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Table of Contents
An earthquake (a quake, tremor, or temblor) is the shaking of the Earth‘s surface caused by a fast release of energy in the Earth’s lithosphere, which produces seismic waves.
See the fact file below for more information about Earthquake, or download the comprehensive worksheet pack, which contains over 11 worksheets and can be used in the classroom or homeschooling environment.
Key Facts & Information
OVERVIEW
- Earthquakes vary in strength, from those so mild that they cannot feel them to those powerful enough to launch objects and individuals into the air and destroy entire towns.
- Earthquakes show themselves at the Earth’s surface by shaking and shifting or altering the ground. When a big earthquake’s epicenter is offshore, it may move the seafloor sufficiently to generate a tsunami.
- Earthquakes can also cause landslides. In its broadest definition, an earthquake is any seismic event that creates seismic waves, whether natural or manufactured by people.
- Earthquakes are primarily triggered by the rupture of geological faults, although they can also be caused by other events such as volcanic eruptions, landslides, mine explosions, and nuclear testing.
- The hypocenter or direction of an earthquake is the zone of the first rupture, and the epicenter is the location straight above the hypocenter at ground level.
EARTHQUAKE FAULT TYPES
- Normal, reverse (thrust), and strike-slip faults are the three primary types of faults that might trigger an interplate earthquake.
NORMAL
- Normal and reverse faulting are instances of dip-slip, in which the movement along the fault is in the direction of the dip, and moving on them has a vertical component.
- Normal faults are more common when the crust expands, such as at a divergent boundary.
- Earthquakes caused by normal faults are typically smaller than magnitude 7. The energy emitted increases around thirtyfold with every unit increase in magnitude.
- For example, a magnitude 6.0 earthquake releases roughly 32 times more energy than a magnitude 5.0 earthquake, and a magnitude 7.0 earthquake produces 1,000 times more energy than a magnitude 5.0 earthquake. An 8.6 magnitude earthquake has the same power as 10,000 World War II-era atomic bombs.
REVERSE
- Reverse faults form where the crust shortens, such as near a convergent boundary.
- Reverse faults, specifically those at convergent plate boundaries, are linked to the most violent earthquakes, known as megathrust earthquakes, which account for nearly all earthquakes of magnitude eight or more.
- Megathrust earthquakes account for over 90% of the total seismic moment released worldwide.
STRIKE-SLIP
- Strike-slip faults are high structures in which the fault’s two sides move horizontally past one other; transform boundaries are strike-slip faults.
- Many earthquakes are triggered by motion on faults that include dip-slip and strike-slip components, referred to as oblique slip.
- Strike-slip faults, mainly continental transformations, can cause significant earthquakes of magnitude eight or higher.
EARTHQUAKE CLUSTERS
- Most earthquakes occur in a series and are connected in terms of geography and timing.
- Most earthquake clusters are made up of little shocks that inflict little harm. However, there is a belief that earthquakes might reoccur in a predictable pattern.
AFTERSHOCKS
- An aftershock is a subsequent earthquake that happens after the original shock.
- The primary sources of these aftershocks include rapid changes in tension between rocks and stress from the initial earthquake and the crust around the ruptured fault line as it responds to the impacts of the main shock.
- An aftershock occurs in the same area as the initial shock. It has a lower magnitude, yet it can still be powerful enough to inflict further damage to structures already damaged by the original quake.
- If an aftershock is more significant than the mainshock, the aftershock becomes the mainshock, and the initial main shock becomes a foreshock.
- Aftershocks can prevail for weeks, months, or even years. In general, the greater the magnitude of the mainshock, the stronger and more frequent the aftershocks, and the further they will last.
EARTHQUAKE SWARMS
- Earthquake swarms are clusters of earthquakes that strike a specific location within a short period. They vary from earthquakes followed by a succession of aftershocks in that no single earthquake in the series is the primary shock. The 2004 activity at Yellowstone National Park is an example of an earthquake swarm.
- A swarm of earthquakes hit Southern California’s Imperial Valley in August 2012, the most significant documented activity in the region since the 1970s. An earthquake storm occurs when a succession of earthquakes strike a fault in clusters, each one prompted by the shaking or stress redistribution caused by the last earthquakes.
- These storms recur over time, comparable to aftershocks but on neighboring parts of the fault, and a few of the latest earthquakes are as devastating as the earlier ones.
