what causes earthquakesand what do plate tectonics have to do with earthquakes?
An earthquake is basically a rapid movement of the ground, usually back and forth and up and down in a wave motion. It is caused by the rapid release of energy as the tectonic plates move. Friction between the plates must be overcome before they move. When the force is great enough, the plates suddenly move as friction can no longer hold them. This sudden movement sends out waves of energy through rock and water. The ground and water then shake as the waves of energy pass through them. This all has to do with plate tectonics.
Earthquakes happen at particular places under the ground where the earth flips, usually along a fault. The place where the quake starts is
called the focus. This may be hundreds of kilometres deep in the earth. The point of the earth’s surface directly above the focus is called the epicentre. Buildings near the epicentre are usually the most heavily damaged.
Earthquakes cause damage to buildings on land, and can cause landslides. However, they also cause destruction in the ocean. An earthquake under the ocean can cause a huge wave called a tsunami. These waves can be 100 metres high and cause massive destruction if they collide with the and near where people are living. It is therefore important to design buildings to withstand earthquakes in places where earthquakes are common, such as Los Angles, Tokyo and Christchurch. Engineers have found that the most effective solution is vibration control. This employs dampers, which arte structures that move in opposition to the waves and oppose their effects. Base isolation has
also been effective which include pads, springs and bearings that allow buildings to suppress the waves by moving rather than vibrating with the Earth.
Earthquakes happen at particular places under the ground where the earth flips, usually along a fault. The place where the quake starts is
called the focus. This may be hundreds of kilometres deep in the earth. The point of the earth’s surface directly above the focus is called the epicentre. Buildings near the epicentre are usually the most heavily damaged.
Earthquakes cause damage to buildings on land, and can cause landslides. However, they also cause destruction in the ocean. An earthquake under the ocean can cause a huge wave called a tsunami. These waves can be 100 metres high and cause massive destruction if they collide with the and near where people are living. It is therefore important to design buildings to withstand earthquakes in places where earthquakes are common, such as Los Angles, Tokyo and Christchurch. Engineers have found that the most effective solution is vibration control. This employs dampers, which arte structures that move in opposition to the waves and oppose their effects. Base isolation has
also been effective which include pads, springs and bearings that allow buildings to suppress the waves by moving rather than vibrating with the Earth.
Actual earthquake event: tangshan (china) earthquake
- Date: July 28. 1976 (China time zone)
- Magnitude: 7.8
- Depth: 7.5
- Epicentre: 39.60°N 118.20°E / 39.60; 118.20 (Tangshan, Hebei, China)
- Country or Region: People's republic of China
- Casualties: 650,000 dead, 2nd deadliest earthquake in history
- Magnitude: 7.8
- Depth: 7.5
- Epicentre: 39.60°N 118.20°E / 39.60; 118.20 (Tangshan, Hebei, China)
- Country or Region: People's republic of China
- Casualties: 650,000 dead, 2nd deadliest earthquake in history
The Tangshan Earthquake, also known as the Great Tangshan Earthquake, was a natural disaster that occurred on Wednesday, July 28,
1976. It is the largest earthquake of the 20th century by death toll. The epicentre of the earthquake was near Tangshan in Hebei, People’s Republic of China, an industrial city with approximately one million inhabitants. The number of deaths initially reported by the Chinese Government was 655,000. Another report though indicates that the actual death toll was much higher! A further 164,000 people were recorded as being severely injured. The earthquake hit in the early morning at 03:42:53.8 local time and lasted 14 to 16 seconds. Chinese Government
official sources state that the magnitude was 7.8 on the Richter scale, though some sources list it as a higher 8.2. It was followed by a major 7.1 magnitude aftershock some 16 hours later, increasing the death toll. The earthquake was generated by a 25-mile long Tangshan fault, which runs near the city and ruptured due to tectonic forces caused by the Amurian Plate sliding past the Eurasian Plate.
1976. It is the largest earthquake of the 20th century by death toll. The epicentre of the earthquake was near Tangshan in Hebei, People’s Republic of China, an industrial city with approximately one million inhabitants. The number of deaths initially reported by the Chinese Government was 655,000. Another report though indicates that the actual death toll was much higher! A further 164,000 people were recorded as being severely injured. The earthquake hit in the early morning at 03:42:53.8 local time and lasted 14 to 16 seconds. Chinese Government
official sources state that the magnitude was 7.8 on the Richter scale, though some sources list it as a higher 8.2. It was followed by a major 7.1 magnitude aftershock some 16 hours later, increasing the death toll. The earthquake was generated by a 25-mile long Tangshan fault, which runs near the city and ruptured due to tectonic forces caused by the Amurian Plate sliding past the Eurasian Plate.
