The concern that the planet is experiencing an escalation in seismic activity is a common public question, fueled by frequent reports of global events. Earthquakes are a natural phenomenon resulting from the movement of tectonic plates that make up the Earth’s crust. Given the continuous energy release along fault lines, it is understandable why people might perceive an increase in frequency. Determining if the globe is genuinely becoming more seismically active requires a careful look at long-term, standardized scientific data.
Understanding Magnitude and Global Monitoring
To accurately track seismic events, scientists rely on standardized measurement tools and a global network of sensors. The severity of an earthquake is primarily quantified using the Moment Magnitude Scale (MMS), denoted as Mw. This scale is the standard tool used for reporting moderate to large earthquakes because it relates directly to the total energy released and the physical size of the fault rupture.
The MMS superseded the older Richter scale for larger events. The Richter scale, while effective for local, smaller quakes, often underestimates the size of very large earthquakes. Global monitoring is conducted by networks like the Global Seismographic Network (GSN) and institutions such as the U.S. Geological Survey’s (USGS) National Earthquake Information Center (NEIC). These networks utilize seismometers that continuously record ground motion, providing the historical data necessary for long-term analysis of global trends.
Analyzing Global Seismic Data Trends
Analysis of the historical seismic record shows that the frequency of large tectonic earthquakes has remained stable over the last century. When examining significant events, specifically those with a magnitude of Mw 7.0 or greater, the statistical average has not increased. The long-term average for Mw 7.0 and greater earthquakes is approximately 15 events per year globally.
Some years see slight variation above or below this average, which is typical for a natural process, but these fluctuations do not indicate a sustained upward trend. Data collected by the USGS and other international bodies confirm there is no evidence of an increase in the number of these large events. This stability suggests that the fundamental tectonic processes driving large earthquakes have not accelerated.
Factors Influencing the Perception of Increased Activity
If the actual data for major earthquakes shows stability, the public perception of increased activity is influenced by two main factors: improved detection and instantaneous global communication. The number of seismograph stations operating worldwide has dramatically increased since the mid-20th century. This growth means scientists can now detect and precisely locate many smaller earthquakes, those in the Mw 3.0 to 5.0 range, that would have gone unnoticed decades ago.
These newly detectable events contribute to a higher count in the total number of recorded earthquakes each year, creating the illusion of a global increase. Simultaneously, the rise of instant global media and social media platforms amplifies the coverage of every seismic event. An earthquake that might have been a local news story 50 years ago is now immediately broadcast worldwide, making it seem as if the number of events has risen dramatically.
Earthquakes Triggered by Human Activity
While the global frequency of large earthquakes is stable, there is a distinct, localized increase in seismic activity known as induced seismicity, which is directly linked to human actions. Induced seismicity refers to earthquakes and tremors caused by altering the stresses and strains within the Earth’s crust. These events are generally smaller than natural tectonic quakes, but they represent a genuine increase in specific regions.
The most common cause of induced seismicity is the deep injection of wastewater, a byproduct of oil and gas operations, particularly in the central and eastern United States. Injecting large volumes of fluid into disposal wells increases the pore pressure in the subsurface, effectively lubricating pre-existing fault lines and causing them to slip. For example, in parts of Oklahoma, the rate of Mw 3.0 or greater earthquakes increased significantly since 2009, a spike directly correlated with the rise in wastewater injection.
Other human activities that can trigger these localized events include the impoundment of water behind large dams and certain enhanced geothermal energy projects that involve fluid injection. These human-triggered events are geographically specific and do not signal a change in the planet’s overall tectonic behavior, but they are a real source of increased seismic hazard in the affected areas.