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 earth's crust) to shift. According to Mark Petersen, head of the U. S. Geological Survey's 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 idea of the passage?

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

Residents of six U. S states have experienced an increase in earthquake activity in recent years.