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Frequency of earthquake is defined as how often a given earthquake with certain magnitude occurs. On average, earthquakes with a magnitude of 2 and smaller, which are called small earthquakes, happen several hundred times a day worldwide.
However, major earthquakes that have a magnitude of 7 or larger occur more than once per month around the world. With regard to the great earthquake, which has a magnitude of 8 and greater, occur about once a year.
Knowing the frequency of earthquakes is important from an engineering point of view. This is because it helps to improve and enhance codes by which seismic resilient building can be constructed.
Frequency of Earthquakes Worldwide
Over the years, developments in technology have enabled different seismic agencies, such as the National Earthquake Information Center, to record a greater number of earthquakes in the world compare with past records.
Based on the records of the national earthquake information center, 16 major earthquakes can be expected in any given year which involves fifteen earthquakes in magnitude 7 range and the remainder earthquake with a magnitude of 8 or greater.
Outstandingly, the largest total number of major earthquakes with magnitude equal or greater 7 were 24 which were occurred in 2010. However, in other years, the total of major earthquakes was below 16 per year expected based on the long-term average.
It may seems that the number of earthquakes have creased in recent years, However, this is not the case based on the statics of seismic agencies, but rather the impact of earthquakes has increased due to raise of populations, as a result higher number of people would be at risk when an earthquake hit.
An increase or decline in earthquake number per year is part of normal fluctuation of earthquake rate. Additionally, the increase and decrease of earthquake frequency are not a sign that major earthquakes are imminent.
Fig. 1 shows the annual number of earthquakes worldwide, and Table 1 presents the frequency of earthquakes of different magnitude around the world since 1900.
Table 1 Frequency of Earthquakes Worldwide Based on Magnitude and Annual Average
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