early warnings and predictionsWell water in a village outside of Tangshan reportedly rose and fell three times the day before the earthquake. Gas began to sprout out of a well in another village on July 12 and then increased on July 25 and 26. Animals also gave warning that something was about to happen. One thousand chickens not far from the city refused to eat and ran around excitedly chirping. Mice and yellow weasels were seen running around and looking for a place to hide. In one household in the city of Tangshan, a goldfish began jumping wildly in its bowl. As well as such signs, the night preceding the earthquake, July 27-28, many
people reported seeing strange lights as well as loud sounds. The lights were seen in a multitude of hues. Some people even saw flashes of light; others witnessed fireballs flying across the sky. Loud, roaring noises followed the lights and fireballs. Workers at the Tangshan airport described the noises as louder than an airplane. This is an indication what nature often gives advance warning of an impending earthquake. As well as these signs, more than half a month before the earthquake struck, Wang Chengminof the state of Seismological Bureau Analysis and Prediction Department had already concluded that Tangshan region would be struck by a significant earthquake between July 22 1976 and August 5, 1976. Abnormal signs were mentioned for Beijing, Tianjin, Tangshan, Bohai and Zhangjakou regions. Most took the warnings very seriously, whilst others didn’t! |
DAMAGEThe high loss of life caused by the earthquake can be attributed to the time it struck, as well as how suddenly it struck and the quality and nature of buildings in China. The earthquake lacked the foreshocks that
sometimes come with earthquakes of this magnitude which could have acted as a warning. It also struck just before 4a.m, when most people were asleep and unprepared. Tangshan itself was thought to be in a region with a relatively low risk of earthquakes, very few buildings therefore were not built to withstand an earthquakes and the city lies on unstable soil. Therefore, hundreds of thousands of buildings were destroyed. The earthquake devastated the city over an area of roughly 6.5 kilometres. Many of the people who survived the initial earthquake were trapped under collapsed buildings. Tremors were felt as far away as Xian, which is approximately 760km away. 85% of the buildings in the city collapsed and became uninhabitable. |
DEATH-TOLLMany official figures state that the Tangshan earthquake killed over 650,000 people, which makes it the deadliest earthquake in modern times, and the second deadliest in recorded history. It is worth noting that the population of Tangshan when the quake hit was around 1.6 million people, this means that close to half of the city’s population was killed!
aFTERMATHThe Chinese Government refused to accept international aid from the United Nations, and insisted on self-reliance. Shanghai sent 56 medical
teams to Tangshan, in addition to the People’s Liberation Army who was of great assistance. Rebuilding infrastructure started immediately in Tangshan, and the city was completely rebuilt. Today Tangshan city is home to nearly three million people and is known as the ‘Brave City of China’. |
NOW IT'S YOUR TURN! JUST IMAGINE...
Only imagine the pain, shock and grief that those in Tangshan would have felt! Imagine being in their position, well now you can…
It is 3a.m and you are lying in bed, in a deep sleep. You are suddenly awakened by a thundering roar- what is that you think? Is it a plane? Suddenly the ground starts to violently shake and your legs start to wobble beneath you. You hear your family screaming and you barely have enough time to hide under a table. The thunderous noise- louder than an aeroplane continues for 16 seconds, as does the violent shaking, your ears are being pierced and your head is shaking...
Suddenly the ground stands still- and there is absolute silence, to a point where all you can hear is your own deep breathing!!! Yet, there’s one more problem, its dark, you’re confused, still half asleep and trapped!
What do you do now… Well, you close your eyes and pray for help, you pour out your heart to God! It feels like it has been hours until help finally arrives. Waiting to be released there are millions of things that run through your mind... Am I still alive? Is my family ok? What happened? Will I continue to live...When you are finally released from the rubble that was on top of you, you collapse! You're hungry, thirsty, confused and in pain! Yet, amongst all the thoughts darting through your mind, amongst the tightening of your chest, you know that there is only on thing to do now... Find your family!!
- Watch the following video, it is a re-enactment of the night of the Tangshan earthquake... (click the link)
http://www.youtube.com/watch?v=CReDCDapZ1M
- Watch the Tangshan earthquake picture story:
By Tijana Chetcuti - 9B ©
It is 3a.m and you are lying in bed, in a deep sleep. You are suddenly awakened by a thundering roar- what is that you think? Is it a plane? Suddenly the ground starts to violently shake and your legs start to wobble beneath you. You hear your family screaming and you barely have enough time to hide under a table. The thunderous noise- louder than an aeroplane continues for 16 seconds, as does the violent shaking, your ears are being pierced and your head is shaking...
Suddenly the ground stands still- and there is absolute silence, to a point where all you can hear is your own deep breathing!!! Yet, there’s one more problem, its dark, you’re confused, still half asleep and trapped!
What do you do now… Well, you close your eyes and pray for help, you pour out your heart to God! It feels like it has been hours until help finally arrives. Waiting to be released there are millions of things that run through your mind... Am I still alive? Is my family ok? What happened? Will I continue to live...When you are finally released from the rubble that was on top of you, you collapse! You're hungry, thirsty, confused and in pain! Yet, amongst all the thoughts darting through your mind, amongst the tightening of your chest, you know that there is only on thing to do now... Find your family!!
- Watch the following video, it is a re-enactment of the night of the Tangshan earthquake... (click the link)
http://www.youtube.com/watch?v=CReDCDapZ1M
- Watch the Tangshan earthquake picture story:
By Tijana Chetcuti - 9B ©
