Page 42 - CCPS Monograph - Natural Hazards

A monograph is a learned treatise on a small area of learning; a written account of a single thing. (MS
2019)

The Richter magnitude scale is a mathematical device to compare the size of earthquakes. The
magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by
seismographs. Adjustments are included for the variation in the distance between the various
seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in
whole numbers and decimal fractions. For example, a magnitude 5.3 might be computed for a
moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the
logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase
in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale
corresponds to the release of about 31 times more energy than the amount associated with the
preceding whole number value. (USGS 2019c)

The Saffir-Simpson Hurricane Wind Scale (SSHWS) is a 1 to 5 rating based on a hurricane's sustained
wind speed. This scale estimates potential property damage. Hurricanes reaching Category 3 and
higher are considered major hurricanes because of their potential for significant loss of life and
damage. Category 1 and 2 storms are still dangerous, however, and require preventative measures.
In the western North Pacific, the term "super typhoon" is used for tropical cyclones with sustained
winds exceeding 241 kph (150 mph). (NOAA 2019d)

Table G.5 Saffir-Simpson Hurricane Wind Scale (adapted from NOAA 2019d)

Category Sustained Winds Types of Damage Due to Hurricane Winds
1 119-153 kph Very dangerous winds will produce some damage: Well-
64-82 kt constructed frame homes could have damage to roof, shingles,
74-95 mph vinyl siding and gutters. Large branches of trees will snap, and
shallowly rooted trees may be toppled. Extensive damage to
power lines and poles likely will result in power outages that
could last a few to several days.
2 154-177 kph Extremely dangerous winds will cause extensive damage: Well-
83-95 kt constructed frame homes could sustain major roof and siding
96-110 mph damage. Many shallowly rooted trees will be snapped or
uprooted and block numerous roads. Near-total power loss is
expected with outages that could last from several days to
weeks.
3 178-208 kph Devastating damage will occur: Well-built framed homes may
(major) 96-112 kt incur major damage or removal of roof decking and gable ends.
111-129 mph Many trees will be snapped or uprooted, blocking numerous
roads. Electricity and water will be unavailable for several days to
weeks after the storm passes.
4 209-251 kph 113- Catastrophic damage will occur: Well-built framed homes can
(major) 136 kt sustain severe damage with loss of most of the roof structure
130-156 mph and/or some exterior walls. Most trees will be snapped or
uprooted, and power poles downed. Fallen trees and power
poles will isolate residential areas. Power outages will last weeks
to possibly months. Most of the area will be uninhabitable for
weeks or months.

Assessment of and planning for natural hazards 39

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