Earthquakes of varying magnitudes regularly occur on Earth’s surface, resulting in casualties, destruction and significant economic damage. Thus, 6 earthquakes of magnitude 5.0 or higher and 25 earthquakes ranging from 4.0 to 5.0 were recorded in the last 24 hours. Seismologists and geophysicists are developing theories and technologies that make it possible to forecast impending seismic events and reduce risks for residents of potentially dangerous regions.
There are sensors installed on the surface of our planet and in the oceans that read vibrations caused by movements in the Earth’s interior. Seismic stations process data and analyze activity in tectonic fault zones. Engineering surveys make it possible to build seismically resistant houses and use dams to protect coastal regions prone to tsunamis. Early warning systems can warn people about the onset of earthquakes, giving them the opportunity to take refuge in safe places. But will scientists ever be able to stop an earthquake or reduce its strength to a safe level? Several groups of seismologists and geophysicists from Europe and the USA are engaged in this issue.
The wave nature of earthquakes
It is known that seismic tremors occur in fault zones where tectonic plates meet. They are constantly in motion, creating contact zones with various loads. Friction forces cause the plates to move, leading to the accumulation of deformation stresses that are abruptly released. When the threshold elasticity value is reached, the plates begin to move abruptly, releasing a large amount of energy in the form of seismic waves. There are two types of seismic waves:
- surface waves propagate along the Earth’s surface similar to the circles formed by a stone dropped into water;
- body waves travel through the rock layers directly from the earthquake’s hypocenter.
Surface waves cause the greatest damage to buildings and people. They are responsible for the destruction of buildings and infrastructure, the formation of cracks in the ground, road surface damage and the formation of landslides. Is it possible to create a buffer zone that can absorb seismic waves instead of making houses and buildings earthquake-resistant?
How to absorb seismic energy
Developments for preventing earthquakes is based on the theory of French seismologist Philippe Gueguen. In his opinion, the rocks that make up tectonic plates behave differently during seismic movement. Thus, regions where hard rocks of crystalline shields emerge on the Earth’s surface are more susceptible to the effects of seismic waves. Zones with loose and less dense sedimentary rocks are able to absorb earthquake energy more strongly.
The most effective buffer in absorbing seismic waves are underground sources of water and natural gas. Therefore, their increased ability to absorb seismic waves can be used not only in monitoring the intensity of earthquakes, but also in seismic exploration of mineral resources.
Metamaterials
Earth science researchers are developing methods to control seismic energy using metamaterials. These are man-made materials having unusual physical properties. They have electromagnetic, acoustic, seismic, thermal and mechanical properties that natural materials do not possess. Metamaterials consist of periodic, electrical or mechanical structures that behave like a homogeneous material, but do not exist in a natural state.
Seismic metamaterials can be used to create devices that limit the propagation of surface waves during an earthquake. They can be laid both in the foundations of buildings and used to structure the soil. By installing metamaterial tubes into the ground, it is possible to change the direction of seismic waves and even create barriers to filter destructive frequencies.
Help of nature
Official science has not yet included changes in animal behavior before an earthquake in the list of accurate precursors. Birds, mammals and amphibians do not always react in the same way to the onset of seismic activity, and in some cases, they do not have such sensitivity at all. Many seismologists do not use animals for short-term earthquake forecasting due to behavioral instability and lack of information about response mechanisms to approaching earthquakes.
At the same time, research has shown that plants can serve as a natural barrier to the propagation of seismic waves. Thus, in areas planted with tall trees, the strength of an earthquake is approximately 6 times less than in open areas. Planting several rows of trees can help naturally absorb seismic energy and protect nearby buildings from destruction.