To resist seismic vibrations, buildings or structures are placed on some type of bearing or shock absorber, which can be as basic as blocks of rubber 30-50 cm (12-20 in) thick. These rubber pads are used to support the construction columns as they descend to the foundation. The vibration from an earthquake is transmitted through these bases into the ground, where it is dissipated by friction and/or viscosity changes in the soil.
The Japanese have a phrase that describes this process well: "absolut shokubutsu" which means absolutely solid foundations. This technique is used extensively in Japan for modern buildings as well as traditional ones. It was also used extensively in many other Asian countries until recently when it was replaced with more sophisticated methods such as deep excavations or large concrete bases.
In Japan, buildings over 10 meters high must be designed to meet seismic standards. If a building does not satisfy these requirements, then it cannot be considered safe for use as a residence.
Even if a building meets all the requirements set forth by law, it does not necessarily mean that it will survive an earthquake. There have been cases where old buildings have collapsed even though they complied with all the regulations. After analyzing several of these incidents, researchers concluded that advanced techniques were used on some buildings to improve their stability during an earthquake.
Reinforced beams and trusses can also assist avoid building bending and collapse during and after an earthquake. Buildings and structures with specially built foundations can also assist reduce damage. The insertion of flexible cushions to the base is another sort of fundamental modification. These devices absorb some of the energy from an earthquake, preventing it from being transmitted to the structure.
Structural engineers should be involved in any project that might affect ground stability or cause buildings to collapse. They should be consulted before any major construction project begins so they can give an opinion on how best to protect against collapse.
Engineers work with architects and other design professionals to create structures that are safe for use. They may also review existing buildings to see if modifications need to be made to make them safer or comply with current codes. After a disaster has occurred, structural engineers help search for causes of the failure and recommend remedies.
They also help communities develop safety programs following an incident such as a flood or earthquake. This includes educating people about hazards in their community and providing information on how to protect themselves.
Structure-borne noise is one danger that many people are unaware of. It can occur when vehicles drive over bridges, pipes inside buildings vibrate causing rooms above them to shake, and similar incidents. Noise pollution can have serious effects on those who live near airports or other areas of heavy industry.
Engineers can lessen the force that a structure is subjected to in addition to reinforcing it against seismic shocks. They install what are known as base isolators, which isolate the building's foundation from the movements of the earth. These devices allow for the construction of higher-rise structures and prevent expensive repairs from being needed later.
Other ways engineers have helped reduce damage from earthquakes is by using design techniques called "seismic mitigation." The goal of seismic mitigation is to reduce the impact of an earthquake on a building within its expected limits. For example, by adding additional support to a building's framework, engineers have been able to increase its resistance to collapse during an earthquake.
Finally, engineers can aid in the recovery process after an earthquake has occurred. They may be called upon to assess the stability of damaged buildings and recommend solutions for their rehabilitation. For example, an engineer might suggest replacing a floor joist if it was found to be sagging during a reconstruction project.
Seismic activity occurs everywhere on Earth, but most earthquakes occur along plate boundaries or in subduction zones. Plate tectonics explains how plates move over time: As one plate moves under another, friction between the plates causes them to heat up and melt, forming a deep layer of liquid rock called "asthenia".