Hayward Fault Model Overview
We are constructing models of the Hayward fault using rock property data from the Hayward fault geologic model, the Bay Area geologic model, and the Bay Area velocity model.
Our new mesh has cells small enough to resolve the details of the Hayward fault geologic model, and the proposed locked patches along the fault.
Fig. 1. Finite element mesh. The mesh measures 400 km by 300 km by 100 km deep. In the picture, north is at upper left.
The smallest cells are cubes 625 meters on a side. The smallest cells are too small to be seen clearly at this scale. The mesh contains about 850,000 cells, all of which are quadratic hexahedra. The smallest cells are clustered around the fault. Away from the fault, cells become larger.
This image is colored by Vs (shear wave velocity). Close to the fault, rock property data comes from the Hayward geologic model. Farther away, rock property data comes from the Bay Area geologic model.
Fig. 2. Close-up of center of mesh. The smallest cells are 625 meters on a side. North is at upper left.
White squares lie on the fault, at intervals of 10 km. The upper left (northernmost) square is located at Point Pinole. So these squares correspond to the conventional Hayward fault coordinate system, with the upper left square at the 0 km mark and the lower right square at the 70 km mark.
The image is colored according to Vs (shear wave velocity). The San Leandro gabbro is visible as an elongated green area in the center, running from the 30 km mark to the 50 km mark along the fault. Note the sharp change in Vs across the fault in the upper left portion of the image.
Fig. 3. Close-up of fault plane, viewed from the west. The smallest cells are 625 meters on a side. North is at left.
White squares lie on the fault, at intervals of 10 km. The left (northernmost) square is located at Point Pinole. So these squares correspond to the conventional Hayward fault coordinate system, with the leftmost square at the 0 km mark and the rightmost square at the 70 km mark.
The image is colored according to Vs (shear wave velocity). The San Leandro gabbro is visible as the brown area running from the 30 km mark to the 50 km mark. The curved blue-and-green area from the 10 km mark to the 30 km mark is rock unit "fn" in the Hayward geologic model. The blue-and-green trapezoid at the left edge of the image, at about the -20 km mark, is rock unit "gvl" from the Hayward geologic model. The image shows that the finite element mesh is fine enough to resolve details of the Hayward geologic model.
The purple dots are relocated seismicity data. The white polygons are proposed locked patches. Both are from Waldhauser and Ellsworth.
Fig. 4. Close-up of fault plane, viewed from the east. The smallest cells are 625 meters on a side. North is at right.
White squares lie on the fault, at intervals of 10 km. The right (northernmost) square is located at Point Pinole. So these squares correspond to the conventional Hayward fault coordinate system, with the rightmost square at the 0 km mark and the leftmost square at the 70 km mark.
The image is colored according to Vs (shear wave velocity). The San Leandro gabbro is visible as the brown rectangle running from the 30 km mark to the 55 km mark. The green trapezoid immediately to the right of the San Leandro gabbro, at the 20 to 30 km mark, is rock unit "cro" from the Hayward geologic model. The image shows that the finite element mesh is fine enough to resolve details of the Hayward geologic model.
The purple dots are relocated seismicity data. The white polygons are proposed locked patches. Both are from Waldhauser and Ellsworth.
