Potential for larger earthquakes in the East San Francisco Bay Area due to the direct connection between the Hayward and Calaveras Faults

Abstract

The Hayward and Calaveras Faults, two strike‐slip faults of the San Andreas System located in the East San Francisco Bay Area, are commonly considered independent structures for seismic hazard assessment. We use Interferometric Synthetic Aperture RADAR to show that surface creep on the Hayward Fault continues 15 km farther south than previously known, revealing new potential for rupture and damage south of Fremont. The extended trace of the Hayward Fault, also illuminated by shallow repeating micro‐earthquakes, documents a surface connection with the Calaveras Fault. At depths greater than 3–5 km, repeating micro‐earthquakes located 10 km north of the surface connection highlight the 3‐D wedge geometry of the junction. Our new model of the Hayward and Calaveras Faults argues that they should be treated as a single system with potential for earthquake ruptures generating events with magnitudes greater than 7, posing a higher seismic hazard to the East San Francisco Bay Area than previously considered.

Evaluation of the SBAS InSAR Service of the European Space Agency’s Geohazard Exploitation Platform (GEP)

“…However, sometimes Earth scientists are prone to work with less accurate data, especially if they intend to delineate areas that are in motion, regardless of the local accuracy. Examples of this are the works of Galve et al [6], Lu et al [50], and Chaussard et al [51], which analyzed karst subsidence, landslides, and active tectonics with coherence thresholds of 0.4, 0.6, 0.5, respectively. This is especially true if the main goal of the analysis is to carry out a preliminary exploration to select points that are to be visited later in the field.…”

The role of space-based observation in understanding and responding to active tectonics and earthquakes

“…They have also been used to investigate the spatial variation of rheology and frictional properties on faults, from the detection of heterogeneous rheology in the lithosphere, both at the large scale and in weaker localized regions around the fault82, to using spatial83 and spatio-temporal84 variations in aseismic creep on faults to infer spatial variations in dynamic frictional properties. These data can be used to map variations in frictional coupling on subduction megathrusts85, and to map structural complexity on continental faults at depth, showing how deep shear zone localization can differ from surface structural complexity and segmentation86, and highlighting deep crustal connections between branching faults87. This information is not only important for the fundamental understanding of earthquake and fault mechanics, but is also crucial for understanding both the likely propagation of ruptures in large earthquakes, and the proportion of plate-tectonic movement that is accommodated by earthquakes and by slow slip or creep.…”

Repeating Marmara Sea earthquakes: indication for fault creep

“…Aster & Scott 1993;Vidale et al 1994;Chaussard et al 2015). The similarity of event pairs recorded at specific stations was quantified by their cross-correlation coefficient (0 ≤ ccc ≤ 1).…”

“…The most prominent examples are the M up to 2 repeaters along the Parkfield section in central California (Nadeau et al 1995;Rubinstein & Ellsworth 2010) and several repeater spots along the Hayward-Calaveras section in the eastern San Francisco bay area (Waldhauser & Ellsworth 2002;Chaussard et al 2015).…”