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Hairline vertical cracks in reinforced masonry wall of shopping mall

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I need some advice. I was asked to look at some earthquake damage at a local shopping mall. The department store manager was sited by the city after he recent Anza quake for damage at two corners that turned out to be nothing more than lost mortar at the junction of two walls that were at the store entry and intersected at an angle.
However, as I was checking the exterior of the building which is a decorative masonry block about 16 feet high (one story with suspended ceilings inside) I noticed that there were some very fine hairline fractures spaced between ten and fifteen feet apart that extended through the head joints and through the blocks (fracturing the masonry) above. The walls are essentially 100% solid and over 100 feet long. The cracks are not new and appear in places to show signs of an underlaying efflorescence that gave the impression of either a lighter color showing through or a mineral extraction that is a very light coating (it can not be rubbed off).
At least two sides of the building were accessible for me to walk and I have not had a chance to see any drawings to find out if interior walls may be pounding the masonry during past and more recent earthquake activity. The building was constructed in 1974 (there was a bronze plaque in the flatwork outside the store).
I don't want to mention the store at this time, but would like to get some thoughts if others have seen this type of hairline fracture in other masonry structures - specifically high bay retail establishments with large interior floor space and most likely panelized roof framing. Other portions of the building were different block configuration and I was not able to gain access into these areas to see if there were any indications of cracking like I saw.
The location is the California desert in the Palm Springs to Indio area so we are talking about high differences of interior and exterior temperatures during the summer (my thoughts are temperature induced cracking).

Please e-mail me privately as I get this in digest format and will be leaving for a work/vacation back in Chicago and will be checking mail regularly once I reach Chicago (I'm driving). I would like to have some suggestions for the client who is responsible for all repairs to the building.


PS (Pictures available by request)


Dennis S. Wish, PE
California Professional Engineer
Structural Engineering Consultant (Photo Blog) (Launch to Professional Discussion Blogs)


760.564.0884 (office - fax)

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