GMT
5
:
19
/
8
:
19

How to predict an earthquake

How to predict an earthquake

The Earth consists of a solid outer shell called the lithosphere. This layer is divided into tectonic plates that are in constant movement. They can slide against each other, diverge or converge. Their convergence leads to subduction (collision), the accumulation of energy, the extreme value of which causes an earthquake. Is it possible to accurately predict the time and strength of earthquakes? Such a forecast could help save lives in the disaster area and develop effective early warning systems.

Forecasts and models

Seismologists and geophysicists have been focused on identifying earthquake precursors for a long time. Research and collection of information about precursors are based on the detection of anomalous phenomena near the seismic activity source preceding a disaster. These include:

  • series of microearthquakes;
  • soil deformation;
  • disturbances of aquifers, electromagnetic fields;
  • unusual animal behavior.

But precursor events did not allow for the development of reliable seismic activity models or understanding of their mechanisms. Therefore, many scientists have focused on solving three main problems:

Monitoring of major faults in the regions

The method makes it possible to predict the extent of ground movement in a region that could be caused by the rupture in case of its destruction. Large faults are monitored using seismometers, which track the amplitude and frequency of vibrations that can be generated during earthquakes. The information collected in a potentially dangerous region serves as the basis for calculating the seismic risk.

Determining the threshold of approaching catastrophe

The assessment is based on the historical study of earthquakes, such as searching for information in archival documents and evidence of destruction preserved in geological layers.

These data and geodetic measurements make it possible to assess the rate of stress generation along the fault and establish the periodicity between two earthquakes in the same segment. The threshold method predicts with high confidence several large and destructive earthquakes in the San Andreas fault zone (California), as well as in Japan, Chile, Turkey and Greece.

It should be noted that there are several limitations to accurately forecast earthquakes using the threshold method. Researchers use local data and are limited to a global overview of past events. Historical archives allow going back in time no more than a few centuries. Therefore, knowledge about the seismic fault cycle, which usually lasts from 10 to 1000 years, can be very fragmentary.

Acoustic forecast

Modern models can predict the location and strength of an earthquake. But no one can answer the crucial question – when a catastrophic event will occur, and whether the earthquake warning system will activate in time in the region. Recent discoveries by seismologists related to the abnormal deformation of the Earth’s crust and the activity of faults give encouraging results.  It was found that low-frequency seismic noises appear in the fault zone immediately before an earthquake. Scientists are trying to decode recordings of acoustic noise in order to be able to make a short-term forecast (a few hours or minutes) before the formation of a seismic rupture.

How do scientists predict earthquakes in practice

Scientists from the US Geological Survey are closely monitoring the movement of the Pacific and North Atlantic lithospheric plates. In the northern zone of the San Andreas fault (Parkfield), earthquakes occur with a regularity of approximately 22 years (1881, 1901, 1922, 1934, 1966). In 2004, tremors with a magnitude of 6.0 were recorded, and Parkfield, located in the center of California, is preparing for a new earthquake within the next 5 years (taking into account the uncertainty interval). Therefore, modern seismic equipment has been installed in the region to detect the slightest anomalies that can be interpreted as precursors of the next earthquake.