- It found a similar pattern in a series of approximately a dozen earthquakes that struck Turkey’s North Anatolian Fault in the twentieth century. It has been inferred from previous anomalous clusters of significant earthquakes in the Middle East.
INTENSITY AND MAGNITUDE
- The quaking or vibrating of the ground is a widespread event that has likely been known to humankind from the beginning of time. Before the invention of strong-motion accelerometers that could directly detect peak ground speed and acceleration, they approximated the strength of the earth-shaking based on the observable effects, which were classified on several seismic intensity scales.
- The origin of such shaking has only recently been recognized as fractures in the Earth’s crust, with the strength of shaking at any particular point depending not only on local soil properties but also on the severity or magnitude of the rupture and its distance.
- Charles F. Richter devised the first scale for quantifying earthquake magnitudes in 1935.
- Subsequent scales have kept a fundamental feature: each unit indicates a ten-fold change in ground shaking amplitude and a 32-fold difference in energy intensity of Earth quaking and magnitude of earthquakes. Subsequent scales are likewise modified to have the same numeric value within the scale’s limitations.
- Although earthquake magnitudes are commonly described in the media as “Richter magnitude” or “Richter scale,” most seismologists prefer to define an earthquake’s strength on the moment magnitude scale, which is based on the actual energy produced by an earthquake.
FREQUENCY OF OCCURRENCE
- It is predicted that around 500,000 earthquakes happen each year that can detect with existing technology, and approximately 100,000 of these may be sensed.
- Minor earthquakes happen all the time in locations like California and Alaska in the United States, as well as El Salvador, Mexico, Guatemala, Chile, Peru, Indonesia, the Philippines, Iran, and Pakistan, the Azores in Portugal, Turkey, New Zealand, Greece, Italy, India, Nepal, and Japan.
- More significant earthquakes occur less often, with an exponential connection; for example, nearly ten times as many earthquakes of magnitude 4 occur in a given period as earthquakes of magnitude 5.
- For instance, the average recurrences in the (low seismicity) United Kingdom are an earthquake of 3.7-4.6 per year, an earthquake of 4.7-5.5 every ten years, and an earthquake of 5.6 or bigger every 100 years. It is an illustration of the Gutenberg-Richter law.
- Most of the world’s earthquakes (90% and 81% of the largest) occur in the Pacific Ring of Fire, a 40,000-kilometer-long (25,000-mile-long) wedge zone that mostly surrounds the Pacific Plate.
EFFECTS OF EARTHQUAKE
SHAKING AND GROUND RUPTURE
- Earthquakes primarily cause shaking and ground rupture, leading to more or less catastrophic damage to structures and other stiff structures.
- The degree of the local consequences is determined by a complicated mix of the size of the earthquake, distance from the epicenter, and regional geological and geomorphological factors, which may enhance or limit wave propagation. Ground acceleration is used to quantify ground shaking.
- Even low-intensity earthquakes can cause substantial shaking on the ground surface due to specific local geological, geomorphological, and geostructural factors.
- It is known as site or local amplification. It is primarily due to seismic motion transmission from hard deep soils to soft superficial soils, as well as the effects of seismic energy focalization caused by the characteristic geometrical placement of such deposits.
- Ground rupture is an apparent breaking and shifting of the Earth’s surface along the fault path, which can be several meters in the event of significant earthquakes.
- Ground rupture is dangerous for big engineering projects such as dams, bridges, and nuclear power plants. It necessitates accurate mapping of existing faults to detect those likely to breach the ground surface over the structure’s lifetime.
SOIL LIQUEFACTION
- Soil liquefaction arises when a water-saturated particle (such as sand) briefly loses its strength due to shaking and turns from a solid to a liquid.
- Due to soil liquefaction, stiff structures such as buildings and bridges may tilt or descend into the liquefied deposits.
- Soil liquefaction, for example, caused several structures in the 1964 Alaska earthquake to sink into the ground, finally falling on them.
HUMAN IMPACTS
- An earthquake can inflict injury and death, road and bridge destruction, general damage to property, and building collapse or instability (possibly leading to future failure).
- The aftermath may bring sickness, a shortage of necessities, emotional implications for survivors such as panic attacks and sadness, and higher insurance rates.
LANDSLIDES
- Earthquakes can cause slope instability, resulting in landslides, a severe geological hazard.
