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?