Earthquake hazard map showing peak ground accelerations
Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location. PGA is equal to the amplitude of the largest absolute acceleration recorded on an accelerogram at a site during a particular earthquake.
Color white in the map indicates a very small probability of experiencing damaging earthquake effects (low risk) while colored red in the map which is near major active faults capable of producing the most intense shaking (high risk) as indicated in the Seismic Design Categories.
Seismic hazard is the hazard associated with potential earthquakes in a particular area, and a seismic hazard map shows the relative hazards in different areas. The maps are made by considering what we currently know about: Past faults and earthquakes.
How do you read a geological hazard map? The map title indicates what type of information is being presented by the map. For example, the title “tsunami-prone areas” indicates that the map presents the places along the coastal areas that are prone to tsunami hazards.
PGA is calculated using attenuation function that describes the correlation between the local ground movement intensity the earthquake magnitude and the distance from the earthquake’s epicentre.
Spectral acceleration, with a value related to the natural frequency of vibration of the building, is used in earthquake engineering and gives a closer approximation to the motion of a building or other structure in an earthquake than the peak ground acceleration value, although there is normally a correlation between ..
The seismogram is “read” like a book, from left to right and top to bottom (this is the direction that time increases). As with a book, the right end of any horizontal line “connects” with the left end of the line below it. Each line represents 15 minutes of data; four lines per hour.
These include ground shaking, landslides, liquefaction, and in some areas, tsunamis. These primary hazards often produce secondary hazards such as ruptured utility lines, hazardous spills, and fires.
Hazard maps are developed to illuminate areas that are affected or vulnerable to a particular hazard. They are typically made for natural hazards such as earthquake ground motion, flooding, landslides, liquefaction, and tsunami.
Hazard maps are developed to illuminate areas that are affected or vulnerable to a particular hazard. They are typically made for natural hazards such as earthquake ground motion, flooding, landslides, liquefaction, and tsunami.
This map shows you the distribution of damaging earthquake shaking across the United States. This map does not show specific faults or earthquakes, or other hazards besides earthquake. The USGS Qfaults database shows specific faults.
On the other hand, hazard maps produced by municipal governments usually contain the following information in addition to the areas at risk of disasters: sketches of evacuation routes and shelters, evaluation of disaster possibility and frequency, a warning and evacuation system, and disaster-related basic information.
But even more important, the information must be perceived as explaining a hazard that may adversely affect life, property, or socioeconomic activities. This can be accomplished by providing three elements-location, likelihood of occurrence (frequency or return period), and severity.
Geologic maps are used for a variety of purposes, including petroleum, mineral, and ground-water exploration; land use planning; and natural hazard studies.
Geologic maps include strike and dip symbols showing the orientation and slope of rock beds, which we covered in an earlier lab (see Tilted Beds and Strike and Dip). Some geologic maps also show the orientation of the foliation in metamorphic rocks with special foliation strike and dip symbols.
Geohazard maps are specialized maps that indicate the hazard susceptibility of areas. These maps are useful for disaster preparedness and management. The geohazard maps developed by MGB contain information on areas susceptible to rain-induced landslides and flooding.
In earthquake engineering theory, the bedrock motion with highest response is the Peak Ground Acceleration (PGA) and the free surface motion with highest response is the Peak Surface Acceleration (PSA).