The Hayward fault runs through some of the most densely populated regions of the San Francisco Bay Area, and has a high probability of failing with a Magnitude 7+ earthquake within the next 30 years.

The identification of regions where high amplitude ground motions are expected is important for seismic hazard assessment. Shown here are 3-D simulated ground motions in the San Francisco Bay Area due to scenario earthquakes of Magnitude 7.1 along the Hayward fault (north and south segments combined). We consider three rupture scenarios:

(Click images to enlarge. Then double click large image to animate. )
Bilateral		North-to-South propagating		South-to-North propagating	Color Key: Green (positive S potential) Greenish Blue (negative S potential) Red (positive P potential) Redish Blue (negative P potential) Other colors (e.g., white, yellow) represent areas where the S and P potentials overlap. The color intensity indicates the amplitude of the ground motion.

The movies show simulated ground motions (S/shear and P/compressional wave potentials) for each of the three rupture scenarios. The simulations last 90 seconds in real-time. Note the high amplitude and long duration ground motions in the San Pablo Bay (north of the Hayward fault), in the Santa Clara Valley (south of the Hayward fault), and in the Livermore Valley (east of the Hayward fault).

Grid Details:

These simulations were performed with E3D, a finite-difference seismic wave propagation code implemented on massively parallel supercomputers at Lawrence Livermore National Laboratory. The simulations utilize a geologic model developed at the University of California at Berkeley.

The 3D finite-difference grid dimensions are 175 km in the northwest direction, 100 km in the northeast direction, and 40 km in depth. The grid spacing is 0.25 km. The Hayward fault is modeled as a uniform rupture along a linear fault 82 km long and 10 km deep. The rupture velocity is 2.5 km/sec and the rise time is approximately 2 seconds. The upper frequency of the source is 0.5 - 1.0 hz. The earth velocities range from 1.5 - 8.0 km/sec.

Attenuation and topography are not included in the calculations. The simulations are made to 90 seconds.

Source:

Shawn Larsen (Lawrence Livermore National Laboratory), Doug Dreger, Mike Antolik, Christiane Stidham (University of California at Berkeley).