Question

select the best evidence to support the statement \there has been a large increase in the number of earthquakes since the 1970s.\ there may be more than one correct choice. within the central and eastern united states, the number of earthquakes has changed dramatically over the past few years. between the years 1973 - 2008, there was an average of twenty - one earthquakes of magnitude three and larger in the central and eastern united states. this rate jumped to an average of ninety - nine magnitude three or larger earthquakes per year in 2009 - 2013, and the rate continues to rise. in 2014, alone, there were 659 magnitude three and larger earthquakes. most of these earthquakes are in the magnitude 3 - 4 range, large enough to have been felt by many people, yet small enough to rarely cause damage. the change in the number of earthquakes prompts two important questions: first, are the earthquakes natural or manmade? second, what should be done in the future as we address the causes and consequences of these events to reduce associated risks? adapted from united states geological survey, \induced earthquakes\

Explanation:

The evidence needs to show a large increase in earthquake numbers since the 1970s. The following details compare earlier and later periods to demonstrate this growth:

1. The 1973-2008 average of magnitude 3+ earthquakes (21 per year) vs. the 2009-2013 average (99 per year) shows a sharp rise.
2. The 2014 total of 659 magnitude 3+ earthquakes shows a continued, dramatic increase from the earlier baseline.

Answer:

• Between the years 1973-2008, there was an average of twenty-one earthquakes of magnitude three and larger in the central and eastern United States. This rate jumped to an average of ninety-nine magnitude three or larger earthquakes per year in 2009-2013, and the rate continues to rise.
• In 2014, alone, there were 659 magnitude three and larger earthquakes.