Abstract
Earthquakes occur fast and instantaneous such that it becomes challenging to figure out when the next one will occur. Due to the devastating effects of earthquakes, human beings have been trying to predict them since the first-century in China. Methods and techniques have been designed towards this end. Earthquakes have a short propagation time, meaning that they can only be predicted on the basis of having in place a preparation phase. Hence, various types of predictions have emerged over time to enhance the preparation phase. The methods discussed here include data mapping, radon gas emissions, early tremors (foreshocks), dilatancy theory, animal behavior, earthquake lights, electric signals, Syzygy, ambient light, magnetometers, hydrochemical precursors, temperature change, water level, oil wells, and theory of seismic gap. Though the rate of accuracy in the use of a single method could be low, the methods can be used in combination for a higher level of accuracy.
The Various Methods of Earthquake Prediction
Introduction
Earthquakes occur so often with effects that are devastating to humans, property, and infrastructure. Earthquakes are sudden and immediate events, making it challenging to prepare and take measures to mitigate the impact. Predicting their occurrence would go a long way in saving lives and the cost associated with the events. Experts have shown that while there are many traditional types of predictions, it is still a long way from having accurate predictions. It is not only important to predict the occurrence of an earthquake, but its epicenter location and the severity of the event. There are various methods that have been used as a source of data to predict earthquakes. Some of the techniques, and the focus of the discussion, include, data mapping, radon gas emissions, early tremors (foreshocks), dilatancy theory, animal behavior, earthquake lights, electric signals, Syzygy, ambient light, magnetometers, hydro chemical precursors, temperature change, water level, oil wells, and theory of seismic gap.
The Various Methods
Dilatancy Theory
In prediction research, most of the work is centered on the Dilatancy theory. The prediction method is based on the reality of the outcome of stress on a rock. Expansion of the rock when pressure is exerted, dilation due to micro-cracks, and fractures, are the basis for the occurrence of earthquakes. The changes on the rock could be the cause of seismic waves of diverse velocity and varying electrical resistance. The analysis of the changes has been used as the possible indicators of the buildup that lead to major earthquakes (The geography site, 2006). Figure 1 shows the prediction of earthquakes using seismic dilatancy models and seismic gaps.
(Source: Shar, 2014).
Theory of Seismic Gap
Seismicity gap is one of the ways that scientists have used to predict earthquakes. The theory is founded on the reality of the gap being the section where there is earthquake as opposed to other neighboring regions along the plate borders. From a study carried out by soviet seismologist S.A. Fedotov, it was concluded that those regions where there has not been major activity are the most prone to earthquakes. In Kurile Island, three of such regions suffered earthquakes based on the predictions. In fact, the earthquake along the San Andreas Fault was predicted using the theory (see figure 2)
(Source: Mohita, 2016).
Data Mapping
Use of empirical data can be effectively used in predicting the occurrence of an earthquake. Information such as tremors has been used in the past. From the map, it is possible to discover the records of earthquakes on May 16, 2016, of a magnitude of 2.5 or above) (Gray, 2016).
(Source: US Geological Survey (USGS) as cited by Gray, 2016).
The data in conjunction with what has happened historically and the geological composition of the region provides the information on the area most likely to be hit by an earthquake.
Radon Gas Emissions
The emission of radon gas is an important indicator of an impending earthquake as rock masses emit it before the occurrence. Following the Tashkent earthquake in Russia in 1966, an outlandish spike of the gas was observed close to the epicenter. Speculations were made that the gas had been escaping into the water for several days before the earthquake. Under stress, research has indicated that the rocks tend to emit a great deal of the gas, leading to its great concentration in the water (Gray, 2016). Figure 3 below shows how the radon gas is emitted.
(Source: Kriscenski, n.d).
Early Tremors (Foreshocks)
Past occurrences have indicated that the minor tremors transpire before the occurrence of the major earthquake, suggesting another type of prediction. For example, in 2009, when a major earthquake hit L’Aquila in Italy, there were a number of foreshocks that occurred for a number of months (Gray, 2016). The foreshocks act as major cues for the possibility of a major and strong earthquake. The occurrence of foreshocks successfully predicted the Bhuj earthquake which occurred in 2001. Hence, with careful assessment, the minor tremors can serve as a pointer to a more serious earthquake (see figure 4)
(Source: Liu & Zhou, 2012).
Unusual Animal Behavior
Animals can be used to predict earthquakes based on the potential for the disturbance in their habitat. There is no doubt that animals have some powerful sensory perceptions, some of which are unique to their species. Thus, it is possible for some animals to perceive the disturbance in their ecosystem, and based on the way they react, experts can foretell the possibility of an earthquake (The geography site, 2006). The behavior of the animals before the occurrence was widely publicized following the 1975 Haichang earthquake in China.
