Have Magnitude 6.5+ Earthquakes Increased?

Major earthquakes receive a lot of media attention these days. Major earthquakes do not need to occur near land to earn a breaking news banner on major news websites. The widespread prevalence of major earthquake reports in the media leads to the question: “Are major earthquakes becoming more common these days?” I will address this question by examining trends in magnitude 6.5 and greater earthquake activity since 1900 in this article.

Why Care About Major Earthquakes?

Why should we care about major earthquake activity? Luke 21:11 suggests that we will hear about great earthquakes-rather than regular earthquakes-in diverse places prior to the Second Coming of Christ.

“And great earthquakes shall be in divers places, and famines, and pestilences; and fearful sights and great signs shall there be from heaven.” (Luke 21:11)

Why bother conducting a study about trends in magnitude 6.5 and greater earthquakes when I’ve published studies on magnitude 7.0 + and magnitude 8.0 + earthquake activity?

• A major reason why it may be useful to look at trends in magnitude 6.5 and greater earthquake activity over time is that magnitude 6.5-6.9 earthquakes are relatively more common than magnitude 7.0 and greater earthquakes. This means that we may be able to better spot a noticeable trend in earthquake activity than we can by studying only the strongest earthquakes.
• Magnitude 6.5 to 6.9 earthquakes are not minor events. Earthquakes of this magnitude can cause a lot of destruction. For instance, the 1994 Northridge, California earthquake was a magnitude 6.7 that caused up to $20 billion in damage.

I again utilized two data sources to account for the magnitude 6.5 and greater earthquakes that have taken place since 1900.

• The U.S. Geological Survey’s Centennial Earthquake Catalog dataset. I rely on this dataset to account for magnitude 6.5 and greater earthquakes that have taken place from 1900-2007.[1]
• The U.S. Geological Survey’s Preliminary Determination of Epicenters (PDE) dataset. I rely on this dataset to account for magnitude 6.5 and greater earthquakes that have taken place since 2008.[2]

Magnitude 6.5 + By Year

The following graph illustrates magnitude 6.5 and greater earthquake activity each year since 1900.

The graph shows that there has been a lot of fluctuation in magnitude 6.5 and greater earthquake activity through time. However, it seems there has been more magnitude 6.5 and greater earthquake activity in the past 15 years compared to several years in the 1970s and 1980s.

Magnitude 6.5 + by Decade

In addition to graphing magnitude 6.5 and greater earthquakes by year, I aggregated magnitude 6.5 and greater earthquake data by decade. Here is the breakdown:

Interestingly, the 1940s and 1950s were two most active decades since 1900 in terms of magnitude 6.5+ earthquake activity. The 1990s, 2000s, and 2010s were three of the most active decades of the past 50 years in this chart.

Notes of Caution

We can say that magnitude 6.5 and greater earthquake activity is up in recent decades, but we are limited to only talking about the time since 1900 to today since there is a lack of measurable data to compare recent years with different periods in history. We cannot adequately compare recent years with time periods like the 1840s, 33 AD, etc. Therefore, we cannot talk about today being an unprecedented time.

Another caveat is that the earthquake numbers in the early portion of the 20th century are probably understated.  The reason is that there were not as many devices that could measure earthquake activity in the early portion of the 20th century as there were in the latter portion of the century.

I hope you found this article informative.  If you have any questions or comments please share in the comments section below.

Notes

1. Centennial Earthquake Catalog numbers from 1900 to 2007 were obtained from a text file found on the USGS’s Centennial Earthquake Catalog page: http://earthquake.usgs.gov/data/centennial/centennial_Y2K.CAT ↩
2. PDE numbers for 2008 to the present were obtained on September 2, 2020 from the USGS’s Search Earthquake Archives, which can be accessed at the following link: http://earthquake.usgs.gov/earthquakes/search/ I set the custom magnitude at 6.5 and set the search range starting on January 1, 2008. Under advanced options I selected: “US – National Earthquake Information Center, PDE”. Under output options, I choose CSV and ordered results by time: oldest first. ↩