John's Blog



The 5.4 earthquake that struck Chino Hills almost exactly a month ago luckily caused only minor damage but it reminded us that we live in earthquake country. If the earthquake prompted you to become better prepared for the next seismic event then at least there is something positive that came out of that nerve-racking event.

As an official Post-Earthquake Evaluator of Buildings trained by the Governor's Office of Emergency Services, I'm qualified to identify damage to structures and rapidly evaluate their potential threat to life.
One of the most common issues found after an earthquake is cracks in structures, so a basic understanding of the two major types of structures is important for everyone.
These two types are wood and heavy materials. But, are all cracks created equal? What do they mean?

Wood Frame
Wood frame buildings are very flexible and can move quite a bit without suffering much damage to the integrity of the structure. The plaster and stucco on wood walls is very rigid so it will crack.
However, the plaster and stucco can crack without any fundamental damage to the structural integrity of the wood structure itself.

When a wood framed wall has shifted a small amount such as an inch, or less, over 10 feet, even though the plaster or stucco surfaces may be cracked, is usually only a minor issue. However, a shift in a wood frame structure of more than an inch often means the structure has been compromised and requires further investigation by an engineer to determine the extent of the damage and repair.

Heavy Materials
Heavy materials such as concrete block, brick and stone tend to suffer more serious damage than lightweight structures because they are much less tolerant to movement. A masonry chimney or a concrete block wall can appear straight and stable after an earthquake and yet could have suffered damage that severely compromises its structural integrity, creating a potential hazard in the next quake. From a layman's eye, look for cracks in the stucco, concrete, mortar or brick, however, it takes an expert with trained eyes and special equipment to determine the safety of these masonry structures.

Chimneys are another component of the home that must be structurally sound as well as fire safe.
It is interesting to note that the National Fire Protection Association states that there are three times to inspect a chimney:

  • When a chimney was repaired
  • Upon the sale or transfer of property
  • After a seismic event or other incident likely to cause damage.

Water Pipes and Drain Lines
Earthquake shaking can also damage water pipes and drain lines. Look for wet spots or leaks under a house that could be a result of those kinds of issues. Also, an oversaturated area of the lawn or sinking area of a driveway or walkway could be an indication of an underground break in a water pipe or drain line. Finding that sort of issue should prompt you to contact a professional sewer line inspector. For water leaks, contact a plumber to evaluate and locate the exact source of the problem.

Pools are usually very strong rigid, reinforced concrete. But, if they move enough to be damaged by a quake you might see cracks or chips in the plaster. Also, tiles or stones may loosen or fall off.
Or, check to see if the water is level with the top of the pool.

In general, you should always inspect your home or building IMMEDIATELY after an earthquake. If you spot any issues, handle them as soon as possible. Also, you should know where your water valve, electrical power main and gas meter are, especially if you have to shut them off.
Getting prepared now before the next quake and having an idea of the tell tale signs of structural problems caused by earthquakes will greatly increase your survival and the survival of your loved ones.

John A. LaRocca is a Post-Earthquake Evaluator of Buildings, a qualified member of the California Real Estate Inspection Association (CREIA) and a licensed general contractor. For other questions or comments, contact him at (818) 951-1795 or

Comment balloon 0 commentsJohn LaRocca • September 09 2008 11:47AM