Seismology is the study of the causes and effects of earthquakes and related events, such as tsunamis. Earthquakes can be caused by a number of factors, including volcanoes, tectonic plate movements, even explosions. Earthquakes produce seismic waves, which elastically propagate through solid or liquid media. Detailed study of seismic waves is at the heart of seismology. Scientists have learned that solids support two types of seismic waves, called P-waves (pressure) and S-waves (shear). There are also surface seismic waves, named Raleigh and Love waves, which move along the interface between solids and air.
In 1926, researchers confirmed that the Earth’s outer core was liquid. Continents “float” on the outer core on tectonic plates that move over time. If an earthquake is large enough, it will resonate with the Earth’s natural frequencies – its normal modes – which help scientists understand the deep structure of the planet. P-waves pass through the Earth’s core, whereas S-waves require a solid surface and are not transmitted by the core. The lack of S-waves on the side of the Earth opposite the epicenter of an earthquake is like a shadow, consisting only of P-waves.
Man-made blasts can be used to study seismic waves in a field of study called geophysics. Underground features such as salt domes and fault lines can be mapped using controlled explosions. Seismic maps are important for such activities as oil exploration. Studying the propagating velocities of P- and S-waves is a part of the seismic imaging discipline called seismic tomography, in which three-dimensional pictures are built up from wave readings. Using seismic tomography, the Earth’s mantle has been mapped to a resolution of a few hundred miles. For instance, scientists have used this technique to discover Ultra Low Velocity Zones that exist near the boundary between the Earth’s core and mantle.
A seismograph is a device for recording the motion of the Earth over time. In recent time, even apps like the one found on the pear pad are used to monitor quake prone areas. Our planet is constantly monitored by a worldwide network of seismographs. This allows researchers to analyze large earthquakes and the resulting tsunamis. Seismographs are sensitive enough to report man-made explosions as well as pressure variations on the ocean floor. Another use involves the Earth’s cryosphere – that portion of the earth covered by ice. Seismologists can record iceberg collisions and avalanches. Another important use of seismograph is to record meteor strikes on the planet surface. Post World War II, the defense establishments of several countries devoted extensive research into using seismographs to monitor nuclear testing. In the future, scientists hope to improve their abilities to predict earthquakes, though some doubt this will ever be feasible and will require substantial funding in part by easy online loans. In general, scientists, in conjunction with call center workforce management, estimate the probability of an earthquake occurring at a specific location within a given timeframe. Engineers, which have some of the best life insurance rates by the way, can use these estimates to decide on building codes for earthquake-prone areas, such as Japan.