Charles F. Richter

What the Richter scale measures

Richter's magnitude is a logarithmic index originally designed to express the amplitude of seismic waves recorded on a specific instrument. A one‑unit increase represents a tenfold increase in measured wave amplitude and roughly an order‑of‑magnitude increase in released energy. The original formulation is often referred to as local magnitude (ML), tied to the response of a particular seismometer.

Origins and development

Working at a Californian research laboratory in the 1930s, Richter collaborated with colleagues to create a simple numeric scale that allowed comparisons between earthquakes. The method was tailored to regional records and to the instruments available at the time, which made it practical for routine seismic reporting.

Uses, limits and successors

The Richter magnitude helped standardize earthquake reporting and improved public understanding and hazard planning. However, for very large or distant earthquakes the scale "saturates" and underestimates total energy. Modern seismology often uses moment magnitude (Mw) for large events, but Richter's approach remains foundational in teaching and historical catalogs. See more about how scientists study earthquakes.

Notable facts

• The original scale is commonly abbreviated ML (local magnitude).
• It is logarithmic: each whole number step corresponds to a tenfold amplitude change.
• Designed for particular instruments and regions; later adapted and supplemented by other magnitude measures.

Richter's work left a lasting legacy in seismology and public communication: a compact, intelligible way to convey the size of seismic events that shaped decades of research, emergency planning and media coverage.