HOW HAS THE JAPAN EARTHQUAKE SHORTENED DAYS ON EARTH?
From a marine scientist perspective, we can understand how the earthquake was formed and what changes took place in the tectonic plates that were involved in the quake. The movement of the plates was due to subduction of the Pacific Plate under the Philippine plate and the friction resulted in an earthquake. Because the subduction was so abrupt, everything on the plates also shifted which decreased the diameter of the earth by a very small amount but still large enough to shorten the day slightly. This is explained further lower down using diagrams to illustrate the shifting of the plates.
The earth is divided in layers of different composition so different structures. The crust is the superficial layer therefore the one we are in contact with. It is divided in two main parts the oceanic crust and the continental crust(that forms the tectonic plates), they have respectively a density of 3g.mol-1 and 2.7g.mol-1. Considering these densities and the amount of the crust; we can easily come to the conclusion that the masses involved are huge and a small movement can change a lot of things as the axis the Earth
From the physics point of view, it was explained how a change in the diameter of the solid spherical earth causes a change in the earths's period, that is, the length of the day on earth.
From a marine scientist perspective, we can understand how the earthquake was formed and what changes took place in the tectonic plates that were involved in the quake. The movement of the plates was due to subduction of the Pacific Plate under the Philippine plate and the friction resulted in an earthquake. Because the subduction was so abrupt, everything on the plates also shifted which decreased the diameter of the earth by a very small amount but still large enough to shorten the day slightly. This is explained further lower down using diagrams to illustrate the shifting of the plates. The earth is divided in layers of different composition so different structures. The crust is the superficial layer therefore the one we are in contact with. It is divided in two main parts the oceanic crust and the continental crust(that forms the tectonic plates), they have respectively a density of 3g.mol-1 and 2.7g.mol-1. Considering these densities and the amount of the crust; we can easily come to the conclusion that the masses involved are huge and a small movement can change a lot of things as the axis the Earth
From the physics point of view, it was explained how a change in the diameter of the solid spherical earth causes a change in the earths's period, that is, the length of the day on earth.
A lower R(new) value (new radius) will give us a lower T(new) value (new period) and vice versa. This explains how, due to the reduced radius of the earth, the length of the day, that is, the Period of the earth was also reduced.
The length of a day would only change if the speed of the earth's rotation changed, i.e. the time it takes to complete one full rotation. A smaller radius simply means the surface of the earth would be moving slightly slower; the overall time it takes to complete a rotation didn't change.
ReplyDeleteThink of a pendulum that would take 24 hours to swing back and forth from a fixed point. Whether you pick a point on the end or in the middle of the pendulum (varying radii from the center point), the time of the period doesn't actually change. The point at the end of the pendulum simply moves faster to cover more distance in the same amount of time.
So whether the diameter of the earth is bigger or smaller (different radii from the center of the earth), the period of one day remains constant. If the diameter of the earth got smaller as a result of the earthquake, then we on the surface are just moving slightly slower than before.