Why do Buildings Collapse during an Earthquake?

What is an Earthquake and How to measure its Intensity and Magnitude? How does it affect the Land? What are the Reasons behind a Collapsed Building during an Earthquake?
why do buildings collapse during an earthquake
Photo by Jose Antonio Gallego Vázquez on Unsplash

Natural disasters are something that every human fear because of the havoc unleashed by them, which is sometimes beyond repair. The first written evidence of an earthquake is from the Zhou Dynasty, China in 780 BC. But have you ever seen or given a thought to how do earthquakes affect buildings, and how do buildings sway during earthquakes? Let’s start this topic and uncover all the facts related to why do buildings collapse during an earthquake.

1. What is an Earthquake?

When there is a sudden release of energy in the lithosphere, seismic waves are generated which leads to the shaking of the Earth’s surface and this phenomenon is known as an earthquake. It is also termed a tremor, quake, or temblor. An earthquake is measured by its intensity that can be weak enough that you hardly feel it and violent enough to bring down an entire town. (See How are Earthquakes Distributed on the Map?)

2. How to measure the Intensity of an Earthquake?

Intensity can be defined as the severity of the shaking of the ground and its possible effect on people and the environment as a whole. Intensity can vary depending upon the location of the place from the epicenter of the earthquake. The intensity of the earthquake is measured by the Mercalli scale.

3. How to measure the Magnitude of an Earthquake?

why do buildings collapse during an earthquake 2
Photo by Nadiia Ganzhi on Unsplash

Magnitude means the size and power of the earthquake. There is only one magnitude of an earthquake, unlike intensity which varied geographically. Magnitude is generally measured by the Richter Scale and Moment Magnitude Scale. For example, an earthquake of magnitude 7.0 hit Ilocos Sur, Philippines on 27-July-2022.  Must read what is the difference between Oceanic Crust and Continental Crust?

4. What are the Effects of an Earthquake?

An earthquake with a higher magnitude tends to do much damage to the area it hits. Ground rupture, shaking, soil liquefaction, tsunamis, landslides, fire, and floods are the various impacts an earthquake can have. Looking for why do buildings collapse during an earthquake? Read till the end. (See How Convection Current causes the Lithospheric Plate to move?)

5. How does Ground Rupture damage Buildings?

Ground rupture is the main deformity caused by earthquakes. This is the reason behind the damage to many buildings and landforms. Ground rupture can be seen in the form of breaking and displacement of the Earth’s surface. (See How are Typhoons formed?)

6. How can Shaking damage Buildings?

The levels of shaking vary due to factors like geo-structural features, local geological features, and geomorphological features. The shaking takes place when the seismic waves travel from the lower portions of the Earth to the upper portion through soft superficial soils.  (See Why are people afraid of storms?)

7. How do Buildings sway during Earthquakes?

why do buildings collapse during an earthquake 3
Photo by Sarah Crego on Unsplash

Soil liquefaction is the situation when a land loses its stiffness and strength when huge stress is applied to it in the form of an earthquake. This is the situation when land that is solid behaves like a liquid. Such a condition can tilt or shake rigid structures like buildings and bridges. Here sinking means the buildings collapse upon themselves. (See Why do people live near Volcanoes?)

8. How do Earthquakes form Tsunamis?

A tsunami is a condition when huge water waves rise from the water bodies like oceans due to a major displacement in the underground of the oceans. Large waves rising due to this can wash away and completely destroy even far-off coastal areas too. Tsunamis are caused when the magnitude of the earthquake is 7.5 or more. (Also read Is the Eye of a Hurricane Calm?)

9. How can Landslides occur from Earthquakes?

Another factor in why do buildings collapse during an earthquake is a landslide. Landslides are the result of shaking of the land which can be dangerous for people living in mountainous regions. Landslides often block roads, injure people, and damage buildings and houses in the area. It also hinders rescue operations. (See How are Volcanoes Distributed on the Map?)

