Question 2:

(1)  I know California, especially the San Francisco Bay Area & Los Angeles, is famous for their seismic or earthquake activities. How do I know my house is safe from the shakes?

Answer:

I grew up in a city where reinforced concrete building & steel framed skyscrapers were typical.  To fullfill the master's degree thesis requirement, I researched methods to strengthen R/C beams.  So when I was asked to design wood buildings right out of college, I really didn't know where to begin.  It may be simple to build a wood house, but indentifying the adaquecy of the paths the lateral forces induced by an

earthquake may not be that easy. To assist concerned homeowners, California Existing Building Codes, CEBC Chapter A3, identify three major weaknesses commonly found in residential houses:  i) the connections between the exterior walls and the cripple wall at the perimeter of the houses, ii) the bracings of the cripple walls and iii) the connections of the exterior walls or cipple walls to a continuous concrete footing/foundation.  These weaknesses are so critical for houses to withstand the earthuakes that the Californian Building Code permits homeowners to commence the remedial strengthening without applying a building permit.  It is, as usual, advised to check with the building official in your city/county first to make sure they have adopted provision A301.1.  A publication called "How You Can Strengthen Your Home For the Next Big Earthquake In The Los Angeles Area" printed by Department of Building and Safety of The City of Los Angeles in 2005 is a good reference for DIY Homeowners.  However, the printed version of thevbooklet may not be available anymore, but electronic copy is still available for download over the internet. 

To start, determine if your house was built on concrete slab-on-grade (Figure A below) or raised floor (Figure B to E).  If there is a basement in the house and its floor is below the grade surrounding the house, or a floor hatch at the lowest floor level in the house, it is a raised floor system.  If no hatch is found, tap the carpet/wood flooring lightly with a hammer or mallet.  If it sounds hollow, very likely it is one of the raised floor systems (Figure B or C).  

Once the floor is determined to be raised, check to see if the perimeter footing is made of concrete.  Dig some small 12" deep holes against the exterior walls below the floor in the backyard or sideyard to find out if there is any footing underneath the joists If not, the house is supported .

on grade and strengthening is required as early as possible.

If concrete is found within the 12" deep holes, it is likely a raised floor without any cripple wall (Figure B). Otherwise, it is a cripple wall system shown in Figure C.

When any of the connections shown in Figure B & C are missing, similar to Fig. D & E, strengthening is still required, but simply by providing the missing components.