Fault Creep Rate
Fault creep rate can be estimated from just two components of LOS
deformation if one assumes there is no fault-normal displacement
[Xu et al. , 2018]. By making that assumption we measure
fault-parallel and vertical creep rate along each individual strand
within the San Andreas Fault system (Fig. 5, Table S1). The method,
which is similar to the Bufford & Harsh [1980] method, is to
fit a linear model to the LOS data over a flat area on each side of the
fault (up to 3 km) and record the offset of the linear models at the
fault location. The along-fault offset locations have a typical spacing
of 10 km and roughly follow the locations from the study of Tong
et al. [2013]. Some areas of fault creep have a velocity step up to
1 km wide; In these cases, the linear fit is confined to the flatter
part of the LOS data on each side of the fault (e.g., Fig. 5a, at
Hayward fault). The fault creep rates estimated in this study are
presented together with a compilation by Field et al. [2009]
(Fig. 5a). Fault vertical differential (Fig. 5b) shows no systematic
pattern along these faults. However, not accounting for the vertical
offset will bias the horizontal offset estimates. A few larger vertical
offsets (Fig 5b) are associated with subsidence at fault step-overs.