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<br /> <br />shake, and to shake more intensely. As a result, one principal factor in determining <br />anticipated levels of shaking hazard in any given location is the magnitude of expected <br />earthquakes. The intensity of ground shaking felt in one area versus another, however, is <br />based on the magnitude and other factors including distance to the fault; direction of <br />rupture; and, the type of geologic materials at the site. For example, softer soils tend to <br />amplify ground shaking, while more dense materials limit ground shaking impacts at the <br />site surface. <br />Ground shaking is commonly characterized using the Modified Mercalli Intensity (MMI) <br />scale, which illustrates the intensity of ground shaking at a particular location by <br />considering the effects on people, objects, and buildings. The MMI scale describes shaking <br />intensity on a scale of 1-12. MMI values less than 5 don’t typically cause significant damage; <br />MMI values greater than 10 have not been recorded. <br />Table 3 MMI Intensity Table11 <br />Intensity Building Contents Masonry Buildings Multi-Family Wood- <br />Frame Buildings <br />1&2 Story Wood- <br />Frame Buildings <br />MMI 6 Some things thrown <br />from shelves, <br />pictures shifted, <br />water thrown from <br />pools <br />Some walls and <br />parapets of poorly <br />constructed <br />buildings crack. <br />Some drywall cracks. Some chimneys are <br />damaged, some <br />drywall cracks. Some <br />slab foundations, <br />patios, and garage <br />floors slightly crack. <br />MMI 7 Many things thrown <br />from walls and <br />shelves. Furniture is <br />shifted. <br />Poorly constructed <br />buildings are <br />damaged and some <br />well-constructed <br />buildings crack. <br />Cornices and <br />unbraced parapets <br />fall. <br />Plaster cracks, <br />particularly at inside <br />corners of buildings. <br />Some soft-story <br />buildings strain at <br />the first floor level. <br />Some partitions <br />deform. <br />Many chimneys are <br />broken and some <br />collapse, damaging <br />roofs, interiors, and <br />porches. Weak <br />foundations can be <br />damaged. <br />MMI 8 Nearly everything <br />thrown down from <br />shelves, cabinets, <br />and walls. Furniture <br />overturned. <br />Poorly constructed <br />buildings suffer <br />partial or full <br />collapse. Some well- <br />constructed <br />buildings are <br />damaged. <br />Unreinforced walls <br />fall. <br />Soft-story buildings <br />are displaced out of <br />plumb and partially <br />collapse. Loose <br />partition walls are <br />damaged and may <br />fail. Some pipes <br />break. <br />Houses shift if they <br />are not bolted to the <br />foundation, or are <br />displaced and <br />partially collapse if <br />cripple walls are not <br />braced. Structural <br />elements such as <br />beams, joists, and <br />foundations are <br /> <br />11 ABAG, (2013). Modified Mercalli Intensity Scale