Risk Frontiers





				[New Zealand] [Dowrick, 1996]
					MM1 *People* Not felt except by a very few people under exceptionally favourable circumstances MM2 People Felt by persons at rest, on upper floors or favourably placed MM3 People Felt indoors; hanging objects may swing, vibration similar to passing of light trucks, duration may be estimated, may not be recognised as an earthquake. MM4 People Generally noticed indoors but not outside. Light sleepers may be awakened. Vibration may be likened to the passing of a heavy traffic, or to the jolt of a heavy object falling or striking the building. Fittings Doors and windows rattle. Glassware and crockery rattle. Liquids in open vessels may be slightly disturbed. Standing motorcars may rock. Structures Walls and frame of buildings, and partitions and suspended ceilings in commercial buildings, may be heard to creak. MM5 People Generally felt outside, and by almost everyone indoors. Most sleepers awakened. A few people alarmed. Fittings Small unstable objects are displaced or upset. Some glassware and crockery may be broken. Hanging pictures knock against the wall. Open doors may swing. Cupboard doors secured by magnetic catches may open. Pendulum clocks stop, start, or change rate. Structures Some windows Type I cracked. A few earthenware toilet fixtures cracked. MM6 People Felt by all People and animals alarmed. Many run outside Difficulty experienced in walking steadily Fittings Objects fall from shelves Pictures fall from walls Some furniture moved on smooth floors, some free-standing unsecured fireplaces moved Glassware and crockery broken Very unstable furniture overturned Small church and school bells ring Appliances move on bench and table tops Filing cabinets or ‘easy glide’ drawers may open [or shut]. Structures Slight damage to Buildings Type I Some stucco or cement plaster falls Windows Type I broken Damage to a few weak domestic chimneys, some may fall. Environment Trees and bushes shake, or are heard to rustle. Loose material may be dislodged from sloping ground, e.g. existing slides, talus slopes, shingle slides. MM7 People General alarm Difficulty experienced in standing Noticed by motorcar drivers who may stop. Fittings Large bells ring Furniture moves on smooth floors, may move on carpeted floors. Substantial damage to fragile contents of buildings Structures Unreinforced stone and brick walls cracked. Buildings Type I cracked with some minor masonry falls. A few instances of damage to Buildings Type II Unbraced parapets, unbraced brick gables, and architectural ornaments fall. Roofing tiles, especially ridge tiles may be dislodged. Many unreinforced domestic chimneys damaged, often falling from the roof-line. Water tanks Type I burst. A few instances of damage to brick veneers and plaster or cement-based linings. Unrestrained water cylinders [Water Tanks Type II] may move and leak. Some windows Type II cracked. Suspended ceilings damaged. *Environment* Water made turbid by stirred up mud. Small slides such as falls of sand and gravel banks, and small rock-falls from steep slopes and cuttings. Instances of settlement of unconsolidated or wet, or weak soils. Some fine cracks appear in sloping ground. A few instances of liquefaction [i.e. small water and sand ejections]. MM8 People Alarm may approach panic. Steering of motor cars greatly affected Structures Building Type I, heavily damaged, some collapse Buildings Type II damaged, some with partial collapse Buildings Type III damaged in some cases A few instances of damage to Structures Type IV Monuments and pre-1976 elevated tanks and factory stacks twisted or brought down Some pre-1965 infill masonry panels damaged A few post-1980 brick veneers damaged Decayed timber piles of houses damaged Houses not secured to foundations may move Most unreinforced domestic chimneys damaged, some below roof-line, many brought down. Environment Cracks appear on steep slopes and in wet ground Small to moderate slides in roadside cuttings and unsupported excavations Small water and sand ejections and localised lateral spreading adjacent to streams, canals, lakes etc. MM9 Structures Many Buildings Type I destroyed Buildings Type II heavily damaged, some collapse Buildings Type III damaged, some with partial collapse Structures Type IV damaged in some cases. Some with flexible frames seriously damaged. Damage or permanent distortion to some Structures Type V. Houses not secured to foundations shifted off Brick veneers fall and expose frames Environment Cracking of ground conspicuous Landsliding general on steep slopes Liquefaction effects intensified and more widespread, with large lateral spreading and flow sliding adjacent to streams, canals, lakes