Earthquakes are a part of life in Southern California. The SCSN is an agency that seeks to mitigate seismic hazards through scientific comprehension of earthquakes. As we learn more about how earthquakes work, we learn more about how to deal with them. Shown below is ShakeMap, one SCSN product that is a direct result of the science and technology that has been generated from earthquake research. ShakeMap Scenarios have also been created to model past and future events, affording first responders an opportunity to proactively design a response scenario for a major earthquake that may happen in the future. Earthquake Scenarios describe the expected ground motions and effects of specific hypothetical large earthquakes. In planning and coordinating emergency response, utilities, emergency responders, and other agencies are best served by conducting training exercises based on realistic earthquake situations, ones that they are most likely to face. Scenario earthquakes can fill this role; they can be generated for any potential hypothetical future or past historic earthquake by the following steps. First, assume a particular fault or fault segment will rupture over a certain length relying on consensus-based information about the potential behavior of the fault. For historic events, the actual rupture dimensions may be constrained based on existing observations or models. Second, estimate ground motions at all locations in a chosen region surrounding the causative fault. These earthquake scenarios are not earthquake predictions. That is, no one knows in advance when or how large a future earthquake will be. However, if we make assumptions about the size and location of a hypothetical future earthquake, we can make a reasonable prediction of the effects of the assumed earthquake, particularly the way in which the ground will shake. This knowledge of the potential shaking effects is the main benefit of the earthquake scenario for planning and preparedness purposes.
ShakeMap Developed for Potential M7.1 Puente Hills Fault Scenario
The image above is a scenario only. The ShakeMap shown above is for planning scenario purposes only. Image copyright 2003, 2004, 2005 California Institute of Technology and United States Geological Survey (USGS). ShakeMap may be preliminary in nature and presented prior to final review and approval by the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete, and conclusions drawn from such information are the sole responsibility of the user.
Aftershock probabilities and forecast models have been combined to create the 24-hour aftershock probability map for California. This is a time-dependent map giving the probability of strong shaking at any location in California within the next 24-hours. For this purpose, “strong shaking” is defined as Modified Mercalli Intensity (MMI) VI, or the level of shaking that throws objects off shelves. The image below is the most recent 24-hour model. To visit the STEP webpage, click the image below: