Interseismic coupling and refined earthquake potential on the Hayward‐Calaveras fault zone

E. Chaussard, R. Bürgmann, H. Fattahi, C. W. Johnson, R. Nadeau, T. Taira & I. Johanson

Journal of Geophysical Research: Solid Earth
November 11, 2015

Interseismic strain accumulation and fault creep is usually estimated from GPS and alignmentarrays data, which provide precise but spatially sparse measurements. Here we use interferometricsynthetic aperture radar to resolve the interseismic deformation associated with the Hayward and CalaverasFaults (HF and CF) in the East San Francisco Bay Area. The large 1992–2011 SAR data set permits evaluation ofshort- and long-wavelength deformation larger than 2 mm/yr without alignment of the velocity field to aGPS-based model. Our time series approach in which the interferogram selection is based on the spatialcoherence enables deformation mapping in vegetated areas and leads to refined estimates of along-faultsurface creep rates. Creep rates vary from 0 ± 2 mm/yr on the northern CF to 14 ± 2 mm/yr on the central CFsouth of the HF surface junction. We estimate the long-term slip rates by inverting the long-wavelengthdeformation and the distribution of shallow slip due to creep by inverting the remaining velocity field. Thisdistribution of slip reveals the locations of locked and slowly creeping patches with potential for a M6.8 ± 0.3on the HF near San Leandro, a M6.6 ± 0.2 on the northern CF near Dublin, a M6.5 ± 0.1 on the HF south ofFremont, and a M6.2 ± 0.2 on the central CF near Morgan Hill. With cascading multisegment ruptures the HFrupturing from Berkeley to the CF junction could produce a M6.9 ± 0.1, the northern CF a M6.6 ± 0.1, thecentral CF a M6.9 ± 0.2 from the junction to Gilroy, and a joint rupture of the HF and central CF could producea M7.1 ± 0.1.

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Robert M. Nadeau

Berkeley Seismological Lab
Alumni - Data Science Fellow