Table of contents hide 1 2 What causes earthquakes? 3 4 The Tsunamis 5 6 Earthquake Measurement 7 8 Disaster Preparedness 9 10 Famous Earthquakes 11 12 Earthquakes and Tsunamis - Causes and Information by Nola Taylor Redd
Almost every year, a great earthquake occurs somewhere in the world and captures the attention of the public. Meanwhile, every day, thousands of smaller tremors often go unnoticed by most people.
Although we generally consider the soil as being solid and stable, the earth, in fact, is constantly changing under our feet.
Earthquake: What Does 'Magnitude' Mean?
The scales of magnitude and intensity
What causes earthquakes?
The Earth's crust ranges from 3 to 45 miles deep (5 to 70 kilometers).
The bark is a thin, hard shell that floats in the densest and hottest rock mantle. The crust is divided into several pieces known as tectonic plates that are in constant motion, sliding over each other at the limits known as faults.
As they slide over each other, tectonic plates get caught in sheer rock patches. They join together like velcro. However, even though the limits of the fault are locked together, the plates still move, pulling the tangled sections.
This pull can further break the earth's crust, creating more faults near the boundaries of the plates.
An earthquake occurs when the pressure accumulated along a fault becomes stronger than the pressure that holds the rocks together. Then the rocks on both sides of the fault suddenly tear apart, sometimes at supersonic speeds.
The two sides of the fault slide rubbing each other, releasing the accumulated pressure. The energy from this separation radiates outward in all directions, including towards the surface, where it feels like an earthquake.
Although tectonic plates slide at a normal rate over time, the way the fault releases stored energy is different with each earthquake, said Shimon Wdowinski, a geophysicist at Rosentiel University, School of Marine and Atmospheric Sciences of Miami.
“Every earthquake does not repeat exactly what happened before. Sometimes there is a big earthquake, sometimes there are two or three together, ”he told Live Science.
"There is no regularity."
A large earthquake is often followed by replies, which are smaller earthquakes that result from the crust's adjustments to the main earthquake.
These replies can help scientists point out the origin of the main earthquake, but they can create problems for those who suffer the consequences.
The tsunamis
If the earthquake occurs in the ocean, it can push up powerful waves, known as tsunamis. Sudden movement up or down the seabed during an earthquake creates large tsunami waves, similar to a child splashing in the bathtub.
Earthquakes can also trigger tsunamis by triggering submarine landslides, which also displace huge amounts of seawater.
In this photo taken by a tourist Eric Skitzi of England, tourists watch as the tsunami waves hit the shore from a safe place inside the Casuarina Beach Hotel complex in northwest Penang, Malaysia around 1:00 p.m. local (0500GMT) Sunday, December 26, 2004. The lifeguards of the hotel complex observed that the waves were huge and sounded warning to all tourists from the entire beach area of the hotel to run to the security area. On Wednesday, the Malaysian government canceled New Year's celebrations across the country, urging people to pray this weekend that the country is safe from future disasters such as the recent tsunamis in which at least 65 Malaysians died. Credit: AP Photo / Eric Skitzi
Earthquake Measurement
The size of an earthquake, or magnitude, depends on how large its mother fault is and when it has slipped.
Because these defects extend from the surface to several miles deep, geologists cannot simply visit the source to calculate these numbers. Instead, they are based on a tool known as a seismograph, which measures seismic waves or vibrations, of an earthquake.
The magnitude of an earthquake is classified on the scale of magnitude at the moment, not on the Richter scale . The scale of magnitude of the moment offers a better idea of the tremors and the possible damages of earthquakes of all kinds in the whole world.
Earthquakes with magnitudes less than 3 occur every day, and are generally not felt by people. A magnitude of 3 to 5 is considered minor, while an earthquake with a magnitude of 5 to 7 is moderate to strong. At the high end, these tremors can be destructive to cities.
Earthquakes 7 to 8 are important; About 15 of these occur annually. Every year, at least one earthquake with a magnitude greater than 8 - a "big" earthquake - wreaks havoc. An earthquake with a magnitude of 10 has never been measured, but it would create widespread devastation.
By using the readings of at least three seismographs, geologists can triangulate the origin of the earthquake. In the failure, that origin is called hypocenter, on the surface, the epicenter.
