Earthquakes: Facts & Information-Deadliest to Earth

 Something is stirring beneath the surface.

Earthquakes can occur suddenly and carry a great deal of energy when they form beneath the surface of the planet. Therefore, it is not surprising that they are one of the most deadly natural disasters in our world.

When seismic waves, which contain enormous amounts of energy, are released from the Earth's crust, earthquakes OCCURS. The waves originate at the source of the stress or hypocenter, and when they reach the surface, they can seriously destroy the infrastructure.

The United States Geological Survey estimates that there are about 20,000 earthquakes every year, or about 55 per day (USGS). For our benefit, the bulk of these pass completely unnoticed and are ineffective enough to do no harm.

The number of big earthquakes (defined as those with a magnitude of 7 or above) that occur annually is predicted by scientists by looking at long-term data going back to about 1900. According to USGS, we have exceeded this amount about 12 times in the past 40 to 50 years, and in 2010 alone, we had 23 significant earthquakes.

But given that these seismic monsters are essentially impossible to anticipate and completely unpreventable, that's about as far as our ability to predict earthquakes can go. Rather than devoting time and resources to ineffective prevention initiatives. Humans have discovered the importance of readiness and the right infrastructure. According to a proverb, "buildings kill people, not earthquakes."

To ensure that new structures or renovations to existing ones are done with earthquake protection in mind, several earthquake-prone locations have enacted strict building codes. Numerous instances of construction upgrades range from unique steel frames made to sway without compromising the structure's structural integrity to rubber shock absorbers installed in the foundations to help absorb tremors.

Surprisingly, big skyscrapers can be built to endure significant ground trembling. Some buildings are constructed with big stabilising balls called "dampers" that move back and forth to counter any movement of the building itself. When there is the seismic activity or strong winds, these dampers aid in stabilising the structure.

👉WHAT CAUSES EARTHQUAKES?

Numerous events, such as volcanic eruptions, landslides, and even meteor strikes, can cause earthquakes. However, plate tectonics, which is located far beneath our feet, is the primary reason for earthquakes.

The lithosphere, the outermost layer of Earth, lies between the atmospheric above and the atmosphere of the earth below (the upper layer of the earth's mantle). This layer is made up of several plates that jostle around on top of the asthenosphere like parts of a puzzle in motion.

The asthenosphere is located between 62 and 155 miles (100 and 250 kilometres) below the Earth's surface and has temperatures between 2,370 and 3,090 degrees Fahrenheit (1,300 and 1,700 degrees Celsius). According to the educational website Study.com, the asthenosphere layer is solid yet has enough elasticity to "flow" due to the high temperatures (opens in new tab). Under conditions of heat convection, this ductile layer can flow slowly(opens in new tab) and carry rocks and magma through the Earth, aiding in the movement of tectonic plates.

Friction stops two plates from sliding past one another with relative ease, which results in stress building up at the point of contact when they try to move past one another. Despite being slowed, the plates continue to travel, so eventually, something has to give.

At some point, the rock slips, releasing enormous amounts of energy in waves that eventually reach the surface of the Earth through the interior and cause the shaking we experience during an earthquake. The epicentre of an earthquake is the location on Earth's surface that is directly above the focus, or hypocenter, of the quake.

According to a USGS statement, earthquakes can occur anywhere on Earth between the surface and around 700 kilometres below the surface (opens in new tab). The British Geological Survey(opens in new tab) estimates that over 80% of them happen around the border of the Pacific Ocean, in a region known as the "Ring of Fire," where plate boundaries are common. However, some earthquakes can occur directly in the centre of the plate, far from any boundaries. Although little is known about these so-called intraplate quakes(opens in new tab), some geologists assume that they are the result of pre-existing faults that originated deep beneath the Earth's crust.

EARTHQUAKES: HOW Are They Detected and Measured?

Seismology is the field of science that studies earthquakes and similar occurrences.