- While emergency workers are working to rescue people, the risk of a landslide may continue.
FIRES
- Earthquakes can start fires by breaking electricity lines or gas lines.
- It may be difficult to control the spread of a fire once it has begun if water mains rupture and pressure are lost.
- For example, in the 1906 San Francisco earthquake, the fire killed more people than the earthquake itself.
TSUNAMI
- Tsunamis are long-period, long-wavelength sea waves caused by the rapid or abrupt displacement of massive quantities of water, such as when an earthquake happens at sea.
- The distance between wave crests in the open ocean might exceed 100 kilometers (62 miles), and wave durations can range from five minutes to one hour.
- Tsunamis travel at speeds ranging from 600 to 800 kilometers per hour (373-497 miles per hour), depending on ocean depth. Large waves generated by an earthquake or a subsurface collapse might quickly overwhelm surrounding coastal communities.
- Tsunamis may also spread thousands of kilometers across open water, wreaking havoc on distant coasts hours after the triggering earthquake.
- Subduction earthquakes of less than magnitude 7.5 do not generally create tsunamis. However, certain cases have been documented. Earthquakes of magnitude 7.5 or more are responsible for most devastating tsunamis.
FLOODS
- Floods may occur as a result of earthquakes if dams are destroyed. Earthquakes can generate landslides that block rivers, causing them to collapse and flood.
- The topography under Tajikistan‘s Sarez Lake is at risk of catastrophic flooding if the landslide dam constructed by the earthquake, known as the Usoi Dam, fails during a future earthquake. According to forecasts, the flood might affect almost 5 million people.
PREPAREDNESS
- The goal of earthquake engineering is to anticipate the impact of earthquakes on buildings and infrastructure and design such structures to reduce damage risk. It can seismically retrofit existing constructions to increase their earthquake resistance.
- Earthquake insurance can protect building owners financially against earthquake-related losses. A government or business can use emergency management measures to reduce risks and prepare for repercussions.
- The Igor expert system is a component of a mobile laboratory that supports operations leading to seismic evaluation of masonry structures and the planning of retrofitting activities on them. It has successfully been used to evaluate Lisbon, Rhodes, and Naples systems.
- Individuals can also go through preparatory procedures, including securing water heaters and heavy things that could damage someone, discovering utility shutoffs, and learning what to do when the shaking begins. Earthquake preparedness includes the risk of a tsunami triggered by a big quake in regions near large bodies of water.
Earthquake Worksheets
This is a fantastic bundle which includes everything you need to know about earthquake across 23 in-depth pages. These are ready-to-use Earthquake worksheets that are perfect for teaching students about an earthquake (also known as a quake or tremor), which is the violent movement of tectonic plates in the Earth’s crust. Earthquakes are usually quite brief but may recur over a long period of time. They are the result of a sudden release of energy in the Earth’s crust.
Complete List Of Included Worksheets
- Earthquake Facts
- Earthquake Crossword
- Select the Synonym
- To Do or Not To Do
- Word Epicenter
- It’s Your Fault!
- Earthquake-Proof
- Richter Scale
- Fictional Quakes
- Help Sasha!
- Today’s Headline
Frequently Asked Questions
What is an earthquake?
An earthquake (a quake, tremor, or temblor) is the shaking of the Earth’s surface caused by a fast release of energy in the Earth’s lithosphere, which produces seismic waves.
What are the three main types of faults?
Normal, reverse (thrust), and strike-slip faults are the three primary types of faults that might trigger an interplate earthquake.
Where do most earthquakes occur?
Most of the world’s earthquakes (90% and 81% of the largest) occur in the Pacific Ring of Fire, a 40,000-kilometer-long (25,000-mile-long) wedge zone that mostly surrounds the Pacific Plate.
How do earthquakes affect human life?
An earthquake can inflict injury and death, road and bridge destruction, general damage to property, and building collapse or instability (possibly leading to future failure). The aftermath may bring sickness, a shortage of necessities, emotional implications for survivors such as panic attacks and sadness, and higher insurance rates.
How long can aftershocks happen after an earthquake?
Aftershocks can prevail for weeks, months, or even years. In general, the greater the magnitude of the mainshock, the stronger and more frequent the aftershocks, and the further they will last.
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Link will appear as Earthquake Facts & Worksheets: https://kidskonnect.com - KidsKonnect, June 22, 2018
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