Micro Seismic Hazard Analysis

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Soft ground effect - summary• Soft soil overlying bedrock almostalways amplify ground shaking• Given specific ground conditions andsufficient duration of the quake,resonance can occur, resulting in evenlarger amplifications• If a structure has a natural frequencysimilar to the characteristic site periodof the soil, very large damage or totalcollapse may occur
Soft ground effect - example• 19 Sept. 1985 Michoacan earthquake,Mexico City (M 8.0, MMI IX)• Epicenter far away from city (> 100 km)• PGA’s at rock level 0.04 g - butamplification due to soft ground: 5 x• Greatest damage in Lake Zone: 40-50 m ofsoft clay (lake deposits)• Characteristic site period (1.9-2.8 s) similarto natural period of vibration of 5-20 storeybuildings• Most damaged buildings 8-18 storeys
Page 3 and 4: Basic physical concepts and definit
Page 7 and 8: Site effects due to low stiffness s
Page 9: Site effects due to low stiffness s
Page 12 and 13: Characteristic site period• The p
Page 14 and 15: Natural frequency of buildings• A
Page 16 and 17: Examples of natural frequencies ofb
Page 18 and 19: Vertical standing waves• Vertical
Page 20 and 21: Summarising: building resonance and
Page 24 and 25: MichoacanearthquakeCollapsed 21-Sto
Page 26 and 27: Theoretical methods• Numerical me
Page 28 and 29: How do we carry out a groundrespons
Page 30 and 31: What do we use to quantify theexpec
Page 32 and 33: SHAKE• The equivalent linear appr
Page 34 and 35: 1D ground response analysisAssumpti
Page 36 and 37: Transfer Function as technique for
Page 38 and 39: Define the transfer function (2)•
Page 40 and 41: Effect of transfer function onAmpli
Page 42 and 43: Procedure to account for nonlineari
Page 44 and 45: General, simplified profile as assu
Page 46 and 47: Standard Spectral Ratio Technique (
Page 48 and 49: Nakamura’s or H/V method (1)• S
Page 50 and 51: Nakumura’s or H/V method (3)• M
Page 52: Nakumura’s or H/V method (5)• I
Page 55 and 56: Site effects due to surface topogra
Page 57 and 58: Liquefaction
Page 59 and 60: Liquefaction - general (2)• Commo
Page 61 and 62: Liquefaction - governing factors (2
Page 63 and 64: Liquefaction - governing factors (4
Page 65 and 66: Liquefaction - governing factorssum

Micro Seismic Hazard Analysis

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