Although these maps have been used by the U.S. Geological Survey, no warranty, expressed or implied is made by the USGS as to the accuracy of the maps and related material nor shall the fact of distribution constitute any such warranty, and no responsibility is assumed by the USGS in connection therewith.

The Pacific Northwest, including the South Sound, is listed at 40% for a quake in the next 60 years... not real encouraging, but not real discouraging, either... 

Acceleration

When it is changing from one speed to another, it is accelerating (faster) or decelerating (slower). This change from one speed, or velocity, to another is called acceleration. During an earthquake when the ground is shaking, it also experiences acceleration. The peak acceleration is the largest acceleration recorded by a particular station during an earthquake.

An accelerograph records  the acceleration caused by an earthquake; its also commonly called an accelerometer.
 

Hazard maps help save lives and property

America's first line of defense against earthquakes has historically been the construction of buildings that can withstand severe shaking. Cities and counties rely on the seismic design provisions in building codes to ensure that structures can resist earthquakes. The variations in the seismic threat across the country are depicted on maps in building codes as zones of different risk levels. These building-code maps are based on more detailed shaking-hazard maps prepared by U.S. Government scientists.

This was the 1996 map... our likelihood has gone up a few percentage points

National maps of the earthquake shaking hazard in the United States have been produced since 1948. Scientists revise these maps as new earthquake studies improve their understanding of this hazard. After thorough review, professional organizations of engineers in turn update the seismic-risk maps and seismic design provisions contained in building codes. More than 20,000 cities, counties, and local government agencies use building codes, such as the Uniform Building Code, to help establish the construction requirements necessary to preserve public health and safety in earthquakes.

Shaking-hazard maps have many other applications. For example, the 1976 U.S. Geological Survey (USGS) shaking-hazard map for the United States was used for many years as the basis of design requirements for highway bridges nationwide. Such maps are also used by:

• insurance companies to set insurance rates for properties in various areas of the country,
• civil engineers to estimate the stability and landslide potential of hillsides,
• the Environmental Protection Agency to set construction standards that help ensure the safety of waste-disposal facilities, and
• the Federal Emergency Management Agency (FEMA) to plan the allocation of assistance funds for earthquake education and preparedness.

Shaking-hazard maps can be combined with data about the strength of existing buildings to estimate expected earthquake damage in an area over a given period of time. Although strong earthquakes are less frequent in the Central and Eastern United States than in California, damage in those regions could be catastrophic in a powerful temblor. This is because most buildings and other structures there have not been constructed to withstand severe earthquake shaking. For example, the shaking hazard in Boston is far lower than that in Los Angeles, but the damage to structures throughout the Boston area would be much greater if a strong earthquake struck today. A single earthquake in the Central or Eastern United States could cause as many casualties and as much damage as several earthquakes of similar magnitude in California