Most major earthquakes strike on known failures. Californians, for example, are unlikely to be scandalized if they feel the ground shaking under their feet.
But a map project published by the United States Geological Survey in 2014 reveals that 42 of the 50 states have a moderate to high seismic risk.
Disaster preparedness
Scientists have not yet reached a way to predict earthquakes.
Although animals are reputed to have a sixth sense when it comes to these vibrations, no research has confirmed, much less decided how such predictions could occur. In many cases, animals simply feel the arrival of seismic waves that go unnoticed by people.
However, scientists can identify places that are likely to experience earthquakes in the future.
For example, along the border of tectonic plates on the western coast of South America, researchers have mapped the location of historical earthquakes and found "seismic gaps" - areas without recent major earthquakes or tremors.
And in fact, scientists had forecast a major earthquake in a seismic gap near Maule, Chile, which was hit by an earthquake of magnitude 8.8 in 2010.
"There have been some highly successful forecasts based on the theory of the seismic gap, " said Wdowinski.
Even without such forecasts, there are some basic things that can be done to prepare for an earthquake.
The Federal Emergency Management Agency (FEMA) recommends that all families around the world should have emergency equipment in their home and car, and a plan to communicate with their loved ones in case of any type of disaster (not only for earthquakes). This preparation can make a difference, not only physically, but also emotionally.
If you live in territory known for earthquakes, make sure your shelves are firmly attached to the walls, with heavy objects on the lower shelves.
Keep heavy objects away from beds and living room, and attach accessories such as large televisions to the walls. Find a safe place in each room, under a sturdy desk or table, where you can seek shelter from falling objects.
Reinforced doors can be a safe haven, but most interior doors are not strong enough. A robust desk is likely to provide more protection, according to the United States Geological Survey.
"Earthquakes don't kill, buildings are the ones that kill, " said Wdowinski.
If you are outside, go to an open area, away from structures or bridges.
According to FEMA, many deaths in the 1933 earthquake in Long Beach occurred when people ran outside, only to be crushed by falling collapsing structures debris. Remember that the trembling ground rarely causes injury or death; instead, it is the fall of objects that results from the earthquake. If you are in a car, stop as soon as possible, but stay inside the car.
If you are on or near the beach, move quickly inland to avoid possible tsunami waves .
After an earthquake, proceed with caution. Remember that most earthquakes are usually followed by aftershocks. Keep an eye (and a nose) for gas leaks. If you were inside during the earthquake, move out.
Listen to public service announcements. A battery radio is ideal for your emergency equipment.
Famous earthquakes
1811-1812 Missouri.
In the 19th century, the New Madrid series of earthquakes shook the center of the United States. There were no seismographs at the time, so the researchers used historical evidence to determine that the magnitudes of the earthquakes varied between 7 and 8. Huge waves formed in the Mississippi, causing some parts from the river they seem to flow backwards.
1906 San Francisco, California, Magnitude: 8. Nearly 3, 000 people died from the earthquake in the San Andr s fault and the resulting fire.
1923 Tokyo, Japan, Magnitude: 7.9 One of the world's most destructive earthquakes, more than 142, 000 people died from the collapse of buildings and the resulting fire storm. Elsismo also caused huge tsunami waves.
1960 Chile, Magnitude: 9.5.The largest earthquake ever recorded, the 1960 earthquake in Chile killed more than 1, 600 people, with many of the deaths from the tsunamis. The waves reached 38 feet (11.5 meters) and carried the debris as far as 2 miles (3.2 kilometers) inland.
1970 Per, Magnitude: 7.9.Approximately 66, 000 people died, many of the buildings collapsed and there was a post-earthquake avalanche.
2004 Indonesia, Magnitude: 9.1.The third largest earthquake in the world in this century, the earthquake killed more than 227, 000 people. Powerful tsunami waves crossed the Indian Ocean and devastated 12 Asian countries.
2011 Japan, Magnitude: 9.0.More than 15, 000 people died when an earthquake in northern Japan caused a gigantic tsunami. The tsunami also hit a nuclear reactor, creating new problems for people in the midst of destruction.
See: http://alma-espiritulibre.blogspot.com.ar
by Nola Taylor Redd
Translation of Adela Kaufmann
Earthquakes and tsunamis Causes and information by Nola Taylor Redd
