Earthquake scenario

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An Earthquake scenario is an ideal planning tool to determine the correct emergency responses, and to outline possible high-risk areas. It uses the basics of seismic hazard studies, but usually places a set earthquake on a specific fault, most likely near a high-population area. Most scenarios relate directly to urban seismic risk, and seismic risk in general.

A good earthquake scenario follows some of the latest methodologies from the nuclear industry, namely a Seismic Margin Assessment (SMA) [1]. In the process, a Review Level Earthquake (RLE) is chosen that challenges the system, has a reasonable probability, and is not totally overwhelming.

Several scenarios have been developed over the years, such as for Seattle [2], and New York City [3]. Many of the faults in California have also had this treatment. In general, areas west of the Rockies use urban earthquakes of M7 (Moment magnitude), and eastern cities use an M6. Both types of earthquakes have about an equal chance of occurring in their respective areas, and both would cause equal disruption.

Of even more interest are the various eastern cities that have chosen, for various reasons, not to have an earthquake scenario. This could be due to a lack of interest, or a lack of appreciation of their true risk profile. As an example, take the Greater Toronto area in Ontario, Canada. According to the local seismicity [4], this area has about as much a chance for an M6 as most of the moderate earthquake zones of Eastern North America (ENA), including New York City. As seen on the map, the RLE would be an M6 located in the western end of Lake Ontario, and would follow the New York City scenario, with extensive damage to lifelines, and brick buildings on soft ground.