Can Earthquakes Be Predicted?

Why Are Earthquakes Unpredictable?

We often hear that earthquakes can't be predicted, but the reasons behind this are not always clear. To understand why predicting earthquakes is so difficult, it's important to first know how they occur. Earthquakes happen when a fault line, or crack in the Earth's crust, shifts. Large shifts along the fault can trigger stronger earthquakes, but not the entire fault moves at once. An earthquake usually starts at a specific point, where the stress applied to the fault exceeds the friction in that area. This happens regularly, with about 20,000 earthquakes of magnitude 4 or greater detected around the world every year.

When people ask why earthquakes can't be predicted, they usually mean large earthquakes. Large earthquakes begin in the same way as smaller ones, but they grow bigger. As the magnitude of an earthquake increases, so does the size of the fault rupture. For example, a magnitude 5 earthquake may cause around 2 kilometers of fault rupture, while a magnitude 8 earthquake could span about 250 kilometers. These ruptures spread quickly, and a magnitude 8 earthquake can last several minutes. The movement of the fault changes the stress in surrounding areas and can cause stress to build up on nearby faults, leading to more earthquakes.

Why Is Earthquake Prediction So Difficult?

Scientists have studied whether small earthquakes show early signs that could help predict if they will turn into large ones. A study in 2016 answered this question with a "no." It found that the early seismic signals of both small and large earthquakes appear the same. Whether a rupture grows depends on the existing stress levels along the fault. Over time, this stress builds up due to the movement of tectonic plates and is also influenced by past fault movements and nearby earthquakes. However, measuring the exact stress on a fault is not possible. Scientists can only estimate changes in stress, but this information is not enough to predict when an earthquake will happen.

For an earthquake to grow, stress along a fault line needs to reach a critical level, breaking through the friction holding the fault in place. But measuring this in detail is currently impossible.

Efforts in Earthquake Prediction

Scientists can map active fault lines, estimate how quickly stress is building up, and predict the maximum possible size of an earthquake along a fault. For example, a fault line shorter than 200 kilometers cannot produce an earthquake larger than magnitude 8.5. By studying historical earthquake records, high-risk areas can also be identified.

Sometimes, small tremors called foreshocks can occur before larger earthquakes. However, not every small earthquake means a larger one will follow. For example, a magnitude 4 earthquake is unlikely to lead to a magnitude 7 earthquake. Large earthquakes can sometimes trigger additional earthquakes on nearby faults, but predicting when this will happen is very difficult. The process could take hours, days, years, or it may not happen at all.

How to Minimize Earthquake Impact

The best way to reduce earthquake damage is through long-term planning and following building codes designed to withstand earthquakes. Hazard assessments should consider local soil conditions, the risk of landslides, and potential tsunamis, all of which can either increase or decrease the shaking. By building earthquake-resistant structures, it is possible to prevent not just loss of life, but also damage to homes and livelihoods.

Unfortunately, some people mislead others by claiming they can predict earthquakes using methods like astrology or electromagnetic signals. This kind of misinformation can get in the way of real preparedness. While earthquake prediction is not possible right now, with the right planning and monitoring, we can make communities more resilient to earthquakes.

Conclusion

Earthquake prediction is currently impossible. However, with careful planning and constant monitoring, it is possible to build buildings that can withstand most earthquakes. By focusing on resilience and preparedness, we can lessen the impact of these natural disasters.