Over the last 10 years, the frequency of earthquakes in Oklahoma has jumped up. The Oklahoma state now experiences hundreds of earthquakes a year. Scientists analyze that most of the earthquakes are caused due to extractions of oil and natural gas from underground.  The bar graph below shows number of earthquakes (greater than Magnitude 3.0) Oklahoma experienced during 1978 and 2016.

1. In what year, Oklahoma started experiencing more than 10 earthquakes in a year?
2. In what year, Oklahoma experienced the largest number of earthquakes?
3. On average, about how many times of earthquakes did people in Oklahoma experienced a day in 2015?    a) once a day  b) twice or 3 times a day  c) 5 times a day
4. How many more earthquakes does Oklahoma experience in 2016 than 2010?

Sources: USGS, 2016. Information by region-Oklahoma

__________________________________________________________