simple Jigsaw puzzle. So these floating plates may show three different types of movements – away, next to or under each other.

The subduction zone has tectonic plates that practically are sinking below each other. Over a period of time, certain level of stress is built up in this region. This is what triggers Earth quakes. In general the quakes trigger about 10 to 30 miles below the earth’s surface.

This phenomenon takes place n regions that have strong and rigid rocks in the fault. But when speaking of the region that is under the ocean, the subduction zone lies in soft sediments. These sediments are considered to be soft and rarely trigger big magnitude earthquakes. You need to keep in mind that if the Earth quake is created in soft rocks region then its magnitude is not much stronger.

If there is a difference in the magnitude of the earth quakes that occurred in 2004 and in 2010, then it certainly must have been the different in the region it occurred in the faults. So if it occurs in the soft parts of the fault then it does not created high magnitude earthquake as the energy released in much slower.

But even if this is the case still it does not mean that the earthquake will not cause much destruction. It creates Tsunami that can be very much destructive.

Question 14 (a) Do you think………….

Now when speaking of both these cities, for the next 30 years, you have to keep in mind that these are only predictions made on the basis of human observations. In most cases, these can be approximate, but not accurate. There are over 72 percent chances that we can expect earthquake of magnitude 6.7 on RS.

The earthquake of magnitude 7 will happen in this region is only predicted in 50 to 51 percent cases. If we expect earthquake of higher magnitude than 7, the chances get much lower, which is equivalent to 20 percent.

The fact is that the faults underneath these cities are presently showing slow movements that can possibly trigger earthquakes equivalent to 7 to 72 magnitudes.