Question

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 starts by noting that people in certain states (Arkansas, Colorado, Kansas, New Mexico, Oklahoma, and Texas) are experiencing more earthquakes. Then it explains that an increase in oil and gas drilling (specifically wastewater disposal during it) leads to human - induced earthquakes. Mark Petersen's statement further emphasizes that the high shaking and damage in these six states are mostly from induced earthquakes. So the main idea is about the cause (increase in oil and gas drilling) and effect (increase in earthquakes) relationship in these six states.

Answer:

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