Sidewalk parked cars weak floors whiplash between

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Unformatted text preview: earthquakes every 10- 15 years 1911- 1979: no major earthquakes 1979- 1989: four magnitude 6- 7 earthquakes Currently in cluster of strong earthquakes? The Los Angeles Area •  Moderate earthquakes (like 1994 M6.7 Northridge) likely every 10 years •  Far too few moderate earthquakes in 1857- 2007 to account for observed strain across region Northridge Earthquake, CA, 1994 §༊  §༊  §༊  §༊  Mw 6.7 Pico fault was unknown before earthquake Anomalously strong shaking on some ridge tops and edges of sedimentary basins $15 billion damage, 61 deaths What does the Mercalli Intensity Scale depend on? a)  b)  c)  d)  e)  how much damage occurred in an area the intensity of shaking of the seismograph the amplitude of movement of the seismograph needle the strength of rocks broken along the fault the frequency of the earthquake waves as they reach the seismograph Minimizing Earthquake Damage Collapse of Buildings Reinforced Concrete Types of Structural Damage §༊  §༊  §༊  §༊  Shaiering windows are major source of injuries – safety glass becoming more common Older buildings have loosely- res:ng beams – can pull out, collapse Older houses are not bolted down – can be shaken off their founda:ons Overhanging parapets or external décor can be easily shaken off, fall onto sidewalk, parked cars Weak Floors Whiplash Between magnitude 7 and magnitude 8 earthquakes, about how much harder is the shaking? a)  actually less accelera:on because the frequency is lower b)  not much c)  twice as hard d)  about 10 :mes e)  about 32 :mes Earthquake Preparedness §༊  Plan what to do when earthquake strikes §༊  §༊  §༊  §༊  §༊  If indoors, stay there Usually not enough :me to get out Longer- las:ng earthquakes accompanied by stronger ground mo:ons that would make it very difficult to stay mobile Lie down next to sturdy object, under table or de...
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