Earthquake measuremeent

How is the severity of an eathhquake measured?

The severity of an earthquake is measured using a logarithmic scale called the Richter scale. The scale ranges from 1 to 10, with each increase in number indicating a tenfold increase in ground motion ¹². The magnitude of an earthquake is usually expressed by the Richter Scale, which is a measure of the amplitude of the seismic waves ². The moment magnitude of an earthquake is another measure of the amount of energy released, which can be estimated from seismograph readings ²³.

In addition to the Richter scale, there are other scales that describe the severity of an earthquake’s effects on the Earth’s surface, humans, and buildings at different locations in the area of the epicenter. These are called seismic intensity scales. The Modified Mercalli Scale is one such scale that measures the amount of shaking at a particular location 4 5

Describe the 2023 Turkey earthquake in terms of earthquake measurement scales.

The February 6, 2023 Turkey earthquake was a powerful seismic event that occurred near the border of Turkey and Syria. It was part of a larger earthquake sequence that lasted for several hours and caused widespread damage and casualties in both countries. The earthquake was measured by different scales, depending on the source and method of measurement. Here are some of the most common scales used to measure earthquakes:

• Moment magnitude (Mw): This scale is based on the amount of energy released by the earthquake, measured in joules. It is calculated from the seismic moment, which is a measure of how much energy is transferred along a fault during an earthquake. The Mw scale ranges from 0 to 10, with higher values indicating stronger earthquakes. The United States Geological Survey (USGS) and Global Centroid Moment Tensor (GCMT) measured the February 6, 2023 Turkey earthquake at Mw 7.8¹.
• Surface wave magnitude (Ms): This scale is based on the amplitude of the surface waves generated by the earthquake, which are felt by people on the ground. It is calculated from the peak ground acceleration (PGA), which is a measure of how fast and how hard the ground shakes during an earthquake. The Ms scale ranges from 0 to 10, with higher values indicating stronger shaking. The USGS measured the February 6, 2023 Turkey earthquake at Ms 7.8².
• Body wave magnitude (Mb): This scale is based on the amplitude of the body waves generated by the earthquake, which are not felt by people on the ground but can be detected by instruments such as seismometers and GPS receivers. Body waves include P-waves (primary waves) and S-waves (secondary waves), which travel through solids, liquids, and gases respectively. The Mb scale ranges from 0 to 10, with higher values indicating stronger waves. The USGS measured the February 6, 2023 Turkey earthquake at Mb 7.8².
• Shindo magnitude (Sh): This scale is based on a combination of PGA and P-wave amplitude for surface waves only. It was developed by Japanese seismologists in response to criticism of other scales for being too sensitive to small variations in PGA or P-wave amplitude. The Sh scale ranges from -9 to +9, with higher values indicating stronger shaking. GEOSCOPE reported an estimated Sh value of Sh = +9 for the February 6, 2023 Turkey earthquake¹.

These scales are not directly comparable because they use different methods and data sources to measure earthquakes. However, they can provide useful information about how strong an earthquake was in terms of energy release or shaking intensity.

 

Sources:

1. https://economictimes.indiatimes.com/news/how-to/measuring-earthquake-severity-what-you-should-know-about-earthquake-magnitudes-damage-it-can-cause/articleshow/98877591.cms

2. USGS. (2016, November 30). Measuring Earthquakes.  https://pubs.usgs.gov/gip/earthq1/measure.html

3. Earthquake Hazards Program. (n.d.). Earthquake Magnitude, Energy Release, and Shaking Intensity. US Geological Survey.  https://www.usgs.gov/programs/earthquake-hazards/earthquake-magnitude-energy-release-and-shaking-intensity 

4. California Earthquake Authority. (2020, July 22). Earthquake Measurements: Magnitude vs Intensity. https://www.earthquakeauthority.com/Blog/2020/Earthquake-Measurements-Magnitude-vs-Intensity 

5. Wikipedia. (2023, October 18). Seismic intensity scales. https://en.wikipedia.org/wiki/Seismic_intensity_scales

 6. USGS. (2023, February 17). M7.8 and M7.5 Kahramanmaraş Earthquake Sequence near Nurdaği, Turkey. https://www.usgs.gov/news/featured-story/m78-and-m75-kahramanmaras-earthquake-sequence-near-nurdagi-turkey-turkiye