The March earthquake and subsequent tsunami in Japan killed 20,352 people. Finding ways to reduce the death toll from such natural disasters has captured the interest of scientists in many fields.
There exists several ways to predict an earthquake such as the detection of radon gas emission or electromagnetic changes. However short-term predictions (hours todays) are, in general, unlikely.
At least for now.
Neutrino physics aims to answer some fundamental questions in physics, such as neutrino mass, and matter-antimatter asymmetry, but some think it could also answer fundamental questions about the Earth’s most volatile activities.
Using giant neutrino detectors physicists may be able to predict earthquakes and/or volcano eruptions by detecting geoneutrinos.
Geoneutrinos were first found by the Kamioka Liquid-scintillator Anti-Neutrino Detector (KamLAND) experiment in 2005 and recently by the Borexino Collaboration at the Gran Sasso National Laboratory of the Italian Institute of Nuclear Physics. Geoneutrinos are electron antineutrinos – the antimatter counterparts of electron neutrinos. Geoneutrinos are produced by the radioactive decay of uranium, thorium and potassium in Earth’s crust and mantle.
Geoneutrinos provide us another way to better understand the Earth’s interior besides the usual way of seismology by analyzing the vibrations produced by earthquakes and sensed by thousands of instrument stations worldwide. Geoneutrinos can provide crude information about chemistry, that is to say, how much uranium and how much thorium there is. This will help us to better understand deep-Earth processes which will affect events on the surface such as earthquakes and volcanoes.
A group of Chinese physicists proposed another method for earthquake prediction via neutrino tomography. The idea is to use antineutrinos emitted from nuclear reactors as a probe. As the antineutrinos traverse through a region prone to earthquakes, observable variations in the matter effect on the antineutrino oscillation would provide a tomography of the vicinity of the region. Although they concluded that it is a difficult task with the present technology, “there is hope that a medium-term earthquake forecast would be feasible” with the development of geology, and new detection technology.
Can the NOvA detector being built at Fermilab and in northern Minnesota detect geoneutrinos and make a prediction about earthquakes? The answer is probably no. While the 1,000 ton KamLAND detector sits in an old mine with 2,700 meters, or a little less than 1 ½ miles, of shielding to reduce cosmic ray interference, the 14-kiloton NOvA far detector in Minnesota has only three meters, or about 10 feet, of shielding.
The 222-ton NOvA near detector at Fermilab has 105 meters, or 344 feet, of shielding and will detect a much lower cosmic- ray rate, but it is not big enough to detector the geoneutrinos.
With more and more advanced technologies and geoneutrino-detecting facilities, we may expect that we can have a detailed understanding of Earth’s interior and the source of its internal heat in the near future. Someday, we may be able to predict the occurrence of events such as earthquakes, tsunami and volcano eruptions using our neutrino detectors.
- Xinchun Tian