How Do We Measure Earthquakes?


Quick Answer

The strength of an earthquake is measured by its Moment Magnitude Scale, or MMS. The MMS measures the total energy, or seismic moment, of an earthquake. The seismic moment of an earthquake is measured based on three factors: the distance rocks slide, the area of the fault slide and the rigidness of the rocks that are broken.

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Full Answer

The area around a fault surface after it breaks is known as the fault slips. Earthquake scientists, known as seismologists, use the measurement of the distance that rocks slide along this fault slip when measuring an earthquake's power. The exact area and distance of the fault surface broken up during an earthquake is also calculated when measuring an earthquake. The third factor measures not only the rigidness of rocks broken, but also how hard the rocks were that were broken. Extremely rigid rocks, such as granite, are not easily broken. When strong hard rocks are broken into rigid pieces, the end result is a higher measurement. The MMS is based on numbers relevant to the damage caused and what is felt during the earthquake. Measurements of 9.0 and above causes catastrophic damage and loss of numerous lives. 8.0 measurements result in fallen buildings, busted underground pipes and large rock movement. A 7.0 measurement makes it hard to keep your balance, the ground cracks, roads shake and buildings are damaged. A 6.0 earthquake causes pictures to fall and furniture to move. A 5.0 measurement causes dishes to rattle, some glass to break and cars to rock. 4.0 earthquakes resemble a large truck passing by your house. 3.0 earthquakes may cause concern only if you are sitting still in your house. A 2.0 earthquake makes trees sway and small ponds ripple, and pictures on the walls to sway. A 1.0 earthquake is the smallest measurement, and these earthquakes are hardly felt.

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