Earthquake Lights
Traditionally, and even in the modern days, there are tales about earthquake coming along with some extraordinary lights. These lights in form of lightning, floating orbs, and flames in blue are believed to be emitted by the seismic stress on the underground locks (figure 5). The rocks are confirmed to accumulate electric charges due to the pressure, which can build up to the point that it is emitted as light (Mohita, 2016). Although there is controversy surrounding the phenomenon, the lights are being used as indicators for an earthquake.
(Source: NEW ZEALAND 2016 EARTHQUAKE mysterious lights, 2016).
Electric Signals
Geoelectric changes have been monitored since the 1980s by Greek seismologists as a predictor of an earthquake. The short-term earthquake prediction method, the “VAN” method, was the basis for the development of the calibrated instruments for use in predicting earthquakes (Mohita, 2016). The method has been a subject of major criticisms, some critics attributing it to chance. Regardless of the controversy, the team goes on to make predictions with advanced versions of the tool. Figure 6 indicates the working of the method in practice.
(Source: Jefferson, 2016).
Syzygy
Syzygy has been used as a pointer to the occurrence of an earthquake. The theory was used for the very first time in the 1980s by Iben Browning, a self-proclaimed climatologist. He predicted the occurrence of an earthquake in Missouri, within 48 hours, by calculating the tides exerting optimum force on the crust (Mohita, 2016). The alignment caused the event with the moon and sun (figure 7). Although the earthquake did not happen, there has been a major interest on the relationship between tides and earthquake.
(Source: Howard, 2012)
Ambient Noise
The ambient noise associated with the sedimentary basins has indicated the possibility of an earthquake. From the underground, the noise can be used as the basis for indicating some activities underneath. The stretching of the earth as a result of the stress on the rocks has the possibility of being accompanied by some noise (Mohita, 2016). Hence, if the experts could use strong receivers, it is possible to capture the noise and use the information in predicting an earthquake.
Magnetometers
The possibility of the changes in the Earth’s magnetic field has been used by a number of scientists to reveal the possibility of an earthquake. Prior to the Perú earthquake, such an occurrence was noted. According to a physicist, Friedemann Freund, the occurrence is potentially due to the electric currents produced by the stress on the rocks. Therefore, based on the currents being propagated to the earth’s crust, the magnetic field on the earth is altered, the atmosphere is ionized and infrared energy shot into the air (Mohita, 2016). Though there is controversy in the explanation, there is no doubt that the changes occur prior to an earthquake. Figure 8 shows the working of a magnetometer.
(Source: Fast Fluxgate-Magnetometers, n.d).
Hydrochemical Precursors
Alterations in the chemical composition point to the potential for an earthquake. In the underground water, there are major changes in the chemical composition in Tadzhik and Uzbekistan. It was observed that the buildup of dissolved minerals and gases was the same during the time of inactivity, but in the days leading to the earthquake, there was an increase in the concentration. During the quake, the concentration is at the highest level, but the anomalies begin to disappear in the days after (Mohita, 2016). The ground water became turbid when the Jabalpur earthquake in Madhya Pradesh was observed in 1997.
Temperature Change
Change in temperature has been used as one of the pointers to an impending earthquake. Prior to the earthquake experienced in Przhevalsk in Russia in 1970, and in 1976 in Lunglin in China, an increase in temperature by 15°C and 10°C consecutively was noted (Mohita, 2016). It is possible that the changes in the epicenter have an impact on the general temperature, leading to the increase. Figure 9 shows the changes in earthquake in Calama.
(Source: Lockman & Remijan, 2010).
Water Level
Just before the earthquake, major changes in the levels of water have been noted, explaining its use as an indicator of impending earthquake. In the days leading to the 1946 Nankai earthquake in Japan, there was a decline in the water level. Prior to the earthquakes in Lunglin in China and Przhevalsk in Russia, there was an increase in the level of water (Mohita, 2016). Possibly because of the changes in the earth’s crust, there are fluctuations of the water level in the days leading to an earthquake.
Oil Wells
Prediction of earthquakes based on oil wells is founded on the fluctuations of the flow before an earthquake occurs. In China, Israel, and northern Caucasus (Europe), such changes have been noted before the occurrence of an earthquake, pointing to the potential of this kind of prediction. Before the occurrence of the earthquakes in these regions, there was a noted increase in the flow of oil (Mohita, 2016). The incident occurs as a result of the tectonic stress accumulating and the pressure causing the strata to break. When that happens, there is the potential for oil surges along the oil wells.
Conclusion
Prediction of earthquakes can go a long way in saving lives and loss of property. It is necessary to prepare and vacate those individuals residing in the potentially dangerous regions. Hence, predictions, especially those confirmed to provide factual evidence of impending earthquake have a role to play in mitigating the dangerous effects. Some of the commonly used methods have been discussed. While a single method might be misleading, a combination of these methods can provide factual information, which could be used to predict an earthquake.
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