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Earthquake Facts: Are the Numbers of Big Earthquakes on the Rise?

Updated on March 10, 2018
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Science, nature and the environment, with regard to human impact, are subjects to which Chris applies his passions for research and writing.

Nepal Earthquake 2015; Moment Magnitude 7.8

Source

Are the Numbers of Big Earthquakes on the Rise

This article has been designed to answer one question. Are the numbers of big earthquakes on the rise, holding steady or declining? Facts from the U.S. Geological Survey along with graphs and charts will conclusively answer this question.

Significant Earthquakes During Early 2015

6.7-Kodari, Nepal

6.6-Lamjung, Nepal

7.8-Lamjung, Nepal

6.2-Bella Bella, Canada

6.3-Lata, Solomon Islands

6.4-Su'ao, Taiwan

6.5-Sigave, Wallis and Futuna

3.3-View Park-Windsor Hills, California

6.3-Hihifo, Tonga

3.6-San Ramon, California

NEPAL on April 29, 2015. 5,200+ Dead, 10,000+ Injured, 70,000+ Homes Destroyed

The Need to know about Earthquakes and other Natural Disasters

While this article is about earthquakes, natural disasters of various kinds are all around us in this world. Every region seems to have its own version of catastrophe. Tornadoes and hurricanes, Volcanoes and earthquakes, tsunamis and tidal waves, landslides and sinkholes, wildfires and droughts, floods and snow storms. On occasion, usually following a natural disaster involving one of these phenomena, I hear someone ask a question that usually goes something like this. “Why do people live there if it’s so dangerous?” In response, I always want to say, but rarely do, where can we live that is free from the danger of a natural disaster?

People have different reasons for wanting to know about earthquakes. If a person lives in a location which is known for having significant numbers of earthquakes, especially large or great earthquakes, protecting oneself and family would be the cause for interest. Engineers who design buildings and those who build them must have an understanding of the interaction between manmade structures and this powerful force of nature.

So whether you are checking out a new place to live or are simply curious, we all have some desire or need to know something about earthquakes.

San Francisco, California Earthquake, 1906

Source

Data Collection of Earthquakes: Number and Magnitude

It is likely that all of us have been through an earthquake. It’s just that some of us didn’t realize it, while others were all too aware of what was going on. The United States Geological Survey estimates that every year there are millions of earthquakes worldwide. But facts are facts and estimates are estimates. The fact is, the USGS, in an average year, counts 20,000 earthquakes worldwide, which is 50 per day or 2 per hour.

Many people are under the impression that the number of earthquakes is on the rise. This may be just a feeling they have, but it would be helpful to either prove or disprove those feelings. So the remainder of this article will be devoted to that topic. Are the numbers of earthquakes worldwide on the rise?

Man has only recently become able to measure the strength or magnitude of earthquakes. We’ve all heard of the Richter scale, developed by Charles Richter in 1934, but that measurement has been proven to not be applicable to all places and all magnitudes of EQs. Today, the moment magnitude scale (abbreviated MW) is better suited for the task, specifically because it is globally applicable to all magnitudes of EQs.

The moment magnitude scale is based on the seismic moment of the earthquake. Seismic moment is calculated by multiplying three geophysical properties: (1)the rigidity of the Earth (2) the average amount of slip on the fault and (3) the size of the area that slipped (From the Wikipedia article on moment magnitude scale).

Fukuoka, Japan; Moment Magnitude 7 Earthquake March 20, 2005

The landslide upon the surrounding road of Shikanoshima, Fukuoka following the earthquakes on March 20 and April 20, 2005.
The landslide upon the surrounding road of Shikanoshima, Fukuoka following the earthquakes on March 20 and April 20, 2005. | Source

Number of 6.5+ Earthquakes From 1977 to 2012. Notice the Upward Change Beginning in 1992

Year
Number of 6.5+ EQs
1977
42
1978
58
1979
59
1980
66
1981
45
1982
56
1983
71
1984
49
1985
67
1986
60
1987
71
1988
60
1989
58
1990
71
1991
61
1992
73
1993
82
1994
82
1995
96
1996
86
1997
94
1998
81
1999
83
2000
89
2001
72
2002
83
2003
89
2004
94
2005
86
2006
69
2007
82
2008
95
2009
78
2010
90
2011
60
2012
57

From 1977 through 1991, the USGS counted 20,000 EQs of all magnitudes per year. Beginning in 1992, that figure began to rise.

