People in Pakistan are familiar with earthquakes more than just the word. Pakistan has experienced devastation at the hands of earthquakes. Earthquakes have been a source of constant fear and worry for us. With natural disasters, the control is taken away from our hand and we are left to the devices of nature. The best that can be done is to understand what can be done during and after an earthquake.
What exactly is an earthquake?
First, we need to understand what an earthquake is and why it occurs. The earth consists of three layers. The crust is the outermost layer and core is the innermost. The middle layer is called mantle. The outermost layer of earth, the crust, is broken into pieces. These pieces are called tectonic plates. These plates are further divided into three arbitrary categories: major plates, minor plates and microplates. When these plates meet, their relative motion leads to phenomenon such as earthquakes, mountain building, volcanic activity and ocean trench formation.
The crust rests on the hot mantle. Parts of the mantle are in motion which in turn move the plates. There are three types of motions of the plates. They either move apart, slide past each other or collide into each other. When they move apart, they expose the mantle and new crust is formed. Sliding past each other creates friction and that leads to release of energy causing earthquakes. These plates have continents on top of them. When plates collide into each other one of the plates goes below and melts, which in turn causes the land surfaces on top of them to collide into each other and create mountains. These rock-mass movements create fractures in the crust called faults. Depending on the action of plate tectonic forces, length of faults can vary. These faults do not consist of a single, clean fracture so geologists call these complex deformations, fault zones. These zones are then narrowed by fault planes which represent the fracture surface of a fault. This further narrowed down by demarcation of places where faults are visible or mapped on the surface calling them fault lines. Energy release associated with rapid movement on active faults is the cause of most earthquakes.
How earthquakes affect buildings
Earthquakes with their ground shaking have diverse effects on buildings. Whether the building is residential or commercial, with the movement of the earth below, your building will get affected. Of course, the magnitude is different and that can be because you were concerned about the design of your building, used good material and made sure that the soil on which your building is constructed was compact.
The two most important things in an earthquake are how good the quality of construction is, and what the intensity of ground shaking is. The quality of construction is understandable but intensity, how do we understand that you ask? Worry not for I will hold no information from you. The intensity depends on where the tremors are and how close they are and how shallow their depth is. The closer and shallower, the stronger the shaking. It also depends on soil compaction. Shaking is increased in soft, thick, wet soils. Any building facing such conditions will create a disconnection between the ground and foundation, hence compromising the structure.
What to look for after an earthquake?
Earthquake damage is not something that cannot be observed. There are certain things to look out for. The hazards are apparent, and you should be on the lookout for them after every earthquake and aftershock. These recommendations have been meticulously combined and curated to help you keep yourself safe.
After any tremor, always examine the entire outside of the structure for collapse or any movement off the foundation. So if your columns are not plumb and you think your house is crooked, that is severe damage. Checking the ground for fissures is also a must. Look for areas where the ground may have shifted or there are breaks in fence lines because that means the ground has some internal damage or there is a fault underground.
Another form of structural damage that occurs after earthquakes is the floor or roof pulling away or being separated from the adjacent building supports. This can result in a decrease in structural strength and may lead to a collapse.
If there is any hidden damage that is below the floor, then it is likely that the floor will feel bouncy when you walk on it. You can also experience this in the stairs. If they were solid before the quake and now wobble then that is a sign of danger. Another way of assessing hidden damage is to check the windows and doors. If they are newly jammed, blocked or difficult to open then there is some beam inside that is broken and the weight of the structure is falling on it. Also check the stairwells, basements, attics and other exposed areas for signs of damage such as exposed or cracked beams or roof leaks. Check basement floors and exterior walls for cracks and bulges. Cracks vary in their severity but bulges are indicators of serious damage.
If all that checks out, then the remaining assessment is of the mainframe and sewage and water lines. Sewage and water line damage is not that apparent but there can be signs such as overflowing toilets or unclean tap water.
What to do?
The first thing to do is to completely assess the damage to make sure that your house is not structurally compromised. Gather your valuables and leave the house immediately if you observe any extensive damage. The second thing is to document the damage. Take pictures for insurance claims as well.
There is little you can do if there is any major damage to your building. These complexities cannot be understood by your local thekadaar or contractor so contact a structural engineer. They will check the building for structural integrity and inform you if your house is safe to live in or not. They can also help you remedy the damage already done.
With natural disasters, there is little one can do besides preparing for the next one if caught off-guard. Therefore, if there is a history of frequent quakes or your region is experiencing aftershocks then you should try to earthquake-ready your building. Secure the expensive items and important documents beforehand. Keep them in an easily accessible place so you can secure them immediately in the case of any misfortune. You should also attach your appliances using flexible connections which will decrease the risk of breaking and hazards such as gas leaks or fires.
With such disasters, one can never be prepared enough but these precautions should be known and taken in the case of any unforeseen event. For more information on what to do before, during and after an earthquake, read our blog here. If there is anything you want to add, please use the comments section below.