Summary of my research on the issue:-
"During an earthquake, a wave moves from the rock to the soil and then into the structure, creating a sway in the structure. The key to designing an earthquake-resistant structure is to build a ductile structure rather than a stiff structure. The extent of damage to a structure during an earthquake depends upon the distance of the epicentre from the structure horizontally as well as vertically below the ground. If the epicentre is closer to the surface, the damage tends to be larger in structures that are not resistant to earthquakes. It also depends on the type of soil. During earthquakes, certain soil such as sandy soil or deposited layers undergo soil liquefaction, causing greater damage to structures. Soil liquefaction is essentially when the soil bubbles, heaves or surges to the top surface under great pressure.
Earthquake-resistant design is essentially about ensuring that the damage to buildings during earthquakes is of an acceptable variety, with zero human loss and also that they occur at the right places and within acceptable ranges. In load bearing structures, the brick walls are thick (between 6 inches to 1 foot) and carry the load to the foundation. It may have beams and the slab is typically made of concrete with steel reinforcement. Framed structures, are made of concrete and steel and the load is carried by columns or shear walls to the foundation resting on concrete piles.
Load bearing structures have low resistance to earthquake. The bricks are stiff and have no way to either pull the structure in the direction opposite of the sway or be ductile enough to allow for small movement in the structure. Load bearing structures exhibit instantaneous failure and fall like a pack of cards.
One way to avoid such catastrophic failure in load bearing structures is to create a disconnect between the foundation of the building and the rest of the above ground structure by using the base isolation method or levitating the building during earthquake from its base by having an air compressor fill air between the foundation and upper storeys. Such methods have been recently adopted in USA and Japan, but is not very prevalent in Pakistan.
It is essential to have properly constructed in-fill walls so as to strengthen the buildings. Such strengthening should be done in consultation with a registered structural engineer.
Another method to reduce failure during earthquakes is to design a strong core shear wall. If the shear wall is designed as per relevant code, it can provide necessary stiffness to reduce excessive sway during the earthquake. This is typically done by providing proper core walls as well as by providing base isolation systems but this is generally recommended in taller buildings where they also provide tuned mass dampers and shock absorbers. Tuned mass dampers are essentially a pendulum with a specific viscous fluid which moves the building in the opposite direction of the structure’s natural frequency, thereby avoiding catastrophic failures. Other types of energy dissipation devices such as friction dampers and yielding dampers are also adopted to reduce damage during earthquakes."
Credit - Various sources on internet.