Four Points That Reveal the Progressive Increase of Large Earthquakes

  1. 1977-2012-The chart above shows a great deal of fluctuation in the numbers of EQs above magnitude 6.5. Up to 1992 the USGS had been reporting an average of 20,000 earthquakes (all magnitudes) per year. Beginning in 1992, the numbers began to rise. You can see the increase in the chart by following the numbers of EQs from 1992, which was 73, to 2012. Don't expect a constant upward movement. It goes up and down, but the end result is an overall increase in the numbers of big EQs over the period from 1979 to 1992.
  2. 1992-2010-The USGS has reported, since 1979, an average of ten earthquakes per year above magnitude seven. Beginning in 1992 that figure rose to 12.5 until 2010 when it again increased to 16.7 (Reflected in chart above). This was a 65% increase over the thirty years since 1979.
  3. 2002-2012-According to G. E. Daub, E. Ben-Naim and P. A. Johnson, in their article on Temporal Clustering of Great Earthquakes in December, 2012, "The last decade (2002-2012) has seen a surge in the number of great earthquakes (magnitude M ≥ 8), including three of the six largest events on record in the past century." (Presented at the American Geophysical Union, Fall Meeting 2012).
  4. 2012-2014-But since 2012, (The last year on the chart above) something dramatic has taken place. According to Tom Parsons, a research geophysicist with the U.S. Geological Survey (USGS), the number of large EQs nearly doubled in the first quarter of 2014. Parsons stated that "we have recently experienced a period that has had one of the highest rates of great earthquakes ever recorded.”

Source for the above information is at Discovery News

Historical Perspective

Now lets put the alarming fact that the number of large EQs is on the rise, into historical perspective. There have been numerous spikes of big EQs in history. The chart below, and the important quote following it, illustrate "Clusters" of big EQs during the 20th century.

Twentieth Century Clusters of Big Earthquakes

| Source

"If we only consider data since 1950, when instrumentation worldwide improved and event magnitudes become better constrained, the likelihood that the earthquake catalogue is random becomes remarkably small (~1/1000). We attribute the nonrandom behaviour to clustering in time of large earthquakes, as there are two clusters of events (1950s-1960s, and 2004-present) separated by a long period with no large events."

— Daub, E. G. ; Ben-Naim, E. ; Johnson, P. A. American Geophysical Union, 2012

Will the Upward Trend Continue, or Fall Back to the Previous level of 20,000 EQs per Year?

The number of large earthquakes is clearly on the rise, but it is only an increase over the period of time from 1979 to 1992. There was another "spike" in big EQs in the 1950s and 60s, but that returned to the previous norm. Will this current phenomenon continue unabated or will it end, just as the same kind of rise ended in the 1950s and 1960s? It is difficult at this point in history to make firm predictions based on the data. Scientists have only been collecting seismic data effectively with modern equipment since the early 20th century. A century of reliable data is not enough on which to base firm predictions of seismic behavior or patterns.

Relief for Nepal

Source

The Common Person's Place in the Big Picture of Big Earthquakes

What is the common person's response to what has happened just days ago in Nepal? These Earthquakes are happening more often, as is shown by the information in this article. Some choose to pray, others give to relief organizations. A few go to these places to help with relief efforts and in delivering medical assistance.

The power of the Nepal earthquake was overwhelming. The need following the disaster is numbing to the point that we may do nothing in response as individuals. The link in the grey box in the upper right may help. It is an article published by Public Radio International and contains the information on vetted relief agencies who are actively assisting people affected by the Nepal earthquake.

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