Births on April 26

Charles Francis Richter, American seismologist and physicist (d. 1985)

Charles Francis Richter (April 26, 1900 – September 30, 1985) was an eminent American seismologist and physicist whose name became synonymous with the measurement of earthquakes globally. Born in Hamilton, Ohio, Richter dedicated his scientific career to understanding the powerful forces that shape our planet, primarily through the study of seismic activity.

Richter is most famously recognized as the brilliant mind behind the Richter magnitude scale. This groundbreaking scale, which he first introduced in 1935, provided the world with its first widely accepted method for quantifying the energy released by earthquakes. Before its development, assessing earthquake size was often subjective or limited to local observations of damage. Richter’s innovation brought a much-needed scientific standard to seismology.

The genesis of the Richter scale was a collaborative effort, rooted in the academic environment of the California Institute of Technology (Caltech), where Richter worked alongside his mentor, the distinguished German-American seismologist Beno Gutenberg. Their work was significantly inspired by the pioneering research of Japanese seismologist Kiyoo Wadati, whose 1928 paper explored the characteristics of shallow and deep earthquakes. Wadati's work, particularly his method of adjusting seismic wave amplitudes for distance, provided a crucial foundation for Richter and Gutenberg's logarithmic approach to magnitude.

The scale itself, formally known as the Local Magnitude (M_L) scale, was designed to assign a single number to quantify an earthquake's size based on the maximum amplitude of seismic waves recorded on a Wood-Anderson seismograph at a specific distance from the epicenter. Being a logarithmic scale, each whole number increase in magnitude represented a tenfold increase in measured wave amplitude and approximately a 32-fold increase in the energy released. This allowed for a concise representation of earthquakes ranging from barely perceptible tremors to catastrophic events.

While the Richter scale revolutionized seismology, its limitations, particularly for very large earthquakes or those occurring at great distances, became apparent over time. For instance, it could "saturate" for extremely powerful events, meaning it wouldn't accurately reflect their true size. Consequently, a more sophisticated measure, the moment magnitude scale (M_w), was developed and gradually superseded the Richter scale, especially for larger earthquakes. The moment magnitude scale, introduced in 1979, is based on the seismic moment of the earthquake, a measure related to the physical size of the fault rupture and the displacement along it, providing a more robust and physically grounded assessment of an earthquake's total energy.

Despite the advent of newer, more precise scales, the legacy of Charles F. Richter endures. His scale laid the essential groundwork for modern earthquake monitoring and public understanding. He was also known for his distinct personality and wit, famously quipping, "logarithmic plots are a device of the devil." This humorous remark, attributed to Richter, playfully highlights the complexities and sometimes counterintuitive nature of logarithmic scales, even for the very scientists who utilize them.

Frequently Asked Questions About Charles F. Richter and the Richter Scale

What exactly is the Richter magnitude scale?

The Richter magnitude scale, or more precisely the Local Magnitude (M_L) scale, was a logarithmic scale developed by Charles F. Richter in 1935 to quantify the size of earthquakes based on the maximum amplitude of seismic waves recorded by a specific type of seismograph at a standard distance.

How does the Richter scale work in simple terms?

It's a base-10 logarithmic scale. This means that for every whole number increase on the scale (e.g., from 4.0 to 5.0), the amplitude of the seismic waves measured increases tenfold. The energy released by the earthquake increases by approximately 32 times for each whole number step.

Is the Richter scale still used today?

While the term "Richter scale" is still widely used by the public and media, seismologists primarily use the moment magnitude scale (M_w) for larger earthquakes, especially those with magnitudes above 3.5. For smaller, local earthquakes, various "local magnitude" scales, which are descendants of Richter's original, are still in use.

Who was Beno Gutenberg, and what was his role?

Beno Gutenberg was a prominent German-American seismologist and Richter's colleague and mentor at Caltech. He was instrumental in the development of the Richter scale, contributing significantly to its theoretical and practical aspects, particularly in the understanding of earthquake depths and wave propagation.

Why was the moment magnitude scale developed to replace the Richter scale?

The moment magnitude scale (M_w) was developed because the Richter scale had limitations, particularly its tendency to "saturate" or underestimate the true size of very large earthquakes. The moment magnitude scale is based on the physical properties of the earthquake fault (fault area, average displacement, and rigidity of the Earth), providing a more accurate and consistent measure for events of all sizes.

What did Charles F. Richter mean by "logarithmic plots are a device of the devil"?

This humorous quote reflects the often complex and counterintuitive nature of working with logarithmic scales. While essential for representing phenomena that span many orders of magnitude (like earthquake energy), understanding and interpreting logarithmic plots can be challenging, even for experienced scientists, leading to a playful expression of frustration.