10. How can Fire by Earthquake damage Buildings?

Gas lines and electrical power lines were damaged by the earthquake. This alone can lead to huge fires in residential areas. Fire can damage cities due to delays in extinguishing as the water pipes also get damaged during the earthquake. (See Triangle Shirtwaist Factory Fire Significance)

11. Can Floods damage Buildings during an Earthquake?

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Photo by Juan Manuel Sanchez on Unsplash

If dams are damaged due to an earthquake, then floods can damage towns and cities. Landslips near dam rivers caused by earthquakes may also result in floods and damage to people’s lives and infrastructural facilities. Also, check out how many tornadoes in Tennessee per year.

12. Why do Buildings collapse during an Earthquake?

Over the past few decades, engineers have understood the seismic waves and the possible reasons why do buildings collapse during an earthquake are:

  • Connection detailing is poor between the support members of the primary structure.
  • Design codes are not understood by Structural Engineers.
  • Ductility is insufficient.
  • Irregularity in plan and stiffness.
  • Lateral strength inaccuracy.
  • Short-column leading to column failure.
  • Soil liquefaction. (See Shipwrecks In The Ocean)

13. How do Earthquakes affect Buildings due to Poor Connection Structures?

A building needs to be structurally strong to withstand seismic waves. Poor detailing while constructing the building can cause the building to collapse during an earthquake. Take a look at the connections that are essential to determine how a building would support during an earthquake.

14. What Damage could be done by Engineers due to Lack of Knowledge?

Most buildings suffer because of the stupidity of structural engineers. They are usually unable to understand the behavior of the buildings during an earthquake in that area. They simply have no idea how to adequately design and structure the building to make it strong enough to survive the earthquakes. And this is another factor why do buildings collapse during an earthquake. (See 20 Best Mobile Home Manufacturers in US)

15. How does Insufficient Ductility damage a Building during an Earthquake?

The ability of a material to change its shape without breaking in response to stress is known as ductility. If the building material is ductile, it will deform a little by dissipating the energy from the earthquake. The higher the ductility, the more chances for the building to remain standing during the shaking of an earthquake. But if the material is stiff it will break with the shaking and spreading of the materials. Different countries require different levels of ductility in their building materials. (See 23 Best Modular Homes)

16. How can Plan Stiffness damage?

The regularity of plan and stiffness is in the seismic design of a building. It is necessary to make coordination between the structure and architecture. When the lateral stability elements are located at the center of mass, it shows the stiffness of the building. Take a look at the points here whose irregularity damages buildings.

  • The building center of stiffness
  • The center of mass of the building
  • The distance between the mass and stiffness. Must read about the Outhouse Design. 

17. What is Lateral Strength Inaccuracy?

During an earthquake, the lateral pressure is applied from the seismic waves to the building. The lateral strength means the strength of a structure to resist the chances of fractures arising from the lateral pressure. So, the structure with a weak lateral strength suffers many cracks during an earthquake. Thus, it is a basic reason why do buildings collapse during an earthquake.

18. What is the Short Column Effect, and How does it affect Building?

The short column effect is the plan in seismic design in which effective length is reduced or restricted for some floors or columns of the building. It causes the sheer force in these columns to be magnified in comparison to other floors. Structural engineers need to understand this phenomenon accurately to decide the right column height and avoid column failure. (See 7 Moat Around Castle Facts)

19. How does Liquefaction damage Buildings?

why do buildings collapse during an earthquake 6
Photo by Jan Canty on Unsplash

During an earthquake when the soil/land behaves like a liquid, buildings are brought to the ground. This happens when the buildings are made on shallow foundations. Soil liquefaction disturbs the settlement of the foundation of the building, leading to structural damage.

So, why do buildings collapse during an earthquake is not only because of the tremors but also due to faulty structure. However, the process of how do earthquakes affect buildings and how do buildings sway during earthquakes is mostly due to ductility and soil liquefaction. (Also read What do Tornadoes Sound like?)

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