Question

read the passage.
human activity and earthquakes
when americans think of earthquakes, they tend to think of california, a state known for its frequent seismic activity. in recent years, however, people in arkansas, colorado, kansas, new mexico, oklahoma, and texas have been feeling the ground shake more often. an increase in oil and gas drilling in these states has led to \human-induced\ earthquakes—those resulting from human activity. when wastewater is disposed of during gas and oil drilling, the water is forced deep underground. the resulting buildup of pressure can cause fault lines (cracks in the earths crust) to shift. according to mark petersen, head of the u.s. geological surveys earthquake hazard mapping project, \in the past five years, the usgs has documented high shaking and damage in areas of these six states, mostly from induced earthquakes.\
what is the main, or central, idea of the passage?
residents of six u.s. states have experienced an increase in earthquake activity in recent years.
an increase in oil and gas drilling has caused a corresponding increase in earthquakes in six states.

Explanation:

The passage first notes that while Americans associate earthquakes with California, six other U.S. states have seen more seismic activity recently. It then directly links this increase to oil and gas drilling (human activity) that creates pressure shifting fault lines, citing USGS data. The core idea is the causal relationship between drilling and the rise in earthquakes in these states, not just the increase itself.

Answer:

An increase in oil and gas drilling has caused a corresponding increase in earthquakes in six states.