Crowdsourcing is the practice of obtaining ideas, or content by soliciting contributions from a large group of people, and especially from an online community, rather than from traditional means such as suppliers or employees.
Physical disruption of a structure or equipment item, such as cracking in walls or overturning of equipment.
Earthquake Moment Magnitude or Mw scale
The magnitude is a number that characterizes the relative size of an earthquake. Magnitude is based on measurement of the maximum motion recorded by a seismograph or seismometer. Several scales have been defined and the most uniformly applicable to all sizes of earthquakes is the moment magnitude (Mw) scale, based on the concept of seismic moment. New techniques that take advantage of modern telecommunications have recently been implemented, allowing reporting agencies to obtain rapid estimates of moment magnitude for significant earthquakes.
European-Mediterranean Seismological Centre, http://www.emsc-csem.org/
Global Disaster Alert and Coordination System, http://www.gdacs.org/
The likelihood that natural physical manifestations of the earthquake peril, such as ground shaking, soil liquefaction, surface fault rupture, landslide or other ground failures, tsunami, seiche, may occur and reach or exceed given amounts. These manifestations can cause damage to man-made structures.
A ground failure phenomenon in which loose, granular soils below the water table lose shear strength when subjected to many cycles of strong ground shaking.
The monetary amount needed to repair a level of building damage from earthquake, expressed as a fraction of the building replacement value. Any monetary amount can be reached or exceeded with a given probability within a given exposure period. Alternatively, the frequency of occurrence or exceedance of any given loss can be expressed in terms of the so-called mean return period (MRP). Mathematically, the MRP is the reciprocal of the annual probability (or rate) of occurrence or exceedance. For example, a loss that has 0.01 probability to be exceeded in any given year has a MRP of 1/0.01=100 years or, equivalently, the exceedance of such a loss occurs, on average, once every 100 years.
Mean Return Period (MRP)
Mean return period also known as average return interval is an estimate of the frequency or likelihood of an event, such as an earthquake, flood to occur. It is a statistical measurement typically based on historic data denoting the average recurrence rate over an extended period of time, and is usually used for risk analysis, e.g. to decide whether a project should be allowed to go forward in a zone of a certain risk, or to design structures to withstand an event with a certain probability to occur within the time window of interest.
PGA or PHA
An instrumental measure of earthquake ground motion intensity, normally computed from one or both recorded horizontal components of a triaxial earthquake accelerogram. The PHA can be defined in multiple ways that do not substantially differ from one another in terms of numerical values. The simpler of such definitions defines PHA as the maximum value of the acceleration of the ground recorded from one or both horizontally-oriented axes. PHA is also often referred to as PGA (peak ground acceleration).
Probability of Exceedance
In the context of this risk report, this is the probability that a quantity, such as a given amount of losses, will be equaled or surpassed within the exposure period usually taken as one year, or the building expected useful life (e.g., 50 or 100 years) or the length of frequent terms of investment (e.g., 30 years), given the site’s seismic hazard and the property’s seismic vulnerability. For example, a loss level that has a 10% chance of exceedance in a 50-year exposure period has a 475-year mean return period.
The chance or probability that some undesirable outcome, such as injury, damage or loss, will occur during a specified exposure period.
A long-period wave generated usually by the displacement of some part of the seafloor. In the case of earthquake generated tsunamis the bottom of the sea is displaced by a fault rupture.
United States Geological Survey, http://earthquake.usgs.gov/earthquakes/
The susceptibility of a building, equipment item or component to damage or loss to be damaged by the manifestations of a specific peril.
475-year Peak Ground Acceleration Map
This map depicts the seismic hazard as Peak Ground Acceleration (PGA) with a 10% chance of exceedance in 50 years, corresponding to a return period of 475 years.
1000-year Flood Loss Map
A one-thousand-year flood is a flood event that has a 0.1% probability of occurring in any given year. Its annual exceedance probability is 0.1% or has a return period of 1000-years.
(Note. The relation of return period (T) and annual probability of exceedance (P) is as follow: P = 1 – exp(-1/T). When T is large, P is roughly equal to 1/T. For a 1000 year return period event, P =1/1000 = 0.1%)
The flood loss map has a spatial resolution of 250 m. The flood loss cost values are defined as total flood losses within a grid-cell divided by the total exposure within that cell. The return period of the flood loss map represents 1000 year total flood losses. The total flood loss values include both on-floodplain as well as off-floodplain losses. The exposure and loss values include all coverage types.