
The search for earthquake prediction methods is one of the main tasks of modern seismology. An accurate forecast of the date and strength of destructive tremors in earthquake-prone regions is an opportunity to develop a strategy for safe construction, warning and evacuating people from the disaster zone. Scientists propose many methods, but not all of them are the subject of critical and serious research.
What earthquakes can be predicted and how to determine the timing of their occurrence? The best seismologists and geophysicists in the world have developed a system that allows them to monitor events and determine the risks of destructive tremors in seismically dangerous regions.
What earthquakes can be predicted?
The modern science of seismic activity is aimed at the ability to make earthquake forecasts over various time intervals. Earthquake predictions are classified as:
Long-term forecasts
The method of long-term earthquake forecasting (for several decades) makes it possible to determine the construction technology adapted to the region and to reinforce existing buildings. Long-term earthquake forecasting provides the opportunity to establish the probability of earthquakes of a certain strength and magnitude in the researched region. For this purpose, the following are carried out:
- analysis of historical seismicity;
- field research using instrumental monitoring of seismicity;
- identification of active faults using satellite and GPS technologies.
Long-term prediction of earthquakes, after a sufficiently accurate determination of its probable magnitude and epicenter, as well as the characteristics of soil movement, makes it possible to determine the level of seismic hazard in the region and the approximate time of fault activation. Such forecasts do not allow us to name the exact date and time of the onset of earthquakes, but they make it possible to develop and carry out seismic construction.
Seismic standards are developed taking into account numerous parameters such as the soil characteristics in the region, immediate construction environment, building shapes, choice of construction systems and materials.
Medium-term forecasts
A seismic forecast ranging from 1 month to 1 year allows scientists to accurately identify and monitor imminent changes in the fault that lead to earthquakes. Scientists track changes in the state of the fault by creating catalogs of the seismicity of the region. Using catalogs helps significantly to determine the location (within a few hundred kilometers) of the largest earthquakes expected in the coming year.
Short-term forecasts
Earthquake forecasting in the period from several hours to 3-7 days makes it possible to activate civil defense systems, ensure emergency preparedness and make it possible to temporarily evacuate the population from a potentially dangerous zone. The short-term earthquake forecast is based on the identification of warning signs that appear before a seismic crisis:
- increased microseismicity;
- changes in the physical properties of rock formations due to the opening of microcracks associated with high stresses they are subjected to;
- changes in the velocity and nature of noise in the seismic fault zone;
- radon emissions;
- ground movements recorded as a result of deformations preceding an earthquake;
- abnormal animal behavior.
It should be noted that warning signs appearing before an earthquake do not always accurately indicate its onset. This makes the short-term forecast inaccurate. There are facts of successful prediction by scientists of an upcoming earthquake. Japan launched an earthquake alert system in 2007. In March 2010, a magnitude 6.6 earthquake struck off the coast and the warning system spread through the mass media, and TV channel NHK interrupted the sumo match to tell the population to take shelter.
China is pinning its hopes on ionospheric indicators, changes in which are a precursor to earthquakes. The China Seismo-Electromagnetic Satellite (CSES) was launched in 2018 to monitor electrical anomalies in the Earth’s ionosphere. The detected decrease in electron density in the ionosphere provided a warning 15 days before the earthquakes that struck mainland China in May 2021 and January 2022.
At the same time, scientists have not identified any signs of the earthquake that led to numerous casualties in southeastern Turkey and northern Syria in February 2023. Two devastating earthquakes occurred suddenly without warning and killed thousands of people. This indicates the unpredictability and catastrophic nature of seismic events in the Earth’s crust.