SAN FRANCISCO (KGO) -- When brothers Michael and Aaron Bellings have clients from out of town walk into their real estate office on Castro Street, one question always comes up about the properties they show.
"They want to know if they're in an earthquake zone, what the ramifications are," said Michael Bellings.
The answer isn't always easy to find. Realtors typically hire a firm that prepares what's called a disclosure package.
"A list of anywhere from 200 to 400 documents, which has an earthquake hazard report and a natural hazard report," Bellings said.
Sometimes, that pile of documents can be the bearer of bad news.
"For example, the Marina is one of the most popular districts in San Francisco, and some of the most expensive real estate in the world -- yet, a lot of my clients won't set foot in it because it is in liquefaction," he said.
PREPARE NORCAL: Emergency resources
In 1989's Loma Prieta earthquake, the world saw what liquefaction can do, as blocks of the Marina District were reduced to rubble. Some buildings burned to the ground as others collapsed into the street. It's what led California to begin mapping areas vulnerable to liquefaction and landslides.
The new data supplemented the state's existing practice of mapping properties like the ones damaged in South Napa that had fault traces running through them. When the ground actually splits during an earthquake, it can damage buildings and utility lines far beyond what shaking can do.
Properties that are prone to "ground failure" are required by law to disclose that information to potential buyers -- but the information isn't always easy to find until the transaction is already underway. Now, the California Geological Survey is launching a new app aimed at changing that.
"They can pull this app up on their smartphone while they're standing at the property, and figure out whether it's affected by a hazard zone or not," said California Geological Survey engineering geologist Tim McCrink.
The new app could change the process of buying real estate in California by taking a step that used to come late in the game, and putting it right up front. Bellings said he's watched clients lose interest in a property after finding out the extent of its vulnerability to ground failure.
"Looking at the property video, visiting, loving it, and then realizing that it's in an earthquake zone," he said.
McCrink said earthquake hazards are not always a deal breaker for those looking to buy. With urging from cities and counties, many homes have already undergone seismic studies and retrofits that increase their likelihood of withstanding a major quake.
"It probably has already been investigated, and if a house is there, it's probably already been mitigated," he said.
For new construction, McCrink said the app provides priceless data that would've made a big difference in South Napa.
"Had they known (about the seismic hazards) before they built the house, they probably wouldn't have put them on the fault trace," he said.
Check out the state's earthquake zone app, called EQZapp, here.
Click here for more stories related to earthquakes.