An instrument used to find and gauge ground movements brought on by seismic activity is a seismograph or seismometer. According to the British Geological Survey, a seismogram is a recording of ground motions. The basic building block of a seismometer is a pen attached to a suspended mass that, when the ground shakes, will move owing to its own inertia and record the motions on a rotating disc of paper. More advanced seismometers capture three-dimensional ground motion, including up and down, east to west, and north to south.

This information is used by scientists to determine the magnitude, or size, of the earthquake.

The most well-known method of determining an earthquake's magnitude is the Richter scale(opens in new tab). This logarithmic scale was created in 1935 by Charles F. Richter to compare the magnitude of earthquakes in the California region.

The Richter scale ranges from 1 to 10, with each step representing an increase in the magnitude of 10 times. The amplitude of the waves captured by the seismograph—distance from the centre line to the top of the crest or bottom of the trough of a wave—relates to the magnitude of the earthquake.

This method has a flaw in that earthquake wave amplitudes are also influenced by the seismometer's location in relation to the epicentre and even the type of rock the waves are passing through. Seismometer data must therefore be adjusted in a number of ways to take these environmental variables into account in order to ensure that the computed magnitude is the same regardless of where it was measured.

According to the USGS, as seismometers were deployed all over the world, it became increasingly challenging to modify the data to make it "fit" with the Richter scale because it was clear that the scale only functioned for specific frequency and distance ranges.

Thus, scientists developed a new scale known as the instant magnitude that may be applied globally. The area of the fault surface that is affected times the quantity of energy released at the time of slip on the fault is referred to as the moment. Seismometers may be used to calculate it, and it is correlated with the overall energy released during the earthquake. The most accurate method for estimating earthquake size is moment magnitude.

Using the Modified Mercalli (MM) Intensity Scale, the intensity of an earthquake's impact on Earth's surface is measured (opens in new tab). The scale is rather misleading because it offers a ranking based on observable effects rather than using numerical numbers. This could be deceptive because two earthquakes of the same magnitude that strike two regions with distinct geological make-ups or degrees of earthquake preparedness will result in the ranking of intensity being extremely different.

BIGGEST EARTHQUAKE

A magnitude 9.5 earthquake that hit Chile in 1960 was the largest earthquake ever recorded. According to National Geographic, the earthquake, which was dubbed the Valdivia earthquake after the city that was most severely hit, caused 2 million people to lose their houses, at least 3,000 injuries, and 1,655 fatalities (opens in new tab).

EARTHQUAKE BENEFITS

It may come as a surprise to learn that earthquakes can be useful, but they can actually reveal a lot about the inside of the Earth, including the locations of various geological layers.

Seismometers all across the world detect seismic waves and record their velocities, which provide scientists with a wealth of information on the makeup, temperature, and pressure of the material the waves have passed through.

A glimpse into the tectonic processes at play on Earth can also be obtained from the location and magnitude of an earthquake. According to the Woods Hole Oceanographic Institution, improved tectonic understanding aids scientists in their estimations of the likelihood of seismic events along certain faults (opens in new tab).

ARE THERE EARTHQUAKES ON OTHER PLANETS?

According to the Lunar and Planetary Institute, there are currently no other planets that we are aware of that have lithospheres that are truly separated into plates that are subject to tectonic processes (opens in new tab). However, this does not imply that there are no earthquakes elsewhere in the solar system because there are other ways to cause a seismic event.

Researchers are now able to delve deeper inside these far-off worlds thanks to the discovery of moonquakes and marsquakes.

Moonquakes, according to Horizon magazine, are brought on by:

• Asteroid impacts on the lunar surface
• The interior of the moon is being stretched and compressed by Earth's gravitational attraction.
• The moon's cooling causes buckles and cracks in the lunar crust.
• Thermal earthquakes are brought on by the sun's heating

According to the EU Research and Innovation Magazine, Horizon, the first seismometer on the moon was actually installed there during Apollo 11 and even put to the test by Buzz Aldrin stamping his foot nearby (the instrument recorded it) (opens in new tab). On later Apollo flights, a number of additional seismometers were used, and these gathered important seismic data.

