GEOL 106 Lecture Notes Feb 26.docx

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Geological Sciences and Geological Engineering
GEOL 106
David Alan Hanes

Feb 26 2013 4/3/2013 11:21:00 AM Once Again… RISK ANALYSIS: 1. Understand the hazard 2. Determine the risk from that hazard for the region of interest RISK MANAGEMENT: 3. Determine ways to reduce PH and/or SH 4. Do a “cost”-benefit analysis that determine what you can afford to do 5. Implement mitigation techniques if warranted and to the extent that you choose **NOTE: these are the five steps of risk analysis/management SEISMIC RISK OF AN AREA: Determine ways to reduce PH and/or SH To try and reduce SH… 1. Apply land-use planning and zoning A) use high-risk areas for low population use (e.g. parks, golf course) Or you put in regulated set back locations; restricted from building too close to the fault in particular, don’t build in areas of soft soil or soils that might liquefy 2. Apply stringent building codes A) choose appropriate building materials Good Materials: Wood, steel, reinforced concrete All behave in a flexible way Bad Materials: Heavy masonry, stucco, adobe, unreinforced concrete All the bad materials behave in an un-flexible way BUT, in Machu Picchu, the structures are built out of dry-stone, when earthquakes struck, the individual pieces were able to move back and forth freely EXAMPLES: 2 earthquakes in 1988-89 of similar 6.5-7.0 magnitudes Loma Pricta, California: 65 dead; good building materials Armenia: 50,000 dead; bad building materials choose resistant building design Height of a building dictates the “period of vibration” (how long it takes to sway from one side and back again) The taller the building, the longer the period of vibration NOTE: said we don’t really need to know equation for this, just for interest N/10=buildings have a natural period of vibration of…; where N is the number of stories It is a combination of the period of vibration of the building and the soil; DON’T WANT THEM TO BE THE SAME Like being on a swing, if you pump at the same time as you are flying up you go higher; the amount of sway in buildings increases Ground Periods: Soft Soil=several seconds Solid Rock=<1 second Building Periods: Tall Buildings=several seconds Short Buildings=about 1 second Building shape also has an effect on the amount of vibration HOW TO BUILD A HOUSE TO RESIST SEISMIC QUAKES: Bolt it, bracket it, brace it, block it, panel it TALKING ABOUT DESIGN APPROACHES: (not sure if this is something you need to know) Buildings can have shock absorbers, filled with viscous fluid that helps keep the buildings from collapsing Can have springs with dampers Tuned mass-dampers that keep the building from swaying as much C) legislate construction regulations AIM OF ALL THREE OF THESE THINGS IS TO MINIMIZE DAMAGE TO STRUCTURES, AND ALL THREE LEAD TO AN INCREASE
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