Q: Does it make any difference if a home is located directly upon an earthquake fault, a few yards away or a mile away? My husband, who is no expert, says it doesn't matter.
A: A couple who stands divided on this issue may find their home even more so in the event of a major earthquake. According to David Oppenheimer, a seismologist with the U.S. Geological Survey in Menlo Park, "If the house was right on top of a fault, it would rip the house apart, with offsets of up to a meter . . . if a fault ruptured up to the surface, which is unlikely."
Generally, ground movement during an earthquake is stronger along the fault line.
"Nobody should build right on top of a fault, from a seismologist's point of view," Oppenheimer said.
However, he added that homes a mile away from a fault are still vulnerable and could receive the same amount of damage in an earthquake.
Faults extend some six miles deep into the earth. So a house directly on top of the fault already may be up to six miles away.
In addition, examine other geologic and geographic factors as well as the structure itself. Houses built on an unstable hillside run the risk of landslides while those on landfill near a body of water may not withstand vigorous shaking if the fill loses cohesiveness and liquefies.
To find out where fault lines lie and to determine their potential impact, call the U.S. Geological Survey in Menlo Park at (415) 853-8300.