etc. MM10 Structures Most Buildings Type I destroyed Many Buildings Type II destroyed Buildings Type III heavily damaged, some collapse Structures Type IV damaged, some with partial collapse. Structures Type V moderately damaged, but with few partial collapses A few instances of damage to Structures Type VI Some well-built timber buildings moderately damaged [excluding damage from falling chimneys] Environment Landsliding very widespread in susceptible terrain, with very large rock masses displaced on steep slopes Landslide dams may be formed Liquefaction effects widespread and severe MM11 Structures Most Buildings Type II destroyed Many Buildings Type III destroyed Structures Type IV heavily damaged, some collapse Structures Type V damaged, some with partial collapse Structures Type VI suffer minor damage, a few moderately damaged MM12 Structures Most Buildings Type III destroyed Many Structures Type IV destroyed Structure Type V heavily damaged, some with partial collapse Structures Type VI moderately damaged. Notes Construction types Buildings Type I [Masonry D in NZ 1965 MM Scale] Buildings with low standard of workmanship, poor mortar, or constructed of weak materials like mud brick or rammed earth. Soft storey structures [e.g. shops] made of masonry, weak reinforced concrete, or composite materials [e.g. some walls timber, some brick] not well tied together. Masonry Buildings otherwise conforming to Building Types I-III, but also having heavy unreinforced masonry towers. [Buildings constructed entirely of timber must be of extremely low quality to be Type I]. Buildings Type II [Masonry C in the NZ 1966 MM Scale] Buildings of ordinary workmanship, with mortar of average quality. No extreme weakness, such as inadequate bonding of the corners, but neither designed nor reinforced to resist lateral forces. Such buildings not having heavy unreinforced masonry towers. Buildings Type III [Masonry B in the NZ 1966 MM Scale] Reinforced masonry or concrete buildings of good workmanship and with sound mortar, but not formally designed to resist earthquake forces. Structures Type IV [Masonry A in the NZ 1966 MM Scale] Buildings and bridges designed and built to resist earthquakes to normal use standards, i.e. no special collapse or damage limiting measures taken [mid-1930s to c1970 for concrete and to c1980 for other materials]. Structures Type V Buildings and bridges, designed and built to normal use standards, i.e. no special damage limiting measures taken, other than code requirements, dating from since c1970 for concrete and c1980 for other materials. Structure Type VI Structures dating from c1980, with well-defined foundation behaviour, which have been specially designed for minimal damage, e.g. seismically isolated emergency facilities, some structures with dangerous or high contents, or new generation low damage structures. Windows Type I – Large display windows, especially shop windows. Type II – Ordinary sash or casement windows Water Tanks Type I – External, stand-mounted, corrugated iron water tanks Type II – Domestic hot-water cylinders unrestrained except by supply and delivery pipes. Other comments "Some" or "a few" indicates that the threshold of a particular effect has just been reached at that intensity "Many run outside" [MM6] variable depending on mass behaviour, or conditioning by occurrence or absence of previous quakes, i.e. may occur at MM5 or not till MM7. "Fragile Contents of Buildings" Fragile contents include weak, brittle, unstable, unrestrained objects in any kind of building. "Well-built timber buildings" have: wall openings not too large; robust piles or reinforced concrete strip foundations; superstructure tied to foundations. Buildings Type III-V at MM10 and greater intensities are more likely to exhibit the damage levels indicated for low-rise buildings on firm or stiff ground and for high-rise buildings on soft ground. By inference lesser damage to low-rise buildings on soft ground and high-rise buildings on firm or stiff ground may indicate the same intensity. These effects are due to attenuation of short period vibrations and amplification of longer period vibrations in soft soils. Correlations with EMS Scale Correlations between EMS building Classes and MM building/structure Types are approximately A:I, B:II, C:III, D and E:IV, F:V, no EMS equivalent to MM Type VI. The damage levels in the two scales are harder to compare but EMS grade 5 » destroyed, 4 » heavily damaged, 2-3 » moderate to light damage. References Dowrick D J, 1996, The Modified Mercalli Intensity Scale - Revisions arising from Recent studies of New Zealand Earthquakes, Bulletin of the New Zealand National Society for Earthquake Engineering, 29[2], 92-106.