Seismology

Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth and its surrounding materials. It aims to understand the causes of earthquakes, their size and frequency, and the structure of the Earth's interior.

Seismic waves include P-waves, S-waves, and surface waves. P-waves are compressional and fastest; S-waves are shear and move slower; surface waves travel along the Earth's exterior and often cause strong shaking. Seismographs record ground motion as seismograms, and scientists use the arrival times of waves at networks of stations to locate earthquakes and to infer properties of Earth's interior through techniques such as seismic tomography and travel-time modeling.

Instrumentation: seismometers and seismographs, often deployed in dense networks and in broadband configurations. Magnitude scales: local magnitude (ML) or Richter scale (historical) and moment magnitude Mw, with Mw now standard for larger events. Data are collected by national and international networks such as the USGS, IRIS, and the International Seismological Centre.

Applications: assessing seismic hazards, informing building codes, designing earthquake-resistant structures, and issuing early warning when possible. Seismology also supports monitoring for compliance with nuclear-test treaties and studying tsunamis and volcanic processes. Paleoseismology uses geological records to extend earthquake histories beyond instrumental records.

History: modern seismology emerged in the late 19th and early 20th centuries, with advances in instrument design and theoretical understanding. The development of plate tectonics in the mid-20th century greatly expanded the interpretation of seismic data, linking earthquakes to tectonic plate boundaries.