The island of Taiwan was hit by a strong earthquake this Tuesday (2), Wednesday morning (3) local time. According to the Japan Meteorological Agency, the tremor was of a magnitude of 7.5. Authorities issued tsunami warnings for Japan and the Philippines.
An earthquake is an intense vibration of the Earth’s surface caused by movements in the planet’s outermost layer.
The magnitude of an earthquake is a measure of the intensity of the tremor at the location where it occurred. The largest earthquake ever recorded was 9.5, which occurred in Chile in 1960 (see below for a list of the largest records).
According to the American university Michigan Tech, the potential for damage that each magnitude range causes is of the following dimensions:
- Up to 2.5: It’s not felt, but the seismographs record it.
- From 2.5 to 5.4: It’s felt, but only causes minor damage.
- From 5.5 to 6: Damage to buildings and other structures.
- From 6.1 to 6.9: Causes a lot of damage in densely populated areas.
- From 7.0 to 7.9: It is a large earthquake, with serious damage, such as destroyed buildings.
- 8.0 or more: It is an even stronger earthquake, which can completely destroy communities near the epicenter.
According to the United States Geological Survey (USGS), an earthquake has a single magnitudebut the record of this number is often revised by seismographs with new data.
The earthquake that hit the island of Taiwan, for example, was recorded with different magnitudes:
- The Japan Meteorological Agency said it was 7.5.
- The Euro-Mediterranean Seismological Center said it was 7.4.
The best known scale is the Richter scale, but in practice it is already in disuse (unless it is a small earthquake that was not registered by the large monitoring agencies).
According to the US Oceanic and Atmospheric Service (NOAA), not all earthquakes cause tsunamis.
This will depend on the magnitude and depth. Most tsunamis occur after earthquakes with magnitudes above 7.0 that occur beneath the ocean and less than 100 kilometers below the surface.
Another important factor that determines the power of the tsunami is how deep the water is in the place where the tremor occurred.
Seismographs are devices that record some characteristics of earthquakes, such as:
- Time.
- Location and
- Magnitude
Each seismograph records the tremor in the ground below the point where it is located, but there are modern systems that can amplify the movement so that a distant device can capture a tremor thousands of kilometers away.
The intensity is different at each point
The magnitude of an earthquake is a measure of its size in the place where the tremor occurred, and the intensity is how much each point on the ground was impacted.
The intensity of an earthquake in a location further away from where the geological fault occurred will be lower.
There are other factors that influence the intensity at each point, such as the type of terrain or the direction of rupture that the earthquake caused.
- Chile, 05/22/1960: Magnitude: 9.5.
- Alaska (USA), 03/28/1964: Magnitude: 9.2.
- Sumatra (Indonesia), 12/26/2004: Magnitude: 9.1.
- Honshu (Japan), 03/11/2011: Magnitude: 9.0.
- Kamchatka (Russia), 04/11/1952: Magnitude: 9.0
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