Fault lines

"In the Houston area, there is a lot of salt, and salt has a lower density than water and tries to come up [to the surface] by itself," Khan said. "So salt comes up and fractures the ground."

Subsidence is a result of increased groundwater usage. As more groundwater is pumped from below the Earth's surface, fractures occur at ground level, Khan said.

"In The Woodlands, primarily it's the groundwater [that causes faults]," Khan said.

Fault lines in the Houston and Woodlands areas move an average of 1 centimeter per year, he said.

"That means that's an average," Khan said. "It may move 2 centimeters next year and after that it may not move at all. Not every fault is active."

Michael Bowden, owner of Bowden Appraisals, said local faults typically have a negligable affect on property values.

"In most cases in this area the answer is zero, none," he said. "However, if it's an active fault line, and there are several of those around, it could have an affect on value."