seismology - Earthquake prediction

The study of earthquakes and the propagation of seismic waves through the Earth. By studying the velocity of seismic waves, the structure of the Earth and the discontinuities which define its core, mantle, and crust have been discovered. By using artificial explosions to generate shock waves, the structure of the underlying rocks can be determined, and applied to the exploration for oil and gas.

Seismology (from the Greek seismos = earthquake and logos = word) is the scientific study of earthquakes and the movement of waves through the Earth.

Earthquakes, and other earth movements, produce different types of seismic waves. These waves travel through rock, and provide an effective way to "see" events and structures deep in the Earth. There are three basic types of seismic waves: P-waves, S-waves, and surface waves.

Pressure waves, also called Primary waves or P-waves, travel the fastest and are therefore the first waves to appear on a seismogram. P-waves are pressure or compressional waves that move (propagate) through a material by alternately compressing and expanding (dialating) materials.

S-waves, also called Shear waves or secondary waves, travel slower than P-waves and appear second on a seismogram.

One of the earliest important discoveries was that the outer core of the Earth is liquid. Pressure waves (P-waves) pass through the core. Transverse or shear waves (S-waves) that shake side-to-side require rigid material so they do not pass through the core.

Seismic waves produced by explosions have been used to map salt domes, faults, anticlines and other geologic traps in petroleum-bearing rocks, geological faults, rock types, and long-buried giant meteor craters.

Using seismic tomography with earthquake waves, the interior of the Earth has been completely mapped to a resolution of several hundred kilometers.

Seismographs also effectively discover unusual, otherwise unobserved phenomena such as large meteors striking uninhabited ocean, or underground nuclear tests.

One of the first attempts at the scientific study of earthquakes followed the 1755 Lisbon earthquake.

Earthquake prediction

Most seismologists do not believe that a system to provide timely warnings for individual earthquakes has yet been developed, and some believe that such a system would be effectively impossible.

Various attempts have been made by seismologists and others to create effective systems for precise earthquake predictions, including the VAN method.