California Specific Exam (CSE) Professional Geologist (PG) Practice Exam 2026 - Free Geologist Exam Practice Questions and Study Guide

The strength of an earthquake is most commonly measured by its magnitude. Magnitude quantifies the energy released at the source of the earthquake and is typically measured on the Richter scale or the moment magnitude scale. These scales provide a logarithmic scale where each increase of one unit in magnitude represents a tenfold increase in amplitude of the seismic waves and approximately 31.6 times more energy release.

Magnitude is a crucial concept as it offers a means to objectively compare the sizes of different earthquakes irrespective of where they occur and how they are felt by people in various locations. This makes magnitude the most widely used standard in scientific and public discussions regarding earthquakes.

Intensity, on the other hand, measures the effects of an earthquake at various locations, such as the damage caused and the human perception of shaking, rather than the energy released at the quake's source. Local Magnitude is a specific scale used primarily for smaller earthquakes and is a simpler version of measuring earthquake size, whereas seismic shift is not a commonly used term in the context of measuring earthquake strength. Each of these alternatives provides valuable information, but magnitude is the standard measure of an earthquake's strength.