GEOLOGY

Detailed explanation-1: -Seismic gaps help predict earthquakes because they identify areas along fault lines that have not had a lot of activity.

Detailed explanation-2: -Radon is useful as a potential earthquake predictor, because it is radioactive and thus easily detected, and its short half-life (3.8 days) makes radon levels sensitive to short-term fluctuations. A 2009 review found 125 reports of changes in radon emissions prior to 86 earthquakes since 1966.

Detailed explanation-3: -Which of the following are used to predict an earthquake? All of the above are used to predict an earthquake: foreshocks, changes in ground elevation, locations of seismic gaps along a fault, and changes in the groundwater levels.

Detailed explanation-4: -Seismic Gap. Seismic Gap. Region along an active fault where stress is accumulating because no earthquakes have occurred there recently. Seismic gaps are often flanked by areas that have experienced earthquakes in the near past.