Up until 1977, seismometers were in use. Since there are no functioning lunar seismometers at the moment, scientists are still analysing the data from the equipment.

Scientists are hoping that more advanced seismometers(opens in new tab) will be placed on the lunar surface on the next missions to the moon under the Artemis programme, allowing us to see much deeper inside the moon.

As we turned to look towards Mars, we had to wait a little while longer to see seismic activity there. On April 6, 2019, NASA's InSight Mars Lander used its Seismic Experiment for Interior Structure (SEIS) sensor to find the first marsquake. Since then, the lander has picked up more than 1,300 marsquakes, the strongest one ever recorded on a planet other than Earth (magnitude 5) occurring on May 4, 2022.

            BIBLIOGRAPHY                                                                   

1. Determining the depth of an earthquake. Determining the Depth of an Earthquake | U.S. Geological Survey. Retrieved October 13, 2022, from https://www.usgs.gov/programs/earthquake-hazards/determining-depth-earthquake(opens in new tab)
2. Earthquake facts & earthquake fantasy. Earthquake Facts & Earthquake Fantasy | U.S. Geological Survey Retrieved October 13, 2022, from https://www.usgs.gov/programs/earthquake-hazards/earthquake-facts-earthquake-fantasy(opens in new tab)
3. Earthquake glossary. U.S. Geological Survey. Retrieved October 13, 2022, from https://earthquake.usgs.gov/learn/glossary/?term=richter+scale(opens in new tab)
4. Earthquakes. National Geographic Society. Retrieved October 13, 2022, from https://education.nationalgeographic.org/resource/earthquakes(opens in new tab)
5. Earthquakes. Woods Hole Oceanographic Institution. Retrieved October 13, 2022, from https://www.whoi.edu/know-your-ocean/ocean-topics/ocean-human-lives/natural-disasters/earthquakes/(opens in new tab)
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7. Keesey, L. (April 29, 2020). NASA scientists to make seismometer system to measure Moonquakes. NASA. Retrieved October 13, 2022, from https://www.nasa.gov/feature/goddard/2020/nasa-scientists-tapped-to-mature-more-rugged-seismometer-system-to-measure-moonquakes(opens in new tab)
8. May 22, 1960 CE: Valdivia earthquake strikes Chile. National Geographic Society. Retrieved October 13, 2022, from https://education.nationalgeographic.org/resource/valdivia-earthquake-strikes-chile(opens in new tab)
9. The modified Mercalli intensity scale. U.S. Geological Survey. Retrieved October 13, 2022, from https://www.usgs.gov/programs/earthquake-hazards/modified-mercalli-intensity-scale(opens in new tab)
10. Moment magnitude, Richter scale - what are the different magnitude scales, and why are there so many? U.S. Geological Survey. Retrieved October 13, 2022, from https://www.usgs.gov/faqs/moment-magnitude-richter-scale-what-are-different-magnitude-scales-and-why-are-there-so-many(opens in new tab)
11. O'Callaghan, J. (August 10, 2020). Moonquakes and Marsquakes: How we peer inside other worlds. Horizon Magazine. Retrieved October 13, 2022, from https://ec.europa.eu/research-and-innovation/en/horizon-magazine/moonquakes-and-marsquakes-how-we-peer-inside-other-worlds(opens in new tab)
12. Shaping the planets: Tectonism. Lunar and Planetary Institute (LPI). Retrieved October 13, 2022, from https://www.lpi.usra.edu/education/explore/shaping_the_planets/tectonism/(opens in new tab)
13. What is the asthenosphere? Study.com. Retrieved October 18, 2022, from https://study.com/learn/lesson/asthenosphere-temperature-facts-density.html(opens in new tab)
14. What keeps the continents floating on a sea of molten rock? Surprising questions with surprising answers. West Texas A&M University. Retrieved October 18, 2022, from https://www.wtamu.edu/~cbaird/sq/2013/07/18/what-keeps-the-continents-floating-on-a-sea-of-molten-rock(opens in new tab)
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